Best HVAC option for a small duplex? One system or two?

15 years ago

I just purchased a small (The duplex is in the mid-south, mild winters and hot-t-t-t summers, so I thought a heat pump might be a good option. I also plan to install ceiling fans on both sides.

To start, and in light of the small sizes of the units, I thought I might have duct work run to both with a single heat pump connected and thermostat installed on my side. I would provide heating and cooling for my tenant under this scenario. I wonder, though, if the ductwork could be installed in such a way that it would be easy to add a second unit and divide the two sides at a later date.

Also, would it possibly be more cost effective to install both both heat pumps at one time?

Finally, as bands go, would you recommend an American Standard, a Goodman machine or another brand?

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Comments (10)

ryanhughes
15 years ago
A heat pump would be a good idea. You need two separate ductwork systems if you go with two systems. If the place is less than 1000 sq. ft., I don't see two units being feasible--the zones would just be too small. You might consider zoning a single system or just using a single system with control in your hands. Brand isn't very important as long as it's installed right. American Standard/Trane is good equipment. Get a few estimates.
davidandkasie
15 years ago
for that size i would just buy 2 240V window shakers and put them in. the problem you run into when the control is in the other person's hands is it is never the right temp. 2 of our previous offices had the Tstat in another companies office and they always either froze us out or burnt us up. we literally kept the front door propped open 75% of the time!

honestly you should have this duplex setup with seperate utilities per side. this way YOU don't get stuck for a monthly bill if someone skips out on you. my wife's grandmother rents out several trailers on the cheap. she has all the utilities in her name so they never have to wait to get turned on. problem is tha ta few times a year folks will up and move and never pay the high electric or water bill they owe.

i know you are trying to get some good recurring income, but you need to protect yourself by spending a little up front so it don't cost you a lot later.
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pricing vaires, mary. you may want to look at trane's sister company american standard, if trane pricing is too high. same stuff..different label. I find 15-17 SEER to be good efficiency. good savings over minimum efficiency allowed by law..decent payback period. pairing 15 SEER (for example) with a variable speed air handler unit will give you control over humidity. this upgrade will cost about $500-$700 depending on costs in your area. but it is worth every penny because of removal of humidity that it provides. In La. like Fla. high RH(relative humidity) is what makes us uncomfortable when summer temps are 90 degrees & RH is 90%. controling RH to maintain 50% RH is what makes us comfortable. when RH is lowered, the air is colder, so t-stat can be raised and you still be comfortable. staging the heat strips will save you $$ in heating season by not engaging full stips unless needed. most of the time you'll be using heat of heat pump, not emergency heat. while 2 tons for 1,008 sq ft is a lot of a/c, the cost is the same for 1.5 tons as it is for 2 tons. at the end of the day...most companies will sell you 2 tons. to overcome this oversizing, you need the ability to slow the air speed, so that relative humidity is controlled. thus the variable speed ahu. I'm in a small home also. Over the years I've learned a lot about hvac, due to the type of work I do. when I got ready to put a central system in my house (980 sq ft) I installed a two ton heat pump, 15 SEER with a variable speed air handler, staged heat strips. in the summer..my utility bills are $60 at hottest months (aug, sept) winter...$40. don't think emergency heat has come on this mild winter at all. I planned my system to remove humidity, and have been pleased with the success. in August my indoor RH was 50-55% even on rainy days. having gotten a steal of a deal on a whole house dehumdifier I can lower RH to 40-45% and turn temp at tstat higher. If I hadn't gotten the dehumidifier at such a good price..I'd still be ok, because I planned to dehumidify with vs air handler. without dehumidifier RH is still in acceptable range & comfort is great! lowering the speed of the air removes more humidity and air gets colder. cold..in august..heavenly! don't get hung up on name brands. for each big name is a sister company with same equipment with different label. shop around, get bids that give you good...13 SEER better 14 SEER and best...15-17 SEER bids. get at least 3 bids, then compare. tell hvac companies of any issues...excess dust, hot/cold spots, condensating supply grills etc while they bid your job. then share this info with us, & we will advise you & explain any questions you have. make sure they know that all ducts are to be mastic sealed...not duct or foil tape. duct leakage is a huge problem that isn't often addressed. if you are paying to condition the air..it should all come inside the house.. not leak out in unconditioned space. install trumps brand in my book. making sure that ducts are mastic sealed, and in good shape is often over looked as is the air sealing of return. I test homes for air leakage & ducts for duct leakage, so knowing how much these things leak..and how much it costs for these leaks..it is a worth while investment to seal them, this type of sealing is a quick payback, inexpensive materials, and noticable improvement to do these types of sealing. best of luck.
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funnycide
15 years ago
Is it 1000 sq ft total or is each unit 1000 sq ft? You do not want to share the ductwork. You should make sure each unit has a separate electric meter. If you include the heating and cooling in the rent they will not have any reason to keep the temperature at a reasonable temperature.
tigerdunes
15 years ago
slum

two separate properly sized and installed HVAC and ductwork systems. Only way to go!

IMO
ryanhughes
15 years ago
York has 1-ton units. See if you can get a quote for those, IF the load for each unit is 1-ton, which it may be.
k2vrx
15 years ago
cheaper cost would be zoning system with 2 t-stats however you run into the problem of electric bill as stated above. So you have to figure that one out, spend more money and get a system per side or duke it out with your tenant over electricity costs. As far as brand I would go with Goodman.
miken_2008
15 years ago
If we are talking about 500 sq.ft. units I would really consider a good window or through the wall hotel type unit I just cant see taking on the expense for a whole system for that small of a space

Here is a link that might be useful: Air Conditioning Repair made Easy
slum_lording_it
Original Author
15 years ago
Thank you so much for all the great responses!

@funnycide: The duplex is around 1000 sq.ft. total, each side is around 500sq.ft.. It's small!

@ryanhughes: Thanks for the tip, I will definitely look into York. I'll see if I can find a certified installer 'round here.

@tigerdunes: Two systems, of some kind, seems like the best long-term solution. Having the thermostat on one side makes sense when I'm living there, but would be problematic when I'm ready to rent out both sides.

@davidandkasie, miken_2008, et al.: I'm not entirely opposed to window units, but what would you all recommend for heating?

I fear the existing gas wall heaters are just cast-iron carbon monoxide and soot defusers, not to mention the fire liability.
davidandkasie
15 years ago
they make 240v window shakers with built in heaters. my stepdad has one at his parents; old house and it heats the front better than the old kero heater his mom used.
ryanhughes
15 years ago
I think the most important issue for you know is finding a competent dealer to perform a load calculation (as part of an estimate) to determine the best-sized system for each unit. Make sure it is a legitimate Manual J load calculation, not just a "Each side needs 1.5 tons--I know by experience."

Best HVAC option for a small duplex? One system or two?

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Best HVAC option for a small duplex? One system or two?

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