Adding on

[Stiggy]

Hi all, well adding 1000 sq feet to my house, my existing heatpump is rated at 2.5 tons, it cooks me in the winter and freezes me in the summer.. i need to add some vents by tapping into my existing trunk line, im going to delete 2 vents down stairs and just continue the runs into the downstairs addition, real small rooms that will be open to the addition, anyway kinda like they will be 1 room together now anyway.. my upstairs is the question, what size should i use for my conduit, vent pipe, runs? not sure of the terms used.. should they be the same as my old ones? also is it a bad idea to share the same line with 2 vents even if they are feeding the same room? ( would save $ and time to share the same line)
thanks

[Hube]

If you were only adding a 100 sq ft to the home you could perhaps add or tap into your existing system But for a 1000 sq ft addition this is a whole different situation. Without knowing furnace size, house size, present duct layout and sizes,etc, it would be impossible to give you any exact advice.

You would be best to have some heating/ac Techs to come in and have a "first hand" look at what has to be done, get 2 or 3 opinions/estimates.
good luck.

[lonestarheir]

Just because your system is "cooks me in the winter and freezes me in the summer" I doubt that there is enough to add a 1000 sqft to it, especially an upstairs room. You really want to get a couple of HVAC co's involved and see what they think. A 2 1/2ton system should heat and cool somewhere between 1000 and 1250 sq ft typically. I am pretty sure that before adding that 1000sqft your house is currently more than 250sqft.

Get several pro's involved and figure out what needs to happen


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Brandon
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[Stiggy]

hmm, well yes i se your point and have considered that 1000 sq feet is alot, my existing house is around 1800 sq feet. I was told by a hvac guy that the 2.5 ton unit is really over rated for my existing house as it is and that 1000 sq feet would push it and really a 3 ton unit would be best.. he also said hey you could try it and see what would happen.. like i mentioned i want to extend 2 lines so were the vents are in the ceiling now would be removed and the run extended. if i cant share 2 vents with 1 line then i will need 1 more run. my addition for upstairs is against my upstairs bedroom so what im going to do is take out a window and install a door. The new door has an existing bedroom vent right at its base so i could cap and extend that one vent becasue it will become a hallway. (who need a hall vent in the floor I know its the sq footage that is the issue but in my mind the way im thinking is, really im not trying to add to much (in way of bleeding off the system with 100 runs exct)im just rediverting so to speak, except for 1 line perhaps (to add).. the returns are situated in a way that will pull all the air in the same manner as it did before just from a farther distance.. dont get me wrong im here on these forums for your advise and im listening.
Maybe i dont understand what that extra room will do? it just seems like the airflow is exactly the same as far as the returns are exct..
Thanks for all your advise

[Hube]

Units are sized according to a homes heat/loss heat gain (manual J)...Main Duct work and takeoff sizing is another ball game.(manual D)
Do it right, get a pro to check it out.
You will be glad you did.[8D]

[lonestarheir]

quote:Originally posted by Stiggy

...
Maybe i dont understand what that extra room will do? it just seems like the airflow is exactly the same as far as the returns are exct..
Thanks for all your advise

You couldn't be more wrong. Hate to say that but, your system will only move "x" amount of air. Return air is very important, and you can never have to much, but at the other end, the supply end, every time you add duct or move duct could make a world of difference in how your home heats and cools.

As said before, call a pro to help you out, then that company is on the hook for making it right and you are not. Most companys will come out and give you an estimate at no charge, and at the same time you can pick the "tech's" mind, thus giving you several different points of view on what will and will not work. Then go with the "pro" that you best communicate with. Make sure that he knows what would be your ideal situation.

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Brandon
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[imeduc]

You dont say where you are??? But 2.5 ton for 2800sq ft cant cut it.

like said get 3 bids for the job

ED

My mistakes dont define me they inform me.

[lonestarheir]

quote:Originally posted by Stiggy

hmm, well yes i se your point and have considered that 1000 sq feet is alot, my existing house is around 1800 sq feet. I was told by a hvac guy that the 2.5 ton unit is really over rated for my existing house

I don't know how it would be over rated, maybe under rated. Without doing a manual heat load calculation, it is really hard to determine, but that said most of the time, a typical HVAC unit will cool up to about 500sq.ft. per ton. With that calculation, you are about a ton of air short already, to add to this would be a big mistake, in my opinion.

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Brandon
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[Hube]

Some present day "rules of thumb" (1 ton for 500 sq ft) can be very,very, INCORRECT.
These 'thumb rules' may have worked several years ago, but the ONLY sure way to calculate the right size for SURE is by doing a heat gain calculation (manual J, Hrai, etc.)
These "rules of thumbs only give an approximate 'ballpark' size and sometimes are completely misleading,and out in left field (no pun intended)
Using the correct sizing methods will prevent any "short cycling, or humidity problems.
There are many homes, that although they are 2000 sq ft or so need only a 1.5 to 2 ton unit.(most only have a 18000-19000 gain)


And then again ,there are some homes out (poorly constructed) there that are in the 2000 sq ft range and the heat gain is 60,000 (5 ton)
[B)]

The amount of Insulation R value, location, outdoor design temp, orientation, windows,door sizes and types,and the tightness of construction, etc. if CALULATED PROPERLY can make a huge difference as to comfort and operating costs.

[lonestarheir]

Hube you are exactly right on everything you said, that is why I prefaced my statement with "...Without doing a manual heat load calculation, it is really hard to determine..."

Again, I would suggest to Stiggy to get some pro's involved and see what they come up with

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Brandon
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[Hube]

My previous post was mainly for the benefit of any inexperienced homeowners (including stiggy)... It was in no way intended to chastise or correct any of the experienced pros on this forum.

[lonestarheir]

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Brandon
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