Replacing 24-year-old Noisy Furnace--Looking for Advice

[kurtnm]

Hi,

We are replacing a 24-year-old furnace in a condominium that has a faulty valve. It will cost around $$$ to replace the valve and that seems unwise in a furnace this old. It is an upflow configured furnace (Train BLUI62F960B2 with a Bryant coil). It is in a mechanical closet with a water heater, and a ductless return which is facing the main living space. It is very noisy, and we are told the system is oversized. Our primary concern is noise and cost; we are trying to sell the unit but could be here awhile in this market.

I am told that an 80% efficiency unit makes the most sense due to venting issues. We are on the 2nd and 3rd floor of a three story building, new venting required for higher efficiency units seems impractical. Our square footage is around 2000, and we have some additional air volume with sloped cathedral ceilings.

One estimate I received was for a Coleman modulating 80 furnace with new coil and condenser. I liked this bid, but my concerns are two fold: the contractor specified an identical 5-ton size, while other contractors told us we didn't need such a large unit. Second, if sized correctly, I'm concerned that it will run constantly. This would make the noise factor critical. (It's one thing for a manufacturer to claim it is quiet and another for it to truly be quiet.)

A second option I am considering, but haven't priced, is a Rheem combination tankless heater and furnace. This would replace the equally old water heater, and by removing the water heater from this closet might allow us to place the return in a hallway at right angle to the living space. This would involve some duct work/drywall removal.


1) How do I find out the correct size--is a manual J calc necessary, or can i trust someone's judgment?

2) Do you think it is worth the extra cost to relocate the return (i.e. go with a tankless Rheem system) or should I just go with a modulating furnace, such as the Coleman? (The Rheem would be a two stage, I believe.)

3) Is there a way to find out the actual dBs of the blowers?

Any input would be greatly appreciated, as well as any other suggestions, or alternative equipment to consider.

[jpsmith1cm]

kurtnm

I removed the pricing from your post.

[BaldLoonie]

Must be one huge condo to need that monster furnace and 5 ton drive. 1st step is accurate load calc. Odds are it doesn't need that big unit. Moving less air will quiet things down. Ducted return will help or have them build a box under it and insulate it. A picture of the install would help us understand how it is down now. Ductless return and a water heater in the same closet sounds dangerous now that I think of it.

[kurtnm]

Must be one huge condo to need that monster furnace and 5 ton drive. 1st step is accurate load calc. Odds are it doesn't need that big unit. Moving less air will quiet things down. Ducted return will help or have them build a box under it and insulate it. A picture of the install would help us understand how it is down now. Ductless return and a water heater in the same closet sounds dangerous now that I think of it.

I don't know why it is upside down, but that's the furnace, return register and water heater visible in background (white). I tried posting a flipped version of it and it is still upside down.

[George2]

What size is the A/C. You said 5 ton, but I think you might have been talking about the blower.

I agree with B.L. The new furnaces are much shorter which will allow for a box under.

If there is room, on the side or under the furnace, for a hi-efficiency filter, they do a great job of quieting the noise.

A commercial grade, properly sized RA grille would also help.

[kurtnm]

What size is the A/C. You said 5 ton, but I think you might have been talking about the blower.

I agree with B.L. The new furnaces are much shorter which will allow for a box under.

If there is room, on the side or under the furnace, for a hi-efficiency filter, they do a great job of quieting the noise.

A commercial grade, properly sized RA grille would also help.

The blower is definitely 5 tons. The furnace model number is above, I can't find anything on it due to the age. It is rated to 162,000 BTU/hr, if that tells you anything about the size (I believe it is five tons). It is definitely oversized, no question about that. On for awhile then off for an equal period. The question is, what size should it be? I talked to one contractor about a manual J calc, but there is a significant cost involved. Are there other estimating methods?

So, putting it on a box would mean creating a right angle in the return air, if my understanding of what you are suggesting correct. The headroom in the closet is 7 feet, floor to ceiling.

Would a larger grill make a difference, we might be able to increase the width somewhat (~6") and the height--or are we better matching the grill size to the return size of the unit? Thanks.

[mechanical'al]

the cost of not doing a man j will be far greater (any contractor that doesnt do man. j is just guessing) so what else are they going to guess on quality ,safety, ect. ect.!!!!do your homework get sevral bids and refrences you may even ask to see some recent installs of theirs

[beenthere]

The outdoor units model number would tell us what size A/C you have.

How big is your condo.

A load calc would tell what size heat and A/C you need.

A properly furnace and A/C moving less air would probably not be as loud as your current one is.

[kurtnm]

The outdoor units model number would tell us what size A/C you have.

How big is your condo.

2000 Sq. ft. with high ceilings. Everything is 5 ton. (I got a bid from a contractor, which was lazy, and he specified all 5-ton equipment.) The outdoor condenser unit is a Lennox Mod# HS29-060-1P.

A load calc would tell what size heat and A/C you need.

A properly furnace and A/C moving less air would probably not be as loud as your current one is.

One concern is would the ductwork that I have be sized for the 5-ton blower, and would going smaller create any problems?




(The bid I got: No prices

FURNACE M# CP8C120C20MP12C, 80%, 120K, 5 TON
FF #170 GRILL W/ FILTER
HONEYWELL PRO 4000
EXPANSION VALVE 1TVM09-06, 5 TON R-410A
COIL M# FC60C3XN1 (5 TON) UPFLOW COIL
CONDENSER UNIT M# TCGD60S41S2 (5 TON) 13 SEER

)

[beenthere]

Good chance you only need around a 80,000 BTU 80%. 5 tons still sounds big.

Your duct work is probably under sized for 5 tons. So a smaller unit would move air better and quieter.

[kurtnm]

Thanks for the help. How many tons would that (80K) be? (Current BTUS on furnace is 162,000, it's 24 years old.)

The reason I didn't go with the proposal I received is two contractors told me I could go quite a bit smaller, one told me I could probably go about 3.5 tons. (Unfortunately, he never got me a bid.)

[mechanical'al]

probably and should work??

[George2]

If that is the only return that you have, then it is way too small for the 2,000 cfm needed!

I doubt the supply can handle 2,000 cfm. The 5 ton (now) is not working to it's full ability.

The size of the new equipment will be based on how your condo is exposed to the weather/sun. A manual J would be the most accurate, but it's hard to get one of those.

The new furnace and coil will fit in the closet on a box. No problem. Your new filter should be at least 20"x25", which should be fine on the new (smaller) A/C unit.

[beenthere]

Thanks for the help. How many tons would that (80K) be? (Current BTUS on furnace is 162,000, it's 24 years old.)

The reason I didn't go with the proposal I received is two contractors told me I could go quite a bit smaller, one told me I could probably go about 3.5 tons. (Unfortunately, he never got me a bid.)

Depending on brand, it can be 3, or 4, tons.

[kurtnm]

I got a verbal quote today and the contractor was recommended 4 ton furnace (120k btu) and 4 ton AC, 2-stage for both. I was originally thinking about a modulating 80% furnace, but in a less expensive brand. He liked Carrier. It's a bit pricey. He didn't do any sort of load calc or seem to be interested in doing it. We have cathedral ceilings, it's 2000 sq. feet but a big volume.

[beenthere]

Without a load calc, no way to know what size you really need.

[George2]

In what state do you live? Where is your condo located in the complex? In other words, do you have a condo above, below or beside you?

[mechanical'al]

ya I see no need to do due dilagence when I am asking my customer to spend lots of their hard earned money or how did you say it (carrier a bit pricey) though what the hell he may not be interested in doing a quality install anyway

[kurtnm]

In what state do you live? Where is your condo located in the complex? In other words, do you have a condo above, below or beside you?

We have a smaller unit below part of our unit, and nothing above us. We have an east-west exposure, in NM. I would like to get a load calc but that's another cost, and so far I haven't found a contractor offering to do one. Original windows and doors and typically southwest insulation levels, which is not as high as you would see in the north. Even with a five ton (both furnace and AC) there are periods of time where it can run pretty much continuously, both summer and winter, during the extremes of each season. This is generally the exception, however. The contractor questioned wether we are really getting 5 tons of performance, especially out of the AC. My gut says going smaller than 4 tons would probably be a mistake, but it's right on the edge of 3.5 to 4. He said 2-stage work well with multiple level units like ours. He said that if we went single stage AC (we are unlikely to do so) he would probably go with a 3.5 ton AC. If we go 2-stage he would recommend a 4 ton, and I'm not clear what his reasoning is for the difference. We are stuck using the original lines to the condenser for the old system, and would have to purge them.

Also, none of our system communicates right now, each component is a different manufacturer, the furnace is Trane (original), AC is Bryant (probably original), and the condenser is Lennox, newest component (late 90s to 2002) but still not good quality. We are at 9 Seer according to the contractor. The new system would be fully communicating, of course.

[George2]

We have a smaller unit below part of our unit, and nothing above us. We have an east-west exposure, in NM. I would like to get a load calc but that's another cost, and so far I haven't found a contractor offering to do one. Original windows and doors and typically southwest insulation levels, which is not as high as you would see in the north. Even with a five ton (both furnace and AC) there are periods of time where it can run pretty much continuously, both summer and winter, during the extremes of each season. This is generally the exception, however. The contractor questioned wether we are really getting 5 tons of performance, especially out of the AC. My gut says going smaller than 4 tons would probably be a mistake, but it's right on the edge of 3.5 to 4. He said 2-stage work well with multiple level units like ours. He said that if we went single stage AC (we are unlikely to do so) he would probably go with a 3.5 ton AC. If we go 2-stage he would recommend a 4 ton, and I'm not clear what his reasoning is for the difference. We are stuck using the original lines to the condenser for the old system, and would have to purge them.

Also, none of our system communicates right now, each component is a different manufacturer, the furnace is Trane (original), AC is Bryant (probably original), and the condenser is Lennox, newest component (late 90s to 2002) but still not good quality. We are at 9 Seer according to the contractor. The new system would be fully communicating, of course.

I agree with your contractor that you're not getting the full capicity out of your furnace and A/C because of the return air (for sure) and maybe a short supply side as well.

I tend to agree also with the 3.5 ton single stage or better yet the 4 ton 2-stage. The reason for the 2 stage is that you'll have the extra A/C when you need (and pease of mind) and it'll run on the low stage (better dehumidification) the majority of the time.

Running the extra low voltage wires may be an issue.