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-   -   please suggest me a heat pump system. (http://www.diychatroom.com/f17/please-suggest-me-heat-pump-system-12204/)

caseym 10-08-2007 12:16 PM

please suggest me a heat pump system.
 
i need help choosing a heat pump and air handler combo. i plan on installing the unit and the ducting myself. i will have a professional charge the unit and braze the pipes. my house doesn't have an HVAC unit now. it is a 3 story row-home in baltimore. it is only 900 sqft, only about 700 will be cooled/heated. the windows are double paned about 50ftsq worth, 3 wood doors. the insulation is adequate and the exterior is masonry. and being that it is a row-home only 2 walls face the exterior.

i work for thermo king so i can get very good pricing from our local wholesaler of HVAC systems/parts. so i can't really justify paying $$$ for a professional to do the whole job and triple charge me on the unit.

they sell amana, miller, frigidaire, fujitsu, gibson and mitsubishi. but they won't recommend anything to me and paying $100 for someone to do a manual J work-up on such a small job seems worthless, as the cheapest/smallest units will probably suffice. cost is a major issue. don't wanna spend more than $1500. i don't care about efficiency as i will probably be moving soon. i just want something cheap. can someone please suggest me an air handler, heat pump and heat strip with model numbers, so i can just call them up and order it.

please....:)

thanks in advance.

dmaceld 10-09-2007 10:07 PM

Quote:

Originally Posted by caseym (Post 66936)
i work for thermo king so i can get very good pricing from our local wholesaler of HVAC systems/parts. so i can't really justify paying $$$ for a professional to do the whole job and triple charge me on the unit.

paying $100 for someone to do a manual J work-up on such a small job seems worthless, as the cheapest/smallest units will probably suffice. cost is a major issue. don't wanna spend more than $1500. i don't care about efficiency as i will probably be moving soon. i just want something cheap.

Do it cheap and screw the person who buys your house in a couple years, right? Sorry to be so blunt, but that's exactly what comes across in what you are asking for.

Are you computer proficient with technical programs? If so, spend $50 and buy the use of HVAC Calc for two months. It's a pretty decent program and will give you the exact answers you're looking for.

Your comment about efficiency (I presume you mean SEER and AFUE) is understandable, and I took the same approach when I changed out my system 3 years ago. But, I made darn sure the system was the right size, and I did it with HVAC Calc. 900 sf house doesn't guarantee you'll get by with the smallest unit. It depends entirely on what the walls are made of, how well they are insulated, how good the windows are, and so on. HVAC Calc will help you factor all those in. What you DO NOT want to end up with is either an undersized or oversized heating unit or AC unit. Over or under creates discomfort. On the other hand, you may find your heating/cooling load is so low you can't find a central system that small. In that case wall units may well be the best solution, and possibly the cheapest. Don't sell short the value of doing Manual J calcs, even though they are not 100% accurate.

You'll find potential buyers will be greatly impressed when you tell them you made sure the heating and cooling system is sized right, and you know they will be comfortable both summer and winter because you were. That right there will make $100 look like chump change, if you opt to have someone do the calc for you. There are some free heating/cooling calc programs on the net, but I can't tell you how good they are.

caseym 10-10-2007 06:43 AM

i won't be screwing the person that moves in next. it is a ************ty row home. they'll be thrilled it even has central air.

this is my manual J:
http://i3.photobucket.com/albums/y57...anualjcrop.jpg


do you think a 1.5 ton will suffice?

dmaceld 10-10-2007 09:52 AM

Just out of curiosity, how easy/hard did you find the program to use? Looks like you got all the pertinent data into it.

I would say 1.5 ton for the A/C would work. For sure not any larger. A 1 ton might work but that would be a window unit only, I think. Baltimore is a high humidity area, right? In humid areas undersizing is better than oversizing because the unit will help pull humidity out of the air. If it's available, consider the 1.5 ton condenser and a 1 ton evaporator. The colder evaporator will pull more moisture out of the air. For more info go centralcityair.com. It's an HVAC guy in Houston who has a lot of good discussion about moisture removal in the south. When I changed my system in Louisiana I put in a 3 ton condenser with a 2.5 ton evaporator. Worked good.

As for heat, you can get a furnace down to about 50,000 Btu can't you? You are doing gas/ac combo, right? If you're thinking of using a heat pump for heat you would need a 4 ton unit, way too big for the a/c load.

caseym 10-10-2007 10:11 AM

its a program called HVAC-Calc. it can be had for $49... but i got it from *cough* other means.

i was planning on using the heat pump for heat with just a heat strip for auxiliary. why would i need a 4 ton unit? is that how the hvac-calc finding read?

i just got a quote from aireco i can get the heat strip, air handler and heat pump for $1120.

i think the hvac calc results might be a bit on the high side. there is no option in the program for 65% of my exterior walls are my neighbors which will be maintained to room temperature.

how much do you think a natural gas furnace for use in conjunction with the air handler would run me?

dmaceld 10-10-2007 01:56 PM

Quote:

Originally Posted by caseym (Post 67407)
i was planning on using the heat pump for heat with just a heat strip for auxiliary. why would i need a 4 ton unit? is that how the hvac-calc finding read?

i think the hvac calc results might be a bit on the high side. there is no option in the program for 65% of my exterior walls are my neighbors which will be maintained to room temperature.

how much do you think a natural gas furnace for use in conjunction with the air handler would run me?

You're showing 46,000 Btuh heat loss. 1 ton = 12,000 Btuh so you need 4 tons, or 48,000 Btuh, to cover the heating load.

If a wall doesn't have a heat loss, then don't add it into the program. Put in only the walls with heat loss. That will alter your heat gain number also. If you have only 14,000 a/c load now, your a/c load w/o the common walls may be too low to use a central unit.

Don't know what a gas furnace will run. A few hundred more than the plain air handler I would guess.

With the numbers you have for the difference in heating and cooling you would be running the auxiliary heat a lot. Not good economics.

Redo your calcs leaving out the common walls and see what comes up.

caseym 10-10-2007 02:35 PM

without the common walls i get:
total gain 11400
total loss 29554

dmaceld 10-10-2007 06:41 PM

Quote:

Originally Posted by caseym (Post 67449)
without the common walls i get:
total gain 11400
total loss 29554

So now the question is, can you find central equipment that small? One ton a/c and 30,000 furnace. Maybe that's why there isn't a central system in there now.

If you can't find central that small take a look at two, or three, in-wall heat pumps of 1 to 1.5 ton each. Run one for a/c and 1, 2, or all 3 for heat. Or, ask about a 2 stage heat pump. Run low level for cooling, and low and high level for heating as needed.

I think you've got good enough numbers now to look hard at what options are available. Be inquisitive. You'll find what works best.


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