Truma Combi 4 fault on gas heating

[TerryL]

Been on EHU but now off grid. Up to now everything appeared to be working okay on gas and/or electric. But last night I got a red light so assumed gas had run out, although the fridge was okay, and changed the bottle. Reset but now the heating (on gas only) only works if I set it to both heating and water. On heating only I get the normal green light but the heating doesn't fire up. Switch to both and I also get the orange light, again normal, and the heating fires up. Switch back and the heating shuts down, not instantly but in accordance with it's normal routine. Hob and fridge work normally so I'm happy it's not the supply. The control panel is a Nordelektronica and otherwise seems to be working fine in every other respect; I have considered resetting it by disconnection, wait 30 secs then reconnect, which some years ago did clear another unrelated fault.
I've checked around for any damaged or broken connections but that just about exhausts my knowledge so am I looking at a replacement PSB (?) board. I'm happy to try a Control Panel reset, just worried I'll muck up something else. As it stands I still have heating so at the moment it's not a catastrophe.
Any gas expert with an opinion please?

 

[Ingwe]

Been on EHU but now off grid. Up to now everything appeared to be working okay on gas and/or electric. But last night I got a red light so assumed gas had run out, although the fridge was okay, and changed the bottle. Reset but now the heating (on gas only) only works if I set it to both heating and water. On heating only I get the normal green light but the heating doesn't fire up. Switch to both and I also get the orange light, again normal, and the heating fires up. Switch back and the heating shuts down, not instantly but in accordance with it's normal routine. Hob and fridge work normally so I'm happy it's not the supply. The control panel is a Nordelektronica and otherwise seems to be working fine in every other respect; I have considered resetting it by disconnection, wait 30 secs then reconnect, which some years ago did clear another unrelated fault.
I've checked around for any damaged or broken connections but that just about exhausts my knowledge so am I looking at a replacement PSB (?) board. I'm happy to try a Control Panel reset, just worried I'll muck up something else. As it stands I still have heating so at the moment it's not a catastrophe.
Any gas expert with an opinion please?

I’m not a gas expert (or indeed an expert at anything) but maybe this thread will be of help. At least it will bump your post.

Truma boiler red light coming on

Good evening all, I have a possible problem with my Truma Combi 4 boiler/heater. After it has been on for a while (Blown air heating) a red light on the control knob starts flashing and continues to flash. The Instructions say this is due to low voltage

www.motorhomefun.co.uk

 

[Portland]

How full are your gas bottles

 

[Lenny HB]

I think it could be the regulator, the Combi on heating needs a high gas flow rate often when a regulator fails everything else in the van works OK.

One thing worth trying is the temperature sensor for the heating, if you disconnect it the heater should run at full power.

 

[TerryL]

Think I've maybe not made it clear. The heating is working just fine, but only when it's switched to heat and hot water. On heat alone it's not working.

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[Lenny HB]

That sounds like an control problem possibly a fault on the PCB.

 

[TerryL]

Yes, what I was thinking. But we've got heating so I'll cross fingers and hope it'll be okay until we get home. Might research Truma dealer on our travels.

 

[TerryL]

Update. Tried changing the gas bottles over and it seemed to sort itself out. Happened again few days later but it, or something similar happened again this morning so changed the bottles and all okay, although we'd apparently used a lot of gas. Found a refill station but only got 9 litres in, should have been at least 12 if the bottle was empty.
Checked filter, spotless but took it out for now anyway. Now got 2 theories, first is regulator on the way out. For second, couple of facts - all recent refills in Spain, understand its a mix of propane & butane. Each occasion temp below or close to freezing. Fridge & hob work okay. Could it be butane, being heavier at bottom of bottle, not vaporising fast enough for the heater when all propane has been used?
Be home in a few days so a new regulator and filter cartridge will be obtained, but what does the team think?

 

[Lenny HB]

mix of propane & butane. Each occasion temp below or close to freezing.

That's your problem it can be up to 65% butane in Spain but I wouldn't expect it to be so high this time of year. Not only does butane not gas off in low temperatures it starts falling off around 10° also butane can not supply the flow rate Combi's need.

 

[Basildog]

Needing a near full cylinder to operate the heater is actually often an early indication of regulator failures
Having Butane percentage is also a possible cause , and a combination of the 2 factors could also be in play here

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[Basildog]

Update. Tried changing the gas bottles over and it seemed to sort itself out. Happened again few days later but it, or something similar happened again this morning so changed the bottles and all okay, although we'd apparently used a lot of gas. Found a refill station but only got 9 litres in, should have been at least 12 if the bottle was empty.
Checked filter, spotless but took it out for now anyway. Now got 2 theories, first is regulator on the way out. For second, couple of facts - all recent refills in Spain, understand its a mix of propane & butane. Each occasion temp below or close to freezing. Fridge & hob work okay. Could it be butane, being heavier at bottom of bottle, not vaporising fast enough for the heater when all propane has been used?
Be home in a few days so a new regulator and filter cartridge will be obtained, but what does the team think?

Please don’t at this point do what we occasionally see , Customer rings and says “My bottle’s faulty, you need to look at it , it’s taken us 45 minutes to get 2 litres of LPG in “
Heating works for a little while then they repeat the experiment
When we explain that they’ve overcome the fill stop valve and overfilled the cylinders, we don’t know what we’re talking about

 

[Reallyretired]

I cant see that it could be a gas problem if heat and hot water works, but heat alone doesn't, it will use the same amount of gas flow.

 

[Basildog]

I cant see that it could be a gas problem if heat and hot water works, but heat alone doesn't, it will use the same amount of gas flow.

From memory I am pretty sure that the Truma only ever goes into maximum burn rate in heating mode .

 

[TerryL]

Thanks all. Pretty well convinced it's the propane/butane mix causing the problem which I'll need to get burned off. However I will replace the regulator, not worth the hassle of possibly being a contributor, when we get home in a couple of days.
Incidentally no difference now whether I select just heating or heating+water. Think that may have been finger trouble!