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Posted by Don Keener on April 10, 2007, 7:57 pm
SEER isnt an absolute or constant ratio... its a 'point on the curve'.
Lots of things effect SEER... indoor and outdoor temp, duct restriction,
dirt in the coils, charge, etc etc etc... Most likely... the SEER
rating, like EPA Highway Mileage, is measured at ideal conditions which the
unit may not see all that often.
http://www.advancedenergy.org/buildings/knowledge_library/heating_and_cooling/seer_facts_bulletin.pdf
> On Apr 10, 3:50 pm, gof...@gonefishin.net wrote:
>> >I'm hoping I can get an explanation about SEER that makes sense.
>> >Here's
>> >my situation. I am going to have a Trane XL19i compressor added to
>> >my
>> >existing Trane XV90 heating system (the brand and particulars don't
>> >really
>> >matter...). I am going to have the HVAC work done by a pro, but I
>> >want
>> >to run the electric myself. I am trying to understand the electric
>> >load in
>> >some detail and it just doesn't add up.
>>
>> >I am considering a 36kBTU (3 ton) compressor. The spec sheet says
>> >that it needs a 30A 220V dedicated circuit (which is fine...), but I
>> >am
>> >trying to figure out what the *true* load on the subpanel will be.
>> >The spec
>> >sheet says that the max compressor draw is 15.1A and that the max fan
>> >draw is 2.8A. So, I figure that when the unit is running wide open
>> >it
>> >can be drawing 17.9A.
>>
>> >Here's my confusion. 36000BTU/19SEER = 1895watts. At 220V this
>> >implies 8.6A. What's up with this?
>>
>> >I came up with a number of possibilities:
>> >*the 15.1A on the compressor load is the inrush current at startup
>> >*the compressor never runs at 100% duty cycle (this makes no sense to
>> >me).
>>
>> >What I want to know is when the compressor and fan are already
>> >running
>> >(that is neglecting any startup transients) how much current will this
>> >unit
>> >(compressor plus fan) be drawing from my subpanel.
>>
>> >Any help much appreciated.
>>
>> The manufacturer of your XL19i states on the equipment label that the
>> MCA (minimum circuit ampacity) for a 3 ton condenser is 22 amps and
>> the MOP is 35 amps.
>>
>> If warranty means anything to you, I would recommend you install the
>> electrical as per the manufacturers specifications. - Hide quoted
>> text -
>>
>> - Show quoted text -
>
> Yes, I understand this. I intend, in fact, to use 8 gauge wire to
> minimize the
> IR drop. I also intend to use a 30A breaker to protect the circuit,
> and I have enough
> capacity from my subpanel to supply 30A++. I merely wanted to
> *understand*
> (a concept apparently foreign to old Paul, here) how much current is
> actually
> flowing.
>
> I also stated that I intend to have a pro ( a licensed Trane dealer )
> install the unit,
> but I prefer to do my own electrical. I prefer to do my own work not
> to cheap out,
> but instead because on occasion (not often but on occasion) I have had
> poor
> quality work and damage done by Cro-magnon subs like Paul.
>
> So, back to my original question. If the RLA is 17.8amps, how does
> this reconcile
> with a 36kBTU 19 SEER unit?
>
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