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  1. #1
    Join Date
    Jan 2004
    Posts
    9

    Geothermal for Baseboard Heating

    All the posts I've seen so far for Geothermal for Baseboard Heating have been pretty negative, but none have mentioned the Carrier/Bryant gt-pw water-to-water (50yew). This seems to be advertised as a boiler for hydronic use. It's specs are 140deg water with 32 deg EWT at 2.1 COP or 2.5 at 50deg EWT. 140 deg water will deliver about half the BTU's as 180 deg water but in my case I have cast iron baseboard on almost the entire perimeter of each floor so that it is somewhat oversized. Cast iron also has at least 5 times the contact area of finned copper pipe, so it would seem that it would perform better at lower temperatures and flow rates.
    This unit is expensive and I obviously don't want a failed experiment, so I would appreciate any comments and analysis.

  2. #2
    Join Date
    Nov 2010
    Location
    Missouri
    Posts
    357
    Howdy in my opinion hydronics and geo are two different systems. hydronics is what you would apply on your baseboard heaters, Boiler to heat water and pump to circulate hot water.
    Geo has Heat pump with, if ordered hot water for domestic hot water. through loop inside unit that hot gas from compressor heats, besides it`s other operation is to heat the air and blow into ductwork. Or cool depending what owner has selected at stat. But hot water is generated heat or cool.

  3. #3
    Join Date
    Jan 2004
    Location
    Sanborn, IA
    Posts
    191
    My first concern is that you may need 3 of these geos to make this work.
    Would you spend $50,000 on enough geo and loops to heat the radiators versus $5000 on a new electric boiler?
    $45,000 payback would take a long time considering you are only saving 50% on your utility bills over the electric boiler. (2.1 COP versus a 1.0 COP of an electric boiler)

    this was an off the hip assessment, but i thought i would offer it anyways.

  4. #4
    Join Date
    Sep 2009
    Posts
    17

    Geo for hyronics

    You can use Geo for hydronics. You just have to find one made for it. If you just use a water to water unit, you will have to have to make sure that your btu output on your unit, for heating is the same as your btu out on your baseboard heaters. Hydron module units, which have the highest heating outputs and the best warranties, have a combo unit that does forced air and heat and hydronics. And it shouldn't cost you a fortune to get a Geo. I'm installing 8 ton in a 7000 sq ft house for $30,000. The electric company is giving him a $750 a ton rebate back. If you need any further help just give me a shout at kellerhvac@gmail.com.

  5. #5
    Join Date
    Dec 2011
    Location
    USA
    Posts
    66
    Generally a heat pump will not put out enough hot water in a short period of time to keep up with the heat loss of a home, if you just want to put in floor heating of a small room say a bathroom it could work otherwise I would not advise it. It can supply the hot water for 2 people dishes and baths if the ambient is 20 degrees or lower.

  6. #6
    Join Date
    Jan 2004
    Location
    Here and there
    Posts
    4,803
    Though not the best application I have used water to water with fin tube radiant and have had no problems. Milder climate here and used a 5 ton 2 stage with stage 2 locked out in the cooling mode
    i belong to peta ... people eating tasty animals. all my opinions are just mine.

  7. #7
    Join Date
    Jan 2013
    Location
    Central Virginia
    Posts
    2
    I've been looking into this new 50YEW model as well. I've been think of going geo for years but I'd hate to have to give up my radiators for forced air, which probably wouldn't work very well anyway as all the vents would be in the ceiling. Fortunately a lot of these older systems are way over the needed capacity. I've got 10 big cast iron radiators and if you calculate the capacity at 180º it's over 100,000 Btu/hr. When I moved in it was set at 195º, so capacity would have been more like 115,000, which is what the boiler can put out. All this for a 1300 sf 1-story house. It had single-pane steel casement windows and bare steel heating pipes running through unheated crawl spaces, so the losses must have been tremendous. A lot of insulating has been done since then. I've cranked the boiler down to 160º but even so on really cold nights it might go on 2 or 3 times for 25-30 minutes. So I've still got a lot of spare capacity and I'm sure 140º, which should yield 69% of the capacity at 160º, would be adequate, if these new geo units can really do that. I'd be concerned that in really cold climates a sustained bout of cold weather could get the EWT down to the 30º range, sapping both capacity and efficiency. But here in central Virginia, that's now very rare, we might get a few nights in the teens, but then a few days later it's back near 60º highs. So in principle it should work fine. During cold snaps when you need 140º heat I might only get COP of 2 or so, but most of the time I'd be running 120º or 130º so COP might be more like 3 or even 4. My question is, do I really need a buffer tank when I've got 10 big old radiators worth of thermal mass? That must be the equivalent of a 40-gallon tank, at least. Space in the half-basement is at a premium, especially if I leave the oil-fired boiler in for backup.

  8. #8
    Join Date
    Apr 2012
    Location
    Georgetown Delaware
    Posts
    197
    I am going to be the voice of reason and experiance here. If you have the patience and monies to be your own beta tester, and live with the results, go for it. If not the latter, get off the internet and get a local pro to elp you out.

    A combo geo unit is not designed for radiator/register use, because of it's inability to produce mass btu's when needed. A buffer tank wil not solve that puzzle, just help it. Hydronics and geo are done with in slab typically. You then have the "mass " to be slow and even to match the geo output.
    For a retro fit water to air traditional is your best choice. If you want to maintain your aesthetics, you could leave your boiler and maybe reduce your tonnage to only your cooling load and use the boiler to cover the other % of your heating load.
    Again, you really need boots on the ground to help you figure it out.
    Eric
    Eric Sackett
    weberwelldrilling.com
    Delta P= 8 ATA
    www.youtube.com/weberwelldrilling

  9. #9
    A low temperature heating system like radiant floors is a very efficient way to heat the house. Most hot water recirc systems need 180 degree F water, radiant can comfortably heat the house with 100 degree water. It's a gentler, more even, more comfortable heat than forced hot water or forced hot air.

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Lower water temps are going to be more effcienct for both a mod-con as well as a goethermal water to water. The lower the better on the load return temps. By 140F, you're looking at 120+ return temps and pushing the limits of most units.

    That being said, if your a home that was "well radiated" and you've made thermal envelope improvments, you might be suprised that 140 or even 120F water can actually heat it. My 1920's home originally had enough steam radiator capacity to supply the home with about 300k BTU's (total EDR is around 1400 if i did my calcs right). Actual heat loss is around 65k BTU's now at design, so even 120F water could almost get it done with so much EDR. The main steam supply header looks like 4" with a 2" condensate return... all pipe perfectly sloped back towards the boiler.

  11. #11
    Join Date
    Jan 2013
    Location
    Central Virginia
    Posts
    2

    thanks

    Thanks for your comments. I did expect some discouraging words and I know there is some risk here. That's why these things are subsidized, to get people to try them when they're not fully proven. It's obvious that the manufacturers are proceeding cautiously with these new high-temperature units. Waterfurnace has a only one 7-ton model and Carrier/Bryant has only their 3-ton 50YEW, which by coincidence is just about what I would need. Despite generally positive experiences with geo, you do hear of projects where the calculations didn't hold up and the systems couldn't hold temperature in midwinter. But here in Virginia we've got a relatively warm 60° ground temperature and increasingly mild winters, so that's a big advantage. Still, I suspect I'd be keeping the old oil-fired boiler for backup; it's relatively new and fairly compact. Meanwhile, maybe I'll just try turning down the boiler temporarily to 140° or 130° on a cold night just how much heat the system puts out.

    Radiant floor heat would doubtless be more efficient and is a possibility in the long term, at least for parts of the house. The kitchen and bathroom floors all need replaced anyway, so that would be a good opportunity for PEX installation. Two bedrooms and the living room are wall-to-wall carpeted hardwood on a layer of wood sheeting above accessible basement/crawl space, so that's possible as well. But none of this is going to happen anytime soon. Having it done professionally would push costs beyond any possible savings. In a few years I'll be retired and then I'll have plenty of time for such projects, not to mention even more insulating. The important thing for now is to get the holes bored, the loops installed and a system in place, before the tax credits expire. Hence my interest in a radiator-based system, where the only costs would be the loops and the heat pump.

    Anyone know what the Carrier 50YEW costs?

  12. #12
    Join Date
    Apr 2012
    Location
    Georgetown Delaware
    Posts
    197
    The tax credits will not expire before 2016, barring any bankruptcy proceedings by the govt. lol
    Eric
    Eric Sackett
    weberwelldrilling.com
    Delta P= 8 ATA
    www.youtube.com/weberwelldrilling

  13. #13
    Join Date
    May 2012
    Location
    Nova Scotia, Canada
    Posts
    41
    Sorry Larry, but site rules prohibit discussing pricing. Fortunately there is a contractor look-up feature that may help you contact someone local that may be able to give you some figures.

    Waterpirate (Eric), I noticed in some of your photos where you're running the geo pipe through the foundation that you are running it through a 3-4" pvc sleeve. What are you using to seal it up? The company I worked for previously would run the geo pipe itself through and just use a 2 part epoxy and that did the trick/never leaked. Thoughts?

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