Had power cut at shower time this morning. So ... What power backup would be suitable to keep a combi boiler working for water (not central heating and the pump) when there is a power failure ? I guess just powering the control logic a gas modulating values etc. Would a car battery and inverter be enough for an hour or so ? Simon.
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And the circulating pump, which is probably the biggest drain on the system. Probably, though you could get away with a UPS - they're much cheaper these days and it'd have all the bits in to do the "pick up and run" thing.
Much more than that. I've got an invertor and car battery as backup for my fairly old boiler and that runs for at least 10 hours. I'd say the major consumer of power would be the CH pump. Without that the power consumption should only be a few watts - greater when valves etc operate.
You need to look at the type of inverter/UPS though - some have very poor output waveforms that may not work well into a significantly inductive load like the pump.
For very small generators, I've had good results with soundproofing enclosures.
Take 8 paving slabs. One on the ground. Two at either end, slanting, with a small (~5mm) gap between them. The other two form a box. You end up with two interlocking slanted \_\ shapes, on the base plate. Add several 12V/240V fans to suck air in one hole. Mortar it all up, and put cling film over the top, place the last slab on, on some silicon sealant.
Most combis use the pump to circulate water round the (diverted) primary circuit so as to feed the plate heat exchanger. So the power use running HW is going to be much the same as for CH.
Yup. If you use a UPS there is less chance of having difficulty with flame sensing since you will still have a normal ground reference for the boiler. A line interactive one with true sinusoidal output is probably a good idea for inductive loads like the pump and keeping the electronics happy.
Note that you aren't actually allowed to assume that the supplier's ground connection is still working during a power cut, when generating your own electricity.
Yes this is very true... especially if you are on PME. You should still have some earth reference from you main bonding however in most places unless completely piped in plastic.
If power outages are rare then don't bother, as a kettle on the gas hob will be enough for a quick shave and wash and rub down. If rural and outages are common then you need to look at the problem deeper, like having a small backup genny. A separate CU with essential supplies, fridge, light, TV, CH, could be fed from the genny (could be a wheeled portable unit hung on the wall). A two way manual throw-over switch would switch from the mains supply to the genny supply, so no complications, as mains and genny supply never come into contact. A back up genny is around £100-200. The whole thing can be around £300, so no major discomforts. Also you can use the portable genny for other things.
Combis with integral unvented cylinders will store the hot water.
300 quid to do a major alteration to the house wiring system and buy a reasonable generator for standby use? I'm sure Mr Liquorice will be along shortly with a comment. Which if he wasn't a gentleman would start with s**te...
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