I have/had a heating problem with a customers 1993 Lunar Staturn...the fire will only raise the outside temperature by about 8degsC. The fire and Fanmaster both work well..so what is the problem?.
BS/EN721/1999 as ammended 2004,(Leisure Accommodation Vehicles Safety Ventilation Requirements), states; minimum low level ventilation for vans in this case with 5 to 10 square metres of floor space is 1500sq mm or in real terms an opening of 100x15mm which is but a fraction of the standard door vents capacity. High level ventilation requires more and in this case it is 10,000sq mm which should be taken care of by the permanent ventilation of one closed rooflight which is of the order of 12000mm square even with the blind shut.
While I fully agree that removing the required amount of ventilation is folly to say the least, it would appear that under older standards...excessive low level ventilation was installed providing too rapid an air change.
The Lunar in addition to the door vent has two, (ventilation air not gas drop holes), floor vents one front and one rear which when prevented from directly entering the living space allowed the temperature in the van to rise quickly, reaching for the first time an acceptable level...and under the current BS/EN721 standard is now considered perfectly safe...the remaining ventilation being well in access of the minimum requirement. It is also worth pointing out that a minimum is just that and if this became blocked would cause a problem so an adequate alternate air supply must be catered for.
For smaller vans up to 5msq the minimum figures are 7500 and 1000, and larger caravans/motorhomes, 10 to 15msq floor area = 12500 high and 2000 low. 15 to 20msq = 15000 and 3000 respectively.