Discuss Condenser Name Plate Rates And Actual Loads. SEER Ratings - HVAC - DIY Chatroom Home Improvement Forum


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Old 08-27-2010, 05:38 PM   #1
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Discuss condenser name plate rates and actual loads. SEER ratings


I am installing a used condenser. I am only somewhat familiar with the RLA estimations and am trying to not only determine actual current draw, but also the SEER rating which by my calcs, is ridiculously low....

My condenser is a 2.5T tempstar with an RLA of 13.8A plus the fan at 1.0 FLA. I have plenty of electric experience and realize this is probably peak sustained load but I am trying to get a ballpark of actual draw at 240V. When using these number against the unit which is rated at 8500 watts of cooling, I am getting a whapping SEER of 9.0!!! I sure hope that is not right...

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Old 08-27-2010, 07:10 PM   #2
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Discuss condenser name plate rates and actual loads. SEER ratings


How old is the condenser?

It might only be an 8, or it could be a 10.

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Old 08-27-2010, 07:36 PM   #3
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Discuss condenser name plate rates and actual loads. SEER ratings


Unit was built in 91 and has been in indoor storage for 5 yrs. All the numbers are pointing at around a 9 SEER unit. That is just embarrassing.... I thought most of these were at least 12....
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Old 08-27-2010, 07:41 PM   #4
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Discuss condenser name plate rates and actual loads. SEER ratings


Nope. 12 SEER was a very high efficiency unit in 91.

10 SEER was the standard in 91 up to the end of 95.
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Old 08-27-2010, 07:47 PM   #5
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Discuss condenser name plate rates and actual loads. SEER ratings


Let me ask you something since you obviously are experienced. If you have taken any time to study amp draw over time on a coil, do these take much time to drop down to load amperage? Usually motor starts will pull 8-10x load at inrush but I was wondering about that fan. I think that thing only needs one more amp at full load so that just leaves the compressor. As long as it can drop down in under 5 sec, it should not be a problem to run this system on a 20A circuit. I like to protect stuff a little tighter than recommended.
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Old 08-27-2010, 07:54 PM   #6
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Discuss condenser name plate rates and actual loads. SEER ratings


Using the smallest breaker allowed. Often ends up causing more nuisance/needless no cooling calls then anything else.

How long a condenser takes to drop down to its running amp draw will depend on the outdoor temp and indoor temp at start up.

Its best to use the higher amp draw rating, and wire size. Amp draw drops quicker, and lower then using the smallest wire and breaker.
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Old 08-27-2010, 08:06 PM   #7
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Discuss condenser name plate rates and actual loads. SEER ratings


would you say more than 10sec if a 100F day? Load current really should not be over 14A and I can carry 16A all day/every day with peaks of a minute at 20A, etc.

I realize that is pushing it but I am an electrician and like to dial things in close. I do not have a long run so wire resistance will not be a concern to run a 20A circuit but I certainly hear you... Good advice I think..
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Old 08-27-2010, 08:21 PM   #8
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Discuss condenser name plate rates and actual loads. SEER ratings


Some units take over 15 minutes to stabilize.

I've seen them have amp draws that fluctuate from below to above RLA for 10 minutes.

12 gauge wire should NEVER be used on a 2.5 ton.

PS: The breaker does NOT protect the condenser.
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Old 08-27-2010, 08:35 PM   #9
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Discuss condenser name plate rates and actual loads. SEER ratings


Unit WILL be fused appropriately. I did not realize they could pull such a large draw for 10 min. That just does not seem right but I will heed your warning on that and just run the 30A service.
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Old 08-27-2010, 08:59 PM   #10
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Discuss condenser name plate rates and actual loads. SEER ratings


Picture a conveyor with a loose belt. What happens to the amp draw as the load bounces back and for as the belt grabs and then slips. Until the entire conveyor load is stabilized(in steady movement).

Thats what happens to an A/C system at times. The refrigerant surges through the evap at time during start up. And the amp draw will vary as it does this. until the refrigerant flow stabilizes.

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