Zoning

[shakham]

Hi all,

This is my first post here...let's hope it comes out right and I don't violate any of the rules....I'm want to Zone my home. The temperature swing around the house is very large.

Some details:
I live in Central New Jersey.
2800 sq/ft + unfinished basement (no open ducts).
2 x 3-ton HVAC (Luxaire 10 SEER) - 1 for each floor.

Right now I'm focusing on my upstairs since it has all enclosed rooms, while my downstairs is more open....my goal here is to increase comfort, AND save money. We have unused rooms during the day...and my office is unused at night.

I was thinking of setting up 7-zones (1 for each room).

My questions:
1) I counted 11 - 5" round ducts...that comes out to 660 CFM. A 3-ton needs 1200. There are 3 fan settings on the blower.

a) Am I destined to a frosted evaporator on the low setting (assuming it's slow enough for the ducts)? OR Not enough flow available for the high setting?

b) If we ignore zoning for a minute...what would having a dump achieve?

c) If we put zoning into the picture...will the dump essentially offset any savings from zoning? I mean...if one zone makes the request...doesn't that mean that 120 CFM (assume 2 ducts) will cause the whole system to run with most of the air being dumped back?

2) Retrozone.com recommended the EWC 7000. I was also reading about the Honeywell TZ-4 (+ TAZ-4 expansion). My understanding is that both have temperature sensors to control the vent temperature.

a) I'm assuming multi-stage cooling/heating means the compressor/burner runs at different speeds. I'm assuming I have single stage...does this mean that I shouldn't use the multi-stage feature to control the fan speed?

b) If one zone makes a cooling call, the system turns on, and shuts off all other dampers except 2 for the calling zone. Much of the air will be cycled by the dump. Won't the temperature sensor then cause the AC to short cycle (aka run 4 minutes -> fan goes for 8 -> AC turns back on for 4 minute)?

c) Are there any controllers that wait for a certain number of zones making a cooling call before turning on? I'm thinking it would be useful because then I would reduce the short cycle...no?

3) Based on all the numbers...6-tons seems too big for my place. Is that the case? If so...what are my options, and why did they oversize it?

4) Would it make sense to run the entire house with 1 x 3-ton system by joining the ducts, and adding more zones? Would I need to do this for the winter as well?

5) Do all these CFM issues and sizing affect the heat cycle?

I hope these questions all make sense and paint a reasonable picture. If any folks of you are in NJ, feel free to contact me personally and send me a quote.

thanks,
Amir

[beenthere]

First. Get a load calculation done so you know what size furnace and A/C or furnaces and A/Cs you need.

Then. There are several different zonig systems that can do what you want.
Honeywell has a comunicating system, that auto masters and slaves the zones.
When teh master zone is calling, it also will open the slave zones that need, or will need heating or cooling soon. It prevents short cycling.
If one zone calls for cooling more then hte others in teh summer, that zone becomes the master zone.
If another zone calls for heat more then that zone in the winter, that becomes the master zone.

Carrier has the Infinity zoning system, that is a modulating system.

There is a third one, that I for get the name of. It uses bladders in every supply, and has a sensor in every room, and controls room temp simular to honeywell's communicating system.

2 stage equipment would be good for what you want to do.

[shakham]

First. Get a load calculation done so you know what size furnace and A/C or furnaces and A/Cs you need.

2 stage equipment would be good for what you want to do.

Thanks for the response...

For a load calc...I contact my HVAC folks around here? or is there software?

How would 2 stage work with my system?

[beenthere]

You may have to call several contractors to find one that will do a load calc.
You can do your own. Near teh top op the page, you will see a link to HVAC calc. Its a 50 dollar fee, to use the software, for I think 2 months.

Your zoning panel can be set not to use second stage unless 2 or more zones are calling. Some will let you set it to a percentage. So that 33%, or 50% of the zones must be calling to use second stage.
That also helps to prevent short cycling.

[shakham]

I don't believe my HVAC compressor is multi-stage...would the fan speeds represent the stages?

Or would I use both HVACs together as a 2nd stage...which means I have to bridge the 2 units.

[beenthere]

You can use your current equipment, with a zoning system for each one.
But, It sounds over sized. So it will tend to still use more electric then it should.

Twinning (combining) your existing units and then zoning them would present other trouble.

Your house may only need 3 tons total. Without knowing what size it needs. Too many guesses make it too confusing.

Get a load calc done. Then go from there.

[skippedover]

Open architecture downstairs? Consider a Mitsubishi Hyper Heat system. Put your money into the MHH system and you can stop using fossil fuel for heating the downstairs immediately (leave it in for the very coldest weather, meaning below 0) and use a fraction of the electrical power you use now. Depending on how many rooms you have upstairs, you can either go with a MHH zoned system or zone what you have. One word of caution on zoning; the noise can be very uncomfortable if it isn't done correctly. Our company considers 2-stage equipment (either heating or cooling or both, depending on what the system is) mandatory to do the system properly. We also prefer to use a sophisticated manufacturer system for commonality across the entire installation. We're a Bryant dealer so we use Bryant Evolution equipment and zone system for central systems (no dump system needed, no by-pass needed) and Mitsubishi for open architecture and other rooms where ducts and be run. Likewise the MHH if you've got a specific area or two you want to keep at a higher temperature and let the rest of the place go way cool or warm, depending on the season, when you're not occupying those spaces.

[shakham]

First. Get a load calculation done so you know what size furnace and A/C or furnaces and A/Cs you need.

Okay...I ran 2 different calculators...one was at MrHVAC.

I had to do some reasonable estimates of some of the numbers...it gave me:
cooling: 51K BTU so about 4.5 tons.
heating: 70K BTU

A less accurate calculator... Alpinehomeair...
cooling: 4.8 tons
heating: 95K BTU

I have 2 x 3 tons. Oversized, but not crazy oversized it seems...should work out when I finish the basement (2-3 years from now).

My biggest question....if I calculated that the 5" ducting can handle 650 CFM, and each HVAC needs to run 1200 CFM...

I'm essentially going to be dumping tons to get this to work...so running a 1200 CFM fan and dumping most of it back.

In the situation where only 1/2 the dampers are open, I'll cooling those areas at a rate of 300 CFM, but the system will be wasting electricity at the 1200 CFM rate.

So how will I win in terms of efficiency and reduced electrical usage?

That 60 CFM for 5" duct...what condition is that under? If 200 CFM goes through the same pipe...does that just imply more noise or any other issues?

thanks,
Amir

[beenthere]

What was the sensible of Mrhvac.
Edit out alpine, its a DIY site, and links to it are not allowed to be posted.

The load calc tells capacity at design, not the size of the unit.

Your 5" are moving more then 60CFM. a 3 ton would freeze up if it was only moving 600CFM for any real length of time.

[shakham]

MrHVAC sensible was: 34K BTU

How do I figure the size of the unit needed?

[beenthere]

That would be done with Manual S.

But, I can tell you, that the average 4 ton will meet that sensible.
So that means you have something adding a very high latent load.
Most likely your infiltration.

[shakham]

I know it may get complicated...but is there a reason why I can't zone the entire house (with the 2 HVACs) and use one as the primary, and the 2nd comes on only when more airflow is needed (aka equivalent to a 2nd stage). I'd be running with 3-tons on most days, except when it gets really hot or old, when I'd be running at 6-tons.

At that point, I'd need more than 7 zones, and I can put essentially a large bridge between the two main pipes.

Of course, the second stage HVAC would need something to prevent the air backing through the return ducts.

Anyhow...do they sell anyting to use 2 HVACs together?

[shakham]

That would be done with Manual S.

But, I can tell you, that the average 4 ton will meet that sensible.
So that means you have something adding a very high latent load.
Most likely your infiltration.

Sorry to be so dumb...

The infiltration factor...vol cu ft...what is a typical number?
I have a 12 year old colonial home.

[beenthere]

.33 would be an average.

If your current units are side by side. They could be tied to gether.
Problem comes when one dies. Your stuck with limited replacement options.
Plus, the added controls and devices to make them work right.

You'll have a hard time finding a contractor that can make it work reliably.

[shakham]

Thanks beenthere....I think I have enough to go on right now.

I'll have some HVAC contractors come buy and give me some quotes..then I'll see where I go.