I have moved to an old 5 bedroom house that I plan to renovate, including a complete rewire.
This is also an opportunity to change the domestic supply from 100A single phase to three phase, if I wish.
I am trying to find a website that has a list of typical currents drawn by, or VA rating (not Watts - I don't know the appliance power factors) of, different domestic appliances so that I can calculate if I would exceed the 100A limit of a single phase supply. Anyone know of such a website?
Aside from the danger of 415V in the house, would anyone care to comment on the risk/reward of a domestic three phase supply? (E.g. higher standing charge?). I do not intend to use any three phase equipment in the house.
Are you having all electric space and water heating and cooking ? You might then exceed the 24kW that the supply will feed you. Otherwise I doubt you can come close to needing it. Many UK supplies are limited at
Are you intending to build a workshop with heavy machinery ? Are you going for a fully electric heating, cooking, automation systems etc. etc. ?
If you come close to needing a three phase supply for an ordinary 5 bedroom house without any specific installations that would use it, then you'll also be coming close to bankruptcy with bills you'll receive on using that amount of power.
Using triple phase and neutral supplies is typically used for industrial or excessively heavy domestic installation, i.e. letting out separate apartments, heavy workshop machinery attached to the house etc. etc. So anyone using such a supply is normally making money out of it to justify the need.
A simple test to carry out, is to wonder around the house and total up the load of all the electrical equipment you have plugged in to the mains supply. i.e. heating, lighting, cooking, laundry, food storage etc. etc. and see how much power it would use if it was all running at the same time, even all the little clock radios and things, and I think you'll be amazed at how little it really does draw compared to the supply's capability.
I vaguely remember the woodyard I worked at having to pay three figure numbers for the upgrade. Up to then he was running everything on a diesel genny.
The genny would be viable if you had a means of abstracting the heat. (Think how much oil a CH boiler uses to no other effect but heating, while a generator not only burns the same fuel but supplies the lecky too, also, as well.)
A good ex-military genny would be cheaper than a tranformer on a stick in your garden. And you could use it to annoy the neighbours if they upset you -or even if they haven't (yet.)
OT:
How much oil does a central heater use? And what generators have a comparable fuel consumption? And how much would heat exchangers for the cooling and exhaust cost?
Got a link to that in the Corris site anyone?
Anyone know if you can use old lubricating oil in a diesel? I know that you can use it to spray a jet from an oil-pump onto a firebrick alongside a fan that would work as a blowlamp for melting aluminium scrap etc.
(Yes I know this is getting silly but I didn't start the thread.)
The internal combusition engine's biggest product is heat. Far more heat than power is produced. Extracting "all" the heat, and it produces a hell of a lot, and power (electiucty) it is very efficient. But most people would not use all the heat and power available, so they are very inefficient.
Heat exchangers are not cheap. Many people make their own. It is using all the heat available. Having a small LPG genny, about 1.5 kW/hr, and extracting all the heat is feabile. But you have to extract all of its heat and store it in a large thermal store. Then your house has to be run mainly on LV lights, run from batteries overnight with the genny off, and all appliances run on gas (gas fridges are available). Washing machines, etc, have to be super energy efficient and hot and cold fill, with the hot water comming from the stored water. No appliance should draw more than 1.5 kW.
Now there are Combined Heat and Power Stirling units available.
It's Sunday evening. Mum's doing the washing/drying/ironing, Dad's cooking lunch and four teenage children are showering/doing homework/watching TV. (Putting aside the debate about stereotypical representations) I think that this family could draw the following loads simultaneously:
That's a total 124.5 amps. OK, we can argue that their approach to energy efficiency could be improved. In terms of rating a supply, however, a single phase 100A supply seems inadequate.
High ;-) All the "small" things like fridges, freezers, ch pumps, fans, don't draw anything like the current you suggest, for a start. And 2300W of lighting ?
Only for the small proportion of time it's heating water; "modern" machines use little water compared to older ones. And few have elements above 2kW. So a better figure for the peak draw would be 9A; and with some 15% of the time spent heating, rather than spinning, tumbling, etc., the average figure will be more like 3A.
Not as high as that, but could be 12A, and unlike the washing machine will be sustained for a longer time - 60-90 minutes.
Yes, but again there's a thermostat. If Mum's ironing her linen tablecloth with the steam going full on, you might see an 80% duty cycle; if she's just passing it over her Janet Regier with the iron set a bit under the one-dot position, it'll be a 5-10% duty cycle...
Unlikely to be that high for either, and again will be smoothed by thermostat action.
Same comment as washing machine: heating and drying account for say 50% of the duty cycle, the rest is spent spraying the already-hot water round the washdosh and rinsing its contents with cold water; so average down to 5-6A.
Yes, maybe that high if we've got all 4 plates on the go and something in the oven (each plate 2kW and maybe 1kW oven, but thermostats clicking in and about bring the average down near the figure you suggest).
Ooh, that's a big one, as the bishop said to... but seriously, most MWs are in the 600W-800W range, so 3A rather than the 1.5kW which 6A would mean. And is Dad cooking for real (on the cooker), or just heating something up (microwave)? Shirley he's not using both?
Yes, while it's on; but not for more than 4-5 minutes in an hour.
Hang on. If Dad's cooking, Mum's ironing, and the kids are doing homework on the three computers you've enumerated *and* watching teli *and* got the Hi-Fi on the go, who's left to wash the hair?
Hmm, it's the cat in the shower?
What, immersion *and* CH on the go at once? And there's a 'stat on the immersion; and that's a monster CH pump - steady-run current will be well under 1A.
Possible but profligate!
They're notably pessimistic; but they do show why (a) new builds usually have a 100A mainfuse these days, rather than the 60A which used to be standard; (b) illustrate why the main incomer is a cartridge fuse rather than an MCB (well, there's cost reasons too, and the vulnerability of an MCB to kids turning them off if they're in an outdoor-accessible meter cupboard). (The wired fuse allows getting on for twice the nominal rating to be drawn for a good few minutes before it blows, though it'll rupture within milliseconds with a serious short circuit.) In particular, lots of the loads you mention are thermostatically controlled, and you list the peak rather than the average. The heating effects in the circuit cables (from meter tails down to final circuits) take a while to kick in, so in practice we don't see houses either blowing their main fuses or melting/drooping PVC cables all over the place.
There's also a difference between a single-family house - the case you've suggested here - and "houses in multiple occupation", i.e. converted into flats/bedsits. For a bedsit conversion, it's more likely that there'll be multipe fanheaters/hairdryers/kettles and all sorts going on at once
- in the evening as the occupants come home, say - and Good Practice says you apply lower "diversity" factors (that's RegSpeak for "not all the possible loads will be on at once") in such a case, or in a school domestic science "lab" where all cookers/oven/baby-Bellings *will* be on at once, than for a domestic installation.
uWaves have RF outputs in the 600 to 800W range but aren't that effcient at converting electrickery into RF. 1.5kW for an "800W" uWave isn't too far from the mark.
You mention the regs and diversity, calculating that correctly is what is important rather than simply adding up all the possible loads. TBH you can probably ignore most things that are not "heaters" as they won't take that much power, allow a few kW for them. It's the biggies like water heaters (from washing machines, through kettles and immersions to showers) and space heating that really determine the maximum load.
Well high. You make no allowance for diversity. Many of the ratings quoted are well above the currents actually likely to be drawn. Also, they are peak currents. Most will only draw these for short periods, which are unlikely to be exactly coincident in time. Also, short transient currents above the rating are permitted. It is only if the current remains over the rated current for a long time (i.e. minutes) will it matter.
Only whilst heating water, which might be for ten minutes at a time. Average current much lower.
Again, average current is lower. The rating you give is actually above the
13A fuse, so is too high.
Low duty cycle. Mine only comes on for a few seconds before cutting out for a minute. Average current much lower.
Again, low duty cycle. The compressor only comes on occasionally.
I don't believe a freezer would draw 3A on average.
Only whilst heating, which isn't very much.
If cooking a complex dinner, the average might exceed this.
Only for a couple of minutes.
Only for a couple of minutes.
Hope you don't have neighbours. That would produce about 125W rms per channel on a 50% efficient amplifier, which would blow your ears off, unless you wear baseball caps backwards.
Well over. The power supply is its maximum rating. It will only draw a fraction.
Probably about right.
Only used for a couple of minutes at a time.
Only used for a couple of minutes at a time.
Only used for a couple of minutes at a time. This rating will produce a hurricane.
Should only be used for backup. You do have central heating that heats the water? It is also thermostatically controlled, so isn't a constant load.
This is totally way over the top. Normally, the entire central heating system is fused at 3A.
That's a very little heater. However, it could be a reasonable average in a centrally heated home with thermostatic control.
Does this include floodlighting the football pitch? I have about 10 bulbs, with an average wattage of around 15W, giving 150W ~= 0.6A. Even if you have tonnes of halogen lighting, I'd be surprised to see a figure this high. This is 2.4kW of bulbs, or 24 100W bulbs, all on simultaneously.
This would absolutely covered by diversity calculations. You could probably squeeze it into a 60A supply. Remember, it doesn't matter if the instantaneous current exceeds 100A for a short period. It is the average current drawn over a period of minutes that counts. I doubt that these loads in actual use (rather than pathological timing) would actually exceed 60A).
Would seem like overkill? If not electric heating would not 230 volt 100 amps be OK; unless it's a boarding house with people living, cooking/eating etc. in individual rooms? Reminds one of the old 'shilling in the slot meter' old old digs! Our four bedroom insulated wood frame 1530 sq. ft (main floor) plus full basement has the here standard 200 amp 115/230 volt supply. Wired over head from a pole mounted distribution transformer about 120 metres away. In this somewhat colder and longer heating season than the UK; we have electric baseboard heating with individual thermostats for each room/area. Thirty five gallon hot water heating tank, clothes dryer, dish washer, radios, TV, computers etc. Several other (about five IIRC) typical homes are supplied from the same distribution transformer. No voltage problems. Lights and wall plugs are 115 volt, 'heavy' items, viz. cooking stove (oven +4 hobs), water heater, electric heating is 230 volt. Basement workshop is mixture of 115, and 230 volt for occasional heater and bench saw. On a 24 hour average, cos never is everything 'ON' at once, the consumption is around 4-5 kilowatts per hour, often less. At a maximum, even if one comes home turns up the heat and put clothes on to wash, maybe boils the kettle for a few minutes etc. etc. I doubt if it ever goes up to the 'rated' maximum which in our case is 200 amps X 230 volts = 46,000 watts or 46 kilowatts! Suggestion.
"Pandora" wrote | I have moved to an old 5 bedroom house that I plan to renovate, | including a complete rewire. | This is also an opportunity to change the domestic supply from 100A | single phase to three phase, if I wish. | Aside from the danger of 415V in the house, would anyone care to | comment on the risk/reward of a domestic three phase supply? (E.g. | higher standing charge?). I do not intend to use any three phase | equipment in the house.
About the only requirement for 3 phase (as others have subsequently illustrated with their demand calculations) in a single family household is if there is a high storage space heating and storage hot water load, as all these would come on simulataneously during the off-peak time and there is no diversity applicable.
In a house which is subdivided into bedsits etc, or used as B&B with lots of electric instantaneous showers, or if you run a pottery kiln etc, then things are different.
About the only reason to install a 3-phase supply in a largeish domestic house is if there were going to be 3 or more instant electric showers in use simultaneously.
I looked at doing this but one of the things the supplier insists on is that all phases have the same loading. To do this meant spliting the phases around the house which i thought was too dangerous so ended up with a uprated supply 100amp i think , this was the largest they do at the base price any larger and it was a special job = expensive. Rob
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