HVAC installation


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Old 06-30-08, 07:30 PM
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Smile HVAC installation

I am putting an addition on to my home. It has a new bath
(60 Sqft) larger kitchen (372 Sqft) laundry room (56 Sqft) and an upstairs master bed (190 Sqft) bath (130 sqft) and closet
(45 Sqft). I am basically adding on 427 Sqft upstairs and 315 Sqft downstairs. This makes the total sqft of my home 1562. I am wondering if it would be possible for me to run my own HVAC runs to these new rooms? It will all be open with the new construction so getting at it will not be a problem. I have an existing gas forced air unit Rheem 6.8 amp, blower = 1/2 HP 3400 rpm, 75000 BTU, static H2O pressure .12 to .5. I got these numbers off the inside of the unit and have no idea what any of them mean. I am more than willing to do the grunt work to save the labor costs and how hard can it be to connect heating ducts to my exisiting system? Please give me some good advice before I run off the end of some heating and cooling cliff into an abyss of sorrow.
Thanks
 
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Old 06-30-08, 08:32 PM
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You are doubling the size of your house and in all likelihood your furnace/ac will not be big enough............especially the ac.

You would need to do a new heat loss/gain calculation on the whole building.
HVAC-CALC is one program people claim works well and is only $50.00 for a single use.
 
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Old 06-30-08, 08:40 PM
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Smile HVAC woes

I don't currently have AC. Here in the northwest we rarely need it. My current Sq footage is 840. Really small house. I know I am adding quite a bit. Does that calculator need wall area versus door and window areas to calculate whether my current furnace is big enough? I don't have the drawings back from the architect yet so I could only give my best guess at this point in time. I also have a zero clearance gas fireplace in the current living room that I use 80% of the winter to heat the existing house. With both of these appliances in use do you still think that the furnace isn't big enough? I guess if the answer is yes I could consider using radiant heat in the upstairs bed and bath as a heat source. That would solve most of my HVAC question about how to run duct work. Let me know what you think and thanks for the quick response time. I really appreciate it.
 
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Old 07-01-08, 04:49 AM
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There is a possibility that your current furnace is big enough but no one could know based on a bit of information exchanged in a forum like this.

Your comment "how hard can it be to connect heating ducts to my existing system?" tells me that you do not appreciate the importance of the equipment sizing component of a job like this.
You will be spending a great deal of money to upgrade your house and you may be making a very big mistake by planning to use two other heat sources to make up for a lack of proper sizing.

Someday you may want a/c or a buyer of your home might want it.

The calculation of the heat loss/gain is based on infiltration from walls windows and doors, heat added by equipment and occupancy and the specific requirements for each room.

If using the software is too much then another suggestion I have is to get a RELIABLE sheet metal contractor to estimate this for you.
If you do then you would do well to insist that the ductwork be sized for future a/c as it takes a somewhat higher airflow to cool that it does to heat.

Another possibility is running two furnaces if your layout would suit it.
 
 

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