Adding zone control to an existing HVAC system

[Bert_]

At this point I'm just trying to scope out the possibilities so any input is appreciated.

At my parents house they have trouble with uneven heating. This has been a problem since the house was finished about 10 years ago. The trouble always is that the temperature in the old section of the house is not consistent. The thermostat is in the new section of the house. Air conditioning is the summer does not seem to be as problematic.

A little back ground, The original 26x26 section of the house was gutted and all new mechanicals were installed at the time. The addition was a small 26x50 ranch style house was moved and attached to the old house. It ended up being a pretty big house but it was cheaper than building an addition. The ranch style house was about 10 years old when we moved it and not a lot was changed in it at the time. A new heat pump was installed to serve the whole house. The duct work in the old section is all new and the duct work in the new section is a mix of existing and new.

We have experimented with adjusting registers to no avail. If there is a strong wind from the east it will make that half of the house cold. If the wind is out of the west or north then the old portion of the house gets too warm. There are some large windows but the house is well insulated and not drafty.

The air handler is stamped '08 so not that old. The unit has a variable speed blower and I think the heat pump is 2 stage. It's a Trane 2tee3c65a1000, it's a air-air heat pump with I think 25kw of electric coils . It uses a communicating thermostat. It was sized and installed when the house was redone.

I just want a solution that gives them fairly consistent temps throughout the house. The idea of zoning came to mind since it is a pretty large area to control. I'm not how that would work since the system is already installed. Any other solutions would be greatly appreciated though.

Anybody have experience with that sort of thing? I'm not totally clueless but I know little to nothing about zoning.

 

[bobbyjean]

hi Bert- how about something like this Emerson 1F98EZ-1621 Wireless Easy Install Thermostat System.. you can sense both area's for better temp. control.
any remote sensing unit that works with heat pump will work
using zone dampers could work as well...it will require control and duct mods..
is it a heating only issue or a/c issue as well?

 

[mrramsey]

Hi Bert - I had a similar issue. I spoke to my HVAC guy and he made the following suggestion. He said to try changing the t-stat to an ecobee 4 and place the extra sensor in the coldest room. Then run the blower 24/7. The t-stat uses the average temps of the sensors to control the set point. Certainly has helped to make it more comfortable. My next option was zoning but that will be in the ball park of $4-5k so the $250 for the new ecobee was a inexpensive experiment to try.

 

[yeldogt]

I have zoning in all my houses. First thing is to get a proper heat/cooling load done. This will give you the BTU's needed for each room .. and the whole house. Then you see what the existing ductwork can provide ... and the size and type of heater currently in the building.

With the proper ductwork any type of system can be zoned -- older, single speed systems require larger ducts and bypass strategies. The newest VS systems actually work better with smaller ductwork closer to just what is needed -- maintaining about 120% of the lowest CFM of the unit. How old is the system ? if it's old and may be replaced in the next few years it will be better and cheaper to replace it now with new controls. The new equipment is really amazing when retrofitted into old houses with substandard duct work.

You must see what's required and what's in the house first .. sometimes all you need is a way to partially close off the satisfied areas. So the addition would continue to get full output as the rest of the house is slowly closed off -- this would require a controller and thermostat for the addition. do it once -- correctly and you will save money and aggravation.

 

[terabitdan]

You might want to look at the Keen Home Smart Vents. They are registers that will automatically open and close to maintain temperature in the rooms. Much less than doing a duct based system.

I’ve been looking at them to address similar issues, but haven’t tried them.


Sent from my iPhone using Tapatalk

 

[eddieK]

A properly installed zone control system requires low voltage controlled dampers and a by pass duct, this means the existing duct work needs altering and you have to have enough space to do this. Average cost for this is 3 grand and you just installed several items that can cause nuisance failures down the road.

You said the t stat is located in the new section...does that mean there is older ducting that was just added on to/ attached to? Is the air mover (furnace) in the new section, a distance away fro the existing portion? Duct work in existing portion...is it under sized or broken or leaking or crushed? Does the older section require longer ducts...that were not up sized to create more static/more cfm?

If you are going to this much trouble and cost...why not just up size and/or manual damper control the existing air delivery system? If you need more heat delivered to particular zones all the time this is a wiser investment. Closing grilles does not accomplish the same air restriction/movement as do dampers close to the plenum or at branch wyes.

I cannot count how many times I have found crushed/broken/damaged/under sized ducting while installing a zone control system...because the home owner insisted they wanted the latest thing...

Also we in the trade call that dual thermostat idea "dueling" thermostats...Personally I am not a fan...it's a band aid on a gaping wound. The symptom addressed and the disease ignored.

Along with up grading insulation and limiting heat loss situations this is a much wiser use of your dollars...just my two cents.

 

[Bert_]

The air handler is stamped '08 so not that old. The unit does have a variable speed blower. It's a trane 2tee3c65a1000a with I think 25kw of electric coils. It uses a communicating thermostat.

The thermostat is located in the center of the new house. The air handler is in the new basement.
There is no crushed or broken ductwork. I can't say whether it's sized correctly but this was a new install so one would hope...

If manual dampers would do the job I would be all for that. They aren't necessarily interested in the latest and greatest, just something that works. I was worried since the temp difference isn't consistent they would still be trying to constantly adjust dampers. Some days the problem rooms are about right, some days to hot, some days to cold. It's not consistently colder.

I like the term "dueling thermostats", I had similar thoughts about it without some sort of dampening control.

The old section of the house is 26x26 and the addition is 26x50. The old house was gutted and redone, the addition is actually a smaller ranch style house that was moved and attached to the existing house about 10 years ago. The new section is about 20 years old and hasn't had anything done to it other than the move.

Their current plan is to put in a gas furnace to supply the old section. Though they've talked about that for several years and I don't see that happening for several more at least. I figured zoning would be simpler, but it seems the more I read on it the less I know...

 

[LS6 Tommy]

Hi Bert - I had a similar issue. I spoke to my HVAC guy and he made the following suggestion. He said to try changing the t-stat to an ecobee 4 and place the extra sensor in the coldest room. Then run the blower 24/7. The t-stat uses the average temps of the sensors to control the set point. Certainly has helped to make it more comfortable.

This is the lowest cost option. I've installed ecobees for people with similar problems at least 5 or 6 times. Even with the ecobee, the existing system wasn't designed to service the additional space of the addition and may not even be able to deliver air at the proper temperature just due to the duct length.

You can't just start dropping in controlled dampers to make zones. It casues coil freezing; hi limit trips, short cycling and a host of other problems. Properly converting single zone systems to multiple zone systems (especially when the second zone was an addition) frequently costs more than installing second, single zone system in the addition as it should have been in the first place.

Tommy

 

[PT Doc]

Just to clarify. New addition was completed. Ducts were run to supply this area. No other changes were made? The expectation was that the original air handler was sized appropriately for a 200% increase in square footage? The ranch that was added onto the existing structure had no hvac system?

 

[Bert_]

Just to clarify. New addition was completed. Ducts were run to supply this area. No other changes were made? The expectation was that the original air handler was sized appropriately for a 200% increase in square footage? The ranch that was added onto the existing structure had no have system?

No. The old house was completely gutted, all mechanical were removed and redone. The "addition" was moved and attached to the existing house. That part does have most of it's original duct work but not the original furnace. A new heat pump and associated duct work was installed to serve both sections of the house.

You can't just start dropping in controlled dampers to make zones. It casues coil freezing; hi limit trips, short cycling and a host of other problems. Properly converting single zone systems to multiple zone systems (especially when the second zone was an addition) frequently costs more than installing second, single zone system in the addition as it should have been in the first place.

Tommy

I understand that this can be an issue and that's why I am asking for advise on how to set this up properly. This unit does have a variable speed blower and I'm pretty sure the the heat pump has 2 stages. I was under the impression that it could be set up with multiple zones. But I don't know alot about the unit and this isn't exactly my area of expertise.

At this point I'm just trying to scope out the possibilities so any input is appreciated.

 

[yeldogt]

Just like good radiant .. there are good zoning. It's not rocket science ... it's just not done correctly the majority of the time.

I grew up in a big house .... zoning done back in the 50's prior to my birth ... and an oil system to boot.

Zoning properly done does not require a bypass ... and never needs one with the newest equipment. Small duct work when feeding one small zone may require a by-pass unless you can bleed the excess to the next required zone -- that said I have never needed to do it.

I really don't get why people think it's better to install two system and all the extra equipment when a proper zoned system is IMO better.

Again it's not rocket science -- it's air and duct work and a few controls. There is nothing complex about zone dampers or the controls . Think I have had one modern zone damper fail.

Find a company that installs them -- they know. The people who don't install them .. never learn .. think they don't work ...........and the cycle continues.

Who made the system ? If it's a 2 speed Carrier with VS blower .. it's a question of adding a module and the dampers. You need each zone to be 120% of the lowest CFM of the system.

 

[TheOtherChris]

We started with a 1600sf house.
Then we added on another 1500sf.
Rather than try to have one furnace handle the whole house we replaced the furnace in the old house and added one to the addition so we have two separate thermostats controlling 2 separate handlers. So far it has worked out well.

My point is the more rooms you try to condition with a single handler and central thermostat, the more likely you will have difficulties.

 

[Bert_]

Original post updated for additional clarity.