Do you have a variable speed AC unit and how do you like it? (houses, heat pump)

[Potential_Landlord]

Like everyone else we have the situation that not all rooms are cooled alike. To combat this situation and since we have to replace our old AC unit anyways, I was thinking about a variable speed AC unit. Do you have one and how do you like it? Also, are there true variable speed package AC units out there? - Thanks.

[Pink Jazz]

I never heard of the AC unit itself being variable speed. Typically variable speed refers to the blower in the furnace or air handler, which increases the efficiency of the AC unit. Note that the new furnace or air handler should be properly matched to the correct AC unit or heat pump for maximum efficiency; replacing only one part of the system will never yield maximum efficiency, and if your old AC unit is an R22 unit, you would have no choice anyway (dry charge R22 units are no longer available).

We don't have a variable speed motor in our furnace, however, our furnace does have an ECM blower. All variable speed blowers are also ECM, but not all ECM blowers are variable speed. A fixed speed ECM will be more efficient than a PSC blower, but less efficient than a variable speed ECM.

[Potential_Landlord]

Originally Posted by Pink Jazz

I never heard of the AC unit itself being variable speed. Typically variable speed refers to the blower in the furnace or air handler, which increases the efficiency of the AC unit. Note that the new furnace or air handler should be properly matched to the correct AC unit or heat pump for maximum efficiency; replacing only one part of the system will never yield maximum efficiency, and if your old AC unit is an R22 unit, you would have no choice anyway (dry charge R22 units are no longer available).

We don't have a variable speed motor in our furnace, however, our furnace does have an ECM blower. All variable speed blowers are also ECM, but not all ECM blowers are variable speed. A fixed speed ECM will be more efficient than a PSC blower, but less efficient than a variable speed ECM.

The compressor has variable speed. So it only cools the air as much as required. The fan is on all the time. It runs continuously - both the cooling and the blowing.

[Ponderosa]

Originally Posted by Potential_Landlord

The compressor has variable speed. So it only cools the air as much as required. The fan is on all the time. It runs continuously - both the cooling and the blowing.

It would still cool all the rooms in the same uneven pattern. What you might want to consider is zoned ductless. It will be quite a retrofit though with pipes running all over.

[hikernut]

Do you know how well your ductwork is balanced and sealed? And are there enough air returns?

The HVAC installer went a little crazy on our current house (we are the second owners). There are nine air returns, which is probably a little excessive but I will say all of the rooms get decent air flow.

[Potential_Landlord]

Guys, you all have very good points. I'll discuss this with my wife. However, most likely she'll say the current unit has to go because it's so old and she does not feel safe from a mid-summer breakdown. So we're back to the "what is the best new unit option" question, I'm afraid.

[yukon]

Have you looked in to ductless a/c? Several friends in ABQ installed them in their houses over the past year or two and the units are awesome. Not to mention the power bills are a lot lower too.

[wase4711]

I bought a high end trane, 18SEER, with variable speed compressor, and variable speed fan, and it solved your EXACT problem; my wife was complaining about the same thing..we had a 14 year old Goodman, which was very loud, and froze you out of every room..

[DougStark]

I knew mini split systems offer variable speed compressors, but I didn't know there are now ducted systems that use this technology. I would definitely pay more for one of these variable speed systems if I knew I was going to stay in my home for a while and their reliability is good.

For me, the cold draft when a traditional A/C system comes on is uncomfortable (esp. in the bedroom at night.) My system may need to be balanced better.

[Hal Roach]

Your existing system's compressor runs at two speeds; off and full. Typically, a variable has four; 0, 33, 66, and 100%. You gain massive energy savings by avoiding the 0 to 100 startups.