Hot water vs: forced air

Joe Koepfinger

I could use some advice on alternatives for upgrading my heating system. I currently have a zoned system consisting of a 43 year old natural gas hot water boiler feeding three fan coil units. Each of the fan coil units are close to the boiler (within 15 feet) and they are in pretty bad shape as well (rusting).

I would really like to improve on fuel efficiency and am tempted to replace this whole system with two or three forced air furnaces instead of a new boiler. I would like to know the pros and cons of this approach before I start talking to contractors.

The existing boiler has the following name plate data:

National-U.S. Gas Boiler
net I-B-R 324100 BTU/HR
A.G.A. Input 540000 BTU/HR
Output 432000 BTU/HR
Max. Press. 50 PSI

Thanks in advance for any assistance…

Joe Koepfinger

Geno_2

New System

This is a loaded question[s]. In a nut shell if you have nat gas to the house go with a high eff. boiler and air handlers with an indirect water heater. If you're going to stay in the house get the most eff system you can. Yes it is more money. It drives us crazy when you see 2-3 $45,000 vehicles in the driveway and the customer is crying about replacing 20-30 yr old equipment for $5-10,000 or less. What you have is what's called hydro-air. It is a good set up. If you don't have air cond. already it will be easier to install. Have them put in air handlers with the coils for a/c and upgrade later when more funds are available. Get three estimates and go with the best not the cheapest. It will pay you back.
Geno
Good luck.

lisfjoe

Or---

You could achieve the best comfort and efficiency and put in some baseboard heating. Certainly a bit more expensive than replacing the fan coils but for comfort and cleaniness plus fuel efficiency adding hot water baseboard or radiators is the ultimate.

Either way you go, make your sure your contractor does a heat loss calculation and puts in the right size boiler. By the way, with hot water heat (baseboard not fan coils) you'll most likely need a much smaller boiler because no allowance will have to be made for duct losses. Plus you should get them cleaned out of the mold and dirt that has been accumulating over the years. Stop blowing all that dirt around.

Remember, 88% of people who have hot water heat that had experience with hot air won't go back. (to hot air).

Eric

my thoughts

I will get flak for this one but, I would go with furnaces.
You already have ductwork in place, go furnances. If you were starting from scatch then I would go hydronic.

However,There are a couple of factors to check. Where are you fan coils located at? If you go with furnance you will need flues,combustion air,condensate drains, and maintenance space, at each location.

A furnace will typically have greater potential for higher effeciency. This is because it is heating cold air at 70F and not water at 140 to 160F. Condensing more flue gases increases effeciency (suck out more heat) with a lower entering air or water temperature.


Here's the advantages:

1) furnaces will likely operate for more hours at peak load and high effeciency compared to hydro air. All three fan coils will have to operate for boiler to be fully loaded depending on number of boilers, staging,sizes, ect.

2) Backup- If one furance dies at midnight you can heat house with others.

3) Cheaper.

4) DONT OVERSIZE FURNACES or BOILERS. Get a load calculation. But my guess is with an older home. Infiltration (leakyness) is going to be the largest heating load and is the most difficult to guess(calculate).

Bob Gagnon plumbing and heating

it's not even close

stay with the hot water no matter what it cost. i've read that furnaces now last average 7.5 years, and i get a lot of calls from people whose furnaces are only 8 or 10 years old and they need a new one already. if you have 2 or 3 furnaces how many replacements will you go through in 43 years? i see plenty of boilers 50+ years working fine. but the biggest advantage is the comfort. what is it worth to have a draft free house? or 85 degree tile floors on a zero degree night? what is it worth not to have all that dust blowing around? i was barefoot and wearing shorts on below zero nights this past winter and my house was as comfortable as a warm spring day. you don't even know the heat is on. if you are going to stay in the house i would put radiant on the 1st floor and baseboard on the 2nd floor. the system will last forever and the comfort is unparalleled. i'll admit a lot of people go with forced hot air because the initial costs are cheaper, but it is the biggest mistake they make when building or remodeling. people that i have installed radiant for are my happiest. they shake my hand, pat me on the back and run through traffic in the rain, years after the install, to tell me how much they like their radaint. it is that good. for a luxury car you would pay 2 to 3 times the price of the cheap cars, but you might get radiant and forced hot water baseboard for only 25% to 50% more than forced hot air. it's a small price to pay for a lifetime of comfort. bob

Dale

Half million input

You have a really big gas input. I wonder how big your house is or whether the way you have it set up it's 3 rentals. I guess I would have a blower door test done, seal up the holes, and insulate as much as possible. Then, I would do a heat loss and see what you really need. If it isn't a rental I'll bet twinned furnaces would work, If the heat loss gets alot lower one zoned furnace will work fine. If it is a rental and the motivation is to get the tenants to pay their own gas bill 3 small furnaces would probably be least expensive. I wouldn't do anything with mechanicals until I knew what the heat loss could be with insulation.

Art Pittaway

Some good answers but

first thing is pick your contractor on competence in commercial work. Low bid is usually worth it. You have a 1/2 million btu/hr boiler now, thats light commercial. Others have said do a heat loss, this is manditory if you want to size it right. Ask around and pay a contractor up front to do a heat loss, get the report and his quote, that way he can get paid and you have the data. Boiler or furnace it still takes btu's to heat the house. Get a hndle on what you really need. Use two boilers and stage them, the controls are available at reasonable prices, work very well, then you always have a back up and improved economy. Make sure they do the flue correctly, 3 furnace flues all joining from 15+ feet away sounds like trouble.

Also,on the heat loss, size it for A/C also, an oversize A/C is worse than none, high bills and a cold clamy house.

Consider your domestic hot water requiements, could a boiler fired water heater be an asset? Are you having trouble filling that 800 gal hot tub? You know...the one your wife keeps hinting about.;)

Check out the find-a-contractor spot on this site.
Good luck.

Bob Bona_4

consider

the flak starting.:)

A boiler exists now. Replacing it with a Munchkin or other condensing gas boiler is the way to go. Replace the air handlers with new, maybe even consider variable speed units for more efficiency. There is no way a furnasty, 90+ or other, will be more efficient than this set-up. Remember, AFUE numbers do not equal system efficiency.

I would NOT install furnaces in place of hydro-air. That would be a huge step backwards in terms of longevity and service related issues.

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MikeB34

your comparing...

..apples and handgrenades. Sounds like he has forced air, but using hot water as the heat source. (air handlers.) I am not against hot water systems, in fact I love em..But a new furnace isn't all that bad. ECR International's Olsen division makes a high efficiency that is 95%, the heat exchanger is warratied for LIFE to the orig owner and not pro-rated, comes with 5 year parts warr, (also not pro-rated) The changes you are listing are a major retrofit.and will cost a lot up front.

If he has air handlers, then the ducts are there. I would go the gas furnace.

If it was a new install then I agree with you.

Mike

B.BART

HYDRO-AIR

HAVE A NEW HIGH EFF. BOILER INSTALLED WITH NEW AIR HANDLERS
AC OPTIONAL. THE NEW SYSTEM WILL PAY FOR ITSELF.MAKE SURE YOU USE A CONTRACTOR YOU TRUST DONT SHOP PRICE.

kevin coppinger_4

adding to what...

Bob stated... and to your statement about multiple furnaces... Why settle for one boiler? multiple boilers staged will give better load match and reliability. If one goes you have two or three others to get you by. kpc

Wayco Wayne

Although

I love boilers I think furnaces would make more sense. You would have redundancy if one broke you would still have heat. If you have one boiler taking care of all air handlers and it goes down you are SOL until it's back on line. Also a boiler would have to provide 180 degree water for water coils, a temp where you lose condensing in a high eff. boiler, so efficiency would not be as high, where with furnaces the return air is 70 or thereabouts, which is consensing temps all the time. Most furnaces last 20 years or better. Unless you had plans to add a radiant floor eventually furnaces make more sense. WW

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