Using an inverter to power a gas boiler

espresso

!!!!!! wrote: »

I don't believe that it is a red herring. It may well be a floating earth if the gennerator is disconnected and that can cause some weird problems. It is an avenue that DOES need to be investigated.

A standard mains generator has a floating earth just like the inverter, so unless this particular generator has been modified to link earth and neutral together, then this cannot be the reason that the boiler won't ignite when using the inverter.

The generator should be connected to the properties mains wiring using a a double-pole, break-before-make, changeover switch e.g. a Briggs & Stratton manual transfer switch.

SYNERGY

jalexa wrote: »

Yes, the boiler flame failure device requires an "earthed supply" but the inverter provides a "floating supply". Can be solved but I can't tell you how here. Consult a qualified electrical engineer.

In simple, non tec terms, the flame failure device, ionisation probe, and monitoring circuit work as follows.

Alternating current is supplied to the probe, small electrode, current flows from the probe through the ions in the flame to the large electrode, the burner.

For reasons too long to go into, the large / small electrodes rectify the AC into DC, ie current will only flow from small to large electrode.

The monitoring circuit sees the DC, which has to be at the correct polarity, as a flame, all is well.

If no voltage, it sees no flame so shuts down the gas.

If it sees AC, it sees a short circuit and again shuts down the gas.

What may have happened is that the inverter output has been transposed, ie neutral to live and vice versa.

Or the monitoring circuit may not be too keen on either the quality of the inverter output or the floating nature of the inverter.

In most cases the flame failure device won't work with transposed live/neutral inputs, though everything else in the boiler isn't fussed either way.

Virtually every electrical item in a household will still work with live and neutral transposed, deadly though, due to the fact that even though the item is switched off, all neutrals within it will now be live. :eek:

If HelenF43 were to watch, the boiler when attempting to use it via the inverter, saw flames at the burner for a second or two ( look through the window to observe the burner ), then it shuts down, this points to the flame failure device not liking the inverter output.

bengasman

espresso wrote: »

Yes the boiler should be earthed but no earth will not actually prevent it operating normally...

Yes, it will prevent this boiler from working; it will probably go to lock out mode.

espresso

bengasman wrote: »

Yes, it will prevent this boiler from working; it will probably go to lock out mode.

You are showing that you do not actually understand this issue. The boiler not being connected to earth will not prevent it operating and the boiler and pipework will already be connected to earth if it has been installed correctly.

Most mains generators and inverters provide a floating supply and some types of flame failure detection devices will not work with a floating mains supply. All that is required for the boiler to function normally, is that the generator/inverters neutral is bonded to earth, so that the boiler sees a true live feed with respect to neutral/earth.