central a/c installation


  #1  
Old 04-14-02, 08:32 AM
otter_
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central a/c installation

This may be a dumb question, but its my first go around w/ central air.

My contractor installed the cooling coil in the plenum above the heat exchanger. Is this for a)reasons of efficiency b)industry accepted?

I was reading through my furnace (carrier pav90) owner's manual and it states to never ever never install a coil in this fashion because dripping condensate will result in heat exchanger failure. The furnace mfg specifies that the coil should be installed on the cold air return side.

Is the mfg trying to limit their liability or is my installation wrong?
 
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Old 04-14-02, 08:45 AM
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new one on me

generally evap coils sit directly on top of gas furnaces, the coil cabinet is sized for a match. have heard that evap before heatxchnger is bad idea,. most h/p air handlers have to coil in the return side (before the fan)
 
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Old 04-14-02, 09:03 AM
otter_
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thanks for the info -

furnace is an upflow....fan is in the bottom of the cabinet, heat exchanger is above the fan, cooling coil is above the heat exchanger, drip pan drains to an exterior tank and condensate pump...queried the contracter about the positioing of coil and the answer was that they do it this way all the time. Mentioned my concern about moisture dripping onto the heat exchanger - his reply - call him if water shows up where its not supposed to.

almost forgot----cold air return enters the furnace at bottom of cabinet. This job included installing new furnace and making existing ducts fit and installing split central air.

the central air will be running 4-6 weeks within june-september.
 
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Old 04-14-02, 01:45 PM
ahasbeen
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It is normal and a must that the cooling coil always be on the outlet air side of any heating system. Reason: cold air from the coil will cool the heat exchangers below the dew point causing moisture to accumilate which will eventually rust them out and void warranty. Keep in mind the heat exchangers are exposed to the warm moist ambient air.

If you have water dripping from the coil it will be from a dirty coil or bad/clogged up drain line. Thats a different issue all together.
 
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Old 04-14-02, 05:51 PM
otter_
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thanks to both of you for the info, it makes sense. I should clarify that there is no water drip happening, my comments were based on "what if".

Anybody have any ideas why the furnace mfg (carrier) recommends against placing the coil above the heat exchanger even though it makes sense to have it there?
 
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Old 04-14-02, 07:19 PM
ahasbeen
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I'm guessing you might have mis read or misunderstood what Carrier is saying, about putting the coil above the furnace. Check back with this forum, maybe some of the other pro's out here will clarify, or call your local contractors. Go with it.
 
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Old 04-14-02, 07:48 PM
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Yeah somehting must of be wrong in the book, you go to Carrier.com and you can see in thier pictures with A/C Coil on top of the gas furnace. I never heard of the PAV90 model.
 
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Old 04-14-02, 08:43 PM
otter_
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otherwise known as...58PAV/RAV

Thanks again!
 
 

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