Temp between 1st and 2ndfloors

[derick]

I purchased an approx 1900 sq ft home last year in Northern California. The home is approx 5 years old. The home had only a gas furnace (Bryant 373LAV) located in the attic. During negotiations for the sale, a separate Bryant 563G AC unit was installed outside. Refrigeration lines for the AC were installed during construction of the house. The single air intake is upstairs. Closing all the vents on one floor does not help the situation in either summer or winter.

Here are my problems:
1. During summer, the first floor remains very comfortable. Oddly enough, when we first looked at the home for purchasing, it was approx 100 outside and the downstairs was cool. Remember, there was no AC installed at the time. The 2nd floor does not cool sufficiently. The 2nd floor remains somewhat warm even when the AC is turned on. The single thermostat is located downstairs in the downstairs family room.

2. The upstairs bedrooms farthest away from the AC unit receives very little air flow thru the vents. During the summer months, my son's room never cools completely. Granted, the room is above the garage but the air flow should be better.

3. During the winter, the upstairs is very warm and the downstairs remains somewhat cool when the heat is turned on.

4. It appears that 2 of the vents feeding air downstairs come from ducting feeding 2 upstairs bedrooms. For example, the ducting feeding my son's upstairs bedroom provides air to the family room downstairs.

I plan to get a few names of contractors from trusted friends and get estimates. However, I want to do my homework and get a better idea on the remedy.

I believe I need to get separate ducts run for the rooms downstairs which feed off ducts from the upstairs bedrooms. I think I would like to send virtually all the warm air downstairs during the winter. Conversely, I would like to send most of the cool air upstairs during the summer.

Do I need zone system or could I get manual dampers installed and adjust manually twice a year?

Is there any other possible solutions to consider.

Any information would be greatly appreciated.

[atufano]

Originally posted by derick
I purchased an approx 1900 sq ft home last year in Northern California. The home is approx 5 years old. The home had only a gas furnace (Bryant 373LAV) located in the attic. During negotiations for the sale, a separate Bryant 563G AC unit was installed outside. Refrigeration lines for the AC were installed during construction of the house. The single air intake is upstairs. Closing all the vents on one floor does not help the situation in either summer or winter.

First of all, get a service tech out there to check out your systems.

Second, it sounds like there is not enough return air in the home.

Here are my problems:
1. During summer, the first floor remains very comfortable. Oddly enough, when we first looked at the home for purchasing, it was approx 100 outside and the downstairs was cool. Remember, there was no AC installed at the time. The 2nd floor does not cool sufficiently. The 2nd floor remains somewhat warm even when the AC is turned on. The single thermostat is located downstairs in the downstairs family room.

You may be more comfortable with 2 systems in the home. The system will operate of the one thermostat regardless of the temp of the other rooms.

2. The upstairs bedrooms farthest away from the AC unit receives very little air flow thru the vents. During the summer months, my son's room never cools completely. Granted, the room is above the garage but the air flow should be better.

Have the service tech check out the duct work, also ask them to do a load calculation for your home and see if what you have installed is correct for your home.

3. During the winter, the upstairs is very warm and the downstairs remains somewhat cool when the heat is turned on.

Natural air convection.

4. It appears that 2 of the vents feeding air downstairs come from ducting feeding 2 upstairs bedrooms. For example, the ducting feeding my son's upstairs bedroom provides air to the family room downstairs.

Sometimes they use 1 trunct duct to supply more than one room with supply air. It's common.

I plan to get a few names of contractors from trusted friends and get estimates. However, I want to do my homework and get a better idea on the remedy.

I believe I need to get separate ducts run for the rooms downstairs which feed off ducts from the upstairs bedrooms. I think I would like to send virtually all the warm air downstairs during the winter. Conversely, I would like to send most of the cool air upstairs during the summer.

Do I need zone system or could I get manual dampers installed and adjust manually twice a year?

Is there any other possible solutions to consider.

Any information would be greatly appreciated.

Get several reputable contractors to give you detailed bids and load calculations before you go with someone. Don't judge by price. It's always more expensive to have something done twice.

Without actually looking and measuring your home's equipment it's nearly impossible to determine your best course of action.

Good Luck.

[ironhorse]

You already stated the problem. Assuming the system is operating properly, you have a zoning issue. The thermostat located on the first floor is controlling temp for up and down. Due to natural convection, this never works. You can either spring for a second zone system or just add a zoning kit saving thousands of dollars over a new system. Both will add a second thermostat for the up zone. Both will work independently from either zone. Get a professional tech to inspect the system, and make sure it is properly sized, and that either way can actually be performed easily. He then can help you make the informed decision on which method would be best for you.

[derick]

What does a zoning kit provide?

[tyreman]

While this won't cure your ills of course...
In the summer or AC season close all 2nd floor room doors(all upper rooms) to slow the cold air dropping to the main floor.
Cold air is dense it falls very fast.
In winter have them(2nd floor doors) open.
Additionally see if you can have ductwork balanced and ftpm at each register set.
You MAY be able to throttle down close registers via perm. dampers if there... hence potentilly increasing flow to farther registers.
A lot of the balancing hinges on dampers present at key perimeter piping points as close to takeoffs as practicle and that they are accessable in the first place.
And of course necessary size and installation of duct work and pipe.

[Irascible]

Originally posted by derick
What does a zoning kit provide?

A typical zone system would have a controller that two thermostats talk to. The controller opens and closes motorized dampers in response to what the thermostats request. There is also normally some sort of pressure relief, usually in the form of a bypass damper.

The trick to proper zoning on an existing system isn't what kit they install. It's dealing with existing ducts. Take a look here. It will enlighten and possibly confuse. :^)

[derick]

Thanks.

2 more background questions.

What are the typical creditials of a good HVAC company? Licensed, bonding, certs etc....

Are there any good internet sites to give me guidance on working the numbers for load calculations?

[fanhandler]

Before anything, try this. Switch your thermostat sub-base to fan on. This will allow the fan to run continuously. Watch your temperature results. If it levels out, thwere are methods that will allow you to comfortably run the fan on a full-time basis.

Dick Peters, P.E./CM

[derick]

I tried using the fan only and it really did not affect the situation much. Thanks for the suggestion.