Insufficient power? Morco Boiler

banjolin

Electrical Problem
I have a Morco GB24 mkII installed in an off-grid cabin. Its a condensing gas combi boiler for mobile homes etc. During installation it was powered from a battery and 400w 12/230v Draper Inverter and worked perfectly. Subsequently an off-grid solar kit has been installed with a 375w Victron Pure Sine Wave Inverter. The Victron is also a 12/230v inverter but (with nothing else switched on) the boiler will turn on but will not fire up and we get a fault code F2 (flame loss) repeatedly and ultimately an L2 fault (ignition lockout). When we plug the boiler back into the Draper 400w the boiler works again, using the same battery. There is only a 25w difference in the stated output of the inverters. The power required by the boiler, according to the manual, is 146w, less than half of either inverters output.

I'm faced with replacing five inverters. Is this simply an issue of an under-powered inverter? Will getting a larger output inverter solve the problem? Does 25w difference in rating make that much a difference? I'm at a loss. My plumber is at a loss. My electrician in bamboozled. Morco are no help. Any advice welcome.

2011

I would start by measuring exactly what the boiler consumes when connected to a descent supply followed by a load test on the inverter to see exactly what it can provide in terms of power. Next I would assess the inrush current of the boiler.

banjolin

2011 wrote: »

I would start by measuring exactly what the boiler consumes when connected to a descent supply followed by a load test on the inverter to see exactly what it can provide in terms of power. Next I would assess the inrush current of the boiler.

Thanks. Unfortunately, we are more or less out of time on this and testing is going to take more time than we have. I will have to take a punt and get a higher wattage inverter. It's so annoying that it must surely be a borderline issue with two inverters so similar and one working, the other not.

Tuco88

Keep us posted on how you get on

Bruthal

A test between each pole of the inverter output and earth might show a difference between both inverters. Floating earth might affect the igniter.

banjolin

Ok. We have identified the problem but not found a solution. The boilers were installed and tested using a 10 year old very basic 400w Draper inverter. We therefore assumed that they would run on any inverter, or more to the point, a modern pure sine wave inverter. Nope. I also got a new model of the Draper 400w assuming that it was the same as the old one. Nope. Tried a 500w Durite. Nope. What the new Draper and the Durite have in common is that they are modified sine wave inverters. The Victron is a pure sine wave inverter. I have no clue what the old Draper is.

So out of four inverters, only the discontinued Draper model will work the boiler. If anyone knows how I can get something similar I would be extremely grateful.

Thanks.

banjolin

Bruthal wrote: »

A test between each pole of the inverter output and earth might show a difference between both inverters. Floating earth might affect the igniter.

The main difference between the old Draper and the new models I have tested is that it does not have an external earth connection. All the others I have tried require earthing. Although from what I can glean elsewhere the earth is just for the inverter casing. The Victron apparently does not have a real earth. It is a floating earth. https://forums.whirlpool.net.au/archive/2212276 i would therefore assume that the new draper is the same.

If anyone can enlighten me further on this floating earth issue or maybe suggest a route to a workable solution, I would be very grateful.

Bruthal

Is there an Earth output pin on the one that works.
Does it still work if its not connected?

Overall it would be the power rating and waveform output that would be first things to consider.

Just curious if there is any output earth on the one that works. More in terms of reference to the output 230v rather than actual true earth.

banjolin

Bruthal wrote: »

Is there an Earth output pin on the one that works.
Does it still work if its not connected?

Overall it would be the power rating and waveform output that would be first things to consider.

Just curious if there is any output earth on the one that works. More in terms of reference to the output 230v rather than actual true earth.

Bruthal, after the snippet if info about a floating earth I did one of my semi autistic Google binges last night and educated myself about circuits and earths and from other fora I found snippets about the construction of inverters. You said igniters might not like floating earths. Why you did not say but it seems in this case at least you were bang on. Three inches of four square between the earth and neutral in the socket and I have a working boiler. Five working boilers actually.
Turns out the original old inverter had a proper true earth and that's probably why it had no terminal for the case or chassis earth like the newer ones have.
So there it is. Hope it helps someone else. And thanks again.

2011

Very good Bruthal!
Earthing did not occur to me.

Bruthal

banjolin wrote: »

You said igniters might not like floating earths. Why you did not say

I suspect the igniter sparking onto the gas boiler frame has no return path if the frame is completely isolated from both power supply poles.

brightspark

banjolin wrote: »

Bruthal, after the snippet if info about a floating earth I did one of my semi autistic Google binges last night and educated myself about circuits and earths and from other fora I found snippets about the construction of inverters. You said igniters might not like floating earths. Why you did not say but it seems in this case at least you were bang on. Three inches of four square between the earth and neutral in the socket and I have a working boiler. Five working boilers actually.
Turns out the original old inverter had a proper true earth and that's probably why it had no terminal for the case or chassis earth like the newer ones have.
So there it is. Hope it helps someone else. And thanks again.

What is a "semi autistic Google binge"?