Temp rise and CFM setting....

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Old 02-09-10, 05:56 AM
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Temp rise and CFM setting....

The question applies to an Amana AMV8 80% NG furnace. I think the nameplate rating says 55C for the temp rise.

The lowest CFM setting has a temp rise of 55C. Is this a safe setting or is it pushing it too far to risk? I'd think the nameplate value is a conservative value and it would be fine but hopefully an expert can clarify for me.

Thanks.
 
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Old 02-09-10, 06:19 AM
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Every spec that I've seen always cites a range of temps.

It's kind of hard to hit a number 'dead nuts', considering the difference in CFMs from one setting to another.

Delta
 
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Old 02-09-10, 01:32 PM
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Well, the nameplate inside the cover says 55C. The specbook says 25-55. The sticker inside lists the temp rise at each CFM setting (12 different settings) and the lowest CFM/highest temp rise is 55C.

Is this a safe setting?
 
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Old 02-10-10, 01:33 PM
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Anything you try to do without knowing the pressure drop through the duct system is a flat out guess. You need to measure static pressure in three places just to get the information you need to calculate true airflow. Using just a thermometer, you could adjust the blower to keep the temp rise below the mfg. spec. but you won't learn much from that except that you won't overheat the heat exchanger.

Ken
 
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