Feasibility of Battery Backup/Generator for Boiler/CH/Hot Water etc

Arfa__

Not wanting to get too much into the politics of the media (hopefully just) doom-mongering about possible electric blackouts etc, it got me thinking about the feasibility and costs of running the gas boiler off a battery back, UPS or a small petrol generator. Might also be useful if we have a power cut, as I'm in Scotland and only last year did whole areas not far from me lose electricity for several days.

When growing up, my parent's house just had a solid fuel Rayburn for heating & water. When we had power cuts, my Dad would simply plug the water pump into a little petrol generator. Got us through very well. Obviously, the electrical side there was quite simple and straightforward to switch over. I have a Gas boiler that feeds hot water to a hot water tank and into the CH. It's controlled via a remote control Hive system. 

So, what would be needed to run the electrical side of a typical gas combi boiler, the control stuff and water pumps?

How feasible is it to set this up so one could switch that to a backup electric supply if needed? Even if shortcutting some of it and just relying on manual on/off control.

What would be the best route? Batteries, UPS, generator?

Thoughts, ideas, estimates on costs?

Bendy_House

What's UPS?

Anyhoo, in theory this is perfectly feasible. The good news about boilers, pumps, programmers, 'stats, etc, is that they are ALL powered from a SINGLE source, which is usually protected by a 3A fuse, so not a big power user. 

That's HOW it should be wired up - ONE single switch cuts the power to everything CH. Have a look near your boiler, and ID the isolator switch. I think that would be the best place to add the alternative supply, so you don't go anywhere near your CU, for example. 

Some 'isolators' are actually as 'crude' as a plug in a socket, so that would make things REALLY easy - just unplug from the socket, and plug it in to your new source!

A few provisos: I'm assuming leccy power cuts have no effect on gas supplies, smart meters, etc. Pretty sure they don't, but just in case I've missed something. Also, modern boilers have pretty complex electronics inside them, so the chosen power supply should be very stable and free from nasties like spikes and stuff.

So, best source of power? No idea, but I'd have thought that a battery with a 240V inverter would be smooth and stable? How long will it last? No idea either, but assume the CH system will consume, say, around 1A max, and then only for short intervals - when powering valves and stuff. Just 'running', I'd have thought comfortably under one amp; pump, gas valve, that's about it.

So, a quick and safe way to REMOVE the CH's supply FULLY from the domestic supply, and on to the new source. A double-pole, 2-way switch should do this.

Oh, I have absolutely no idea of possible complications around earthing!

knightstyle

Ok I think you should look at a simple UPS for the boiler, pump and maybe a light or two.  The type and cost will depend on how long do you want backup power for?
Simple UPS with a small battery will last for about 15 mins and cost around £300 these are designed for electronic items which may suffer sudden power loss but will work for what you want.
However if you want a system that will last for hours/days then you need a generator, cheap ones will cost about the same but this will not be a UPS which is designed to come on without a break in the supply.
Another possibility is having an electric car with a 230v outlet, look up V2L.

grumbler

knightstyle said:

Simple UPS with a small battery will last for about 15 mins and cost around £300

I am no expert and had only a brief look.

E.g. this one - about £100, 700W and 15 minutes.

The pump is about 50W. Let's say 70W, hence 150 minutes.

In terms of wiring, my CH+HW system is on one fused switch - this needs only minor simple modification.

Bendy_House said:

What's UPS?

Uninterruptable Power Supply

FreeBear

Bendy_House said: What's UPS?

Uninterruptible Power Supply - Seamless switch over if/when the power fails. Available in capacities ranging from <500W up to 46MW.

Generator - Noisy, requires regular servicing/maintenance, plus a steady supply of fuel. Some models are available with near instant start up in the event of a power failure. Would work best in conjunction with a UPS to cover the time between power out and generator running up to full speed. Also need a way of switching over to the generator when the power fails. It is possible to get a generator with this function built in (at a price).

Battery - Glorified UPS. Can get expensive if you need a large capacity battery. Limited life span (also affects a UPS).

Bendy_House

Thanks folks - UPS sounds ideal, then.

Apodemus

My thinking is to use an inverter run directly off the car.  I probably need pure sine-wave for the CH pump, which probably means either a more expensive inverter or running the inverter through my 1kW UPS.  In addition, I might put a deep-cycle battery in the car, so that the inverter can run for longer between periods of charging.  I think this would work out cheaper than buying a generator and give me a mobile system to also use corded power tools away from home.  In a prolonged outage, I might also be eyeing up the kerosene in my CH tank and use it to power the system through my old SORNed diesel... 

FreeBear

Apodemus said: My thinking is to use an inverter run directly off the car.

Car batteries are designed to provide high current for short periods (i.e. cranking over the engine). They don't do well whith a constant draw and/or deep cycling. For that, you need to look at leisure batteries as used in campers & caravans along with an appropriate charging circuit. That said, a standard car battery will be OK for short periods in an emergency.

knightstyle

As above car batteries are not suitable for this and will not last long.  I am involved in a larger project, using 5KWh batteries and inverters, batteries are about £3k and inverters £2k each.  So you could probably get a decent 10 hour battery system to do what you want for around £3k plus installation if you are not confident in this.

Apodemus

...I did mention the deep cycle battery!  

Arfa__

Cool, thanks for the input, some interesting points. TBH as handy as a UPS might be, it would need to provide power for at least a day or two to be really worth the bother. The house and hot water tank aren't going to cool down so quickly we can't go without for an hour. It'll be in the eventuality of a much longer period without power that would be of bigger concern.

So perhaps the mini generator approach would be the most cost-effective solution.

Current CH appears to be hard wired into a fused isolation box. I'll have a natter with the heating engineer next time they're out to service it and see about effort to facilitate and alternative power source.