Using a 2kw inverter to power our gas combi boilers electrics.

[Gin]

Hi all .

I have a 2kw inverter and two 130ah deep cycle batteries for power cuts .

The gas combi boiler would not work in event of an electrical outage either .

So I have a three pin plug connected directly to the combi boiler electrics , so it can be unplugged from the mains circuit and in theory connected to an inverter or my petrol generator .
However having tried both , neither supplies work .

Apparently it is because both the inverter and the generator have floating earths and the clever circuitry in modern gas combi boilers detect this and refuses to power the ignition .

Can anyone explain to me in terms of an explanation for dummies (me) how to ( by first making sure there is no link to the mains) , that I can physically ground or bond (?) the neutral to earth in a way that does not compromise the mains circuit . Maybe use a short extension lead to bond neutral to earth still all completely separate from the mains circuit ..??

 

[johnb2713]

My Honda generator and the inverter I had in my caravan had earth terminals on the outside, I would try connecting that earth to your household earth or a water pipe / earthing rod etc.

 

[Geoff1946]

Interested in this because I have considered getting an inverter to keep the gas boiler working if we do have significant power issues.

 

[Andy™]

simplest solution would be to make the output from the inverter/generator TNS... simple adapter plugged in linking N-E at the socket

for 1 appliance itll be fine. multiple appliance all plugged in and you may start getting other earthing / related issues

 

[Geoff1946]

implest solution would be to make the output from the inverter/generator TNS... simple adapter plugged in linking N-E at the socket

Yes that's fine as long as the inverter output is isolated, but is that always the case or is it something to investigate when selecting one?
I'm only thinking of a small portable one to run on a leisure battery. Sorry if it's a daft question but I've never dealt with these.

 

[Gin]

simplest solution would be to make the output from the inverter/generator TNS... simple adapter plugged in linking N-E at the socket

for 1 appliance itll be fine. multiple appliance all plugged in and you may start getting other earthing / related issues

I appreciate your reply .! What does making the inverter TNS mean ..How would I adapt ?

Would connecting the Earth to Neutral within the plug do what you are suggesting . So the electricity exiting the boiler returns straight to Earth .?

I am practical but very cautious and know this should be done completely isolated from the mains circuit . I just want to get it right .

(I would use the DCtoAC 2kw inverter ONLY for the boiler and probably just for a couple of hours, if necessary at a time .)


If you could explain it to me in a little detail that would be even more appreciated and thanks .

 

[johnb2713]

Hi all .

I have a 2kw inverter and two 130ah deep cycle batteries for power cuts .

The gas combi boiler would not work in event of an electrical outage either .

So I have a three pin plug connected directly to the combi boiler electrics , so it can be unplugged from the mains circuit and in theory connected to an inverter or my petrol generator .
However having tried both , neither supplies work .

Apparently it is because both the inverter and the generator have floating earths and the clever circuitry in modern gas combi boilers detect this and refuses to power the ignition .

Can anyone explain to me in terms of an explanation for dummies (me) how to ( by first making sure there is no link to the mains) , that I can physically ground or bond (?) the neutral to earth in a way that does not compromise the mains circuit . Maybe use a short extension lead to bond neutral to earth still all completely separate from the mains circuit ..??

A further thought, make sure your inverter is a pure sinewave inverter as opposed to a modified sinewave one, lots of electronics don not like MSW.

 

[kerrykpc]

We have similar issues when we use 110 volt from transformers to feed burners, the issue is how the flame detector works, it sends an AC signal to the flame probe, when a flame is present it acts as a rectifier and allows a small current to flow, microamps, this is detected by the flame supervision circuit in the boiler, with no earth to Neutral connection you dont have a complete circuit., so connecting the earth and Neutral should help, still ensure you have an earth to the boiler from the generating source as well.

 

[johnb2713]

We have similar issues when we use 110 volt from transformers to feed burners, the issue is how the flame detector works, it sends an AC signal to the flame probe, when a flame is present it acts as a rectifier and allows a small current to flow, microamps, this is detected by the flame supervision circuit in the boiler, with no earth to Neutral connection you dont have a complete circuit., so connecting the earth and Neutral should help, still ensure you have an earth to the boiler from the generating source as well.

Every day a school day! I had often wondered how they worked.

 

[Andy™]

I appreciate your reply .! What does making the inverter TNS mean ..How would I adapt ?

Would connecting the Earth to Neutral within the plug do what you are suggesting . So the electricity exiting the boiler returns straight to Earth .?

I am practical but very cautious and know this should be done completely isolated from the mains circuit . I just want to get it right .

(I would use the DCtoAC 2kw inverter ONLY for the boiler and probably just for a couple of hours, if necessary at a time .)


If you could explain it to me in a little detail that would be even more appreciated and thanks .

plug with a 2 core flex L&N to a socket. L&N to L&N and a link N-E at the socket. dont wire anything from the earth on the inverter

 

[Andy™]

We have similar issues when we use 110 volt from transformers to feed burners, the issue is how the flame detector works, it sends an AC signal to the flame probe, when a flame is present it acts as a rectifier and allows a small current to flow, microamps, this is detected by the flame supervision circuit in the boiler, with no earth to Neutral connection you dont have a complete circuit., so connecting the earth and Neutral should help, still ensure you have an earth to the boiler from the generating source as well.

i knew it was something to do with the gas but no idea how it worked (or didnt)

 

[Gin]

I met a great Electrician today who supplied me with a metre long extention lead , and he bonded the neutral to the earth within the three pin socket of the lead .
I can now use the 2kw inverter connected to the Combis three pin plug and the combi`s ignition works fine and the combi runs fine .
So long as the modified lead is not used on the mains circuit then all is ok .

 

[Gin]

Interested in this because I have considered getting an inverter to keep the gas boiler working if we do have significant power issues.

Geoff (by coincidence my name is Geoff also) please have a look at my post . I can now run my combis electrics via the 2kw inverter or the generator so long as I use a short extention lead that has been converted by a local electrician and the inverter is also earthed in the appropriate way via its small earthing stud on the body . Thanks to people who responded to my initial question too . !

 

[Nigel52]

This is a very interesting post but would like more detail on this please. I have 14 x panels of PV and Solaredge inverter as a standard installation.
I also have a 3.5kVa generator and 1500 watt Growatt inverter spare. What is an easy way to make one or other able to power my boiler in the event of a grid failure.

 

[Gin]

This is a very interesting post but would like more detail on this please. I have 14 x panels of PV and Solaredge inverter as a standard installation.
I also have a 3.5kVa generator and 1500 watt Growatt inverter spare. What is an easy way to make one or other able to power my boiler in the event of a grid failure.

I can only tell you how I now can use my petrol generator or 2kw inverter. :

The Combi is usually directly wired to the mains .
So instead the cable exiting the combi needs to have a 3 pin plug attached so it can be physically disconnected from the mains circuit.

An extention lead with three pin plug and socket is needed . The socket of the extention lead needs to have the Neutral directly wired to the Earth inside the socket . (might sound odd but it works and is safe IF this extention is only ever used on its own for this set up. and never attached to the mains circuit.)

The generator should have an earth lead running to earth also usually by an earthing rod skewered into the ground about 6 feet or even more . There is usually a small connection / grounding bolt on the generator body for this . A stanbdard procedure really .

Then you plug the combis 3 pin plug into its socket and the 3 pin plug of the lead then goes into the generator socket . The generator will then run the combis electrics easily .

The reason is otherwise the generator recognises things are not how they should be and does not co operate . Portable generators have what is called a floating earth and modern combis do not like that . So the igntion will not operate .

It is most important the modified extention lead is only used to attach the Combis lead to the generator . Never used attched to the mains .

The same rules apply for an inverter....sorry for long winded reply but it took me a long time to finally "get it" I hired an electrician to modify the socket of the extention lead.

He said it is legal but the first time he had come across the idea/situation and thought it a cool idea .

 

[Nigel52]

I can only tell you how I now can use my petrol generator or 2kw inverter. :

The Combi is usually directly wired to the mains .
So instead the cable exiting the combi needs to have a 3 pin plug attached so it can be physically disconnected from the mains circuit.

An extention lead with three pin plug and socket is needed . The socket of the extention lead needs to have the Neutral directly wired to the Earth inside the socket . (might sound odd but it works and is safe IF this extention is only ever used on its own for this set up. and never attached to the mains circuit.)

The generator should have an earth lead running to earth also usually by an earthing rod skewered into the ground about 6 feet or even more . There is usually a small connection / grounding bolt on the generator body for this . A stanbdard procedure really .

Then you plug the combis 3 pin plug into its socket and the 3 pin plug of the lead then goes into the generator socket . The generator will then run the combis electrics easily .

The reason is otherwise the generator recognises things are not how they should be and does not co operate . Portable generators have what is called a floating earth and modern combis do not like that . So the igntion will not operate .

It is most important the modified extention lead is only used to attach the Combis lead to the generator . Never used attched to the mains .

The same rules apply for an inverter....sorry for long winded reply but it took me a long time to finally "get it" I hired an electrician to modify the socket of the extention lead.

He said it is legal but the first time he had come across the idea/situation and thought it a cool idea .

Thank you very clear. Fairly similar to what I wired up a long time ago for an oil boiler for the 1987 powercuts. I also wired in the heating pumps to the same circuit. You explanation has reminded me how I did this.

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