Raywood said:
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For winter users there have been cases of snow building up and blocking the airflow under the caravan. This then prevents the heater getting air from there and then you can get a reverse flow down the flue. Not sure if newer models have a valve to prevent this but someone out there may know but it is something to be aware of.
The cooker only produces co at dangerous levels if the adjustment is wrong but it still produces CO2 which is still dangerous, but less so, so ventilation is essential.
Hello Ray,
I know your post was well intended but sadly it does contain some factual errors in the bottom part I have quoted.
Reverse flow through the exhaust - sorry but no. The diameter of the flue pipes fitted to current caravan heaters would not allow the the bi laminar flow of fresh air and exhaust gasses for you scenario to work. If there is insufficient air to the burner from the underfloor air intake, then the flame will be starved and will tend to burn very yellow. The lack of free air will also prevent the exhaust gasses to rise through the flue, which will effectively baffle the flame, and it will be extinguished. Provided the heat is installed correctly and is not damaged The resultant exhaust gasses will still be buoyant and will eventually evacuate the flue through the roof.
The older and now no longer used Truma /Carver SB1800 series were significantly different. As a result of the models exemplary thermal efficiency, when operating there the heat exchanger would cool the exhaust gasses to the point where their buoyancy was overcome by the thermal drive from the flame and can be pushed downwards through the underfloor exhaust. Now if the under the floor is fully blocked by snow, then the exhaust gasses would spread under the floor of the caravan and could potentially enter the caravan through the low level fixed ventilation. At no time would the gas flow through the heater be reversed.
With regards to the CO produced by the cooker hob. LPG is a fantastic fuel, it is capable of being burned very cleanly but even the best practical burners are not perfect and they will produce some CO but it will be very small. Anything that compromises the flame will cause the quantity of CO produced to rise. But we need to go back to combustion basics which requires a fuel (LPG) Oxygen (From the air) and a source of ignition or heat. If you remove enough of any of these three basics combustion cannot occur. Fire fighters will tell you if you have a fire you need to remove one of the three to stop combustion.
Now back to the cooker hob, if you have a large flame and you put a cold metal pan over it, if any part of the flame impinges on the pan, the metal will quench the flame and stop the chemical combustion for that portion of the flame resulting with the production of some addition excess CO.
A sure sign of poor combustion is evidence of sooting. You can be certain that if soot is being produced you will have highly elevated levels of CO.
So (sorry 00buzz) the moral of this is keep the size of hob flame small enough so it doesn't imping on the pan, besides which any flames licking up the sides of a pan is essentially wasted heat.