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jamiedolan 10-24-2008 11:37 AM

Adding a register
 
Hello;

I have a "porch" - a room attached to my house that was always called a porch because it lacked insulation and had leaky windows, so it was not heated / cooled. I have replaced the windows, doors, and am properly insulating / sealing it up. So it is going to be like any other room in the house, other than there will still be exterior doors going to it and from it going outside, so I do not plan to always run the furnace to the room, but would like to at times.

It is about 140sqft. What I am looking to know is; can I just tap off of my furnaces output and run a new duct to this room, or should I tap into a current duct that is already in the wall to the room and just try to pull a small amount of air off of that?

Should I install a return for this room, if so, should it go by the floor like my other cold air returns?

Do you think I am safe in adding a register to this room without having someone come out and do a full HVAC size / capacity calculation? Everything now heats and cools very well with no problems.

I am very comfortable installing the ductwork, I have installed a fair amount of it, but have always just been replacing stuff that someone else had designed. My father and I installed the Goodman furnace here ourselves.


Thanks

Jamie

dac122 10-24-2008 12:58 PM

Quote:

Originally Posted by jamiedolan (Post 176218)

It is about 140sqft. What I am looking to know is; can I just tap off of my furnaces output and run a new duct to this room, or should I tap into a current duct that is already in the wall to the room and just try to pull a small amount of air off of that?

Should I install a return for this room, if so, should it go by the floor like my other cold air returns?

Do you think I am safe in adding a register to this room without having someone come out and do a full HVAC size / capacity calculation? Everything now heats and cools very well with no problems.

Hard to say for certain if you have the spare CFMs. You could pay someone to check it out, pay for HVAC-Calc and model it yourself, or just take a chance.

Without knowing the heat load you will probably need between a 6" to 8" pipe. That's just a guess. It should be added to your trunk for a trunk system or plenum for radial system, but not to an existing run. Yes, add a return. Put dampers on both at trunk/plenum takeoff for balancing and/or in case your system can't quite handle heat gain/loss during extreme weather.

You could also get a copy of ACCA's Manual D to know way more about duct design than you care.

jamiedolan 10-24-2008 04:37 PM

Quote:

Originally Posted by dac122 (Post 176267)
Hard to say for certain if you have the spare CFMs. You could pay someone to check it out, pay for HVAC-Calc and model it yourself, or just take a chance.

Without knowing the heat load you will probably need between a 6" to 8" pipe. That's just a guess. It should be added to your trunk for a trunk system or plenum for radial system, but not to an existing run. Yes, add a return. Put dampers on both at trunk/plenum takeoff for balancing and/or in case your system can't quite handle heat gain/loss during extreme weather.

You could also get a copy of ACCA's Manual D to know way more about duct design than you care.

Thanks for your response. If I put dampers on it, which I was planing on, whats the worst that could happen? I would find my furnace could not heat the house up fully in the coldest parts of winter and I would have to close the dampeners down? Or are there other problems that could develop that I am not thinking about?

This 85,000btu Goodman cooks 3,000+ sqft even in the coldest Wisconsin winter. It keeps the house at any temperature I choose, and gets there quickly. The better my ducts are sealed, the better the system seems to operate.

Jamie

dac122 10-24-2008 04:52 PM

Quote:

Originally Posted by jamiedolan (Post 176390)
Thanks for your response. If I put dampers on it, which I was planing on, whats the worst that could happen? I would find my furnace could not heat the house up fully in the coldest parts of winter and I would have to close the dampeners down? Or are there other problems that could develop that I am not thinking about?

Can't think of a downside so long as you put those dampers as close to where you tap your trunk or plenum. That should effectively zone that room. You could even opt for some high end dampers that seal extremely well. You very well may need the supply damper to lower air flow because depending on where you tape it might be too much.


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