ReplyAir flow and fan speeds effect temp rise also the older machine could have a dust build up on the coil or blower wheel reducing the air flow and increasing the temp rise
Regular Guest
2 rent houses.
Same size AH (3 ton) and 10kw heat.
One rent house a 1993 Bryant, 70 amp breaker
Other rent house 2011 Goodman, 60 amp breaker
Similar sq ft, 1348 sq ft and 1377 sq ft
Very similar ductwork layout, same amount of vents, similar size vents.
The Bryant house the heat blows 35 degrees warmer (when compared to the return air at grill) air from the vent closest to the plenum.
The goodman house blows at most 27 degrees warmer (when compared to the return air at grill) air from the vent closest to the plenum.
Ok i asked the hvac guy i use (young guy just started his business in last year or so) how is this possible. His reply was he thinks the older bryant unit heater coil gets hotter. Sounds like bs to me, can someone more seasoned in the heat/air business render an opinion?
Professional Member*
Air flow and fan speeds effect temp rise also the older machine could have a dust build up on the coil or blower wheel reducing the air flow and increasing the temp rise
The 2008 NATE TOP TECH!!!!!
God Speed, Jim. We'll miss you - 2-26-23
Can't tell for sure from here.
Could be the newer system isn't charged right. Or it may be moving more air then the older system.
Professional Member*
entirely too little info,
was this with the h/p & aux. heat or h/p only, or aux. heat only???????????
It`s better to be silent and thought the fool; than speak and remove all doubt.
Regular Guest
straight heat, not a hp
Professional Member*
Originally Posted by hvacman14
This
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Regular Guest
ok so it would be totally ignorant to say because one is on a 70 amp breaker and one is on a 60 amp breaker that the 70 amper 10kw heat would run hotter? Thats basically what this guy is saying which didnt sound right to me. Am i right in thinking this way? 10kw heat is 10kw heat in any case, correct?
Professional Member*
correct.
Professional Member*
10 kw is 10 kw no matter how you figure it, but, the temp rise air flow formula will equate to the rated kw, the older unit can run hotter if the air flow is lower than the other system that it is being compared to, and still produce the same kw
Professional Member*
air flow sound like the issue, or maybe a bad heat strip coil. lack of info to tell.
Ride hard on a Harley!!
Professional Member*
on the breaker is it in the electric panel or on the heaters, it could just be what the manufacture requires. you can get the same tonnage condenser and have a different amp draw all depends on what it is spec out to
Ride hard on a Harley!!
Professional Member*
10000watts/220volts = 45.45 amps.
This is what the heater will draw. The breaker size will not change this. The other things drawing amperage in the air handler are the blower motor and the control transformer.
Your young guy should be able to check running amps on both heaters, and I mean heaters only, not the whole unit, and tell if they are drawing full load amps. If one is NOT pulling about 45 amps, part of the heater strips are out.
Simple as that. I hope this helps.
Professional Member*
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.
God Speed, Jim. We'll miss you - 2-26-23
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.
Professional Member*/ARP Committee
Difference in airflow.
"Better tell the sandman to stay away, because we're gonna be workin on this one all night."
"Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."
"Just get it done son."
Dad adjusted
Professional Member*
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!
Professional Member*
Some 10 kw heaters are 9.6 kw some are 10.0 but the main difference is airflow
Professional Member*
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.
Professional Member*
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?
Professional Member*
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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