View Full Version : Replacing heat pump
02-10-2005, 08:44 PM
I want to replace the heat pump sytem in my two story, 2000sq. ft. house. 1000sq.ft up, and same downstairs. I have single compressor, split system with one thermostat downstairs and one cold air return downstairs. I have had five proposals and thought it would be simple to compare oranges to oranges and prices. However, I got proposals for three different type systems. 1)Two 2-ton heat pumps, two air handlers,(one in attic), two thermostats and two cold air returns. 2)One 2 and half ton heat pump, one air handler, two thermostats and two motor operated dampers out of the air handler. 3)One 2 and half ton heat pump, one thermostat, one cold air return and one air handler with a variable speed fan. There are two people in the house who both sleep upstairs during the same hours. I want to ensure that I don't need to close the downstairs registers to force a/c upstairs during the summer.
If anyone has any info or even opinions on which setup, never mind price, might serve me better I would appreciate hearing from you.
02-10-2005, 08:52 PM
Its hard to get an even temperature on a 2 level home with one system unless you have zoning installed, if this is what your looking for then either zoning (dampers) or 2 seperate systems is the way to go, I would prefer the latter myself if cost is not a huge issue.
As far as sizing goes, there is quite the spread there in your proposals (2 1/2 to 4 tons), Make sure the installing contractor does a load calculation to determine the proper size equipment for your home.
02-10-2005, 09:02 PM
Oddly, the dual system is barely more than the variable motor system and quite a bit less than the 'damper' one. It has been calculated that 2 and half tons is proper capacity so I am not sure if this particular contractor happened to have these sitting around or what. They are only 12 SEER and I understand they won't even be used much longer. Will the fact that the two tonners are too big mean they will be stopping and starting a lot and so using more power?
02-10-2005, 09:45 PM
Originally posted by bigalf
... Will the fact that the two tonners are too big mean they will be stopping and starting a lot and so using more power?
Alf, one problem is with humidity control. If the system is not running, it will not dehumidify.
Cold & wet is not comfortable.
If the humidity is under control, most people are just as comfortable with a room temperature in the summer.
That saves money.
Starting a motor is very hard on it. Long run times, with properly sized systems will save money on energy, plus repairs.
A system takes a few minutes to stabilize and operate at the SEER (efficiency) it is rated at.
Excessive startups means higher electric bills & shorter life of the equipment.
Get it sized right.
A more expensive system, done right, is cheaper in the long run.
02-10-2005, 10:43 PM
Thanks for the response. Do heat pumps come less than 2 tons capacity? And if so, in your experience would they, properly sized, be better than the motorized damper system?
One contractor claims that the motorized damper systems break down a lot and are hard to set up. I find that a little hard to believe as I have had experience with auto controls, valve actuators and so forth and it shouldn't be a big problem.
02-10-2005, 10:58 PM
I am an old schoolteacher.
I haven't done contracting for several years.
All those new gizmos are newer than I have intimate knowledge of.
Motorized dampers do have more parts, but provide a higher degree of control.
Your local contractor's comfort level with dampers, heat pumps, variable speed, etc., should be very high on your list of qualifiers when choosing one system over another.
He is the one that has to keep it running and keep you happy.
Personally, I have two systems in my two-story, but I am thinking about putting in variable speed, with 2 systems.
The smallest heat pump split system is probably a ton and a half, commonly.
Ask your contractor.
02-10-2005, 11:03 PM
Good advice, thanks again.
02-12-2005, 08:47 PM
follow swampfox's advice - he is 100% right
02-12-2005, 09:19 PM
If someone covered this I missed it, but you refer to what sounds like single return openings on each floor. You should have dedicated returns to any room you want good airflow to. Exceptions being kitchen and bathrooms. If you are going to the expense of updating this system I would not take shortcuts on the air distribution system. As you have been advised, seek the advice of a reputable contractor. If none of these guys you have spoken with so far, have run a load calculation, kick em to the curb, and call someone in who will take the time and follow the steps necessary to give you a correctly sized job. His intestest in the "small stuff" will probably be a reflection of his attention to the big stuff. Most everyone here will be more than happy to offer an opinion, but the person looking at the job, and talking to you face-to-face is the one who needs to "get it right."
02-12-2005, 10:23 PM
I may be misinterpreting your concern but to clarify. Each room in the house has an air IN. Each floor will have a 20x25 air RETURN and filter. Are you suggesting I should have an IN and OUT in each room? There will be a thermostat on each floor. My latest contractor says that 2 and 1/2 tons is proper size but that 1 and 1/2 ton is smallest heat pump on the market, giving me a total of 3 tons but split between two floors. These are 14 SEER units. This contractor also spoke against durability of the one unit, two damper system.
All of you who have answered my questions have been a big help and I appreciate it. But, don't go away, I may be back.
In a humid climate,I'd go with variable speed air handler and the best controls and zoning that that brand has.
The best,today is Infinity Zoning ,by Carrier.
Two systems ,equals ,two compressors,four fan motors and coils,to maintain,repair and eventualy replace.Look at zoning.
Every room needs a return "path" for the supply air to get back to the air handler.That can be under the door,though that may not be enough.
Run the fan,feel the air flow,close the door,if the air flow is reduced,that's a problem.
02-13-2005, 10:59 AM
I believe dash reitterated my concern about single return points on each floor. This is an inexpensive way to keep from running individual returns to each space. You won't know it wasn't a good idea to run individual returns until down the road when you come back to this site asking why you don't get good air circulation between all your rooms. The only reason not to run a cold air return from each room (except bath and kit) is to save money. There are some builders that try to cut corners by saying this type of arrangement is fine. If it works, great, but if it doesn't you'll never be happy. Now is the time to address it. Also, if you are going to have two systems, then two (2) load calculations need to be run; for each space served by an independent system. You don't just divide it up by sq. ft / tonnage. You will always have a disproportionate cooling load for the upper floor and likewise a disproportionate heatng load for the lower floor.
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