Earthing and Battery supplied Inverters

[Had8Lives]

Hi All,

When I heard reports on the radio of people not being able to run their gas central heating because of a power cut, it got me thinking. Is there any reason a gas boiler couldn't be run on an inverter and a battery?

I was thinking there might be a potential issue with some ac making it's way onto the grid through water and gas bonding and the PEN connection at the cut out if the property has a TNCS supply. What's your thoughts please?

 

[James]

In theory, yes an inverter will run a boiler.
particular care must be taken to ensure separation from the grid supply, just the same as any other form of backup generation.

 

[Lucien Nunes]

As above, no problem if suitable transfer switch (manual or automatic) is used, no difference between TN-C-S and TN-S supplies as there will be no connection between the two energy sources.

You would need to consider whether the system is safe to run as IT on the inverter (most small inverters are intended for a single piece of equipment floating WRT earth) or whether you need to deliberately make it TN, and therefore also the need for independent earth reference electrode for the inverter as you may not rely on a supplier's earthing facility if not using that supply.

 

[James]

I am personally a fan of running boiler from a dedicated 13A socket.
makes it an easy job to plug it into an extension lead from generator etc if power to property is turned off.

as above, earthing arrangements need to be considered when introducing a new power source.
many boilers need the N to be at the same potential as earth so the single wire flame detection works correctly.

 

[DPG]

I am personally a fan of running boiler from a dedicated 13A socket.
makes it an easy job to plug it into an extension lead from generator etc if power to property is turned off.

as above, earthing arrangements need to be considered when introducing a new power source.
many boilers need the N to be at the same potential as earth so the single wire flame detection works correctly.

My combi is on a 13A plug(top). Unfortunately I don't have a generator!

 

[Had8Lives]

many boilers need the N to be at the same potential as earth so the single wire flame detection works correctly.

I didn't know that. Thanks. So would there be a problem with the flame detection with a TT earthing arrangement?

 

[James]

I didn't know that. Thanks. So would there be a problem with the flame detection with a TT earthing arrangement?

That was the case with my boiler

 

[Lucien Nunes]

problem with the flame detection with a TT earthing arrangement?

A generator supply will never normally be TT, it will be IT (floating) or TN-S (neutral earthed at source and cabled separately to the load.)

A TT sytem is one where the neutral is earthed at source, but the earth is not run as a cable from source to installation, so the installation also needs to be earthed by a rod.

 

[James]

That was the case with my boiler

Sorry I misread TT and read IT, as is often the case with small portable generators.