I just went to put caravan fire on as normal but after a couple of minutes it went out. Then a massive bang and the flume on top of the caravan flu off when it is I don't then a second bang so I have left the caravan. I am indoors now not sure what to do cos I don't want to mess about with gas. To tell you the truth I am a bit shocked and shook up. My son was in his bedroom listening to his radio with earphones on and can running out to me saying what was that bang he heard it above his headphones?
-
We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.
Gas bang
- Thread starter Yellows11
- Start date
Firstly I support the previous comments, as gas safety is paramount.
However if this has recently occurred, its possibly down to the temperature and type of gas being used.
With recent low temperatures, Butane gas does not perform well at ambient temperatures below 5C. It has trouble vaporising inside the gas cylinder causing low pressure or even stopping the flow entirely. High consumption items like the gas fire will further reduce the cylinders temperature that can give rise to unstable gas flows. This might have caused the issue you have experienced.
You should swap to Propane gas for use in near zero C ambient temperatures.
However if this has recently occurred, its possibly down to the temperature and type of gas being used.
With recent low temperatures, Butane gas does not perform well at ambient temperatures below 5C. It has trouble vaporising inside the gas cylinder causing low pressure or even stopping the flow entirely. High consumption items like the gas fire will further reduce the cylinders temperature that can give rise to unstable gas flows. This might have caused the issue you have experienced.
You should swap to Propane gas for use in near zero C ambient temperatures.
I thought it was a typo error 😎
@Yellows11 look on the mobile caravan engineers website (www.mobilecaravenengineers.co.uk and tick 'find an engineer' . I was sorting out a clients leaking tap when an adjacent caravan did the same , the top of the flue landed about 20 foot away, one very shocked caravaner .The problem is the auto ignitor sometimes fails to light the gas , but the gas continues to flow, mixing with air and fills the flue, then the igniter fires it resulting in a large bang, fortunately because both the inlet and flue are not sealed it seldom damages the system. On manual ignitors , pressing the gas valve and pressing that horrible piezo ignitor where you only get one chance, unless you continually press it, if after 20 seconds it doesn't light , let go and leave it a minute for the gas to clear out of the flue
As an add on, if the caravan is parked near a wall, and the wind is blowing, it can stop the flue from operating correctly causing the gas to build up, ignition of the gas, causing a rapid ignition, which then blows out the flame, fresh gas mixes again and the cycle is repeated.
A friend of mine had this happen on his Sterling Eccles Jewel.
A friend of mine had this happen on his Sterling Eccles Jewel.
Here is another link to approved caravan gas engineers. See https://www.approvedworkshops.co.uk/find-approved-workshop
Hello Yellows, whilst the make of caravan is not especially relevant, make model and age of the heater is important. I suspect the forum members have been assuming you some type of Truma or Carver heater which were very similar products. However if it is a Carver model, that makes it at least 24years old, and whilst many will still function quite well, there are reasons why they should be checked(not necessarily taken apart) annually as they age. As you tell us the flue cap was blown off, that should just screw back in place. It was designed to be able to flip out should you encounter a low branch when towing.
As for explosive ignition, you tell us your using Propane which is the better gas in near or below freezing temperatures.
Assuming the heater is in good functional condition, generally once these heaters are lit, the only things that will stop them is exceptional air flow issues around the caravan. If a caravan is parked next to a building, the corners of the building can affect wind direction and strength. If these compromise the flow around flue, excessive pressure may prevent the flue gassed from leaving the flue pipe. This causes the flue gassed to build up in the pipe and eventually baffle the flame on the burner causing it to usually turn candle yellow, if this is sustained, the flame will be starved of air and it will go out.
The heaters flame failure device usually takes between 10 and 30 seconds to cool down enough to close the gas valve, so during this period gas is still being injected and a small excess of combustible mixture can build up below the burner bar. If the baffling is relieved and the natural convection of the flue restblished before the flame failure device (FFD) closes the gas valve, the fresh gas and air mixture will move up into the burner area. In your case you must have a battery operated reigniter. This independently monitors for the presence of a flame using the electrical conductivity of a flame. It will automatically turn on a series of sparks, when the flame is lost. As the excess mass of premixed gas and air reaches the spark probe, it will all reigniter vigorously, and that is the most likely cause of your bang.
If the heater is very old, some internal parts can corroded. I have seen burner assemblies which have lost parts of thier tops which prevents a stable flame from establishing.
So a proper heater service(which needs an internal inspection) I think might be called for.
To prevent or reduce wind issues try and move the caravan away from the building. If it happens on site, sometimes turning the caravans direction a little can make a big difference. In exceptional circumstances you get extension flue pipes that screw in to raise the top of the flue.
As for explosive ignition, you tell us your using Propane which is the better gas in near or below freezing temperatures.
Assuming the heater is in good functional condition, generally once these heaters are lit, the only things that will stop them is exceptional air flow issues around the caravan. If a caravan is parked next to a building, the corners of the building can affect wind direction and strength. If these compromise the flow around flue, excessive pressure may prevent the flue gassed from leaving the flue pipe. This causes the flue gassed to build up in the pipe and eventually baffle the flame on the burner causing it to usually turn candle yellow, if this is sustained, the flame will be starved of air and it will go out.
The heaters flame failure device usually takes between 10 and 30 seconds to cool down enough to close the gas valve, so during this period gas is still being injected and a small excess of combustible mixture can build up below the burner bar. If the baffling is relieved and the natural convection of the flue restblished before the flame failure device (FFD) closes the gas valve, the fresh gas and air mixture will move up into the burner area. In your case you must have a battery operated reigniter. This independently monitors for the presence of a flame using the electrical conductivity of a flame. It will automatically turn on a series of sparks, when the flame is lost. As the excess mass of premixed gas and air reaches the spark probe, it will all reigniter vigorously, and that is the most likely cause of your bang.
If the heater is very old, some internal parts can corroded. I have seen burner assemblies which have lost parts of thier tops which prevents a stable flame from establishing.
So a proper heater service(which needs an internal inspection) I think might be called for.
To prevent or reduce wind issues try and move the caravan away from the building. If it happens on site, sometimes turning the caravans direction a little can make a big difference. In exceptional circumstances you get extension flue pipes that screw in to raise the top of the flue.
Oh yes that can make a difference.
When a gas cylinder is full it contains both gas vapour and liquified gas held under pressure. The liquid will always drop to the lowest point and the vapour will be at the top. The types of bottle used for caravans must be "Vapour Take Off cylinders these have the valve at the top of the cylinder.
The cylinder actually works by using the heat available in the cylinder to boil the liquified gas which produces vapour, as the vapour collects it pressurises the cylinder until the pressure of the vapour matches the boiling pressure of the liquefied content, and it suppresses the boiling. The whole thing dependant on the ambient air temperature around the cylinder. If ambient temperature goes up so will the pressure inside the cylinder, and vice versa.
But also as you use gas, the fact the liquified gas tries to boil off more vapour, uses some heat energy of the cylinder, and it actually cools the cylinder down a bit. That is why you will often find condensation on the outside of working gas cylinder, and in extreme cases frost can form (Ever seen roofers with frosted bottles? incidentally they use Propane)
The common gasses for caravanning are Butane which is good for ambient temperatures above 5C but Propane will continue to work down as low as -40C
Because the cylinder need free access to the ambient air temp to work, never put any sort of thermal insulation around the cylinders.
But the reason I said the fact your Propane gas cylinder was near empty might affect your experience, is that once all the liquified gas has been boiled off there is no way to replenish the gas pressure, so as you use it , the pressure will diminish far more quickly. Not only will the pressure diminish the cylinder but as the gas is released it continues to use the heat energy from the atmosphere to drive the expansion so it can cool, and that can limit gas delivery, until the cylinder warms up a bit more.
This might have occured with your caravan heater.
Somewhere I read about a regulator freezing up and allowing an increase in pressure, apparently the bottle was outside the caravan
I reported that on another forum , an illegal 37 kg free standing bottle with a bottle top regulator and long LP hose into gas locker (also illegal ) . The regulator filled up with water which froze fully open in a cold snap, the resulting flames from the cooker were 1 metre high before they jumped off the burners mantle and went out , fortunately before doing any damage or causing injury.
Re profJohnL comments , most of his comments are valid however IMO his physics and chemistry are a bit off . the pressure in the bottle (propane ) near freezing is far greater ( about 1 Bar at 2 Deg C) than the the outlet pressure from the regulator (0.03 Bar )and the gas flow rate of a Truma S3002 space heater othe equivalent Carver or whale heaters is a lot lower than even a cold 6kg bottle of propane can deliver together with the fact that if the flame slowly dies as its starved of gas then the gas valve will close and not open again until manually activated. On auto ignite systems the ignitor comes on as soon as it detects no flame and will shut the gas valve to let the gas dissipate before trying again, after three goes it will go into 'Lockout' and will The biggest user of gas is the oven , with all three/four rings on as well as the grill and oven. I get see a lot caravans and motorhomes and most (>90%) are propane , in the last year I have only come across 1 motorhome with butane and even in the recent cold snap the tiny Camping gaz bottle (1.8kg) which was nearly empty managed to run the cooker at full tilt , the space heater and the water heater whilst maintaining a respectable 27 mBar out of the regulator.
Prof and Ian
Many thanks for your detailed technical notes. It all helps for us mere mortals to get a better understanding.
One question from me.
Apologies if it is a stupid question.
The gas regulator reduces the pressure from the tank to a usable level. When the pressure drops below the reducers maximum reduction I believe it remains open to “zero”.
Do the fitted gas appliances in our caravans also have gas valves that switch off if the pressure is too low?
I think I know the answer in that the hob starts to emit an odour when the propane cylinder is “empty “ so I guess no?
I have never experienced the “ explosion” described.Have I missed out 😉?
BTW , as you know I do take gas usage very seriously but think of newer people on here wondering😎
Many thanks for your detailed technical notes. It all helps for us mere mortals to get a better understanding.
One question from me.
Apologies if it is a stupid question.
The gas regulator reduces the pressure from the tank to a usable level. When the pressure drops below the reducers maximum reduction I believe it remains open to “zero”.
Do the fitted gas appliances in our caravans also have gas valves that switch off if the pressure is too low?
I think I know the answer in that the hob starts to emit an odour when the propane cylinder is “empty “ so I guess no?
I have never experienced the “ explosion” described.Have I missed out 😉?
BTW , as you know I do take gas usage very seriously but think of newer people on here wondering😎
Gas cookers have flame failure detectors ( thermocouples) which if the flame dies closes the respective valve , similar for each gas device ( it's part of the requirements for gas appliances) as the pressure drops the flame will slowly reduce and not touch the thermocouple which cools and shuts off the gas valve. most human noses can detect small amounts of the gas ( it actually has a 'stench' chemical to make it stand out) well below the LEL (Lower Explosion Limit). and No you haven't missed out :- the 'bang' is very very loud and quite unnerving. On my own Truma S3002 I have fitted an electronic spark generator to ensure the pilot lights first time, every time
What you say is correct provided there is liquified gas still present in the cylinder. The scenario I was describing and have witnessed in testing which was part of my bread and butter employment in years gone by was when the cylinder was literally running on fumes, no liquified gas remaining. the pressure differential was hovering around the regulators control point and dependant on take off rate could drop the pressure in the cylinder to nigh on atmospheric, until the cylinder was warmed by sunshine or other heat source. We were testing appliance for safety when gas cylinders lose their liquified content. It would more noticeable with heavier gas demand products, but I used an example to show how the OP's might have reacted.
Ironically if the OP had just a piezo manual ignitor, under the circumstances he described he would not have had the reignition to cause the bang.
It was certainly the case when starting the Truma or Carver space heaters which only had manual piezo ignition, inexperienced users might not push the spark button repeatedly soon enough or fast enough, and they could get a small delayed ignition explosion, generally much less vigorous than the OP's. A well versed technician could deliberately produce larger delayed ignition events to the dismay of nearby people.
TRENDING THREADS
-
What clever modifications or upgrades have you made to your caravan?
- Started by Malky
- Replies: 60
-
-
-
Mandatory eye tests for drivers over 70 being proposed by HMG. Good or bad?- Started by Dustydog
- Replies: 230
-
-
-
Caravan Battery we think is dead even though we have solar- Started by Saxo Appeal
- Replies: 172
