1. Originally Posted by TwincamDave
10 KW is NOT 10 KW as a blanket statment. It is dependent on your line voltage to the heat strips. If one system has 248 v a/c and the other has 218v a/c they will put out different amounts of heat if all else is equal. Sounds more like a return air leak(pulling in cold attic air causing it to drop the temp coming out a vent) if the voltages are the same.
I believe the 10 KW is 10KW statement was made in reference to it mattering that the old unit had a 70 amp breaker and the new unit has a 60 amp breaker.

And since both units being talked about, were in the same house, the voltage is the same.

2. Difference in airflow.

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Originally Posted by TwincamDave
10 KW is NOT 10 KW as a blanket statment. It is dependent on your line voltage to the heat strips. If one system has 248 v a/c and the other has 218v a/c they will put out different amounts of heat if all else is equal. Sounds more like a return air leak(pulling in cold attic air causing it to drop the temp coming out a vent) if the voltages are the same.
Huh?
Sorry Dave 10KW IS 10 KW no matter what. P=I*E E=I*R Basic Ohm's Law. Does amperage change as voltage does? Of course..., look at the formula.
Can two 10KW heaters put out different temperatures? OF course! But they still draw 10KW. Put 10KW through a heater wire and 10KW through a wet string and see which one lets off the most heat and you will see the difference.
10,000 watts, no matter what numbers you use for voltage and amperage, as long as they multiply together and equal 10,000, is still 10 KW!

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Some 10 kw heaters are 9.6 kw some are 10.0 but the main difference is airflow

5. Originally Posted by blabath
Huh?
Sorry Dave 10KW IS 10 KW no matter what. P=I*E E=I*R Basic Ohm's Law. Does amperage change as voltage does? Of course..., look at the formula.
Can two 10KW heaters put out different temperatures? OF course! But they still draw 10KW. Put 10KW through a heater wire and 10KW through a wet string and see which one lets off the most heat and you will see the difference.
10,000 watts, no matter what numbers you use for voltage and amperage, as long as they multiply together and equal 10,000, is still 10 KW!
Sorry old man but if you take a 10KW heater at 240v. and then put 208v, to the same heater you will get approx 75% of the heat you did at 240v.
41.6 amps with 240volts will produces 34,095 BTU of heat and the same heater with 208volt will draw 36.2amps and produce 25,713 BTUs of heat. You can't use Ohms law to calculate amps into btu's. but you can calculate amps x volts to get your wattage after that you have to multiply your watts by 3.415 to get your btu's. And the last time I checked 34,000 was hotter than 25,000.

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Really stupid question......Does it still heat the house OK? Or is one unit not heating it's area? Why the reason for the outlet temp. question?

7. It depends on what the loads call for BTU wise. If it says you need 32,000 BTU's and you only get 25,000 BTU's then no. You really need to know what your voltage is and the heater rating. Again as I said before it's probly a duct leak on the return side pulling in cool attic air and dilluting the heat being generated.

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Originally Posted by TwincamDave
Sorry old man but if you take a 10KW heater at 240v. and then put 208v, to the same heater you will get approx 75% of the heat you did at 240v.
41.6 amps with 240volts will produces 34,095 BTU of heat and the same heater with 208volt will draw 36.2amps and produce 25,713 BTUs of heat. You can't use Ohms law to calculate amps into btu's. but you can calculate amps x volts to get your wattage after that you have to multiply your watts by 3.415 to get your btu's. And the last time I checked 34,000 was hotter than 25,000.
I second this.

Originally Posted by TwincamDave
It depends on what the loads call for BTU wise. If it says you need 32,000 BTU's and you only get 25,000 BTU's then no. You really need to know what your voltage is and the heater rating. Again as I said before it's probly a duct leak on the return side pulling in cool attic air and dilluting the heat being generated.
This would be a good start. Also checking the blower wheels to see if they are not dirty. One other thing would be considering the difference in years there might be a smaller ton blower drive in one vs. the other... I would need model numbers from both units to tell.

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