[bryanp22]

I was wondering if it’s possible to add a zone system to my existing furnace. I have a gas furnance and was looking at zoningspply.com at the zone board and the rectangle dampers. I have wired an aprilaire in the past, but this obviously is more complicated

My plan is basically to go from single zone to two zones. I have a two story home with a partial finished basement so I was going to make zone one the first floor and the basement and the 2nd floor be zone 2. My duct work seems to be setup so I can use the square dampers fairly easy.

Am I missing anything or is it really cutting the duct work to fit the dampers, wire zone board to the dampers, furnance and then to existing thermostat and adding a second thermostats on 2nd floor? I saw mention of a bypass but not sure the scenarios on when that’s needed.


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[beenthere]

If all of your supplies to the rooms are off the same rectangular duct. You will need to install round dampers in the supplies.

 

[bryanp22]

No they are separate. For second floor it has one rectangular duct going to second floor. For main floor and basement they have two separate sections of rectangular duct.

So how do I know if I need a bypass?


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[user_12345a]

You'll likely need a bypass and discharge air sensor if the furnace and a/c are not 2-stage or variable capacity.

If you proceed with this, get a zoning panel that can stage the equipment, hold both heating and cooling on low when only one zone is calling - get 2-stage down the road.

I don't recommend zoning single stage equipment - with a separate trunk for the second floor, surely you can adjust dampers in the trunks to balance.

 

[beenthere]

You will need a by pass if any of the zones are less than 60% of your systems total capacity.

 

[user_12345a]

^Even if 2-stage equipment is used?

 

[beenthere]

^Even if 2-stage equipment is used?

Yep..

 

[bryanp22]

I have a single stage but the blower has multiple speeds. Will that work?


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[beenthere]

I have a single stage but the blower has multiple speeds. Will that work?


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Still need a bypass. Or a dump zone.


In both heat and cool mode, it still needs to move X amount of air. Or the heat will shut off on high temp, and the cooling will trip the low limit of the discharge air temp sensor.

 

[user_12345a]

bypass can create the same problem though and trip limit, freeze coil or have dats cycle off before that happens.

better to dump the excess air into a hallway or something imo.

I would hold off until the equipment needs to be replaced since 2-stage really minimizes the problem.

 

[tgm1024]

I have almost the same setup in my house and doing manual damper control is driving me nuts. It's not just once a season, and the "in-between" seasons are always top floor vastly different from bottom.

1. I have a single zone two floor house, forced hot air / central A/C, single return on each floor, 1 thermostat and it's on the first floor.
2. Large rectangular duct in basement for the first floor and one for the 2nd.
3. A volume control damper for each one. I suppress one dramatically in winter and the other dramatically in summer.

{sigh} You're not going to like to hear this, but a couple neighbors warn that the HVAC companies in our area are all "shysters", and will suggest over priced thermostats, insist on expensive rewiring in the walls when there are wireless thermostats available for the 2nd floor, and the neighbor next to me ended up with a large old ugly Honeywell thermostat that looked like it was for an office building.

Besides going into this with a kind word and open mind, are there any suggestions for what I should be asking for?

 

[u3b3rg33k]

^Even if 2-stage equipment is used?

Yep..

on that note it's possible to "bypass" into the other zones. you need dampers that can open partially, or bypass ductwork to feed the other side of the other zone, (lots more duct work to do), but often if you're cooling the second floor, the first floor can still benefit from a tiny amount of airflow.

doing it this way also doesn't hurt efficiency like short circuit bypass setups do. I strongly dislike that practice and think it should be put out to pasture.


the other option is to use "smart" VS equipment. the bosch BOVA/2.0 system AC will run the compressor at whatever speed maintains proper system operation regardless of coil airflow (within the 25-110% capacity of the condenser of course). then so long as you meet the minimum airflow target the system will work properly.

a hydronic heating coil and tankless modulating boiler can do the same for heating with gas, just stay above the minimum fire and inlet water temps.

of course this adds significant complexity over a standard self contained gas + split system.

 

[user_12345a]

I have almost the same setup in my house and doing manual damper control is driving me nuts. It's not just once a season, and the "in-between" seasons are always top floor vastly different from bottom.

Probably have a lousy duct system not done correctly and zoning won't fix it but could actually make things worse.

Also possible you have inadequate attic insulation and excessive air leakage - both can drive temperature differences between floors. (for winter air leakage, there's a stack effect - cold air leaks in low and leaks out of the second floor into attic and through window frames, etc)

Besides going into this with a kind word and open mind, are there any suggestions for what I should be asking for?

Don't allow short-cuts to be taken.

You're not going to like to hear this, but a couple neighbors warn that the HVAC companies in our area are all "shysters", and will suggest over priced thermostats, insist on expensive rewiring in the walls when there are wireless thermostats available for the 2nd floor, and the neighbor next to me ended up with a large old ugly Honeywell thermostat that looked like it was for an office building.

Your neighbors probably don't understand what's required to do things properly and think they got ripped off. Wireless t-stats btw aren't cheap, you can look up the cost yourself.

BTW those "large ugly" honeywell stats are better than shiny but crappy stats like nest.

 

[tgm1024]

Your neighbors probably don't understand what's required to do things properly and think they got ripped off.

Wireless t-stats btw aren't cheap, you can look up the cost yourself.

Googling "wireless thermostats" yields wifi thermostats. Unless they're using "WiFi Direct", this would always require a router working. Those are cheap (<$200), but I can't imagine it's what I need.

AIUI, there are three primary ways of me accomplishing a 1->2 zone setup for my home (options presented to my neighbors----feel free to correct me if wrong).

1. They could install a diverter such that either one floor at a time is being serviced. Basically deciding which floor gets its turn. I can't see how this would be comfortable in high demand situations.

2. They can install a diverter that splits variable amounts of airflow to each room. So all rooms could be heated/cooled constantly with different biases as the controller determines necessary.

3. They can install two variable dampers, one in each of the two feeds to the floors. This is an atomatic was of doing the bias that I'm already doing manually.

Is this correct? I need to be armed with fundamentals before I talk to a tradesman.

Thanks guys.

 

[beenthere]

Only 2 ways to zone.


1. With separate equipment for each zone.


2. With a zone panel, and motorized dampers.

 

[tgm1024]

Only 2 ways to zone.


1. With separate equipment for each zone.


2. With a zone panel, and motorized dampers.

Obviously you cannot spec a job with almost no information, but for a 2400 sqft 1 to 2 zone home is this something like $2500ish, $5000ish, or $10,000ish?

 

[beenthere]

Depends on how the duct work is set up. It can be inexpensive, or very expensive.

 

[tgm1024]

Depends on how the duct work is set up. It can be inexpensive, or very expensive.

The ducts themselves? Split right from furnace in the basement into 2 large rectangle ducts.

One large duct going to the attic where it splits to feed the ceiling registers of each room. One large return for the 2nd floor in the hallway.

Another large duct running the length of the basement and feeding only the 1st floor registers. One return for this floor.

 

[beenthere]

Then not too expensive.


1 zone panel
2 motorized dampers
1 bypass damper
1 new thermostat for the new zone(if difficult to run new stat wire, can use a wireless stat)

 

[tgm1024]

Then not too expensive.


1 zone panel
2 motorized dampers
1 bypass damper
1 new thermostat for the new zone(if difficult to run new stat wire, can use a wireless stat)

Ok, Let's see if I understand how this works.

1. The zone panel is fed the information from the two thermostats and makes decisions, right?

2. The motorized dampers control the bias for each primary feed (one for upstairs, one for downstairs)

But 3. .......What does the bypass damper do? The amount that each floor feed gets is already handled by their individual dampers, no?