Desuperheater Issues

Discussion in 'Maintenance and Troubleshooting' started by DMP56, Oct 18, 2010.

  1. DMP56

    DMP56 New Member

    Hi I'm new to the forum.

    Just had a Climate Master Tranq. 27, 5 ton unit installed this past June. I have not noticed much change in my electric bills. My question is: why would I feel a change in my water temp from warm to cold while taking a shower? This never happened prior to the geo install. The Installer appears to have the desuperheater hooked up correctly , 2 - 80 gal tanks, one has power. :)Thanks for any and all input.
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    I would like at how the plumbing is done. Lots of ways cold water can enter hot water lines if done improperly.
  3. geome

    geome Member Forum Leader

    Also, what is the lower thermostat temperature set to in the finishing tank? (Might as well tell us the upper thermostat setting too and confirm the unit is getting power.)
    Last edited: Oct 19, 2010
  4. DMP56

    DMP56 New Member

    Thanks for the reply.

    The desuper HW line goes to the bottom of the storage tank and the return is "T" at the top of the same tank on the cold side where the supply comes in. The HW from the storage tank then continures into the cold inlet of the powered water heater (New) and comes out the HW side of the water heater into the house.

    Both stats are set at 120. Prior to the geo system my HW heater was set the same and I had no issues. Like I stated before, when taking a shower the temp is set and about 2-3 mins. into the shower the water drops to almost all cold. I adjust the valve and the temp is corrected. The Desuperheater flow appears to be setup like it states in the Climate Master manual.

    I'm on well water in South Central Pennsylvania. The system is close loop 2 stage.
  5. geome

    geome Member Forum Leader

    Is the circuit breaker for the finishing tank turned on?

    P.S. I'm a homeowner, not a pro. Not sure why my signature is not appearing. I will ask admin now.
  6. ncgeo

    ncgeo Member

    If not an issue with the circuit breaker on the finishing tank I would suspect the lower element in that tank is burnt out. The operational upper element would provide you the few minutes of hot water, but the volume below that element would be cold, until it is refilled by the preheated water from the DSH tank.
  7. DMP56

    DMP56 New Member

    Got power to both elements. The ohms are 12 on both elements, and the amp draw is 18.87 on the upper element and 18.20 onthe lower element.

    Could a broken cold water supply tube in the finish tank cause this, If so how can I check for it?
  8. ncgeo

    ncgeo Member

    That sounds like a real possibility. Now in the Fall your geo unit is probably running less so not generating a lot of preheated DHW, and that "preheated" water could be short-circuiting the finishing tank. You will need to pull the inlet line off the finishing tank to inspect. The dip tubes I've seen were plastic and lifted right out of the tank inlet fitting.

    Another possibility is a tank thermostst is bad ... even though set at 120 could it be turning off the elements at some lower temperature?

    Also, just to rule out a shower valve issue, I trust you checked for similar symptoms elsewhere (i.e. kitchen or bathroom faucet) Many shower valves are pressure-balancing with a moving spool and something may be going wrong with it.

    This does not seem to be a geo issue; an 80-gal water heater that is fully operational should easily supply 25+ minutes of hot water through a 2.5 GPM shower head.
  9. teetech

    teetech Member Forum Leader

    I would also make sure there is no back flow device in the buffer tank inlet or dip tube.
  10. DMP56

    DMP56 New Member

    No backflow device on the system.

    This does happen on all wayer supply valves throughout the house. It just happen to me this evening during a shower. Nice and warm than it drops in temp and appears to pick back up, if you don't adjust the valve first.

    Never noticed this in the 20 year at this house, until after the geo was installed. I did bump the stat up to 125 on the finishing tank, but no change.
  11. ncgeo

    ncgeo Member

    "pick back up" ... can you elaborate on that, maybe indicating approximate timeframes and temperatures? Is it like a slug of cold water passing through, then normal hot temperature beyond that? Is it immediately reproducible?
  12. DMP56

    DMP56 New Member

    It is like you decribed, surge of cold water and than slowly going back to warm. If you can withstand the cold water change before manually adjusting the valve. It all happens about 2-3 min. into the shower and than another 2 min. to start to warm up again.
    Last edited: Oct 24, 2010
  13. ncgeo

    ncgeo Member

    2 minutes of cold water from a shower head is a fairly large amount (~5 gal), although it may actually be lukewarm water from the tank mixed with cold at the shower/faucet. I would be looking at that dip tube and the element thermostats

    Also, you may want to see if anything changes with the DSH not running. Then you would be introducing all cold water to the finishing tank, similar to having no preheat tank. See if that changes anything. You may already be running in this mode if your geo system is hardly running with the moderate Fall temperatures.

    I have a similar DSH setup running with my geo systems, no issues. Not sure yet if I will run DSH in winter ... although it is more efficient to generate hot water with heat pump than in-tank elements, I notice a big temperature drop of the supply air. DHW preheat is free in the summer but it robs from your space heat in the winter.
  14. geome

    geome Member Forum Leader

    As long as you're comfortable, I'd run the DSH in the Winter. Lots of efficiently produced hot water to be had.

    Even if aux heat is needed, not sure if it really saves anything by turning the DSH off. Hot water will still need to be produced by electrical resistance heating assuming an electric water heater using the elements (as opposed to a heat pump water heater, or something else.)
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Manufacturers describe DSHs of making use of "waste heat", yet as was pointed out they take heating capacity from systems. Op cost calcs show that pct of geo contribution to heating drops with DSH. Might be an interesting discussion or research project to see if DSH saves or costs in a northern heating climate.
  16. ncgeo

    ncgeo Member

    The bottom line is you need a certain amount of heat energy to satisfy space heating and DHW requirements. You would believe it is more efficient to generate DHW through the heat pump, but running the geo unit incurs additional energy expense for running the well pump and blower. So you may want the geo unit to satisfy the space heat as quickly as possible, which would mean using all of the groundwater heat for space heating.

    Also is it worthwhile to preheat 50 gal of DHW which may not even be used? Maybe a wash, since if you don't use the DHW the heat is dissipated to the air space which reduces the heating load.

    Indeed this would require some very detailed analysis, which I am not up to!
  17. geome

    geome Member Forum Leader

    If the percentage of the heat the geothermal system utilizes for DSH is 10% (frequently mentioned here) , then it seems reasonable to me that 10% of the well pump power would be attributable to the DSH operation. I assume the blower running cost is already included in the COP of the geothermal system. I could be mistaken, but it seems to me that getting COP of (let's say) 3 from making hot water with the DSH, reduced by 10% of the well pumping costs, would still be more efficient than the 100% efficiency of the resistance heating elements in a water heater.

    Me either!
  18. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Hot water made with a DSH is usually over 3 COP so to answer last comment first, it is clearly a more efficient way to make hot water but at what cost....
    Lower heating capacity/efficiencies make for longer blower, compressor, well or loop pump operating times = more operating hours.........

    It does get less interesting around here when folks have natural gas or discount water heating electric rates. Once the savings is <$100/yr is it worth it?

    RE: research, I left that for you guys......I don't even have a heat pump. :eek:
  19. clockwalk

    clockwalk New Member

    Storage tank?

    Reading your posts with interest as I am having questions about my Water Furnace desuperheater set up. Is it necessary to have a storage tank plus an electric tank or are you just using a storage tank that you already had in your heating system before you went Geo?
    Thanks Ed
  20. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    DSH needs two tanks to actually deliver promised savings

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