Blow-back in Truma Combi 4E boiler

[MarkV]

I would welcome your comments on the problems I am having with my new Truma Combi 4E dual fuel boiler. It was fitted into our Citroen Relay van as part of a conversion by a small firm in Somerset. In March last year we collected the van and in April experienced 2 explosions in the exhaust so violent that the exhaust cowl disintegrated. We returned from Europe to the conversion company and they told us that we had filled our underlung "Gasit" tank with contaminated gas. They fitted a filter and we set off again and at the Euro-tunnel the same happened and we lost another cowl. We returned to the converters and they exchanged the boiler with a replacement. We used the van for 4 months in Europe without further problems but did not really use the heating.
This December we filled with gas in the UK and set off for France to ski we have had 4 further explosions and lost another cowl. We have noticed also that when we light the gas rings there is an initial flair of flames about 30 cm high before it settles down. I have been in contact with Truma and the,to believe the fault is with the Gasit regulator.
I plan to replace the regulator with a Truma secure motion regulator so I can use the boiler when driving.
Has anyone any similar experiences or advice to give me about what I need to get checked?

 

[MarkV]

The regulator is a "Carvagna" rated at 30 mbar. We have a "Gasit" underslung tank so I have to crawl under the vehicle to see the regulator and it is screwed to the underside of the van. Not sure what the correct position should be but it is alongside the tank.

 

[Siimplyloco]

The regulator is a "Carvagna" rated at 30 mbar. We have a "Gasit" underslung tank so I have to crawl under the vehicle to see the regulator and it is screwed to the underside of the van. Not sure what the correct position should be but it is alongside the tank.

I'm probably showing my ignorance here but isn't the regulator supposed to be above the tank exit? Liquefied gas in the pipes?
John

 

[MarkV]

Not sure about the correct fitting for Gasfit as there is not much useful information on their website but the Autogas website shows an underslung tank very similar to mine with the regulator in the same position alongside so I assume this is correct.

 

[QFour]

Perhaps you have a regulator that is leaking. This would allow gas into the pipes after the regulator at high pressure and the gas could turn back to liquid. Open a gas tap and unregulated gas for a couple of seconds. Would certainly look at changing the regulator first before doing anything else. Its not going to be a pipe issue. You could get the system checked with one of the glass tube thingys the gas guys use. They connect after the valve so may show a leak.

 

[Deleted member 3011]

Two possibilities - first that the propane is being overfilled to the point where liquid propane is "sloshing"into the outlet pipe. German firm who installed out tank said maximum fill for horizontal tanks had to be less than 80% to avoid a problem.

Then if the regulator wasn't higher than the tank, or if any of the pipework from the tank to the regulator is down hill, then liquid would be at the regulator and that would pass through the regulator and give a surge in gas pressure that produces the 30cm high flame.

Either way, it is the gas delivery system that is at fault.

 

[wineciccio]

I think so too, it does sound as though the heater fills up with some escaped gas, when lit up it explodes, I think you have been lucky so far that nothing serious has happened.:cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1::cool1:

 

[Channa]

Two possibilities - first that the propane is being overfilled to the point where liquid propane is "sloshing"into the outlet pipe. German firm who installed out tank said maximum fill for horizontal tanks had to be less than 80% to avoid a problem.

Then if the regulator wasn't higher than the tank, or if any of the pipework from the tank to the regulator is down hill, then liquid would be at the regulator and that would pass through the regulator and give a surge in gas pressure that produces the 30cm high flame.

Either way, it is the gas delivery system that is at fault.

I couldn't have put it better myself. The only other possibility is on a new system the regulator is letting by therefore allowing an increase in pressure in the pipework, because the system is new there is no seepage one gets on worn appliances. The fact the gas is exapanding in the pipes increasing the mbars would explain the 12 inch flame ....definitely a delivery problem.

Channa

 

[Channa]

Let it never be said we can't agree David, Contaminated gas ? ...be interesting an explanation on that one Tony Lee akes 2 valid points the third is the regulator is faulty and "letting by" i.e letting gas into the system when it should close because there is sufficient charge there already. The ignition i would expect a flame surf on the hob then it to settle as the regulator operates as it should..

Channa

 

[MarkV]

I have tried to upload a picture from the Gasit website to show the position of the regulator relative to the tank but I could not. If you look at Welcome to the GAS IT Webshop - Motorhome, Caravan, Catering, Farrier & Road Repair Industry Gas Equipment Manufacturer, Designers, Suppliers & Training Company - GAS IT Leisure Gas - Catering, Motorhome, Caravan, Farrier and Road Repair Refillable G you can see that the tank is an elongated cylinder on it's side, the exit pipe is halfway up the side of cylinder and the valve is at that level. I looked at Autogas Leisure 2000 Limited - Refillable Gas Solutions for Motorhomes and they have the same arrangements so I assume it is OK not to have the regulator on the top of the cylinder.
With regard to overfilling the tank I was told to fill it at the station until it stopped filling so not sure how I prevent overfilling of the tank.

 

[MarkV]

Yes I have a picture of the regulator but cannot paste on here. There is a clearer picture on the Autogas website which shows what looks like a regulator. assumed the pipe shown in the picture you have posted is the fill pipe.

 

[Obanboy666]

Spend some money and take it to a local expert who knows what he is doing. I personnelly wouldn't fanny about with it. All well and good asking and getting advise on the forum but I wouldn't take a chance with the gas system.
I'm surprised it hasn't damaged your boiler or worse still blown you and your van up !

 

[MarkV]

It has been back to a so called expert with a gas fitters certificate twice already. I am happy to spend money on the problem I just prefer to be informed beforehand so that I can ask the right questions. I assume from some of the responses already that the expert's idea that I used contaminated gas is unlikely to be correct.
The great thing about this forum is that there are usually people who have faced the same problem before.

 

[MarkV]

[No message]

 

[Channa]

I certainly would NEVER mount a regulator upside down. It doesnt make sense, you are asking a diaphragm to to work against gravity on what is afterall a very very low pressure we are talikng 30 mbar.(1 bar is 15.6 lbs per square inch (ish) we are talking Regulators are simply not designed to work that way.The pressure equates give or take to 3/4 lb psi to put that in context 35 lbs per square inch in a typical car tyre ?

Furthermore a lot of regulators have a pin hole to evacuate moisture, mounted this way it collects !!! ( slightly OT but valid observation)

A regulator Ideally should be mounted a touch higher than the bottle or tank to eliminate "sloshing " Tony Lee referred too, also if on bottles should you get a " dirty" one you dont drag the havy ends ....verdict a poorly thought out installation.

Channa

 

[Deadsfo]

the Autogas 2000 system has the regulator halfway up the cylinder,it also specifies that the tank is set at an angle relative to the regulator box (the silverbox on the side) ,I cant remember what the angle is something like 110degs from the horizontal whether or not that has something to do with it i dont know

 

[oldpolicehouse]

Hello Mark

I have the same underslung tank. Stako sold by Autogas and Gasit. Here are my thoughts.

I have also had a Gaslow system and from a user point of view they function the same.
Bottles have to be upright to ensure only vapour comes out. Clearly on a horizontal tank the valve box will on occassions be well below the liquid level. The tank has a pipe / valve arrangement inside to ensure only gas vapour comes out. The same as Gaslow bottles a tank only fills to 80%. In my opinion apart from keeping the regulater out of the weather it should not matter where its located. If you look on www.autogas.co.uk/gallery you will note on 4 of the photos you can clearly see the regulater is connected directly on to the outlet valve. The same as mine. You will also notice there is no sign of filter. I rang them up to check this and there technical guy said they never fit one so I think the contaminated gas thing is a red herring. You may want to check your tank has been installed at the right angle 105 deg. This is important so the vapour outlet is at the top. You can check this with an inclinometer (about £5 on ebay) Looking at the gallery again you will see in all cases the tank is rotated so the valve box is nearly touching the mounting frame.
The most likely cause of your problem is a faulty regulater.
Finaly both Autogas and Gasit have very helful tech guys. I've noticed in the past that Autogas do lots of remedial work on badly installed units-usually tanks dangerously just suspended on straps.
Hope this helps its clearly something you need to get sorted.

Blue skies