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#943950 - 08/29/18 07:06 AM zoned systems
sportster Offline
veteran

Registered: 08/11/04
Posts: 1284
Loc: South West Ohio
Anyone running a zoned HVAC system? Thinking about installing one myself since our two story is hotter in the summer on the second floor and colder in the basement in the winter.

Just looking for brands and any issues you came across.

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#943992 - 08/29/18 03:00 PM Re: zoned systems [Re: sportster]
Punky Offline
Carpal Tunnel

Registered: 06/01/05
Posts: 5980
Loc: East Aurora, NY
Unless the house was designed for it, DONT. It never works well.

For best comfort you need 2 separate systems. One for upper, one for lower.

The basement would also need its own system as the climate of basement is far different than any rest of the house.
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#944021 - 08/30/18 07:37 AM Re: zoned systems [Re: sportster]
sportster Offline
veteran

Registered: 08/11/04
Posts: 1284
Loc: South West Ohio
Can you give me the reasons why it wouldn't work, well?

A separate system would require extensive duct work mods for one. The 2nd system would have to be installed in the attic which has an opening barley big enough to get me through!

The temp on the second floor isn't that far off from the first in the hottest part of the day with the bedroom doors shut (72down/76up). I'm going to go in the attic this fall and see how much more insulation I can get up there.

There are no returns currently in the basement with only two supply ducts for a 800sqf basement. If I don't do zoned down there, it will be either a return added with ducts moved or baseboard heaters installed with programmable tstats.

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#944041 - 08/30/18 02:57 PM Re: zoned systems [Re: sportster]
Punky Offline
Carpal Tunnel

Registered: 06/01/05
Posts: 5980
Loc: East Aurora, NY
The great majority of houses in the USA have substandard duct systems. The duct system to the second floors are often much much worse. When you put in a zone system the unit has to be sized to be able to run both at the same time, and have a dump zone when only one zone is calling.

The problem is often that the system requirements for both zones together is more than what the entire duct system can handle. So, when you cut off some of the flow and capacity your problems become worse, especially to the second floor, where overall static pressure of the poor ducts overcome any flow trying to get there.

Also, unless you have returns in each room upstairs, dont shut the doors. No flow, no cooling/heating.

The basement is an entire different biome to the rest of the house. It will need either a mini split heat pump or some other source of heating as well as a standalone dehumidifier. A whole house dehumidifier works very well. Ultra Aire makes very good ones.

Dont duct it with the rest of the house. It will NEVER be comfortable down there. Either too humid or too cold.
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#944070 - 08/31/18 06:32 AM Re: zoned systems [Re: Punky]
sportster Offline
veteran

Registered: 08/11/04
Posts: 1284
Loc: South West Ohio
Originally Posted By Punky
The great majority of houses in the USA have substandard duct systems. The duct system to the second floors are often much much worse. When you put in a zone system the unit has to be sized to be able to run both at the same time, and have a dump zone when only one zone is calling.

The system currently is running three floors with two of the rooms on the first floor with their ducts shut off at the registers.

Originally Posted By Punky
The problem is often that the system requirements for both zones together is more than what the entire duct system can handle. So, when you cut off some of the flow and capacity your problems become worse, especially to the second floor, where overall static pressure of the poor ducts overcome any flow trying to get there.


That statement would be true IF the duct work is/was undersized a lot. A bypass damper would help in this situation although not optimal.

Originally Posted By Punky
Also, unless you have returns in each room upstairs, dont shut the doors. No flow, no cooling/heating.


All rooms with the exception of the bathrooms and basement (currently) have returns.

Originally Posted By Punky
The basement is an entire different biome to the rest of the house. It will need either a mini split heat pump or some other source of heating as well as a standalone dehumidifier. A whole house dehumidifier works very well. Ultra Aire makes very good ones.

Dont duct it with the rest of the house. It will NEVER be comfortable down there. Either too humid or too cold.


I must have gotten lucky with my last two houses because the current one keeps the basement at 68F/51%RH. The old one was a little colder but 47~49%RH but that one had a return. As far as basements go it is how they are built and sealed. The old house I remolded the basement which it never showed signs of water leaks. I spray foamed it and made sure I sealed all the exterior walls. The new house was already finished and has shown no signs of water, plus it was built in 1986 and has an energy certificate with it from the builder (if that really means anything).

When it gets cooler and I can get in the attic I'll know more what I can do to help it up there.

As far as the basement goes, the finish job wasn't that great and the supply ducts are in the ceiling not the exterior walls so I may see about moving them and possibly adding in an extra duct and return that I can open/close.

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#944117 - 08/31/18 06:59 PM Re: zoned systems [Re: sportster]
Punky Offline
Carpal Tunnel

Registered: 06/01/05
Posts: 5980
Loc: East Aurora, NY
Originally Posted By sportster

The system currently is running three floors with two of the rooms on the first floor with their ducts shut off at the registers.


The ducts are shut to try to force more air upstairs? All ducts need to be open for best operation. Dampers in the cellar are what should be adjusting air through the system.

Quote:
That statement would be true IF the duct work is/was undersized a lot. A bypass damper would help in this situation although not optimal.


No, it wont. Ducts are often 1/3 the size they really need to be. You cant guess this by looking at it.

Quote:

All rooms with the exception of the bathrooms and basement (currently) have returns.


That's the way it should be.

Quote:

I must have gotten lucky with my last two houses because the current one keeps the basement at 68F/51%RH. The old one was a little colder but 47~49%RH but that one had a return. As far as basements go it is how they are built and sealed. The old house I remolded the basement which it never showed signs of water leaks. I spray foamed it and made sure I sealed all the exterior walls. The new house was already finished and has shown no signs of water, plus it was built in 1986 and has an energy certificate with it from the builder (if that really means anything).

When it gets cooler and I can get in the attic I'll know more what I can do to help it up there.

As far as the basement goes, the finish job wasn't that great and the supply ducts are in the ceiling not the exterior walls so I may see about moving them and possibly adding in an extra duct and return that I can open/close.


The basement is always a different environment than the rest of the house and it has to be treated separately.

It seems you are set on zoning. I wish you luck. you're going to need it.
_________________________
Opinions should be verified with your local town Board/Inspector/Review Panels

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#944272 - 09/04/18 08:23 AM Re: zoned systems [Re: Punky]
sportster Offline
veteran

Registered: 08/11/04
Posts: 1284
Loc: South West Ohio
Originally Posted By Punky
The ducts are shut to try to force more air upstairs? All ducts need to be open for best operation. Dampers in the cellar are what should be adjusting air through the system.


A zoned system does that automatically. You can set them up so that they don't close 100%

Most systems installed don't use the Manual D calculator. I have talked to a lot of HVAC contactors over the years to find one that actually uses the Manual J and D calculators but have only found a few. Most go by what has worked in the past.

I'm not set on putting one in but this seems to be a much cheaper option than going with a separate system.

Thanks for your recommendations.

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