Inverter query

[norseman]

Hi folks, I wasn't sure whether to post this here or on 'electrics UK' so apologises if I've got that wrong.
I have installed an inverter with the intention of providing standby power to our CH boiler but ran into a problem during the system's first test yesterday. The boiler itself will happily run on inverter power but after the usual pre-ignition time lapse flashes up an error code & will not ignite. I can clear the code & resume normal operation if I switch back to grid power, but the code will not clear when on the inverter.
There is no indication (led & sound warnings) that the load is higher than the inverter's continuous rated power output.

Tech details :
Boiler Baxi duo-tech combi 28 lpg
Inverter Mercury IPS600-12
This is a CE marked unit, not a cheap knock-off.
Pure sine wave with a continuous power output of 600W & the capability of double
that for 2 seconds to cope with a start-up surge.

Any advice greatly appreciated.

 

[Gasguru]

I'm guessing the boiler pcb is failing to detect the flame and locking out after several ignition attempts...what's the code?
How is the boiler connected to the inverter?
Many boilers require the earth connection for successful flame detection (and there are generally 3 types when run from the mains).

 

[ericmark]

I also got caught out with no earth, in theory if it requires to send current through the earth then is should say so in order that the correct supply is used, seen boiler say must use type A RCD, but nothing about the earthing requirements in the instructions but seems some do need neutral bonding to earth to work which would require a special change over relay.

 

[muggles]

As above, it won't work without an Earth

 

[norseman]

All your replies are greatly appreciated & as they follow a similar vein perhaps I can answer in a single post.

For grid power all l I did was to disconnect the original 3 core power cable from the boiler terminal box & re-route to a surface 13A socket.
I then wired a new 3 core cable, complete with a moulded plug fitted with a 3A fuse, to the boiler allowing me to plug into either grid or inverter supply.
The inverter has an earth pin on the casing but I was unsure if it was needed, or if so, where to connect it on the boiler.
The fault code shown is E33 (E133 in the book) which translates as 'gas supply interrupted or ignition fail or flame not detected'

 

[ianmcd]

yes that code will come up if no earth

 

[Gasguru]

In order for the flame detection to operate the boiler requires the Neutral and Earth connected together...now this is normally done via the earth rod (and then via the ground) or at the local sub-station (IIRC) or at your consumer unit.
You'd need to check on the electrics forum for advise regarding inverters and earthing.

 

[ericmark]

One the inverter you can link neutral and earth, it should have been already done. We have three earthing systems, and it seems your inverter is using the IT system (insulated from terrestrial) which when powering a single item is likely the safest, it is also used with shaver outlets, but seems you must change it to a TN system which means as close to the inverter as you can link neutral and earth, what you must ensure is where linked this can never get on to the mains supply, so should be at the inverter. This is the diagram from 17th edition

At the source of energy which in your case is the inverter the neutral and earth are linked, but no where else.

 

[norseman]

Thank you for your reply, but unfortunately I'm not an electrician
Are you saying that an earth wire/cable can be attached to the inverter's external earth connection & if so where on the boiler should the other end be attached?
To the boiler frame perhaps or somewhere within the boiler? When rewiring the 3 core power cable to the boiler I did notice that 2 of the terminal block terminals were linked by a yellow insulated wire, if that's any help.