Zoned system or 2 systems for 1.5 story house?

[zedd]

In early Jan we got a new HVAC system as our old 2 ton unit died. We upgraded and went with a Carrier 4 ton heat pump with a variable speed blower. Our house is a 1.5 story with ~2200ft^2. The heating part of the system works great and the upstairs stayed nice and warm in the winter. However, now that summer is approaching the system is not cooling off the 2nd floor. It absolutely works better than our last unit, however it is not functioning as promised.

The problem we are told is that our ductwork upstairs is inadequate and poorly laid out. We have one supply/return in each bedroom (two of them), one supply for the bathroom, and one supply/return in the entry way/landing area which is open to the main floor below.

The proposed solutions:
A) Add one more supply line to each bedroom and the entry way/landing area. Zone the whole house and install a wireless/remote thermostat for the upstairs. Once the downstairs cools off all air to that floor is redirected to the 2nd floor. Since we would be pushing the whole 4 ton system to the upstairs alone there would be some kind of ducting done allowing the extra volume of air that can’t be pushed upstairs to be recirculated through the HVAC unit.

B) Add one more supply line to each bedroom and the entry way/landing area. Then pull out the 4 ton unit and install 2 smaller units and separate controls for each.

I’m pretty much torn as to what to do and would love to hear any opinions you guys might have as to which option might function better.

Thanks.

[second opinion]

Choose B, A will cost a small fortune and never work with continuing high energy bills and agrivation.

[skippedover]

In early Jan we got a new HVAC system as our old 2 ton unit died. We upgraded and went with a Carrier 4 ton heat pump with a variable speed blower. Our house is a 1.5 story with ~2200ft^2. The heating part of the system works great and the upstairs stayed nice and warm in the winter. However, now that summer is approaching the system is not cooling off the 2nd floor. It absolutely works better than our last unit, however it is not functioning as promised.

The problem we are told is that our ductwork upstairs is inadequate and poorly laid out. We have one supply/return in each bedroom (two of them), one supply for the bathroom, and one supply/return in the entry way/landing area which is open to the main floor below.

So let me be sure I'm understanding this correctly. You had a 2.0-ton system removed and a 4-ton system installed but nobody addressed the ducts in that whole transaction?

The proposed solutions:
A) Add one more supply line to each bedroom and the entry way/landing area. Zone the whole house and install a wireless/remote thermostat for the upstairs. Once the downstairs cools off all air to that floor is redirected to the 2nd floor. Since we would be pushing the whole 4 ton system to the upstairs alone there would be some kind of ducting done allowing the extra volume of air that can’t be pushed upstairs to be recirculated through the HVAC unit.

B) Add one more supply line to each bedroom and the entry way/landing area. Then pull out the 4 ton unit and install 2 smaller units and separate controls for each.

I’m pretty much torn as to what to do and would love to hear any opinions you guys might have as to which option might function better.


So is the company giving you these options the same company that installed the 4-ton system? And who did the load analysis that determined that 4-tons was the proper size for your home? And who did the duct analysis to be sure it was appropriate for a 4-ton system with a variable speed blower? Per chance, the installing company given you benefit of any static pressures in your system? I ask because the higher the static pressure, the more resistance there is to airflow. So squeezing 4-tons of jelly into a 2-ton jar is really going to be painful for the system and certainly would be noisy. I'd recommend a load analysis be done by a reputable company that does load analysis routinely. Then decide on solutions. I don't think right now you've got adequate information to make any kind of a decision.

[wahoo]

Let me get this straight...you took out a two ton system, left ductwork the same and put in a 4 ton system? And they (the contractor) told you this larger system on the same ductwork would work better? But now you're hearing these "tear it all out and replace" recommendations? I can only assume you are talking about about pretty large amount of money spent and yet to spend (if their recommendations are taken)? I would imagine there should have been considerable ductwork changes back when the larger system was installed. Were these changes recommended back in Jan. ??:.02:
How well did the 2 ton system work before?

P.S. You can't just blow 4 tons of AC air out of 4 or 5 outlets, and let the bypass damper dump rest without loss of efficiency. Bypass systems waste efficiency, however the zone attempt would be the least expense at this point. :.02:

[zedd]

So is the company giving you these options the same company that installed the 4-ton system? And who did the load analysis that determined that 4-tons was the proper size for your home? And who did the duct analysis to be sure it was appropriate for a 4-ton system with a variable speed blower? Per chance, the installing company given you benefit of any static pressures in your system? I ask because the higher the static pressure, the more resistance there is to airflow. So squeezing 4-tons of jelly into a 2-ton jar is really going to be painful for the system and certainly would be noisy. I'd recommend a load analysis be done by a reputable company that does load analysis routinely. Then decide on solutions. I don't think right now you've got adequate information to make any kind of a decision.

Yes, same company. The duct work issue was briefly discussed but they said according to their programs they thought the ducts upstairs would work. heh.


Let me get this straight...you took out a two ton system, left ductwork the same and put in a 4 ton system? And they (the contractor) told you this larger system on the same ductwork would work better? But now you're hearing these "tear it all out and replace" recommendations? I can only assume you are talking about about pretty large amount of money spent and yet to spend (if their recommendations are taken)? I would imagine there should have been considerable ductwork changes back when the larger system was installed. Were these changes recommended back in Jan. ??:.02:
How well did the 2 ton system work before?

P.S. You can't just blow 4 tons of AC air out of 4 or 5 outlets, and let the bypass damper dump rest without loss of efficiency. Bypass systems waste efficiency, however the zone attempt would be the least expense at this point. :.02:

The 2 ton system never functioned properly and neither heated nor cooled off the upstairs. We basically just waited for it to die and then (we thought) upgraded. Yes, they thought the old ductwork would work for the new system. They did do some ductwork in Jan and redirected some air to the 2nd floor. (With manual dampers from a bathroom area with 3 supplies.) Yeah, the cost was a bit but the company is thus far sticking to their guarantee to make it right if the variable speed didn't work.

Thanks to all of you for your comments. They have helped.

[second opinion]

Yes, same company. The duct work issue was briefly discussed but they said according to their programs they thought the ducts upstairs would work. heh.



The 2 ton system never functioned properly and neither heated nor cooled off the upstairs. We basically just waited for it to die and then (we thought) upgraded. Yes, they thought the old ductwork would work for the new system. They did do some ductwork in Jan and redirected some air to the 2nd floor. (With manual dampers from a bathroom area with 3 supplies.) Yeah, the cost was a bit but the company is thus far sticking to their guarantee to make it right if the variable speed didn't work.

Thanks to all of you for your comments. They have helped.

Cut your loses and find another company, our industry is based on physics not guessing at the consumers expense and aggravation.

[dan sw fl]

WHAT'S ALWAYS BETWEEN A ROCK AND A HARD SPOT?

An HVAC unit for a 1 & half story.

2.5 ton MAX downstairs if you live in the dessert.
1 ton mini-split upstairs.

[ziggyhere]

pro for having two systems - if one system goes on the blink - the other one will help a little until you can get the other fixed. con - having to maintain two systems, and the initial cost. Get a proper load calc and have you're duct work checked for sizing. No sense in installing a 4 ton system if the duct work can only handle 800 cfm. Mini splits are a nice option if your duct work is all jacked up.

[zedd]

Thanks all again.

The company is actually working with us to correct the problem since they are the ones that sold us on the single large unit. (We went into the bidding process wanting 2 units.)

Anyways, I've told them we want two systems and I'd like a Manual J calc done. They are good with that and we are going from there.

[Mr Bill]

pro for having two systems - if one system goes on the blink .

Yea Buddy! and that my biggest personal argument in Houston, being stranded here for 4 days, could be a matter of life and death in the summer. :grin2: Also if you have 2-2-ton systems one up and one down, or 1-4-ton system zoned, how does the zoned even make sense? the power usage will be a wash, "AND" if you sleep upstairs, you get to run the 1-4 ton all night long, instead of 1-2 ton system. Wow! 1-4 ton really makes a lot of sense. "sarcasm" :grin2:

[superd77]

A zone system would work fine. When only one zone calls the excess air recirculates through the bypass. This will cause the supply air to drop even lower and help the one zone to satisfy faster. I've installed a bunch and if set-up right they work great!!

[precision hvac]

I've torn out plenty of brand new "bigger is always better" systems & started over.
Doubled the size of the system on existing ducts?
Wow.

[wahoo]

If you zone system, make sure they also install "freeze protection" on the system. This will keep coil (indoor) from freezing over if only one zone calls. I can't imagine that you can blow enough air thru your old 2nd floor ductwork for a zone system to function, but surely the HVAC people you hired can figure this out (if they are experienced at zoning systems). Holler back with their recommendations! I'm concerned that they actually doubled the input of the system and didn't expect problems. We often go on estimates where the homeowner asks for a huge increase in size, but simply point out that the existing system won't support the air flow needs. Of course sometimes a "buddy of a distant cousin" will just put the huge system in for them and you'll get a call a year or so later asking "what do I do now?".:gah:

[zedd]

Follow-up.

They are proposing to put in two 2 ton systems. One for the main floor, one for the 2nd floor. The first floor is ~1000ft^2, and the second floor (with an open entry way/staircase) is ~600ft^2.

We have the option of putting the 2nd system in the basement and using the large trunk feeding the existing second floor ducts (with new supplies added), or putting the 2nd system in the attic with all new ducts/returns. (With the attic option we would then close off the existing 2nd floor ducts and just save them 'for emergencies' in the future.)

Thoughts, comments, suggestions?

Edit- I'm leaning towards the 2nd option of putting the new unit in the attic with all new ductwork.

[zedd]

PS the main supply going to the 2nd floor is 8x14" and the return is roughly that size (but quite difficult to measure.)