Heat & A/C advice

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Old 07-15-03, 08:38 PM
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Question Need Heating & Central A/C system advice

I'm getting some conflicting info from HVAC contractors and am wondering if anyone can offer any advice? I want to replace my existing gas furnace and add central A/C in my 55 yr. old, 1600 sq. ft. Cape Cod in southern Wisconsin.

3 contractors have suggested 92%+ AFUE 2-stage 60,000 BTU furnace, probably one with a variable speed fan (ramp up/down type) and a high efficiency air filter. The sales pitch of increased comfort and add'l air filtering because of continuous fan operation makes sense to a novice like me. A 4th contractor did a more thorough job looking at my ductwork (the others really didn't even look) and said that he wouldn't even sell me a 2-stage furnace. He said that because I indicated less flow from the supply in the master bedroom upstairs, the situation might become even worse with a variable speed fan - since the low speed of the initial stage might result in less or no air coming from that supply. He is recommending a 92% AFUE single-stage with high efficiency air filter. He is also recommending 80,000 BTUs because he doesn't want to drop-down more much more than 40k from the existing one. (35+ yr old furnace that says "Input 125,000 BTU, Bonnet Capacity 100,000 BTU")

He said that central A/C might not do a good job upstairs. He said worst case scenario is that because there are only 2 air returns on the 2nd floor the cooling coil could sometimes ice-up due to a lack of return air. The upstairs is 650 sq. ft. of which about 240 is the master bedroom and the rest is a guest bdrm, full bath and hallway. Each bdrm has 1 supply and 1 return. The full bath has 1 supply. The guest bdrm and bath supplies are adequate airflow, but the master bdrm seems to be a bit low for a room that size even after trying to balance the system myself - the master bdrm is the farthest room from the furnace. He is recommending a 2 ton, 11 or 12 SEER A/C. The others recommended that or a 2.5 ton and slightly higher SEER.

Some other things that only the 4th contractor mentioned is the supply under the thermostat should be closed or changed to a return to prevent the furnace from short cycling, and my house has an "opposite" system (returns on the outer walls and supplies on the inner walls). He said that I could also play with the door that closes off the upstairs to see if that would have any effect on upstairs temp.

The 4th contractors seems more knowledgeable and upfront, but I'm more confused than ever. So my questions are:
1) Am I better off going with a single-stage furnace given the lower air flow to the master bedroom? (typically the coldest room) Or should I go with a 2-stage one? I really like the idea of the additional comfort from the continuous air flow with the variable speed fans, but is it worth the risk of a colder bdrm?
2) Is there a chance that my situation could cause the cooling coil to ice-up? And what are the ramifications (short & long term) of that? How can it be prevented?
3) In my climate will I use the A/C enough to justify the cost of a higer SEER? (I'd only envision using A/C when humid, temp over 80 during the daytime or to cool off the house at night) For example, 1 contractor bid me a Lennox 14 SEER w/R410a for only $200 more than a Bryant 11 SEER w/R22 refrigerant.
4) Are there any other options to these issues? (other than adding supplies or returns to the upstairs)

BTW- The past Jan., I used about 230 Therms to heat the house with 1465 degree days over a period of 29 days. I believe that it was a bit colder than normal. I set the temp to 68 during the day and 58 at night.

Thanks a bunch!
 
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Old 07-16-03, 01:28 AM
lynn comstock
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Re: Need Heating & Central A/C system advice

[QUOTE]Originally posted by BHB_RHG
The 4th contractors seems more knowledgeable and upfront, but I'm more confused than ever. So my questions are:
I favor this guy. The contractor is more important than the brand or efficiency.

1) Am I better off going with a single-stage furnace given the lower air flow to the master bedroom? (typically the coldest room) Or should I go with a 2-stage one? I really like the idea of the additional comfort from the continuous air flow with the variable speed fans, but is it worth the risk of a colder bdrm?
I favor the 2-speed. If the ductwork is sized and constucted properly it will work. If not, it won't make much difference in the problem room. The comfort everywhere else will be better.
2) Is there a chance that my situation could cause the cooling coil to ice-up? And what are the ramifications (short & long term) of that? How can it be prevented?
If you get a fan capable of more air the fan can overcome the deficiencies of the duct system. I'd recommend 1/2 ton more air than the standard. (such as a 2.5-ton rated fan on a 2-ton unit. You can always slow the fan speed should you not need it.) It also works better with better air filters (that restrict the airflow).
3) In my climate will I use the A/C enough to justify the cost of a higer SEER? (I'd only envision using A/C when humid, temp over 80 during the daytime or to cool off the house at night) For example, 1 contractor bid me a Lennox 14 SEER w/R410a for only $200 more than a Bryant 11 SEER w/R22 refrigerant.
Chose the contractor first. See what the contractor's sizing and workmanship mean to your final comfort and efficiency at
http://www.advancedenergy.org/root/b...tions/seer.pdf
4) Are there any other options to these issues? (other than adding supplies or returns to the upstairs)
Wait and see. More openings may not help. Everything about the air distribution depends entirely on the understanding and execution of the contractor. Most ductwork fails to produce anything like uniform comfort throughout the house. That is reality in the marketplace driven by LOW prices.
 
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Old 07-16-03, 12:02 PM
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New furnace

Im with Lynn for #4 here . you didnt say what one was for the 410a unit? Up there where you are I would go just for the SEER 12. You dont run the AC that much. Then 410a is still a thing to work on a lot and the freon cost and parts or high. Id Go for a R 22 AC, they still have to make the refrigerant till 2020. ED
 
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Old 07-16-03, 02:40 PM
binford
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more thoughts

I hope you got each contractor to detail what they are going to do and for how much.

This will give you a starting place.

In your neck of the woods I would also look into a Geothermal heat pump. Some of the utility companies are offering rebates too. They are a bit more $$ upfront, so you would have to look at the pay back time. 3-4 years or 10-15 years If it takes 15 years to break even than its not much of an incentive.
Don't use the contractors numbers, use your own. Figure out how much you old system on average cost to heat and cool your house.
 
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Old 07-16-03, 02:48 PM
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Question

Thanks to all of you for the advice.

I've had some people suggest that I inquire about having a blower/fan added to the supply (and/or possibly the return) for the ducts that go to the master bedroom to help increase airflow. Any experience or comments on this? As I mentioned, I was ready to go with a 2-stage, variable speed model because of the increased comfort until the issue of possibly less air flow to the bdrm was mentioned. All of the ductwork appears to the original with the house (pretty heavy-duty aluminum). I had it cleaned last fall so blockage shouldn't be an issue. I guess there could always be a leak somewhere in the supply.

The 4th contractor felt that the 2-stage variable speed furnaces don't work as well in a 2-story house (he may have been thinking of older houses), but another contractor disagreed with that. Any thoughts?

Thanks again!
 
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Old 07-20-03, 10:12 AM
lynn comstock
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[QUOTE]Originally posted by BHB_RHG
I've had some people suggest that I inquire about having a blower/fan added to the supply (and/or possibly the return) for the ducts that go to the master bedroom to help increase airflow. Any experience or comments on this?
This is a last resort type of fix. It is never something that any contractor would design into an new system.
As I mentioned, I was ready to go with a 2-stage, variable speed model because of the increased comfort until the issue of possibly less air flow to the bdrm was mentioned. All of the ductwork appears to the original with the house (pretty heavy-duty aluminum). I had it cleaned last fall so blockage shouldn't be an issue. I guess there could always be a leak somewhere in the supply.
Duct leakage is always a real possibility that can be eliminated by testing for leakage using a duct blaster and other tools.
The 4th contractor felt that the 2-stage variable speed furnaces don't work as well in a 2-story house (he may have been thinking of older houses), but another contractor disagreed with that. Any thoughts?
I think that contractors often disparage ideas that are beyond their capabillities or interests. We cannot offer much opinion about what can or cannot be done because we cannot see the house and all of the circumstances that figure into a design. I am inclined to trust the "can do" attitude of #4. [/B]
 
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