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BlueBSH 03-05-2012 09:46 PM

blower speed on heat call
 
On a heat call, is it better to have a lower CFM or a higher one? factory default on my furnace is the "medium" speed for heat and high cfm for cool calls.. the dealer put it on high speed for heat and cool, same they did with our old furnace... I always thought you wanted it lower speed on a heat call? is this good or so so pratice? seeing the factory suggest medium speed

Plumber101 03-05-2012 09:48 PM

It comes down to what temp rise is.

To little air flow can cause an overheating problem

To much air flow doesn't transfer heat.

ben's plumbing 03-05-2012 09:52 PM

yes you must have the proper temp rise across heat exchanger for proper and safe operation......:yes: so to answer you question..its better to have the proper temp rise based on the needed cfm to operate your furnace in a safe manner

BlueBSH 03-05-2012 09:56 PM

yeah, well this dealer has the idea in their head faster is better.. they don't seem to care about checking rise and cfm / velocity... so im stuck making sure this is all right myself ugh... guess I will have to do the rise check myself and see what the specs are

ben's plumbing 03-05-2012 10:52 PM

Quote:

Originally Posted by BlueBSH (Post 871514)
yeah, well this dealer has the idea in their head faster is better.. they don't seem to care about checking rise and cfm / velocity... so im stuck making sure this is all right myself ugh... guess I will have to do the rise check myself and see what the specs are

measure tempeture in plemun hot air....measure tempeture in return air..subtract cold air from hot air....temp /rise..look at tag on furnace it will tell you what temp rise should be...:yes:

Marty S. 03-06-2012 07:19 AM

Blue,in most cases a higher speed is better. It makes the flue gasses cooler which increases the eff. slightly on your 90%+ furnace by condensing more moisture out of the gasses. Each pound of additional water condensed adds over 1000 BTU to the output with no added fuel. It also makes the exterior of the heat exchanger cooler which transfers heat from the inside of the exchanger faster using the same amount of fuel, equating to another increase in efficiency.


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