See here , where he says ...BTW, just out of interest, why the inverter ? Off grid ? Emergency backup ? Something else ?
.... I have installed an inverter with the intention of providing standby power to our CH boiler ...
One could understand that view, but it would be much less easy to understand why it should apply to boilers if it doesn't (which, as far as I am aware, is the case) equally apply any other domestic appliances which involve electricity, particularly those which also involve water?SimonH2 have you considered that having a boiler lockout in the absence of an earth connection might be seen as an added safety feature...it may actually be required by the test house. When you consider the exposed metalwork and propensity for boilers to leak ensuring earth integrity is of heightened importance.
Neither of those things will make any difference - the boiler will almost certainly be earthed via the gas pipe and the main bonding, and the current needed is minuscule so even 2.5mm² wire is massively oversized in terms of making the boiler workSimon (post#14)... you were partially right. Connecting a 2.5mm earth wire between the inverter's earth bolt & the earth pin of a 3 pin plug inserted into a nearby 13A socket didn't make the boiler function properly, however it did allow allow the boiler to fire up for a few seconds several times before the E33 error code appear, an improvement on the previous lack of any attempt to fire & an error code shortly after switching the inverter on.
I guess the next thing to try is earthing the inverter to the boiler casing itself.
Would the use of a larger gauge earth cable (I have some 6mm) make any difference, though the heavier wire would be a bit large for the terminals.
The difference is likely to be because the boiler is only applying a tiny current, and there will be stray capacitance involved.Thank you for that Simon, what puzzles me is why my latest attempt (post #21) resulting in the boiler making several attempts to fire before showing 'error' whereas without the earth it wouldn't even try before bringing up the error code.
In my limited experience of household electrics things either work or they don't, unlike DC components in vehicles.
i would start with a simple test. Join Neutral and earth in the plug and try it out. Clearly, dont leave the link there and dont use it like that on the actual mains supply (though if its RCD protected you'll trip the RCD anyway)
If the boiler runs happily like that, then you can see about modifying the inverter to suit.
The difference is likely to be because the boiler is only applying a tiny current, and there will be stray capacitance involved.
Place two conductors in close proximity and there will be both capacitive and inductive coupling between them. So if there's AC on one of them, then there will be some AC coupled to the other. When you earthed the case of your inverter, it will have created another path for some of this coupled signal to go down - and this may have been enough to change conditions enough to change the behaviour of the boiler, but not enough to completely stop the "fault" being detected.
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