Dual Zone HVAC?

cbailey31February 8, 2014

Hi all-
I am about to begin finishing a basement in a 1900 sq ft ranch house. We live in Wisconsin so the basement is always about 10 degrees colder than the main level.

I'm considering adding a dual zone to our existing hvac system, which has a Lennox G51MP furnace. The goal is to use the second zone in the winter to make the basement more comfortable. In warmer seasons, there's really no need for the second zone because the basement is cooler and therefore more comfortable, as long as we run the dehumidifier to keep moisture under control.

Any opinions about whether the second zone is a good idea or not? Is my furnace adequate to run both zones?

Thanks very much for any input!

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I'm in a similar situation - 50's ranch, around 1200 sq. ft, in the Chicago area. When I finished the basement, I put it on a separate zone, although I have hot water heat. The finished area is very pleasant. Most of the homes in my development have forced air and many of my neighbors ignored the heating aspect when remodeling the basement - they just cut a few holes in the ductwork for the basement. Their basements are usually not warm enough in winter.

You should get a good HVAC guy in to take a look. Maybe your furnace is sufficient or maybe a separate one should be installed for the basement.

    Bookmark   February 9, 2014 at 6:05AM
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Having a zone for the basement is the best way to control the temperature. In general it is a good idea.

A basement has very little heat loss, so it does not take many BTUs to raise the temperature. Do you know the size of your current furnace? In all probability it should be able to handle the needs of the basement.

You furnace is a single stage. There is a potential problem of trying to heat the basement zone with a furnace that can only run at one speed. It could be made to work if you have the proper size supplies and return. You need to find a HVAC contractor who is good at zoning (most are not) to determine how to properly set up two zones.

    Bookmark   February 9, 2014 at 9:49AM
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Hi Mike-
My furnace is a G51MP-36B-070. Does this tell you anything about the size?

My intent is certainly to check with an HVAC pro but wanted to go into the conversation with enough info that I feel somewhat informed, knowing there are some contractors that are not necessarily good at dual zone design. I don't want them telling me this will be no problem if their design will not work with my particular furnace.

Any further input is much appreciated.

    Bookmark   February 9, 2014 at 10:37AM
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This appears to be a 70K BTU furnace (62K BTU output) with a 3 ton blower. It should be sufficient for a 1900 sq. foot house and basement, but the contractor should verify this.

What is your location and what are your average low temperatures? Have you ever had problems keeping the house warm on the coldest days of the year?

Here is a link that might be useful: G51MP furnace

    Bookmark   February 9, 2014 at 3:09PM
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Hi Mike-
We're in South Central Wisconsin and our average in the coldest months of December and January is a low of around 10 degrees, high of 30 degrees.

We have not had any issues keeping the house warm enough, though we like to keep it around 68 degrees, not a whole lot higher than that in order to keep the bills reasonable.

Thanks again

    Bookmark   February 10, 2014 at 6:37PM
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Is this a fully underground basement or walk-out? Is there any heat in the basement now?

Is the basement one big room or are there partitions?

This post was edited by ionized on Mon, Feb 10, 14 at 18:57

    Bookmark   February 10, 2014 at 6:41PM
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