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Old 06-12-2010, 04:39 PM   #1
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lowest r/a temp


What would be the lowest r/a temp for a residential r22 split system with a fixed orfice before the coil starts to freeze.

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Old 06-12-2010, 04:45 PM   #2
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Personally, I don't know. Some units can have a 65F return and not freeze. others freeze if the return is at 68.

Depends on both the CFM being returned, and the total heat of the air being returned.

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Old 06-12-2010, 04:52 PM   #3
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Long time no see/hear guy. Also depends on the humidity. I do have one customer who keeps her house at 65 (severe asthma, tight closed house) so you can run them that low. Must drive the humidity in her house down to 35% RH or lower from running it that long.
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Old 06-12-2010, 05:10 PM   #4
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Thanks for the reply, the reason I ask is the house has a valted ceiling with a loft. The thermostat is on the main level and reads 75f and the return is a floor register. It is A 2.5 ton ac and the air handler is in a crawl space. The air entering the coil is 65f and is starting to freeze. I think the only option I have is to try and install a highwall r/a in this finished house. I have not been able to check the system out properly because the outdoor temp is only a high of 70f lately.
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Old 06-12-2010, 05:13 PM   #5
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lowest r/a temp


Is the CFM thru the airhandler enough? There is some method (beenthere will know) of testing it by running the burner and checking the temp rise over 10 minutes. I would have to hunt it down for you.
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Old 06-12-2010, 05:17 PM   #6
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Hey Yuri I have been real busy. My company keeps growing and just trying to keep control. I have fourteen on payroll and eight trucks. But still doing mostly commercial and custom homes.
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Old 06-12-2010, 05:23 PM   #7
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Quote:
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Is the CFM thru the airhandler enough? There is some method (beenthere will know) of testing it by running the burner and checking the temp rise over 10 minutes. I would have to hunt it down for you.
CFM=BTU output divided by (temp rise times 1.08).
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Old 06-12-2010, 05:36 PM   #8
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lowest r/a temp


As my boss said "more techs = more headaches" LOL. He was not in a good mood. Congrats anyway.
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Old 06-12-2010, 05:40 PM   #9
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Thanks guys I'm going to try a couple things the next time when its a little hotter outside. I will check the static on the air handler but i am pretty certain I have plenty of air. I am going to take some 12" flex and tape 2 flex runs to the floor r/a and extend them up to the loft to see how it worx. The floor register which is within 10' is 36 by 12 and is a floor r/a grill.
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Old 06-12-2010, 06:03 PM   #10
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36X12 filter grille is good for about a 1.5 ton unit. What size is this unit.
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Old 06-12-2010, 06:07 PM   #11
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" It is A 2.5 ton ac and the air handler is in a crawl space. The air entering the coil is 65f and is starting to freeze" (from above). Must need a bigger grill/what size?
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Old 06-12-2010, 06:14 PM   #12
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" It is A 2.5 ton ac and the air handler is in a crawl space. The air entering the coil is 65f and is starting to freeze" (from above). Must need a bigger grill/what size?
WELL. If that had been in bold in hit post. I would have seen he posted size. ROFL

If he adds one to the loft. It could be the same size.

If he just wants to increase the one in the floor. Then 24X30. But doubt he has the joist cavity for one like that. Would take some carpentry work to install it.
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Old 06-12-2010, 06:47 PM   #13
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Hey Been the duct for the return air is directly below the floor grill. This grill is a steel floor grill and does not restrict any air. The return duct is 10' long and 24 by 14. The grill travels across three 12" joist cavities. I have my ductulator at the shop but I believe it is more than enough air. I think the problem is that all the registers are on the floor and the return (no registers close enough to short cycle the air). I will let you know what happens. Thanks again.
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Old 06-12-2010, 06:58 PM   #14
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hey Yuri just a question. That lady that keeps her house at 65 what refrigerant is it. Is it tx or fixed. Is the super heat and subcooling good. Is the compressor getting any liquid back. Just curious.
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Old 06-12-2010, 07:06 PM   #15
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She had a Carrier r22 2.5 ton with piston that worked good until the a coil went out. we replaced it with a xc14 2.5 ton with tx valve. 3 ton blower in a carrier mxa I believe. Did the approach with the lennox and it works well even with a tight merv 16 and pureair. kinda scared me with the merv 16 but it is okay. Decent sized ductwork. She does get it properly serviced yearly.

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