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mjbxx 03-15-2009 03:52 PM

Temperature Rise
 
Goodman 5 Ton Heat Pump with Variable Speed Airhandler

Outdoor Temp = 46
Supply Air Temp = 103
Return Air Temp = 70
-----------------------
Temperature Rise = 33

Is this temperature rise to high or ok in relation to CFM setting? The temperatures were taken with the heat strips off and thermostat set to 72. The airhandler is currently set at 1530 CFM.

beenthere 03-15-2009 03:59 PM

Too high period.

Indicates too low of an air flow for the unit.

mjbxx 03-15-2009 04:15 PM

Got it. Should I just increase the CFM setting to correct? And what should the temperature rise be?

Plumber101 03-15-2009 04:21 PM

You may have a setting of 1680 but is this your actual CFM

To calculate CFM follow this

CFM = (Volts X Amps X 3.413) divided by ( Temp rise X 1.08)


Your system may be under charged. I would have it checked. Keep in mind the only true ways to check a charge in a heat pump are

1. Checking super heat and sum cooling in a/c mode on a warm/hot day
2. Weighing the freon in on a cold day.

It is best to check charge in the summer just before going into winter.

Also your second stage heat can be set up for stages to come on in the fall/winter. As the tempout side drop the effenicy of the heat pump drops as well.

On the days where it is cold it is not as simple as adjusting blower speed to get more heat. There are other factors as duct work as well.

Is this a new install, replacement or an appliance that you have had for a while.

What made you check temp rise?

beenthere 03-15-2009 04:24 PM

27

You shouldn't be 33 until 55 or better outside.

You should have 1850 or better CFM.

Goodman generally want 400 CFM per ton in heating mode.

mjbxx 03-15-2009 04:33 PM

If what you are saying is true, then why does Goodman allow for a 15% reduction of the trim adjust setting which lowers CFM to 1530 from 1800?

beenthere 03-15-2009 04:56 PM

For comfort.

It lowers the efficiency, but gets you a warmer discharge temp.

They, like most manufacturers, don't tell you that part.

They also don't tell you that it increases the amount of time it takes to defrost the coil.

mjbxx 03-15-2009 10:05 PM

OK. Should I just place the system back to 1800 CFM? I have to say that since I lowered the CFM on the system, the house has been much more comfortable and in fact, the system does not seem to run as long as the previous setting. I suppose if our next electric bill rises, I'll know it is not as efficient.

beenthere 03-15-2009 10:21 PM

Set it to where it makes you comfortable.

hvaclover 03-15-2009 10:40 PM

Quote:

Originally Posted by beenthere (Post 244963)
For comfort.

It lowers the efficiency, but gets you a warmer discharge temp.

They, like most manufacturers, don't tell you that part.

They also don't tell you that it increases the amount of time it takes to defrost the coil.

I didn't know that:eek:

beenthere 03-16-2009 04:25 AM

Your actually removing less heat from the discharge gas.

With the lower indoor air flow, it doesn't supply as much heat to the outdoor coil to thaw it.


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