Installing a generator

[Dave Liquorice]

The timescale for risk and duration I'd not take 10 years, 5 is better IMHO. Particulary if there are any new developments in the area, industrial or residential.

Depends very much on the freezer. Our energy class A would struggle to keep stuff frozen that long. ISTR that 12hrs is a safer assumption. Household insurance normally covers the value of freezer contents, but be aware of weasle words...

But are rather smelly and don't produce much light unless you have the pressure variety which need tending (pumping up regulary) and can be tricky to light (meths for preheating etc...). Camping gas lanterns produce lots of really good light like a pressure paraffin lamp but are less smelly, easier to light (some have built in piezo igniters) and don't need tending.

Yep, being able to have a hot drink or even basic hot food will make life a lot more comfortable.

[meow2222]

yes, but...

1. old TVs with unregulated power rails (early 80s and before very roughly) are vulnerable to voltage swings, and using them on a gen is a bit of a gamble.
2. A surge protector is wise when using electronics on a portable gen, as load dump produces inductive surges, and electronic kit can really object.

I don't think I've ever seen a TV that even approaches 900w continuous, so I'd be very surprised if that were a problem. Re start current, CRT sets do run a gulp of current thru the degauss coils for a second or so, but even if beyond the gen's rating it would be very unlikely to stall it that quickly. So there shouldnt be a problem there either.

portable gens are usually run IT, with no earth. An earth rod would improve safety, but is not a requirement.

NT

[Steve Firth]

Impossible to achieve with a small cheap generator. However those that work via and alternator/inverter with electronic control of voltage and frequency provide stable operation under a wide range of loads.

[Andy Wade]

This is acceptable only where the genny is used to used to run a single load on a temporary basis. For anything else, proper earthing is necessary.

For a permanent standby installation you need to earth one side of the generator's output to define neutral point and create a TN-S system.

See

a previous post of mine on the subject, including a wiring diagram.

You are also supposed to consult your supplier and/or the local DNO if you intend to install standby generation. They like to approve the connection arrangements and aren't at all keen on people back-feeding the mains.

[Appin]

The message from [e-mail] (Steve Firth) contains these words:

I believe Honda have some which work that way.

I wonder how reliable the inverter electrronics are in the long term?

[Piers Finlayson]

I'm not convinced about this. I was reading about this very subject last night in The Electrician's Guide to the 16th Ed, and it states:

"Where generators are intended to operate in parallel with the mains supply, the Supply Company must be consulted ..."

Earlier it clearly distinguished between b) using a genny as a backup in case of failure of the supply c) for use in parallel with the supply.

In additon, the 17th Ed regs note that the electricity distributor must be informed about generators intended to provide a parallel supply, but make no mention of this being a requirement for standby supplies.

[Andy Wade]

[Supplier/DNO liaison]

Whereas the actual 16th ed. says "Requirements of the electricity supplier shall be ascertained before a generating set is installed in an installation which is connected to the public supply." [Reg. 551-01-01, final para]

I read that as applying to both the parallel embedded and switched standby cases. I suppose though that ascertaining the requirements can be done by reading published information (if any), so doesn't necessarily involve any liaison.

Yes, that does appear to be the case. However take note of Regulati "21. Where a person operates a source of energy as a switched alternative to a distributor's network, he shall ensure that that source of energy cannot operate in parallel with that network and where the source of energy is part of a low voltage consumer's installation, that installation shall comply with British Standard Requirements."

and "British standard requirements" is defined as being the 16th ed., so that still holds sway legally until they get round to amending it again.

[Steve Firth]

More reliable than the engine.

[Appin]

The message from [e-mail] (Steve Firth) contains these words:

Well, there are Hondas and Hondas. It is generally reported that the Honda lawnmower engines generally sold in the UK are not up to the quality of the Japanese-made engines, but whether that's a correct asessment or not I simply don't know. Whilst I can see the point of making energency use of a generator which is in regular use for other purposes, I'm not convinced that it's a very wise basket into which to put all one's provision for the emergency of a power outage which is going to occcur, in all probability, once or twice in a decade.

To me, emergency equipment which is not in regular and frequent use should be of a low-tech, simple and inherently reliable nature, easy to deploy rapidly with minimal fuss.

[Piers Finlayson]

Interesting. Thanks for this. I don't have the actual 16th Ed (as you might have gathered).

I would agree that, if it doesn't specify, it applies to both parallel and standby. However, I take this this as "consulting" the supplier rather than asking them "to approve". I guess their requirements may be to approve the connection arrangements!

[tony sayer]

In article , Roger Mills scribeth thus

I bet its cleaner than most mains supplies, which rarely look like sine waves anymore;!...

[Steve Firth]

Power cuts in rural areas happen more frequently than that.

Why you should think that an alternator/inverter should make a generator less reliable is something that I do not understand. And anyone buying a generator for standby use should run it from time to time.

[The Wanderer]

Yes.

It is, or was, a condition of giving a mains supply of electricity, that any connection of a generator *had* to be notified to the local distribution company. That many people have never actually signed a supply agreement, let alone read the small print on the back, is another matter. There again, there are a great many standby generators that have been bought and used that have never been notified to the local distribution company.

Not unless it's generation that is intended to run in parallel with the distribution network.

Their *requirements* about standby generators are ensuring that if the generator is to be used on an installation connected to the supplier's distribution network there is no possibility of the generator back-feeding into said distribution network, and that the earthing arrangements for the generator meet, or perhaps more importantly, don't compromise, PME approval where appropriate.

It's *your responsibility as the designer of the installation to comply with those requirements, same as you are supposed to comply with the requirements of BS 7671.

Having said that, they may also place restrictions on the actual occasions of use of the generator, such as during periods of non-availabilty of mains supply, and for short periods (say 2 hours per calendar month) for testing purposes.

[Appin]

The message from [e-mail] (Steve Firth) contains these words:

I live in a VERY rural area. At one point the power supply was so erratic that the Electricity Supply Company fitted a POD on our premises to telephone them automatically to report interruptions. I think the record was 65 breaks in supply -- most of them very short-term -- in the course of a year. However -- and this is a very big "however" the problems were down to

1. 50-year old medium voltage cables on the overhead line -- insulation perished away to nothing
2. Iffy insulators
3. aged and erratic auto-reclose breakers

The line was overhauled and critical portions subject to bird strikes were rewired with insulated overhead wire. All insulators were inspected and all iffy breakers replaced. Hard standings were installed in two locations for big mobile generators which could supply up to 500 homes and agreement was reached that in the event of any outage lasting more than twelve hours such a generator would be brought in.

Since that time there have been no major outages lasting for many hours.

I do know something about the sorts of situation which CAN arise -- have a look at the current situation elsewhere --

?sid=103613&sc=98> > To me, emergency equipment which is not in regular and frequent use

Should, yes. But in how many instances will that actually happen in the real world? A generator in regular use for other purposes is an excellent idea as a backup. A "dedicated" one with old fuel in the tank, water and/or sludge in the fuel lines, gunge in the carb if it's a petrol model and damp electronics isn't my idea of a great backup provision.

[Roger Mills]

Indeed!

[Roger Mills]

As a bit of an aside, I believe there are some systems - using wind and/or solar power etc. - where you can feed surplus power into the grid and 'sell' it back to your electricity company. What happens in the event of a power cut - does there have to be some mechanisn to prevent back-feeding under such circumstances?

[The Wanderer]

'Fraid I don't know the answer to that one, but I would imagine so. Been out of the industry for some years now. Most of the 'export back to the supplier' schemes have come about in recent years.

[tony sayer]

[Piers Finlayson]

Was wondering this myself. The guide to the 16th ed regs say that you need to have an isolation switch for a parallel supply which is accessible to the supply company at all times. Perhaps they have a record of people which such systems and go round and turn them off manually - but seems like a lot of effort!

[Roger Mills]

I'm not sure whether you could do it with some sort of contactor, which automatically dropped out if the mains failed. It would have to be able to tell the difference between the real mains and your locally generated 'mains' - and I don't know whether it could.