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Old 11-14-2011, 08:48 AM   #1
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Adding HVAC lines on existing HeatPump system


Hey, Love the forum, I read and learned so much on this site but this is my first post. We just built a 1500 sq ft ranch home with a full unfinished basement. We just learned we have another baby on the way and have quickly outgrown our new home. Id like to start finishing the basement for additional room. Heres my question. Right now the main level of the home is serviced by a 13 seer Goodman HeatPump. The trunk runs down the center of the home and has lines branched off for their respective rooms. The air handler is placed close to the center of the house. Am i able to tap into the trunk and run more lines to heat the basement? It would be one heatpump and air handler heating close to 3000 sq feet. The basement will obviously be insulated. Im assuming i would need more duct work for the return air, so am i able to extend the existing return air duct? Thanks for any help.

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Old 11-14-2011, 07:15 PM   #2
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Adding HVAC lines on existing HeatPump system


Its not really a good idea to try and add more drops to an existing duct system. Since this is a basement, you might be able to zone the system. This will depend on your climate and heat loss/gain of the home.
A good contractor needs to look this over and give you some options..

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Old 11-14-2011, 08:32 PM   #3
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Adding HVAC lines on existing HeatPump system


Run a separate trunk line for the basement, and use a zoning system. basement won't take much to heat it.
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Old 11-14-2011, 08:36 PM   #4
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Adding HVAC lines on existing HeatPump system


So beenthere, when calculating the heat load on the basement, is it the same as the rest of the house, or are there factors you don't need? We don't have basements around here so I don't have any expertise on this...
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Old 11-14-2011, 09:12 PM   #5
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Adding HVAC lines on existing HeatPump system


Basements are generally sublevel, so they have ground for insulation, the walls and floor are surrounded by 55F temp, so its only a 15 degree difference your doing.
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Old 11-15-2011, 06:50 AM   #6
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Adding HVAC lines on existing HeatPump system


Hey beenthere if he runs a drop and get a unbalance system or create a neg. pressure that will cause alot of inflatration that could cause a problem and he is doubling his heat load we dont know the size unit. he has 13 seer but what btu rating. just a thought
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Old 11-15-2011, 10:25 AM   #7
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Adding HVAC lines on existing HeatPump system


I'm no expert so please tell me what you mean by zoning....1/2 my basement is underground and 1/2 sticks out. I'm built into the side of a hill. I'll look to see what size BTU and Ton the heat pump is. Can someone please explain negative pressure. Thanks
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Old 11-15-2011, 11:57 AM   #8
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nag. and pos. pressure in the home on an imbalance hvac system, will cause large amount of air leakage in the home. Supply and return ducts should have balaced airflow to maintain neutral pressures of the conditioned space.
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Old 11-15-2011, 06:06 PM   #9
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Adding HVAC lines on existing HeatPump system


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Hey beenthere if he runs a drop and get a unbalance system or create a neg. pressure that will cause alot of inflatration that could cause a problem and he is doubling his heat load we dont know the size unit. he has 13 seer but what btu rating. just a thought
He has to run both return and supply to the basement areas to be conditioned. And then there won't be any negative pressure issues.


He is not doubling the load. The floor of the first floor will now be above a conditioned space, and the ceiling of the basement will now be below a conditioned space.

An 80 sq ft R19 wall above grade exposed to 0 degree outdoor and 70 degree indoor loses 295 BTUs an hour. A below grade R19 wall at 70 indoor and a ground temp of 55 degrees only loses 63 BTUs an hour.
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Old 11-15-2011, 06:09 PM   #10
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Adding HVAC lines on existing HeatPump system


Zoning.

2 or more thermostats controlling one unit. Each thermostat can be set to a different temp. Zone dampers are installed into the duct work that open and close By way of a zone panel that energizes or De-energizes them based on weather or not that thermostat is calling for heat, or cooling.
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Old 11-15-2011, 06:13 PM   #11
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Not knowing all the particulars it is hard to advise on what the best solution is, but, I am not particularly fond of zoning for a basement, insulate the walls well and add necessary supply and returns and if the unit is capable then the OP will be fine.

Zoned systems add complexity that may not be necessary.

Again we don't have all the necessary information to make a qualified call on this one.

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Old 11-15-2011, 06:50 PM   #12
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Not knowing all the particulars it is hard to advise on what the best solution is, but, I am not particularly fond of zoning for a basement, insulate the walls well and add necessary supply and returns and if the unit is capable then the OP will be fine.

Zoned systems add complexity that may not be necessary.

Again we don't have all the necessary information to make a qualified call on this one.

Mark
Zoned systems can be made complex. But for a basement add on an the original conditioned space, there is no reason that a zoning system has to be made complex.
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Old 11-15-2011, 07:15 PM   #13
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Zoned systems can be made complex. But for a basement add on an the original conditioned space, there is no reason that a zoning system has to be made complex.
At a minimum, a motorized damper, damper controller and speed control for the distribution fan, this is not necessarily complex, but it does add complexity.

As I said, we don't have enough info on this system to make qualified recommendations. Btu rating, fan size (cfm and static ratings), existing duct sizes and losses.

You never know, adding a few vents in the basement just might inprove on the existing system and the overall comfort of the home.

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Old 11-15-2011, 07:19 PM   #14
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Adding HVAC lines on existing HeatPump system


No speed controller is involved for zoning a residential system.


Yes, 2 thermostats, a zone panel, 2 motorized dampers, and a barometric bypass damper for his system. Honeywell makes some very nice simple to install zoning systems.
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Old 11-15-2011, 10:34 PM   #15
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Adding HVAC lines on existing HeatPump system


Instead of fan speed control, you would use a bypass damper. It feeds from the supply, back into the return. It has a counter-weight (adjustable) to keep it closed when running the larger zone.

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