DIY Doctor

Warm Air Units

Postby Ralf 2007 » Wed Oct 24, 2007 11:05 am


Just wondered if any one could help me becasue i cannot seem to find information regarding warm air units and their ventilation requirements.

I am currently trying to write up a portfolio for a gas course i am studying but i am not sure whether warm air units require air for ventilation when installed within a compartment (i.e. cooling vents to allow heat generated by the appliance to dissipate).

Also am i correct in thinking that warm air units obtain their combustion air via the flue, or are there some types that gain their combustuion air from the room they are situated in.

Any info would be appreciated.
Ralf 2007
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Simply Build It

Postby htg engineer » Fri Oct 26, 2007 11:02 pm

Warm air units do require ventilation, working out the ventilation is very similar in working out the ventilation for any open flued appliance, apart from you don't minus the 7(cm2) adventitious ventilation.

So - for a appliance taking the air from an internal space/room, you need the maximum rated heat input then it's:

heat inputx10 for the high vent
and heat input x20 for the low vent.

Then the external door or wall you take the maximum rated heat input -7 adventitious ventilation x5 (like any open flued appliance)

For ventilation for a compartment direct to outside it's maximum rated heat input x5 for top vent and x 10 for low vent.

Hope this helps
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