Using an inverter to power a gas boiler

helenf43

Hi we run off grid for our electricity and have bought an inverter to power lights and gas boiler when the generator is turned off. We have a 1000w true sine wave inverter which works great for tv and lights but the boiler (Worcester 241 junior) won't work on inverter - it comes on for 30secs then its almost as if it can't ignite and keeps resetting any ideas on how to get it to work on the inverter???? we are desperate to get it to work esp with winter approaching and a small baby at home thx helen

energysavingexp

does it trip the inverter

rogerblack

The obvious question arises - would it actually work on mains?
The second one - not all 'true sine' inverters actually are - what's the brand?

espresso

helenf43 wrote: »

Hi we run off grid for our electricity and have bought an inverter to power lights and gas boiler when the generator is turned off. We have a 1000w true sine wave inverter which works great for tv and lights but the boiler (Worcester 241 junior) won't work on inverter - it comes on for 30secs then its almost as if it can't ignite and keeps resetting any ideas on how to get it to work on the inverter???? we are desperate to get it to work esp with winter approaching and a small baby at home thx helen

You have not really provided enough information e.g. make/model of the inverter but it is common for these to go into a power saving mode. This is to conserve your battery, when less than a pre-determined load is drawn. This load value may be user programmable e.g. it may be set to only 15W.

The Worcester 24i junior draws a maximum of 140W and most of this will be the water circulation pump, so it is possible that it is not drawing enough load to bring the inverter out of it's power saving mode.

Will the boiler ignite when the inverter is already supplying other appliances e.g. your TV?

helenf43

energysavingexp wrote: »

does it trip the inverter

Hi thx for replies will try and answer as best I can

Will get make / model of invertor and let u know in ten mins

It doesn't work with lights on will try with tv and get bk to u on that one

Boiler used to work fine on mains it is less than three months old

The invertor does not trip with boiler

Since writing my last post we have figured out when we run invertor via generator boiler comes on but we can only have either heating or hot water not both together?? But then if we switch generator off and invertor goes onto batteries as soon as we turn hot tap on or central heating kicks in off thermostat it stops working again and appears to be unable to ignite???

rogerblack

No hot water at the same time as CH may well be normal.
It's designed to run one or the other often, with a changeover valve.
I'd first want to measure the voltage and frequency of the inverter - do you happen to have an energy meter similar to http://www.ebay.co.uk/itm//320503970289 (I have no knowledge of this seller) that will measure both voltage and frequency?

macman

helenf43 wrote: »

Hi thx for replies will try and answer as best I can

Will get make / model of invertor and let u know in ten mins

It doesn't work with lights on will try with tv and get bk to u on that one

Boiler used to work fine on mains it is less than three months old

The invertor does not trip with boiler

Since writing my last post we have figured out when we run invertor via generator boiler comes on but we can only have either heating or hot water not both together?? But then if we switch generator off and invertor goes onto batteries as soon as we turn hot tap on or central heating kicks in off thermostat it stops working again and appears to be unable to ignite???

You have a combi boiler. When a combi has a demand for hot water, then the diverter valve diverts all the flow to the DHW circuit. You cannot have the CH on when it is supplying hot water. Once the hot tap is closed, it should then switch back to supplying the CH circuit as long as the stat is still calling for heat.

jalexa

helenf43 wrote: »

it comes on for 30secs then its almost as if it can't ignite and keeps resetting any ideas on how to get it to work on the inverter?

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.

undaunted

Simple soul that I am can I ask why if you can run the boiler on either mains or generator you want to persist in trying to run it on battery?

If it's run on a 12v battery & is drawing upto 140w on top of lights, tv etc surely this is only going to give you a short life (two or three hours?) before it needs charging anyway

espresso

helenf43 wrote: »

But then if we switch generator off and invertor goes onto batteries as soon as we turn hot tap on or central heating kicks in off thermostat it stops working again and appears to be unable to ignite???

What is the spec of the batteries that are used to supply the inverter?
What is used to charge these batteries?
What is the state of charge of these batteries?
What is the spec of the cable used between the batteries and the inverter?

If the inverter is supplying say 500W at 230V, the batteries will need to able to supply approx 50A (assuming 12V) and the DC cable will need to be sized accordingly to prevent a voltage drop which would effectively kill the output from the inverter.

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.

This is a red herring! Yes the boiler should be earthed but no earth will not actually prevent it operating normally and depending on how the generator/inverter has been connected, it may still be earthed.

System

espresso wrote: »

This is a red herring! Yes the boiler should be earthed but no earth will not actually prevent it operating normally and depending on how the generator/inverter has been connected, it may still be earthed.

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.