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  1. #1
    Join Date
    Apr 2010
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    Default Replacing old radiators with forced air/ac

    Looking for more opinions on this. I’m in Wilmington, Delaware and I’ve taken a 2,000 SQ FT 1930 colonial 2 ˝ story house on uninsulated concrete pad (no basement or crawl space) down to the studs (attic area is 3rd floor). The original house has large radiator heat throughout and no AC. The radiators are in “series” so you can’t turn one off without shutting off all others. The boiler and heater are in the middle of the downstairs on the backside of the fireplace (that will be the centerpiece of the house so these must move) taking up about 14 SQ FT. The 1989 first floor addition (kitchen, breakfast nook, bedroom, bathroom) had (I removed them) baseboard electric heat that left the rooms cold. No AC there either. The radiators have always been an issue as they take up a lot of room and dictate where furniture must go. I’m planning for a modern, open floor plan and need to move the “works” out from the middle of the house to a corner. I also want a more unified system, better balanced temperature and/or zoned heat/air. Also, the radiator pipes really eat up ceiling space that I could use to expose beams/raise transition areas. I’ve been bringing in HVAC guys and they’ve agreed removing the radiators and installing forced air/heat is a good move even if it means loosing the efficient radiators. Been getting quotes in the $10,000 range. Thoughts?

  2. #2
    Join Date
    Feb 2008
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    554

    Default Re: Replacing old radiators with forced air/ac

    tropic:

    You didn't say if you have a steam boiler or forced hot water---I'll assume the latter.

    I've never been a fan of forced hot air for various reasons, I think you'd be better off with FHW, since the supply mains are much smaller than air ducts and FHW can deliver a lot more heat faster than forced air---this could be important if the slab can't be effectively insulated & continues to keep the house chilly in winter.

    Speaking of insulation, spend as much $$$ as you can on having insulation blown into the outside walls and attic---they should be R19 and R40, respectively---also replace any old or loose windows with double pane or storms---it's amazing how many people buy a new heating system for thousands & don't spend a few hundreds on insulation and windows---the heat or cooling has to stay inside the building, or you'll waste a lot on fuel & feel uncomfortable.

    While you can combine heat and AC in the same ducts with FHA, the ducts would be large & they have mini-split AC units you can install if you go with FHW.

    Is there a nat. gas pipeline available, or do you use oil or propane??

    Excellent new boilers the size of a large suitcase are available in cast iron or stainless steel ranging from 83% AFUE efficiency to 95% AFUE for more expensive condensing boilers.

    Many boilers these days are designed to be wall-hung to save on floor space.

    The high-end boilers don't even have a chimney, just a plastic exhaust vent & condensate drain.

    Many Home Depots carry the reliable Slant/Fin line of boilers---go in & take a look at them, check the pricing.

    Excellent entry level boilers cost $1500, plus installation and have a lot more heating punch than FHA and have quiet operation.

    There are thin-style baseboard and steel panel radiators and kickspace HW heaters for tight spots like the kitchen & bath.

    If your winters are not too cold, you might be a good candidate for sub-floor radiant FHW heat, if there is access to the floor joists---radiant tends to be expensive & you might have trouble finding a tech who is well experienced in the install---but it does eliminate radiators & other convectors & is highly efficient.

    You should get at least 6 estimates from the various heating contractors in your area---the price quotes and choice of equipment will vary widely---also ask friends, family & co-workers if they have had a recent heating system install & if they were satisfied.
    Last edited by NashuaTech; 04-13-2010 at 05:16 PM.

  3. #3
    Join Date
    Apr 2010
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    2

    Default Re: Replacing old radiators with forced air/ac

    Thanks for the great response!

    You didn't say if you have a steam boiler or forced hot water---I'll assume the latter.

    Forced hot water.

    Speaking of insulation, spend as much $$$ as you can on having insulation blown into the outside walls and attic---they should be R19 and R40, respectively---also replace any old or loose windows with double pane or storms---it's amazing how many people buy a new heating system for thousands & don't spend a few hundreds on insulation and windows---the heat or cooling has to stay inside the building, or you'll waste a lot on fuel & feel uncomfortable.

    I am replacing ALL the windows and ALL insulation. It's down to the studs. Also planning to loose the old water heater and go with tankless.

    While you can combine heat and AC in the same ducts with FHA, the ducts would be large & they have mini-split AC units you can install if you go with FHW.

    I've looked into those and the cost is already surpassing the $9,500 quote I'm getting for the whole new FHA/AC system.

    Is there a nat. gas pipeline available, or do you use oil or propane??

    Gas

    Excellent new boilers the size of a large suitcase are available in cast iron or stainless steel ranging from 83% AFUE efficiency to 95% AFUE for more expensive condensing boilers.

    Many boilers these days are designed to be wall-hung to save on floor space.

    The high-end boilers don't even have a chimney, just a plastic exhaust vent & condensate drain.

    Many Home Depots carry the reliable Slant/Fin line of boilers---go in & take a look at them, check the pricing.

    Yes, this is what I'm going with as of right now.

    If your winters are not too cold, you might be a good candidate for sub-floor radiant FHW heat, if there is access to the floor joists---radiant tends to be expensive & you might have trouble finding a tech who is well experienced in the install---but it does eliminate radiators & other convectors & is highly efficient.

    Winters are cold (in the teens for a month at a time). The whole first floor is concrete so I'd have to jack out the whole foundation to lay radiant. Don't think that's in the cards. I am planning to use electric underfloor radiant in the bathrooms though.

    You should get at least 6 estimates from the various heating contractors in your area---the price quotes and choice of equipment will vary widely---also ask friends, family & co-workers if they have had a recent heating system install & if they were satisfied.

    That's what I've been doing. Thought i'd try here to for more expert advice. The cost/hassle issue with keeping the radiators would be I'd have to run all new water lines and install new radiators to the four rooms (900 SQ FT) in the addition while also running AC ducts/PVC or a two unit ductless unit. Now were WAY past $10,000, I have a big hanging ductless unit messing with my design and two three separate heat/ac units (not counting the radiant electric floor heat.

    I'd love to hear more of your thoughts before I rip out the radiators tonight. You have good insight. Exploring every angle before there's no turning back!

    Thanks again NashuaTech!

  4. #4
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: Replacing old radiators with forced air/ac

    It's hard to tell from here but maybe a high pressure duct system would work.
    The ductwork doesn't take up much room and you'll get a good mix of air.
    You can use zoning with it as well.
    It's a niche item.

  5. #5
    Join Date
    Feb 2008
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    554

    Default Re: Replacing old radiators with forced air/ac

    tropic:

    I would strongly recommend you avoid splitting up the install between FHW, elec.radiant & a tankless hwh.

    Try to keep it all FHW to save $$$ on fuel & the install, as well as getting a very comfortable heating system---installing separate zones & thermostats is very easy with FHW, much easier than FHA.

    Thus you could have FHW composed of rads, or mix it with rads,baseboard, kickspace heaters, high output baseboard, small fhw radiant in the bath using a 3-way mixing valve on the same system, & an indirect 40 gallon HWH for the domestic HW taps---all tied into & run by a single 80k btu FHW boiler.

    Google "a little floor warming please" by Siegenthaler to get a diagram & story on how this is done using the same FHW system.

    Indirect hot water heaters by Triangle Tube Phase 3, Weil McLain **** Plus, or TFI Everhot are recommended---since they use the hot boiler water to heat the domestic supply via a heat exchanger, there is no need for a separate gas burner/flue.

    The "heating help" site below shows various piping schemes that can be used to pipe the convectors if you want to change the piping from a series loop to perhaps a one-pipe monoflo (diverter tee) piping arrangement---if the existing piping on the rads is copper, I would re-use it---click onto Loop Hot Water Heating, then onto Diverter Tee---it's possible to go thru the floorboards at each radiator & modify the piping arrangement into a diverter tee one-pipe system & thus retain the rads.

    The thing about FHW is that it is so flexible---you can always easily add some of the above components on at a later date, if you don't have the $$$ now to buy everything all at once---you should do a heat loss calculation for each room (Google "heat loss calculation" to get some ****** calcs).

    A HLC is roughly assigning 40 btu/hr of heat per sq.ft of floor space (assuming 8' ceilings & not too many windows)

    Thus a 15' X 20' room = 300 s.f. X 40 = 12,000 btu/hr needed to heat the room.

    Baseboard puts out approx. 560 btu/hr per ft.; thus, 12,000/560 =21.43 feet of baseboard needed.

    There is a high output baseboard avaialble that puts out 800 btu/ft/hr, which would reduce the amount of baseboard needed: 12,000/800= 15 ft. of baseboard needed for the above room.

    If you use radiators instead of baseboard Google "determining radiator output"---generally, you assign 170 btu/hr for each sq.ft. of radiator, then multiply by the # of radiator sections---thus, a 24 section rad 1/2' wide & 1.5' high = .5 X 1.5 = .75 sq.ft. X 24 = 185 sq.ft. X 170 = 3060 bu/hr output for this rad.

    Other boilers to consider would be Buderus,Burnham,Crown,Dunkirk,Hydrotherm,New Yorker,Peerless, Utica, Weil-McLain---these are carried by heating parts distributors----See Yellow Pages under "Heating, Equip & Parts.

    Google "boilers product list" & click onto the 3/26/10 XLS version, or click onto "view as HTML if your system doesn't support XLS; Google "furnaces product list" to see recommended furnaces.

    You can also go to the counterman at these heating parts disribs to ask for 2 or 3 recommendations for a good heating system installer in your area--go in the P.M. between 1 pm & 5 pm when it's not so busy.

    On the other hand Gabrilson made a good point about checking out the hi-velocity, small diameter duct system (unico) that provides FHA and cooling--site below.

    http://www.unicosystem.com
    http://www.heatinghelp.com/article-c...s/17/Hot-Water
    Last edited by NashuaTech; 04-17-2010 at 09:58 AM.

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