The saga of the Lidl inverter genset

Hi everyone,
Before I go any further, I feel I should point out from the start that this is a rather long post. However, there are quite a few insights into Lidl's stocking policy which might help you deal with their rather odd approach to customer service as well as insights into why there are so many, easily remedied, problems with this particular product (and, no doubt, with other similar products).
I've made references to a total of four [NOTES] which contain most of the vital information regarding the issues of the generator and the reasons why, despite these issues, they can still be an excellent choice for anyone wishing to keep a computer or two running and all the house lights on during protracted outages which may well start to become common all too soon in urban areas that have, over the past 30 years or more, been traditionally free of such outages.
What I'm trying to say is, please take note of the [NOTES], they're an important part of the saga as well as a source of useful information for anyone choosing a generator to backup an existing UPS setup.
As some of you may have noted, I recently purchased one of these excellent (fsvo 'excellent') Parkside PGI 1200 B2 generators from our recently opened main Lidl store the Sunday before last whilst accompanying SWMBI on a shopping trip.
I'd been hoping to see the return of these gensets, since even at their earlier price of 129 quid last year - all silly faults aside[1], they're the best value for money for any genset in the class of "Inverter"[2].
We hadn't seen any announcement in Lidl's leaflets regarding them so you can imagine my surprise when I spotted a half pallet's worth just stood there waiting to be grabbed. Even more remarkable was their price drop of 30 quid, down to an irresistible double digit price tag of just 99 quid! Move aside, Marland. You're no longer the sole UK owner of a 99 quid PGI 1200B2 genset - club membership has just been widened to include the great unwashed. :-)
It was the very first item that went into the trolley that SWMBI had selected for its petiteness and ease of handling. We hadn't planned on a very big "Shop" (we rarely do) so it wasn't long before I was paraphrasing under my breath from the "Jaws" movie, "We're gonna need a bigger trolley!".
When we got home, I headed for the basement looking for a can of 15W-40 or suitable substitute only to be faced with a flooding coal hole that was threatening to inundate the rest of the basement, and so a new thread in this NG was born :-( namely:
Recommendations for a SELF PRIMING (not a submersible!) cellar pump.
which you've all no doubt seen, if not read. As a consequence of the saga of the flooded basement, I didn't get a chance to test the genset out until the following Sunday when it proved to be faulty[1] and too late to return on the off chance that there'd be any more left until the Monday. Amazingly, there were still some left (two in fact) so I exchanged it after declining their initial offer of a full refund.
This time, the problem was that I couldn't start it no matter how hard I tried. Eventually, it dawned on me that the red light that kept lighting up for a few seconds each time I cranked it on the pull cord, was an "Oil Low" warning light. I gave it a rest, thinking my 35 year old sprog would be home soon enough to yank the recalcitrant bugger into life whilst I could positively identify that it *was* only the oil warning lamp that was lighting up each time - any excuse to take a breather.
My sprog duly returned home from work and we were able to remove the spark plug to check for sparks of which there were none until I disconnected a loose bullet connector that just happened to be the low oil sensor (literally a float sensor rather than a pressure sensor like on pre ecu car engines). We were then able to see sparks at the plug points, proving that the problem was a faulty sensor or a framing fault on the oil sensor lead hidden under the plastic cowling covering the engine/pm generator sub assembly within the outer casing.
Since we could see that the oil level was just past the high mark through the dipstick/filling/drain hole, we left the bullet connector disconnected and it fired up first pull after we refitted the spark plug and HT lead.
Indeed we left it running for a few minutes to warm it up, thinking, "If this blows up, it blows up! It's not our fault that the Oil Level warning sensor circuit had a fault.", before connecting it to the input of the APC SmartUPS2000 to prove that it could actually supply stable enough power to satisfy the (not quite so) picky mains quality demanded by the UPS before it will transfer back to mains power[3].
The test was a complete success but I hadn't seen the youtube video and the all important comment at that stage which would have shed light on both this and the first genset's problem, so decided to take it back for a second exchange attempt the next day - it was after 10pm by the time we had given up on our abortive attempt to trace the oil level sensor wiring by trying to disassemble it without disturbing the single screw hidden under a warranty tamper-proof sticker that would have made the job so much easier.
It was quite a struggle trying to reassemble the engine unit back into the casing by torchlight alone but we eventually accounted for every single nut, bolt, washer and screw, if not the mystery location for the end of a fuel pipe coming off a 3 port gubbins attached to the base next to the fuel tap. We simply left it dangling where it naturally wished to dangle and closed everything up[4].
I marched into Lidl the following day (this Tuesday) and, with a straight face, explained that this one couldn't even be started, and "Do you still have that other genset available for exchange?" to which the answer was no. Thus dismayed, I accepted the refund.
I'll say this for Lidl, I've never had a problem over refunds on DoA kit. However, it doesn't make up for their shit stock control system where half of it must be in mobile storage at any one time, clocking up thousands of UK motorway miles per annum as it trundles endlessly from warehouse to store with the unsold stock (sometimes all of it) going back again before going out on yet another trip the next time they go 'On Special Offer'.
It seems that, unlike in the Aldi setup, the store managers in Lidl have virtually no autonomy, obliged as they are (according to one such manager I spoke to) to 'Follow Orders' which are basically, "Withdraw from Offer" to make room for next week's offers (since the shop itself is its own warehouse space - there's no "back of store storage area" in Lidl stores).
I found all this out when I went back to the new Lidl store to verify with my own eyes that I hadn't been fobbed off simply to avoid a possible third return claim and got this explanation about the way Lidl stock is rotated around the country as an excuse for not being able to dispose of 'faulty stock' when I'd enquired after the Parkside inverter gensets and was immediately shown a pallet with one still stacked there.
Strangely enough, it looked like the second one I'd returned the day before and I said as much which lead to that very illuminating chat, re: the way Lidl manages its stock. When I tried to blagg it back at a slightly reduced price to account for the lack of any warranty protection (I had seen that all important youtube video and the even more illuminating comments by that stage[1]) I was told this wasn't possible due to safety concerns with faulty product.
It was even a "No" to my asking if he could be so good as to check the other two or three local Lidl stores for stock, so I was left bereft of a cheap inverter genset - the only class of genset suitable to back up my UPS protected supply[3]. So I left the store believing that by now, there'd be no chance of my ever finding one in another Lidl store. However, I had the XYL (SWMBI) waiting in the car for me to try a more distant Lidl from which she wanted to buy some uncommonly available items and some odds and sods. I'd only swung by the new store to try my luck with the manager before searching further afield anyway.
The other, more distant store didn't have any gensets in stock either so that seemed to be that. Heading back home, I decided to give our longer established local Lidl a punt, leaving SWMBI sat in the car whilst I nipped inside to confirm the situation. Incredibly, there was a stack of three waiting to be snatched up. I swiftly nipped back out to grab a trolley and, with some restraint, picked *only* two after deciding which of the three to leave behind by the state of its packaging.
After seeing just how expensive even a 900W rated inverter genset was, a mere 198 quid for a pair of 1000/1200W inverter gensets seemed too irresistable to let slip. Besides, I figured I'd save myself at least one return trip by 'bulk buying'. I was expecting problems along the lines of "The Stock Faults" leaving me a choice of which one to swiftly sort out and keep and which to return. I'd have been quite happy to keep both if they were both fully functional with no sign of any issues but, as it happened, there was something to choose despite them both being fully functioning when tested, unlike the first two I'd bought nearly a fortnight earlier.
Once I'd decided which was the 'keeper', it was just a matter of draining the fuel and oil and reboxing the "Return Item" for a refund. Since I'd purchased them on a single debit card transaction, I was half expecting a problem of one sort or another but the refund went so slickly, I forgot to ask for an amended receipt before leaving with my 2nd "REFUND COPY" ticket from Lidl in the past 11 days.
I've made a note of the original purchase details on the back of the ticket just in case I ever have to make a warranty claim or accept a refund on the other genset within the next 12 months since it'll be tied to the original purchase transaction record which, in the event, is all I should need anyway.
[NOTES]
[1] Ah, yes! Silly faults indeed! The fault on the first genset seemed at first to be a fatal failure of the inverter protection in the face of an inductive PF correction circuit I'd made up for the previous 2.8KVA Power Craft unit I'd bought from Aldi some 5 or 6 years ago for an eye watering 180 quid.
I'd simply forgotten to disconnect my homebrewed inductor from the basement lead before plugging it into the Lidl generator. the lagging current, whilst within the amperage rating limit of the old conventional 2.8KVA unit was obviously stressing the output of the smaller Lidl genset since, as soon as I plugged in, the generator started to labour, producing a noticeable amount of vibration before it, presumably 5 seconds later, tripped out to the wattless overload.
A restart after unplugging the PF inductor from the basement end of the emergency power lead seemed to be ok and I had the joy of briefly witnessing a successful transfer back to "Mains Power" by the UPS for several seconds before the overvolt?/overload light lit up causing the UPS to go back to battery power. It may have only run for a matter of seconds but this was only one second shy of running several seconds longer than it ever had with the 2.8KVA genset.
It looked as though I had fatally wounded my brand new generator but, in hindsight, it was most likely just a loose plug/socket connector where the extra vibration of the overload had been the penultimate straw with the brief successful run being the final straw. This was a problem described in the comments by dean handley (9 months ago) to the following youtube video:
<
https://www.youtube.com/watch?v=JTTGvjbY8_s

You can jump to the 6 minute mark for the useful mains waveform reference (which looked even more flat topped than I've experienced with a real 'scope or a CoolEdit Pro recording of the low ac voltage output of a cheap wallwart transformer) and then jump to the 14 minute mark shortly before he manages to start the generator up and skip to the 15 1/2 minute mark for the scope shot where, quite predictably, you get to see a "perfect sinewave" spoilt only by the use of a rather crappy 'oscilloscope'.
For a radio ham, he sure doesn't seem to know very much about electricity. For a kick off, there was no need to connect a 12v car bulb to the transformer secondary. Then there was the lack of understanding over the lower voltage (11.1vac on the generator's 233/234 no load output and 11.4vac when on 240 to 245vac mains). He's obviously never looked at a scope trace of the mains waveform before otherwise he wouldn't have been quite so surprised to see the inverter genset's output being purer than the mains supply.
This is something I've witnessed when testing the SmartUPS2000 with an ancient twin beam valved 'scope as the test load when hooked up to its own 1vac 50Hz calibration source (a 1v winding on its own transformer). It looks like his "Oscilloscope" is of rather questionable quality since it reproduced the waveform clipping as a perfect flat top with none of the slight downward tilt (on the positive peaks - reversed for the negative peaks) which I've observed using both the scope and in a CoolEdit Pro recording of an 8vac wallwart secondary via a resistor attenuation network to reduce the line input to half a volt or so in order to eliminate clipping in the sound adapter's input buffer amp.
Anyway, getting back to the low oil level warning failure with the first replacement genset, this was also a described issue by dean and one that, like the loose connector issue, seems to be related to Lidl's policy of endlessly transporting their stock around the country as things alternate between 'On Offer' and 'Withdrawn' to cater for the lack of "Back of store stock storage" space.
I'm wondering just how hard you have to hit an immovable sharp edged object in order to rupture the fuel tank. If true, that's a surprising and worrying deficiency in a hand portable genset. It might not be true (maybe just an opinion) but I've seen flexible plastic items shatter when bounced off the edge of stonework, notably the plastic bucket that my XYL chucked down the basement stairs for me to catch. It fell short and bounced off a step 2/3rds the way down which knocked a sizeable chunk out, leaving a hole about 70mm in diameter a quarter of the way up the side of the bucket.
I'd expect any domestic appliance with a fuel tank would have to pass a a safety test against rupture from impact before it could be sold in the EC. As for the "fuel leak" from the carburettor’s drain port, I suppose that might be due to inadequate tightening of the drain port screw which possibly explains why they were all so fekin' tight when I tried loosening them off to prove that fuel was actually reaching the carburettor.
There doesn't appear to be a sealing washer involved since the difference between just dribbling and completely shut off is a tiny fraction of a turn where it suddenly hits the limiting closed position. The first time I slackened this screw off, purely out of idle curiosity you understand, I was surprised by a sudden pooling of fuel on the patio table immediately under the genset.
It hadn't occurred to me that the transparent tubing leading through a hole in the base of the genset was to divert the drained fuel away from a hot running engine and potential ignition source. The fire risk in the event of the drain screw working loose when it was running remained but at least it was outside the confines of the generator. In any case, this feature is purely there to allow a full drain down of the carb float chamber at the end of the season prior to being put into storage and the tiny amount of fuel involved (unless you forget to shut off the fuel tap first!) can readily be absorbed with a cloth rag that can then conveniently be used to mop up any oil spillage from off the XYL's precious patio table.
[2] The inverter class of genset is the only type you can guarantee not to overvolt in response to leading current loads such as shunt capacitance loading from filters and weird mains input networks in older (and possibly current) APC SmartUPS and, now being increasingly seen with sub 6 watt LEDs that use a "Wattless Capacitor Dropper" as a ballast for the LED strings. Given enough such LED lighting loads these days, the classic 50Hz alternator gensets running at 1500/3000rpm might overvolt to the lighting load alone, blowing several lamps before the problem "cures itself" by attrition.
[3] That rather glib expression "Noisy", "unstable" "emergency generator" power sources not being of a high enough quality to allow the UPS to revert back to "Mains Power" being supplied by an emergency generator. rather implies a problem due to voltage sags under transient loads (indeed, such implication being reinforced in the reader's mind by the actual phrase "voltage sags under transient loads" being printed in the APC SmartUPS manual (and no doubt repeated by other makes and brands of UPSes).
Not only that but references to harmonic distortion, frequency instability, and voltage transients as show stopping defects of emergency and standby generators are also touted as excuses as to why only the most expensive of 50KVA and above gensets can tolerate having as much as 10% of their rated output going into UPS protected loads (and only whilst there is a 50% or greater loading made up of purely resistive loads such as heater elements and incandescent lighting), totally ignoring the real problem with small cheap generators which is that quite modest amounts of capacitive loading will upset the AVR by over-riding its control of the alternator's output voltage by sending the rotor into saturation totally independently of the magnetisation current being supplied by the AVR circuit to the extent that this can happen even when the AVR stops feeding any current at all into the rotor field winding!
Most UPSes will tolerate pretty well all of the nonsense deficiencies touted against basic petrol/gasoline generators, even slow drifts up and down in frequency within +/-3% which even basic gensets can readily achieve unless badly calibrated to begin with - easily fixed by a simple speed governor adjustment in any case.
Harmonic distortion? Not a problem unless you're generating a damn close approximation to a square wave. Provided the generator is not wildly overvolting, its output can be otherwise extremely dirty and still be utilised by most UPSes as substitute mains power, even if you do have to de-sensitise the UPS to such 'dirtiness'.
Brief dropouts? No problem for an IBM PC or clone: they can typically ride out a half second or more break in supply and you won't be left wondering about 'silent' random data corruption since it will reset in the event of a power outage so brief that it only just exceed the PC's PSU 'hold up time' - if it doesn't reboot, nothing has happened to the internal voltage rails that could have corrupted memory contents and disturbed the operation of the main CPU and all the other micro controller chips used in a desktop PC.
The real issue with cheap alternator gensets is their propensity to excessively over-volt in response to capacitive loads such as PCs and UPSes (and, these days, cheap capacitor ballasted LED lamps). Inductive loads don't upset the AVR feature of conventional alternator gensets although they obviously reduce the power factor which can limit the real power output by causing an over-current trip.
The problem with the 2.8KVA Power Craft generator was that every time the SmartUPS2000 tried to transfer back to "Mains Power" (the generator output) the capacitive loading sent the generator's output voltage north of the 275vac mark which caused the UPS to switch back to battery, disconnecting the capacitors from the generator which then dropped back to its calibrated 230vac level causing the UPS to repeat the cycle until I gave up and transferred it back to the mains supply.
The inverter genset doesn't suffer from capacitive load induced AVR failure, just the standard effect of reactive load currents limiting the maximum power output to less than their VA rating. It's this feature that makes them more versatile than the traditional alternator genset and so useful for powering today's modern electronic kit.
As Chris Howard discovered when making that long winded youtube video, the inverter output produces a purer sine wave than the Public Supply Utility (PSU) just like the synthesised sine wave output of any decent UPSes manufactured over the past quarter of a century, if not longer for the more specialised and expensive UPS kit.
When I was testing the last two generators, I put a cheap ex-Maplin "Energy Monitor" (digital watt meter) in line so I could measure the actual power consumption of my test load (SmartUPS2000 powering my NAS4Free box and its own BackUPS500 UPS along with this Desktop PC and Asus 23 inch 1080p monitor). The first test, with the desktop PC monitor switched off, produced a peak wattage loading of 250W which settled down to just over 200W due to the UPS batteries charging current tapering off after the initial shock of having to provide power to its protected load during the change over from mains to genset power.
Not only was there the loss of power due to the act of physically unplugging the UPS from the mains so as to plug it into the genset socket, there was also the delay involved in the UPS bringing its inverter into phase with the 'mains' so as to minimise current and voltage transients on transferring back to mains power. The time required varies from just a second or so to several seconds, typically 5 to 7 seconds.
All in all, the battery pack which will have had to supply power for around 10 seconds so would be absorbing close to maximum charging rate once the mains supply was restored, swiftly dropping towards zero after some 5 to 10 minutes. ISTR a no load output voltage reading on the energy monitor of 233vac at 50Hz which dropped just one volt on the 250W load (after I'd switched the monitor back on and allowed time for the battery pack charging current to settle close to zero).
The other generator showed readings about a volt higher. I noted the PF figure was 60, presumably a percentage figure which, given all of the capacitive loading of the UPS when in pass through mode, seemed a reasonable figure. Presumably, this figure is likely to improve as more unity PF loading is applied but I haven't had the time or the inclination to do any more exhaustive testing than this since, despite its relative quietness compared to its predecessor, it's still quite a loud noise source for an urban environment (basically, I don't want to presume too much upon my neighbours' largesse in the matter of noise pollution).
I'm considering recycling the bricks in a breakfast bar pillar that'd been removed and laid on its side in two parts by the backdoor some years ago and which now is being used as an elevated support for a planter and some plant pots. The idea being to build a flat roofed "Doghouse" to securely house the generator with enough room to fit sound absorbent material without overheating the generator for want of adequate ventilation. For the moment, that's just an initial thought for a future project that will allow me to run the generator without needlessly disturbing my immediate neighbours.
[4] I did spot where this pipe went to on the two new generators I'd bought on the Wednesday when I removed the inspection/access panel for the carburettor and air filter but I was none the wiser about its function since it disappeared through a hole in the inner casing right next to the carburettor. Since this mystery hose hadn't appeared to have been held onto anything with a hose clip, I was reluctant to pull too hard on it in case it slipped off a pushfit connection nipple somewhere under the engine cowling and out of reach without "Some Disassembly" being required.
--
Johnny B Good

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I do try to be succinct...

--
Tim Lamb

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snip lampoon
I must say that as a prospective buyer of one of the Lidl generators I thought almost every word was actually useful.
--

Roger Hayter

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On Sun, 22 Apr 2018 12:36:30 +0100, Roger Hayter wrote:

You know what, that saga was so long, I'm not entirely sure what the lesson(s) was/were and whether they would be as useful as I thought. Thank you for that unexpectedly positive comment. I do realise the risk of the converse of the saying "Less is more." when making such long and detailed posts like this. I think I need to improve my "Risk Assessment" skills. :-(
As I said in my follow up to Bill's hilarious lampoon, I'm going to restrict any more such lengthy posts to a mere two pages worth at most should I ever be tempted to write yet another 'Saga' (at least that's my intent).
The only (lame) excuse I can offer is sleep deprivation; I didn't finish that post until just before 7:30am having started it sometime in the wee small hours around two in the morning. I'm a night owl but that was more of a 'late night' than usual even by my normal standard. :-(
--
Johnny B Good

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On Sun, 22 Apr 2018 12:36:30 +0100, Roger Hayter wrote:

Well, Roger, here's some more thoughts on that Parkside inverter genset that I've since had in the past fortnight or so. Not quite a Saga this time! :-)
I've been googling for ways to reduce the noise pollution that this rather neat Honda EU1000i 'knock off' generates. Inevitably when you land up doing your research on youtube, you get to see an awful lot of 'generator videos' demonstrating various means of reducing noise pollution with various models of generator (and in all bar one case, rather indifferent results for the expenditure involved).
What struck me was the startling resemblance of the Honda eu1000i and its bigger brother, the eu2000i models, to the Parkside inverter genset, in particular the carburettor/air filter components as well as the oil fill/check/drain hole and its location along with the pull cord and exhaust pipe and air cooling vent locations.
In effect, that Parkside generator would seem to be a slightly more powerful version of the Honda eu1000i wrapped in a differently styled carapace. The Honda uses a 49.5cc engine and is rated for 900/1000 watts whilst the Parkside uses a 53.5cc engine and is rated for 1000/1200 watts.
What's missing from the Parkside is a 12v battery charging port and a synchronisation link interface to combine the outputs of a pair. What's missing from the Honda, otoh, is some 10dB or more of noise pollution. There don't seem to be any obvious signs of sound damping in the Honda case mouldings so, presumably, the Honda engine would seem to be of a more rigid construction designed to reduce noise pollution, possibly aided by a better exhaust muffler[1].
There are far more youtube videos about eu2000i generators than there are about its smaller sibling, the eu1000i but I did manage to track a video of one being disassembled here:
<
https://www.youtube.com/watch?v=uuwvlJonnH4

(only 360p quality I'm afraid) which might offer a clue to the reduced noise pollution. The engine fan ducting cowl looked to be either a die cast part or, more likely, a pressing made from heavy gauge aluminium sheet which may be providing improved shielding of the mechanically generated engine noises.
I suspect the carburettor assemblies at least, all originate from the same suppliers used by Honda (or at least patterns of the Honda spec parts). Owners of these neat little, if not quite so quiet, Parkside inverter gensets, might find servicing info for the Honda eu1000i (and very likely the eu2000i) very useful to servicing and troubleshooting the PGI 1200 B2, including the dual/triple fuel adapter kits available for the small Honda inverter gensets (Propane/Natural gas).
[1] I saw a couple of videos where various silencer upgrades had resulted in only a couple of dB of noise reduction, often compromising the engine performance.
The most impressive results came from simple sound deflectors, in one case a matter of 10dB being achieved just by laying sheets of plywood/ plasterboard round all four sides, resting at an angle of 45 degrees against the top of an open frame generator, leaving large gaps to allow the generator to breathe and stay cool.
This was quite obviously, as the youtuber explained, down to the effect of reflecting the noise emissions into the grassy soil he'd parked the generator on. Whilst I was impressed, I wasn't too surprised and it's given me an idea or two for my own setup. :-)
--
Johnny B Good

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On 03/05/2018 05:26, Johnny B Good wrote:

Almost certainly not. Having worked in a Chinese products importing roll for 25 years and visited many Chinese factories I can assure you they are extremely good at copying. Their copies vary enormously in quality despite looking exactly the same externally.
Mike
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On Thu, 03 May 2018 08:25:11 +0100, Muddymike wrote:

Thanks, Mike.
It's no wonder I had such suspicions! Mind you, I did qualify them by the "Pattern Parts" reference. :-)
Well, copies or not, it does look like some of the dual/triple fuel conversion kits made for a Honda eu1000i (possibly including the eu2000i) will likely suit the PGI 1200 B2 (possibly even the PGI 1200 A1) gensets.
And, in lieu of an actual service manual, the Honda service manuals, if downloadable, or at least a youtube strip down video, would provide very useful guides to anyone contemplating repair of their Parkside knock offs.
Mind you, since there are so many other makes of similar inverter gensets around, which as far as I could tell, also seem to use virtually identical components, Honda manuals won't be 'The only game in town' as inspirational guides to repairing that Parkside genset (also suggesting that paying 3 or 4 times as much for these alternatives won't necessarily get you a better genset).
With regard to the idea of using sound deflectors to mitigate the nuisance noise levels imposed on your neighbours, it strikes me that there are two ways to deflect the noise. The first one already mentioned of deflecting the noise downward into grassy soil is fine when you've got a suitable patch of garden to stand it on but, when it needs to be parked on hard standing, it seems a better setup of the panels might be to lean them outwards so as to deflect the noise upwards and away from the horizon. Either way should achieve the desired effect.
The other option of running the generator inside a soundproof box brings a whole new set of problems such as providing the necessary ventilation, usually using a large fan or two to provide forced ventilation. Not only does the power consumption of a large fan reduce the net power available, the ventilation provision (fans and associated vents) often severely compromises the soundproofing benefit of the enclosure which ideally should be fabricated from brick or concrete panels with sound absorbers installed within (but not applied as panels completely covering the walls to act as counterproductive thermal insulation).
I saw a lot of such ill conceived attempts at enclosing generators in such housings, intended to trap the noise emissions, on youtube and the use of lightweight materials was the predominant error in their design. There's a lot to be said for the KISS approach to this problem (aka, intelligent use of sound deflector panels). In short, all these youtube videos of "Generator dog houses" were, in essence, best regarded as "How Not To" videos for all the help they were. :-(
--
Johnny B Good

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On Thursday, 3 May 2018 18:07:49 UTC+1, Johnny B Good wrote:

The principle is known & simple enough. Provide a sepentine path for the sound, ie at inlet & outlet. I would have though the exhaust would be capable of driving ventilation.
NT
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On Thu, 03 May 2018 11:18:01 -0700, tabbypurr wrote:

I'm rather surprised that the youtubers hadn't at least done some homework on the basic principles of noise suppression before spending on their ill fated follies (noise suppressionwise - the other aspects of protecting them from the elements and possible theft wasn't so much in question).
Not so much serpentine as a zig-zag on the intake side to reflect the sound back into the main chamber for multiple 'visits' to the sound absorbent blocks or curtains within.
As you say, the exhaust *is* put to good use to accelerate the slower moving engine cooling air that is exhausted in a vent that surrounds the exhaust outlet (as per the Honda and the Parkside gensets) using the same principle as the one used by turbofan jet engines on commercial airliners to improve thrust efficiency. In this case, the slightly warmed engine cooling exhaust is also put to use in cooling the exhaust muffler box, allowing the use of such snug fitting plastic housings in this 'suitcase' class of generator.
With that in mind, I think I'd design my brick "Doghouse" not only to have ample room within for sound absorbers (curtains or blocks) but also to allow for generator size upgrading.
Rather than have a relatively small exhaust aperture in a 'back wall' (just bigger than the rear exhaust vent of the genset), I'd extend the back out for another meter or two and then mount a sonically transparent tube just a little larger in diameter than the rear vent of the machine, around which I'd fill the gap with suitable sound absorbing fibre, terminating the end of the tube to the end of the doghouse extension with a rigid panel.
Leaving the inner side of this packing held in place with an acoustically transparent panel would contribute to the sound absorbing materials used within (possibly to the extent that it could even suffice all on its own).
I think I spotted a reference to the engine rev range between eco idle and maximum load somewhere on the 'net', possibly relating to the earlier PGI 1200 A1 model (it isn't mentioned in the specification section of the printed user guide), where ISTR figures of 3900 and 4300 rpm which struck me as a rather conservative ratio between eco idling revs and flat out. I think the figures for the Honda eu1000i were 3000 and 4300 rpm respectively, still a conservative ratio imo.
The reason I'm interested in engine rev figures is that it decides the lowest fundamental frequency of engine noise (65Hz and 50Hz respectively for the Parkside and Honda gensets) and half those frequencies in the case of single cylinder 4 stroke engine exhaust sound pressure waves[1].
To be fair, the higher the rpms, the higher the frequency, which eases the problem of absorbing the sound energy at these shorter wavelengths. Also, of course, the lower torque demand means lower mean cylinder pressures making for a quieter exhaust note at partial load. Still, since we ideally need a quarter wave resonant structure within which to place sound absorbent material for maximum effect, it's a vital consideration when it comes to sizing our rigid enclosure.
A quarter wavelength in air at 20 deg C for 65Hz works out to 1.32m (at 0 deg C it's 1.27m - the speed of sound in air goes up with temperature). However, a quarter wavelength sound absorbing resonant cavity needs to be within a room with a dimension of at least half a wavelength in order to function properly. If we're going to size up a rigid enclosure to act as a resonant absorber it needs to have a dimension of a minimum of half a wavelength for any sound absorbers to work effectively.
In this case, that works out to 2.64m or 104 inches (nearly nine feet! 8' 8"). I think, if I was going to embark on a brick 'doghouse' for an emergency genset, I'd go for a 4 1/2 by 4 1/2 by 9 foot tunnel split by an acoustically transparent panel with an exhaust vent sized hole linking to an acoustically transparent tube of the same cross-sectional area leading out to a back wall vent with acoustic absorbent material filling the surrounding space in the exhaust half of my 'doghouse'.
The front door would be a reasonably substantial panel sealed against the front with rubber gasketting suitably vented with zig-zagged trunking into the interior space designed to reflect any noise back towards the exhaust end of the enclosure where they'd be dissipated into the exhaust vent sound absorbing lining.
Even with zig-zagged trunking, the necessary vents will compromise the noise containment performance to some extent but there are limits as to how long a 'serpentine' path you can use before the issue of restricted air flow starts to rear its ugly head. In any case, there's little point in making the front door noise leakage any more than 2 or 3dB quieter than the exhaust vent leakage.
As to whether I embark on such a major DIY project (and Gawd knows, I could do with the exercise!) is another thing altogether. I might be more inclined if I had more than a vague notion that my plan was theoretically sound (forgive the pun). It looks like a little more research is needed before I embark on what could turn out to be an unwanted folly.
[1] The pulses of exhaust gas going into the muffler from the exhaust port approximate to half cycles of twice that frequency so although the fundamental is half that of the vibration frequency due to the engine revs, a significant portion of the exhaust energy is carried in the 2nd harmonic which the muffler attenuates whilst magnifying the fundamental which probably explains the barely perceptible improvements made by replacing a generator's weedy muffler with that from a motorcar designed for a four, or more, cylinder car engine where the 'tuning' factor is less critical than for a single or twin cylinder 4 stroke engine.
--
Johnny B Good

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Quite. Only need to look at modern 'Lucas' products like replacement distributors. Look much the same until you open them up. But then they are cheap, and you generally get what you pay for.
--
*When a clock is hungry it goes back four seconds*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 04/05/2018 11:01, Dave Plowman (News) wrote:

Unfortunately many poor quality Chinese copies are being sold at near genuine item prices, particularly by online sellers. I'm fed up with trying to buy decent quality by paying a higher price only to receive crap!
My sales team use a particular style of swivelling iPad cases. They last about a year before the corners break from the case. I spotted a more expensive different make that offered the same features so ordered one. I received a far inferior product despite paying a higher price!
It went back.
Mike
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The aforementioned Lucas copies tend to be cheaper than having an original overhauled properly - hence selling well. But there are lots and lots of complaints about them. Failing totally, or not working perfectly. Making me wonder who buys them and are happy with the purchase.
--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Garage down the road from here has a skip full of duff Chinese copy parts so they tell me!...
--
Tony Sayer


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This is was what happens when you move people into a newly constructed building to start getting money back so fast the the mains haven’t been connected, the people whose money you have taken and others object to the racket and you get someone “intelligent” to box the generator in.
http://www.bbc.co.uk/news/uk-england-hampshire-37478840
GH
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