Boiler won't work off generator

[Bronco]

As a young man, I was an electrician, but now I'm getting on, I am strictly DIY.

I used to have a cheap old 900W petrol generator connected to a dedicated twin socket which I used to run my gas central heating boiler (plus essential TV) in the event of a power failure. It worked fine, but eventually it gummed up, got harder to start, and the pipes rotted.

So last year I bought a Hyundai P1PE 2200W Portable Petrol Inverter Generator, and religiously test ran it every couple of months to make sure it would start when I needed it. But the first time I needed it, the gas boiler would not fire up - the pump runs, ignition sparks can be seen, but it won't fire. I've since tried it with a load connected to the generator, but still no go. Needless to say, the warranty has run out now.

Looking online, it seems that it might be something to the sine wave not being smooth, or not compatible with the boiler electronic controls.
I wonder if anyone has come across this problem before, and whether there is a relatively easy fix?

 

[James]

The issue is that the new generator has a floating nutrual. I.e it is not connected to earth. It is known as an IT system
I for independent T for terra (earth)

the boiler flame detector is not being recognised as the N is not bonded to earth anywhere.

 

[James]

It may be possible to Bond earth and N together at the generator and the issue will likely be fixed.
you may well need an earth rod as well, and rcd protection should be considered.

 

[Bronco]

It may be possible to Bond earth and N together at the generator and the issue will likely be fixed.
you may well need an earth rod as well, and rcd protection should be considered.

Good thinking James. For the generator earth connection, I am using the property earth block (which is connected to PME and bonded to gas & water), but as you rightly point out, that does not necessarily mean that the generator 'floating' neutral is connected to earth. And good point about RCD protection for the dedicated socket. Something like this might do the job. British General 900 Series 13A 2-Gang SP Switched Passive RCD Socket White - Screwfix - https://www.screwfix.com/p/british-general-900-series-13a-2-gang-sp-switched-passive-rcd-socket-white/3133J?tc=JL5&ds_rl=1249401&gclid=CjwKCAjww7KmBhAyEiwA5-PUShPeLHc89egbtACmJ7vfbVPmi-QDkeT6vQ4zIwoiQMIrRWJ89cK5vBoCm6wQAvD_BwE&gclsrc=aw.ds

 

[James]

You can’t rely on the distributors earth in the event of a power cut.
an alternative earth path is required.
imagine for instance that the power cut is because a jcb has just sliced your supply cable in half.

 

[Bronco]

You can’t rely on the distributors earth in the event of a power cut.
an alternative earth path is required.
imagine for instance that the power cut is because a jcb has just sliced your supply cable in half.

Yes James, that is true. Although I would have thought the cross-bonded U/G water main and gas main would find a path good enough for a 2500W generator with low fault level (and to operate a 30mA RCD), but you are right, a separate pin is required.

 

[James]

In all honesty the parallel paths from service pipes is Lilley to give you a good enough return but it is not enough, to be compliant it will need a rod.

 

[James]

this might be helpful

 

[Bronco]

Thanks everyone. I have sorted it, with advice from forum members and the generator supplier. As James JSP properly surmised, the generator had a floating neutral (IT). Although I had earthed the frame, that did not mean the neutral was at earth potential and the boiler flame sensor would not recognise it. The solution was to put a link between E and N in the dedicated 13A plug which plugs into the generator. The other end of the (fixed) cable is a dedicated 13A twin RCD socket outlet, which the boiler is plugged into during a power cut. I also fitted an earth pin, which the generator, gas, and water pipes are bonded to. The boiler now fires up fine.