Pennsylvania Desuperheater Pressurising my water system.

Discussion in 'Maintenance and Troubleshooting' started by jrolinger, Feb 13, 2015.

  1. jrolinger

    jrolinger New Member

    Hi Guys,
    I have a 3 ton Waterfurnace envision series with a 50 gallon preheat tank for the desuperheater. System has been in and running good for about 5 years. A few weeks ago the pre tank sprung a leak and the company installed a new one under warranty. The tank heats up great and we are in the heating season now and it runs a good bit.

    The problem is I found out that my house water pressure gets really high (150psi) when this unit is running and of course starts leaking out the pressure relief valve. I'm thinking possibly the desuperheater is the culprit. Never had a problem until recently.

    How could the pressure be increasing that much from the desuperheater? I can open a faucet and lower the pressure, but within an hour it's back up to 150 psi and that sure doesn't seem to be from expansion. I do not and never did have an expansion tank on the water system and this problem just started.

    Could someone please enlighten me on this as to what could be causing this much pressure in the system.
    Thank You, Jim
  2. heatoldhome

    heatoldhome Geo Student Forum Leader

    Did they install a check valve (one way valve) when they changed the preheat tank?

    As you heat water it expands and needs some place to go. Usually the little bit of extra water from expansion is pushed back into the well pressure tank (if you have a well) or the city water supply.
    If they installed a check valve then you need to remove that or add a expansion tank to absorb the extra water from expansion.

    I would call the installer back and ask them to fix the issue as they know exactly what you have in your home and they should know how to best fix it.

    Also check how it's piped. Maybe the despuperheater pump is actually pumping pressure into the tank?
  3. jrolinger

    jrolinger New Member

    There is no check valve at the preheat tank. It is city water and the check valve is after the water meter. My pressure gauges are before and after my pressure reducing valve where city water enters house. Normally 120psi from city and 70psi after prv.

    How is it possible for the desuperheater pump to be pressurizing the system when it is in a loop in/out of the tank. Only thing I can think of is pressure coming from compressor into the heat exchanger. But then I would be losing Freon, correct?

    Heat expansion was never a problem in the past without an xtank and for the pressure to rise that quick, is the reason I don't think it's the problem.
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    There may be a back flow device in the dip tube, here is a drawing from Bergy of DSH plumbing.


    Attached Files:

  5. jrolinger

    jrolinger New Member

    I see where you mean now. Is there a way to tell if it was removed without disconnecting the piping?

    The water temperature feels like it is flowing through both pipes from desuperheater.
  6. jrolinger

    jrolinger New Member

    Okay, so I talked to the installer and he believes pressure is from heat expansion and they should've offered to upgrade to install an X-tank when new preheat tank was replaced. One should've been put in from the beginning, but now I'm going to put one in and I'll post back my results.

    Thanks for all the help!
  7. jrolinger

    jrolinger New Member

    So, I installed an expansion tank and set it to equal the house water pressure. So far it seems to be absorbing the heat expansion from both the desuperheater preheat tank and propane water heater. I did notice the water pressure increased from 70psi to 150psi when the propane water heater kicked in. It only runs maybe twice a day, so I think I've had this problem for awhile. I didn't notice it until I put gauges on the water lines after my the line into bottom of toilet tank blew off during the night (luckily I was at home) and the preheat tank started leaking.

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