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Old 05-12-2010, 04:34 PM   #1
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Newbie with questions about a 4 ton rheem

hey,great site new to the site,thought i would ask some questions about my install im trying to do mostly my self to save on cost.My house is approximatly 1500 Sq Ft cedar loghouse and has never had heating or cooling besides a wood stove and window air conditioners. So i thought it was time to install one so i went and bought a 4 ton rheem air handler Model#[rbhc21j18sfc] and bear with me i have a lot of questions to ask this is all new to me.

#1 It has a heat strips installed, but its not really a heat strips, the air handler has i guess what are called factory installed incoloy sheath heaters wrapped around the blower assembly rated at 18.00kw are these enough to heat 1500 sq ft or should i order a bigger heating kit?

#2 Also the electrical it has two 60 amp breaker on the front panel and i have read that it takes 2 #6 copper wires to power it and handle the amps but the wire is not cheap at my local lowes,can i use a jumper kit to combine those two circuits into one to save on wire so i only have to run one wire to the air handler will this be safe?

#3 Also what is a good size supply duct for a 4 ton unit after the plenum? I cant seem to find an answer any where to this question.I have found plenty talking about return size but not supply size for a 4 ton.

#4 Also it is a upflow unit and i have built a return box approx. 2ft X3ftX24 inches tall. well insulated with perma R board doubled up.That it sits upon, going to a 20x20 filter grill which being a log house this is as big as i could go with the limited space and it is hard cutting through a 6 inch thick cedar logs with a chainsaw,to fit the return grill.And my house has limited stud walls almost all the interior walls are 6 inch cedar logs which i do have a crawlspace under the house which is where i will run my supply duct work so is a 20X20 grill and is the return plenum box i built close enough to give it enough air?

#5 Also for a condenser unit outside do i have to get a 4 ton as well? I thought about a heat pump, but right now all i can afford is a regular condenser and later i will upgrade when i get the cash.So i will only have air handler electric heat till i upgrade so will 18.00 kw be enough for 1500 sqft.

Thanks so much, i hope someone cam answer my questions.


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Old 05-12-2010, 11:20 PM   #2
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doubtful your going to get an answer here the questions your asking demonstrate your lack of hvac knowledge(not trying to offend you) and many on here dont want the responsibility of giving you advise you probably dont want to hear.

in a nutshell:
#1 18 kw is overkill but will work
#2 yes if code allows but wire will be doubled in gauge so its even more expensive
#3 unless youre in the desert and have no insulation 4 ton is about 1 1/2 tons (average) more than you need
#4 20/20 is to small
#5 again unit is too big but you could likely go 3 1/2 ton outdoor unit (still to big)cost differance from strait cool to heat pump is about 300 to 500 dollars do it now dont run on straight elec. your first elec bill with heat on will be as much higher as the differance between buying a heat pump and strait a/c

my advise: pay someone to come in and size your system properly give you duct design and sizes and proper wire sizes than do the work yourself....... good luck


Last edited by kennzz05; 05-12-2010 at 11:32 PM.
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Old 05-13-2010, 10:50 AM   #3
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Thank you so much i was just cant ever get a person that knows what there doing hvac wise to tell me if i am doing this correctly without having to pay. I Mean what happend to the days where people would share the knowledge free of charge?
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Old 05-13-2010, 05:58 PM   #4
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The biggest problem is it's impossible to know the size of equiptment needed without doing a load calculation. The fee a HVAC company charges to size and draw out a plan for you will be saved many times over the life of the equiptment. Also remember when they are working on your DIY plan that's hours taken away from other bids. Those other bids are what keep the employees receiving a paycheck.
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Old 05-24-2010, 11:53 PM   #5
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hvac calculation

google hvac computer systems and the program and manual will lead you in the right direction re sizing of unit
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