Gas Boiler & Petrol Generator

[Roger]

Has there already been discussion of the difficulties of running (condensing) gas boilers off generators?

[MuddyMike]

I don't recall one. My gas condensing boiler happily runs off my generator though.

Mike

[Dave Plowman (News)]

It will probably depend on how good a sine wave the generator produces. Many don't.

[Roger Mills]

You mean apart from the fact that boilers require gas but generators provide electricity?

Ah, I guess you mean using a generator to provide the electricity for the control electronics (plus pumps, motorised valves etc. in the overall system)?

In that case, it's perfectly feasible, but there are a few things which you may need to do:

1. Use an inverter-based generator which produces a clean, stable AC output
2. Earth the generator with an earth spike
3. Feed the boiler/CH system via an RCD
4. If the generator output is floating, you may need to short N and E together - otherwise the boiler's ignition system may not fire.

I've wired my (non-condensing, but the principle is the same) boiler to a 13A plug rather than an FCU. In the case of a power cut, I can unplug it from the mains and plug it into the generator via an extension lead which has an RCD plug at the generator end. My genny has two 13A output sockets. In the unused one I have a (suitably labelled) 13A plug with N and E connected internally, and no external wiring.

[Roger]

In message , "Dave Plowman (News)" writes

Two of my neighbours have bought generators to run their heating during mains failures, one a 2kW, the other a 3kW. Neither will. They have twigged the need to link N on the generators to earth. (Why ever is this???)

The pumps start and run, but the boiler controls don't go thro the start-up sequence - indeed one displays a code saying its control system is faulty.

One has also been tried with a 1kW electric fire connected to the gene as well, before the heating is switched on, so that the load on the gene is mainly resistive. Makes no difference. The waveform has been looked at on this one and is reasonably sinusoidal, with and without the 1kW load. This one - a 3kW Briggs & Stratton - won't run a 500W UPS for the computer either, even tho it was recommended as suitable for running computers and electronic systems. Baffling. Ten years ago, 3kW Honda and Kawasaki generators used to run radio transmitters, laptops and even a small microwave oven for me with no problem at all.

[geoff]

In message , Roger writes

It's because flame sensing is referenced to earth

Normally earth is connected to neutral at the local s/stn

connecting N - E on the genny should work

If the electronics doesn't sense the flame then either the main gas doesn't come on, or it times out after a certain time and tends to go into lock out