Chuns Posted January 27, 2016 Share Posted January 27, 2016 Hello, all, I wonder if anybody has a view on this... Here are the symptoms. The cooker, fridge, and freezer all work fine, but the Combi6 hot air heater, not the hot water side, shuts down, claiming there is a "pressure issue". I use LPG, bought in garages. I only discovered this problem recently as up until then the only use was in summer, though I can remember, I think, using the heater on a chilly morning. The van is barely 6 months old, and the last fill I did was in France. My local Moho specialists (Autovan Services, great to deal with) undertook some rigorous diagnostics and having got the heater to run satisfactorily with another bottle of gas, concluded that the problem most likely lay with the gas, with a remote chance it might be the bottle. The curiosity is that everything else works, just the warm air heater (not the hot water heater) gets precious about its supply. Has anybody ever met this issue before? I'd be grateful for any thoughts. Regards Peter Link to comment Share on other sites More sharing options...
Charles Posted January 27, 2016 Share Posted January 27, 2016 Can you turn the regulator up a bit? Because the heating uses more gas than the other things the pressure might be dropping too much. If it works ok off another gas supply what else can it be. Link to comment Share on other sites More sharing options...
Keithl Posted January 27, 2016 Share Posted January 27, 2016 Chuns - 2016-01-27 8:05 AM .. the last fill I did was in France. Peter, Your line quoted above is the answer to your problem. LPG in the UK is typically near 100% Propane whereas in France it can be nearer 100% Butane. Google for "GPL France" for more info. You will have to run out your french GPL and refill with UK LPG to get your heater to work again. Much like swapping a cylinder of Calor from Butane to Propane for the winter. Keith. Edit to add some info on percentages in other countries, try this link... http://www.mylpg.eu/useful/lpg-mixture Link to comment Share on other sites More sharing options...
Tracker Posted January 27, 2016 Share Posted January 27, 2016 I was considering getting a second refillable bottle but in view of the foregoing maybe it would be as well to carry on using a Calor as the second back up bottle as the cost and convenience savings on a second refillable are not that great compared to the inconvenience of having no heating when it's chilly. Link to comment Share on other sites More sharing options...
Robinhood Posted January 27, 2016 Share Posted January 27, 2016 If, as above, you have taken a fill in France which is largely Butane, this could indeed account for your issues. The space-heater will have a significantly higher draw than the other devices, and with a mix of gas that is struggling to remain at pressure at current temperatures, it could well fall below the required pressure. Keith's advice: Keithl - 2016-01-27 8:49 AM You will have to run out your French GPL and refill with UK LPG ...is sound, but with one additional proviso. UK LPG is likely to be substantially propane (especially at this time of year). If you have sufficient capacity, a UK fill might improve the mix sufficiently such that it would work better. Link to comment Share on other sites More sharing options...
Tracker Posted January 27, 2016 Share Posted January 27, 2016 In the old days when it was cold and before we switched from the blue butane to the red propane we used to fill a large thermos flask with hot water each night and if the gas was slow or non existent in the morning fill a hot water bottle and place it in the gas locker. It usually got us going! And then we discovered propane - problem solved! Link to comment Share on other sites More sharing options...
andytw Posted January 27, 2016 Share Posted January 27, 2016 Robinhood - 2016-01-27 9:50 AM If, as above, you have taken a fill in France which is largely Butane, this could indeed account for your issues. The space-heater will have a significantly higher draw than the other devices, and with a mix of gas that is struggling to remain at pressure at current temperatures, it could well fall below the required pressure. Keith's advice: Keithl - 2016-01-27 8:49 AM You will have to run out your French GPL and refill with UK LPG ...is sound, but with one additional proviso. UK LPG is likely to be substantially propane (especially at this time of year). If you have sufficient capacity, a UK fill might improve the mix sufficiently such that it would work better. Just thinking this out. If you have a half bottle of butane and you fill the other half with UK LPG then yes you will have a 50/50 mix of the liquids. But if it remains cold and you now use this bottle then surely only the LPG will evaporate off into gas so eventually you will be back at a half bottle of butane ? This is all assuming the temperature remains cold and below butane operating temperatures. The only way I see of using the butane is to have warmer weather. Or am I wrong ? andytw Link to comment Share on other sites More sharing options...
Charles Posted January 27, 2016 Share Posted January 27, 2016 When you mix propane and butane it is an Azeotropic blend so it has a single higher evaporating pressure not two, which would be a zeotropic blend. I looked into it the other day when bottle pressure was being discussed. I didn't think French gas was 100% butane. That's pretty useless in winter. Link to comment Share on other sites More sharing options...
Robinhood Posted January 27, 2016 Share Posted January 27, 2016 andytw - 2016-01-27 10:02 AM Just thinking this out. If you have a half bottle of butane and you fill the other half with UK LPG then yes you will have a 50/50 mix of the liquids. But if it remains cold and you now use this bottle then surely only the LPG will evaporate off into gas so eventually you will be back at a half bottle of butane ? This is all assuming the temperature remains cold and below butane operating temperatures. The only way I see of using the butane is to have warmer weather. Or am I wrong ? andytw ..as Charles says, the mix will vaporise, not one of the constituents. This is supported by the info in Keith's link above, which outlines the usable temperatures of the various mixes. The higher the proportion of propane, the lower the (lowest) vaporisation temperature is. Link to comment Share on other sites More sharing options...
Robinhood Posted January 27, 2016 Share Posted January 27, 2016 Charles - 2016-01-27 10:11 AM I didn't think French gas was 100% butane. That's pretty useless in winter. ...100% is not likely, but the summer mix could be 65-70% butane. After all, this form of LPG is basically sold as a propulsion fluid, where consumption is in the liquid phase, not vapour as is required for domestic use. Link to comment Share on other sites More sharing options...
Charles Posted January 27, 2016 Share Posted January 27, 2016 70% butane mix then, would stand at 21.5psi at 4c So it would evaporate until the liquid reaches about -17c according to the chart I've looked up... So it should work for some time before that point. I think it's a regulator problem.. or the chart is wrong. Link to comment Share on other sites More sharing options...
Tracker Posted January 27, 2016 Share Posted January 27, 2016 All this techy stuff is all very well but in the interests of keeping it simple, if it were my van I would blow some warm air around the gas bottle and if that fixes the problem job done. If not at least he will know what it isn't, but I would say that seeing that the heater did work on a propane bottle chances are there is nowt wrong with the system just the wrong gas. I would always do the inexpensive and simple things first in a process of elimination. Link to comment Share on other sites More sharing options...
Charles Posted January 27, 2016 Share Posted January 27, 2016 Agreed, if that cures it, it must be a very high percentage butane. Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 27, 2016 Share Posted January 27, 2016 Just a thought, but as the water heating side of the Truma apparently works OK, what about turning that on (don't forget the water! :-D), plus the fridge on gas, and all hob/oven burners? That should place quite a high total demand on the gas supply - though possibly not as much as space heating. If they all run OK, I'd be a bit inclined to suspect the heater side of the Truma may have a fault. At that point, and in view of the age of the van, I think I'd then talk direct to Truma's technical department for their suggestions. Link to comment Share on other sites More sharing options...
Robinhood Posted January 27, 2016 Share Posted January 27, 2016 Charles - 2016-01-27 10:54 AM 70% butane mix then, would stand at 21.5psi at 4c So it would evaporate until the liquid reaches about -17c according to the chart I've looked up... So it should work for some time before that point. I think it's a regulator problem.. or the chart is wrong. If Autovan tested through the same regulator on a separate Propane bottle (that would be nice to know) then regulator fault is unlikely, but not impossible. Given the scant details, and a potential 6Kw draw from the heater, my money is still on a combination of demand and a high Butane content. I can see the same chart as you, but I think the demand is the critical thing. For instance, a 7kg Calor Butane bottle is only rated at supporting 7Kw demand in good conditions. Truma's view on the use of Butane at temperatures lower than 10 degrees is clear in their troubleshooting guide for the Combi (extract attached). Brian's advice is also reasonable - as a test fire up all the appliances (all hob burners, water heater, fridge) but the heater, and see if the pressure drops off. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 27, 2016 Share Posted January 27, 2016 The useful link Keithl provided earlier indicates that (from April through October) French autogas can be expected to be Grade C type with a propane: butane ‘mix’ of 40%:60% down to 30%:70% resulting in a 0°C temperature threshold for a minimum pressure of 150 kPa. As Peter’s (Chun’s) last refill in France would have involved Grade C ‘summer’ autogas, as has already been concluded it’s the high-butane-content gas that’s now causing the problem. Link to comment Share on other sites More sharing options...
Charles Posted January 27, 2016 Share Posted January 27, 2016 30% propane, 70% butane mix at 150kpi = 21.7psig = 4.4c Therefore would be OK for a good while evaporating down to -17 before the pressure reaches zero. On the other hand 100% butane would be about 6psi at 4.4c (0c = 0psi) so it's much more likely the gas in his lpg tank is 100% butane. Data taken from engineeringtoolbox.com graph PS. My phone won't open the jpg file above. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 27, 2016 Share Posted January 27, 2016 Whatever, but a Combi 6 is a greedy beast and Truma does not advise that propane be used to feed it without good reason. Brian suggests experimenting by having the gas-fuelled cooking equipment, fridge and the Combi’s water-heating running simultaneously and - one might think - that should cause the Combi to go into failure mode. But the reality is that Peter’s Combi’s blown-air heating will run satisfactorily on gas when the gas is not coming from the bottle that has French ’summer’ autogas in it. Having had a long discussion with a Truma(UK) techncian at the last NEC Show, it soon became apparent that there are major differences between how a Combi works and how its Trumatic C-Series ancestor does. So, if Brian’s suggested experiment failed to force Peter’s Combi into failure mode, but the heater becomes sulky as soon as blown-aire heating is selected, I wouldn’t be too surprised. As has been mentioned regularly on this forum, it’s well recognised that French autogas can be problematical when used to fuel motorhome habitation appliances during cold weather, to the extent that bottle/tank heaters are advertised in French leisure-vehicle accessory catalogues. I make every effort to have my user-refillable bottles full of UK 100% propane autogas if I’m visiting France before April. I vividly recall having the Trumatic C-3402 heater in my Herald stop working on a frosty mid-March morning in Normandy and, on opening the gas-locker door, finding that the gas-bottle (with French autogas in it left over from an Autumn trip to France the previous year) has a ring of ice round it showing the level of the liquid gas inside. There might be a problem with Peter’s heater, or with his regulator, or with his gas-bottle’s delivery-valve (which I had happen once), but the K.I.S.S. diagnosis is that it’s the butane-rich French GPL that’s the culprit. Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 28, 2016 Share Posted January 28, 2016 Derek Uzzell - 2016-01-27 6:53 PM.................... Brian suggests experimenting by having the gas-fuelled cooking equipment, fridge and the Combi’s water-heating running simultaneously and - one might think - that should cause the Combi to go into failure mode. But the reality is that Peter’s Combi’s blown-air heating will run satisfactorily on gas when the gas is not coming from the bottle that has French ’summer’ autogas in it. ................................... I missed the bit about the heater running properly on Autovan's cylinder, so yes, I agree. Almost certainly that the low temperature gassing ability of the French autogas mix is inadequate for the demand of the Truma in heating mode, but remains sufficient for lower demand consumers. Forget the hob etc! :-) Link to comment Share on other sites More sharing options...
Tracker Posted January 28, 2016 Share Posted January 28, 2016 It can't be that urgent as the OP has not been back to see the words of perceived wisdom - perhaps when winter starts! Unless he had a look and got confused by all the techno babble when all he wanted was a simple solution? Link to comment Share on other sites More sharing options...
Randonneur Posted January 28, 2016 Share Posted January 28, 2016 Tracker - 2016-01-28 6:57 PM It can't be that urgent as the OP has not been back to see the words of perceived wisdom - perhaps when winter starts! Unless he had a look and got confused by all the techno babble when all he wanted was a simple solution? That's the problem Rich, you ask a simple question and the answers go into the realms of a novel. Although they are correct, simplifying replies helps numpties like us. Link to comment Share on other sites More sharing options...
Tracker Posted January 28, 2016 Share Posted January 28, 2016 Randonneur - 2016-01-28 7:28 PM Tracker - 2016-01-28 6:57 PM It can't be that urgent as the OP has not been back to see the words of perceived wisdom - perhaps when winter starts! Unless he had a look and got confused by all the techno babble when all he wanted was a simple solution? That's the problem Rich, you ask a simple question and the answers go into the realms of a novel. Although they are correct, simplifying replies helps numpties like us. What I really need to know is how did you find out that I too am a numpty! Is it that obvious? Is it because I's old? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 29, 2016 Share Posted January 29, 2016 Tracker - 2016-01-28 7:33 PM Randonneur - 2016-01-28 7:28 PM Tracker - 2016-01-28 6:57 PM It can't be that urgent as the OP has not been back to see the words of perceived wisdom - perhaps when winter starts! Unless he had a look and got confused by all the techno babble when all he wanted was a simple solution? That's the problem Rich, you ask a simple question and the answers go into the realms of a novel. Although they are correct, simplifying replies helps numpties like us. What I really need to know is how did you find out that I too am a numpty! Is it that obvious? Is it because I's old? Simple answers to your questions... 1: Everybody knows. 2: Yes. 3: No, it’s just the way you are. Link to comment Share on other sites More sharing options...
Tracker Posted January 29, 2016 Share Posted January 29, 2016 Thank you Derek for that profound observation and it's so nice to see that your sense of humour implant has at last taken (lol) - always assuming that you were joking? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 29, 2016 Share Posted January 29, 2016 I never joke. Link to comment Share on other sites More sharing options...
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