Hydronic geo pump for existing baseboards?

Discussion in 'General Discussions' started by jacurt2, Feb 28, 2014.

  1. jacurt2

    jacurt2 New Member

    Hello,
    I just had a company come out yesterday and they are in the process of completing calculations etc. before sending me a quote and proposal. Their design is suggesting a w2w pump to supply my existing baseboard heat that is currently powered by a propane boiler. This pump would also supply 2 air handler units that will go in the attic (my understanding at least, I'm new to this). My question: can geo supply the baseboards with water much hotter than 120? If not then this seems impractical to me. I'm sure I'm omitting a ton of important details so let me know what you guys need. Our house is an 1820 farmhouse in SE Pennsylvania, roughly 2700 sq ft. All ductwork originates from the attic and there is limited opportunity for new ductwork in the basement. Any ideas? I'm all ears.
     
  2. jacurt2

    jacurt2 New Member

    With some fierce googling, I found that the WaterFurnace Series 5 (502W12) can put out higher temps (150F) than other w2w systems. Does it make more sense to use this as opposed to a lower temp Bosch model? Not sure if my guy can do WF though, may be a moot point. Maybe I'm making too big an issue of the temperature output difference.
     
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Waterfurnace and Climatemaster have high temp units. Others may have as well. You can also increase baseboards. Just need to do some number crunching.
     
  4. jacurt2

    jacurt2 New Member

    Thanks for the response! Increasing baseboards isn't an option for me. What are the implications of using a higher temp unit on the rest of the system?
     
  5. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    No real implications, especially on a distribution system already setup for high temperatures. Just the cooler the load water, the greater the efficiencies. But these high temp units are designed specifically for these purposes (retrofits).
     
  6. moey

    moey Member

    Increasing the baseboards may just be using a baseboard that looks nearly identical that has two rows of elements rather then the typical one. It would put out more btu's per foot at a lower temp.
     
  7. jacurt2

    jacurt2 New Member

    Thanks! I may consider replacing the baseboards then, however I'm going to ask the builder about using a high temp unit. There just doesn't seem to be a downside to using one for my purposes
     
  8. geoxne

    geoxne Active Member Forum Leader

    -High temp W2W units have the highest efficiency ratings, however be aware they have a dismal COP of 2.1 during high temp operation (30F source EWT, 140F load EWT) and require higher flow rates per ton.

    -High temp W2W units load side max EWT is 140F (only 10F greater than "medium" temp units).

    -They are not available in different capacities (WF is 7 tons, CM is 10kw or a bit shy of 3 ton). Fewer capacity choices make it difficult to size the system to actual load.

    Good design with W2W requires heating with the lowest possible temperatures to get reasonable efficiencies. The payback is approximately one additionl COP for every 20F drop in load system temperature. Outdoor Temp Reset control should be considered to lower system temps when possible. Upgrading baseboard will help.

    Heat load as well as heat output of baseboard at lower temps should be calculated.
     
  9. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Ask the contractor to show you other homes they have done with water to water applications. In the HVAC biz geo guys are less than 1 in 10, hydronic guys are less than 1 and 10 so good geo hydronic guys are less than 1 in a hundred.
     
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    There are ways to use lower water temperatures besides base board emitters. I have seen the two pass emitters but have not used them. I crunched the numbers and the result showed improved heating ability for the two pass units.

    Radiant panels are not just for floors. The hot topic at the RPA is installing them in walls and ceilings.

    There are also panel radiators available in the US now that will cover a load at low temperatures and some look like sculptures.

    Mark
     
  11. jacurt2

    jacurt2 New Member

    Thanks for all the thoughts guys. I'll keep you posted on what the contractor recommends. Is the low COP when the high temp model is running hard that big of a deal?
     
  12. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    I have installed 3 of the WF high temp units and DOC has installed 6 or 7 of them. I know 4 of his was in a church with existing baseboard.

    The 3 that I did were 3 separate houses, all with some type of baseboard and air handler combination. Being this winter as super cold, I have not have one problem with the 3 I did. Must have high flow on both load and source and also strainers and flow switches. One of the houses I did had baseboard and copper that had to be atleast 40 or 50 years old and the strainer will plug about every 3 weeks (unit will trip on HP, so time to clean strainer) so those are couple of design things to think of.
     
  13. jrh

    jrh Member

    If there is already ductwork throughout the home. You could simultaneously heat through ductwork and baseboards. The baseboards might not need to add much to meet the load. This can be done with water temps under 120.
     
  14. jacurt2

    jacurt2 New Member

    There is ductwork for the ac but it's probably not adequate to completely heat the house. I guess I'm wondering if the heat from 120F water running through the baseboards is going to be worth the costs or would it be better to pay more to run the higher temp model.
     
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    "I guess I'm wondering if the heat from 120F water running through the baseboards is going to be worth the costs or would it be better to pay more to run the higher temp model."

    That's why you need to seek out an uber competent designer. The math will answer your question.
     
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    As always a heat loss calculation is required, or all is speculation.

    Sizing water to water systems requires knowing what you have in radiation. Measure the liner feet of base board and I will give you a number. We then pick a machine that will do that number.

    Do not discount the duct work as it may only do part of the job in heating.

    There are now control systems available to allow radiant cooling.

    Mark
     
  17. jacurt2

    jacurt2 New Member

    There's about 240 linear feet of baseboard.
     
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    At a design water temperature of 180* F the average 3/4" ID base board element will give off about about 600 BTUH of heat per running foot at 1 gpm, so you can get rid of 144,000 BTUH with what you have at the 180* temperature.

    Do we need that much? We do not know without the heat loss.

    What can the propane boiler make? How big is the current air conditioning system?

    So what happens next? We feed the same base board 110* water? We get 160 btuh per foot. 120* gives us 210 btuh per foot. 130* gives us 260 btuh per foot. 140* gives us 320 btuh per foot.

    If we design for the regular temp W2W we can supply 68,000 btuh which may not be enough on a design day, but it would sure put a dent in the load. That is all based on just moving 1 gpm. If we add a bigger pump those numbers btuh go up. If we speed up the water to 4 gpm our btuh per foot climbs to 270.

    The numbers I fed you are from the great folks at Slant Fin. The numbers came from their web site. Thanks Slant Fin folks. www.slantfin.com/#&panel1-5en

    I did the math so watch for errors I did the calculations while typing this post.

    All is not lost on this project yet. The biggest flow I have is 4 gpm. We can add more and get more heat. There are plumbing and piping tricks that can leverage a hydronic system .

    BBL

    Mark
     
  19. jacurt2

    jacurt2 New Member

    Thanks for crunching those numbers Mark! It certainly give me more hope about this. I'll bring up these points with installer. The bigger pump seems like a great idea that most would probably overlook.
     
  20. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Again if this is new news to your installer you may need a different installer.
     

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