To zone, or not to zone. That is the question.

[NHSoxFanatic]

I have received several estimates for a new central air/heat pump system in my house. I have narrowed the selection down to two contractors. Both spent a lot of time taking accurate measurements, took the time to do an accurate load calc and are recommending similar-sized heat pumps and configurations. They are differing in one area that has me a bit confused. One is recommending three zones to match the current three zones baseboard heat in the house, the other is recommending against zoning. I am hoping to get some independent advice on why I might go one way versus the other.

A quick description of my NH house: It is a 3,050 sqft colonial with a large unfinished attic (the future location of the air handler). The home does not have ductwork yet, instead it has forced hot water baseboard heat fed from an oil furnace. The closets in my home are quite large, allowing ducting to be passed through them, down to the first floor. The current baseboard heat has three zones (1st floor, second floor, large master bedroom).

Here is the general configuration that was recommended by both contractors.

- (1) Two-stage 16-SEER heat pump, 4-ton
- (1) variable speed air handler, installed in the attic
- Dual fuel thermostats to tie into my oil heat, should the outside temp drop below 38 degrees

- The difference comes in when one supplier is recommending an un-zoned system, saying that a zoned system wouldn't allow sufficient airflow across the coils. The second supplier is strongly recommending three zones and would tie the zones into the existing zones for the baseboard heat. The second supplier says that the two-stage compressor and variable-speed air handler are designed exactly for this kind of zoning.

My gut tells me that we would have hot and cold spots without zoning. My Master Bedroom is 26x28 and that is the last place that I would want to experience temperature swings.

Can anyone weigh in on what the advantages and disadvantages of each may be?

Thanks!

[Kevin O'Neill]

In your case i would zone the house the same way it was zoned before. That way you caqn use the same thermostats for both the air and water loops, just add relays for the hydronic zone valves. it will be a control nightmare otherwise.

[Anderson Air]

I vote for zoning as well.

[BaldLoonie]

Would be nice but remember cold air falls so the first floor will stay cool even without much air getting to it. Friend had 2 story and zoning and almost never turned the 1st floor stat on, cold air fell from upstairs and kept it very comfy. So you may be paying a lot for zoning and don't need it.

[skippedover]

I have a 3-zone system in my own home and it works wonderfully. You haven't said what kind of zone control system will be used, however. There are equipment manufacturer zone systems and after market zone systems, each having its own advantages and disadvantages. The issue with zones is the imbalance in system demand when a small zone calls independently from the other zones. AC/HP systems must maintain a certain minimum airflow over the coils or problems can result. In order to maintain that minimum airflow, a 'relief strategy' must be part of the zone calculation and installation. Carrier/Bryant zone systems using the Infinity/Evolution control systems do all of that calculating and adjustment automatically with no input from the installing company. Other systems may have similar logic but most require some sort of external strategy such as a barometric by-pass or a dump zone. Absent a relief strategy, the system could suffer from excessive noise and/or equipment problems.

If your home has a physical layout where one area gets more sun at certin times of the day or one area is more remote from the main footprint, these are good reasons to zone. Zone control is usually installed with the intention of maintaining even temperatures in those areas that might otherwise be hot or cold when controlled by a remote thermostat.

[Todd S 2]

Would be nice but remember cold air falls so the first floor will stay cool even without much air getting to it. Friend had 2 story and zoning and almost never turned the 1st floor stat on, cold air fell from upstairs and kept it very comfy. So you may be paying a lot for zoning and don't need it.

I agree (in this case) with B.L. A/C zoning is probably not needed. However, when the heating kicks in, the zoning would make things much more comfortable. That said, your hot water is coming on at 38 degrees. If money is no issue, go with the zoning. Or you can add it later, if you find you need it.

[beenthere]

I'd zone it.

As baldloonie says. The first floor probably won't need A/C often, if at all.
Except when you have company, or do a lot of cooking. Then its nice to have the zoning, and not have to freeze the other areas to cool the first floor.

[NHSoxFanatic]

Thank you for all the great feedback.

To respond directly to the response from 'skippedover', it was a Carrier representative that recommended the three zone system, the other system was a Trane. Your comments are very much in line with the feedback that I got from each of those companies.

We are very happy with the current zoning of the water loops and are leaning towards keeping that control.

The layout of the house is such that the first floor zone gets more heating from windows in the afternoon (west-facing). With a large palladian window and 4 other large windows, there is quite a heat gain in the afternoon.

Cheers to all!

[skippedover]

Now about those Red Sox....

[wdgmartin]

Hey Kevin - Thanks for your posts. On an off subject question for quick reference:

Can you tell me if a Carrier 2.5 ton r410 (model: 24ACA330A03000) will work with the Carrier 2.5 coil (mod. CK5AXA030T14AAAA)?

Looks like the coil is 22 or 410 is that correct?

Thanks for any help - No email addresses in post, please put it in your profile. (charlotte area)