Wisconsin W2W heatpump refrigerate question

Discussion in 'Maintenance and Troubleshooting' started by heatoldhome, Jun 19, 2016.

  1. heatoldhome

    heatoldhome Geo Student Forum Leader

    This is unrelated to Geo but I figured the very intelligent people here could point me in the correct direction.

    At work I'm dealing with a AEC portable chiller.
    3.5 ton I believe.
    No reversing valves on this guy.

    I wasn't around when this unit started acting up but I'm told it would keep popping the high refrigerant pressure switch.
    I verified this today and it pops within 20 seconds of the compressor starting. Again I wasn't around but they had the local hvac place come out and the guy told us he thought the heat exchanger on the hot side was plugged. It's a serviceable heat exchanger so I opened it up today and it's clean inside. I ran water though and it has good flow. I verified good waters flow through the other cold side also. (Visual check)

    So after verifying water flow I hooked up a set of gauges to see what I can see. (I though maybe the high pressure switch was going bad)

    When I start the unit up and the compressor kicks in it ramps up quickly to 325-350psi and trips.
    The weird thing is the low side ramps up also to about 125-130 psi.

    These units have a hot gas bypass valve so I jumped that so it would stay in bypass. With that the unit will stay running with pressures around 180 on the high and 125 on the low.

    We are going to have the hvac guy back out this week but wondered if you guys could help me to help them figure this out. (Also I want to learn what I can about this too)

    It has a inline refrigerate filter and what looks to be a veritable temperature controled tvx valve.

    With the unit off the pressure takes a while but it settles to about 80 psi on both sides.

    R-22 unit.

    Forgive me if I'm not using the correct terminology and please correct me if I'm wrong.

    Thanks for the info.
    Last edited: Jun 19, 2016
  2. mrrxtech

    mrrxtech Member

    Here is the manual for the AEC portable unit. PSA-3.5 appears to be 3.5 hp from scanning through the manual. I didn't see a table for expected Freon side pressures, and no set point on the compressor relief.

    The Trouble Shooting Table didn't have Freon Side Relief listed as a problem, but a relief valve changing it's relief Setpoint is a potential problem in the system.

    I would check the flow path of the system this Unit is cooling, I suspect a solenoid in the system being cooled is not opening or there is a clogged component downstream of the Unit.

    This system seems simple enough as drawn, got to go, but will look at it again soon. Ron

    Last edited: Jun 21, 2016
  3. mrrxtech

    mrrxtech Member

    I took a look at the Tech Manual Index and found the Freon Side High Pressure cutout set point to be 290 psi, per the bold Red information below. The 325 psig trip must be a valid trip.

    This points to the problem being in the Condenser side cooling water system. The Freon would heat up and pressurize on both the suction and discharge of the compressor and trip the compressor off to protect it from lack of cooling.

    If the Evaporator side lost its heat load, I would think a low Freon pressure protection would occur since the Freon would stay in the liquid state and could damage the compressor if it continued to compress liquid Freon.

    Section 8 Trouble Shooting has a Trouble Shooting Table starting on page 52. It's not much of a TS Table in my opinion since it doesn't describe your problem.


    "The high-pressure cutout is an electro-mechanical cutout device. It opens the compressor control

    circuit if the refrigeration system compressor discharge pressure exceeds 375 psi (2,413.25

    kPa/24.1 bars) for the PSA Series air-cooled chiller and 290 psi (2,413.25 kPa/24.1 bars) for

    the PSW water-cooled chiller."

  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Find and check the water flow cotrol valve.
  5. heatoldhome

    heatoldhome Geo Student Forum Leader

    Well this heat pump is open loop on the cold side with a 30 gallon tank. It has one pump that just circulates from the tank through the exchanger and back to the tank. It has flow. I can see visually that it has flow. But can't measure the flow.

    At this point the machine side doesn't matter to much until the 30 gallon tank cools down below setpoint.

    It's possible the cold side exchanger is coated with crap but still has flow. I'll have a look but I would think it would run lonher then 20 seconds even if it has poor heat exchange.

    Also for testing I had a garden hose pushing water through the hot side. It heats the water when it runs.

    Thanks for the replys.
  6. heatoldhome

    heatoldhome Geo Student Forum Leader

    Local hvac guy plans to come out and remove and measure the refrigerant.

    He suspects over charge (unlikly)
    Or tvx valve or solenoid valve.
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    The water flow control devise acts just like a txv, but with water flow.
  8. heatoldhome

    heatoldhome Geo Student Forum Leader

    The water control device is a manual ball valve with the handle removed. And clear label that says factory set don't adjust. So of course I marked the position and opened it up. No change. Returned it to prior setting.
  9. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Sorry Andy:

    Good work. I was thinking a temperature activated valve that adjust to the load.


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