This is an update on the subject. Last year I posted on the subject of a Climatemaster Tranquility 27 heat pump with the Climadry feature, and documentation issues pertaining to water valve selection and wiring in an open loop configuration. Following CM's documentation, my installation uses a Taco Heat Motor Zone Valve to provide well water to the unit, and the Y1 line from their ATP32U04 thermostat was routed through the valve, to make sure that water was flowing before the compressor came on. Of course, with a closed loop installation, the circulation pump could just be wired in parallel with the compressor contactor, as there would be no water hammer issue as when the water supply is from a domestic water supply system at some pressure. The humidity line from the thermostat (DH) was connected directly to the H terminal on the DXM board.

As noted before, the system did not operate correctly in cases when the thermostat signaled a need for dehumidification without further cooling (DH active, Y1 not active). The system would quickly shut down on high refrigerant pressure without water flowing to absorb the heat. On reviewing their technical literature in detail, it seemed obvious to me that the designers of their DXM board probably anticipated this scenario but that the technical manual folks either overlooked it or weren't informed of how to wire things accordingly. Below is an email I sent to the tech staff at Climatemaster a few weeks back.

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Climatemaster documentation of the installation of a Tranquility 27 heat pump is flawed for the case of a unit with Climadry installed for use with ground water. Specifically, your description of water valve wiring under "Electrical - Low Voltage Wiring" (IOM:A, page 244, Figures 21, 22) recommends routing thermostat output Y1 through a slow-closing water valve with an end switch, so that the Y1 signal is passed on to the CXM board (DXM in the case of Climadry) only when the water valve is open.

For use with Climadry, CM thermostat ATP32U04 can call for heat pump operation by signaling on either or both of outputs Y1 and DH. When temperature is satisfied but a humidity setting is not, only DH will be active. The presence of only DH at DXM terminal H causes the DXM board to engage the compressor, which requires that water be running. Without water running, the result is a fairly quick fault 2 (high pressure). Therefore, Y1 cannot be used to control the operation of the water valve.

Fortunately, the design of the DXM board provides a means to control the operation of a slow acting water valve. There are two Accessory Relays on the board. Tables 1 and 2 on page 519 of IOM:K show the DIP Package 2 switch settings for the different "relay personalities" that may be selected. Switches 2.1, 2.2, and 2.3 for Accessory Relay 1 or 2.4, 2.5, and 2.6 for Accessory Relay 2 would be set ON/OFF/ON to select "Water Valve - Slow Opening." As noted on page 524 of IOM:K, under "water Valve/Slow Opening:

If an Accessory relay is configured for Water Valve/Slow Opening, the Accessory relay will turn on 60 seconds prior to the Compressor Relay turning on.

Since Accessory Relay 1 must be assigned to "Reheat Option - Dehumidistat" in a Climadry-equipped unit, that leaves Accessory Relay 2. This of course rules out its use for Digital NSB or Outside Air Damper.

Since the Accessory Relay provides only 60 seconds of delay before turning on the compressor, any water valve used must be able to open within that time. This precludes the use of a Taco Heat Motor Zone Valve such as their model 5101G, which can take 90 seconds to open when starting cold. Taco has a better valve for the purpose, in their Zone Sentry line. Per Taco, they have a version for an open loop system (ground water), their part number V075T2B1ZA024Q4A1. Their specifications say that it opens typically in 5-6 seconds, but up to 20 seconds the first time (to charge an internal capacitor). Power draw also is much lower than by a heat motor zone valve. If it were not for that longer open time when first used (or perhaps after an extended period of non-use), one might think that the valve could be driven by output A in parallel with the compressor contactor. I imagine 5-6 seconds is fast enough to prevent refrigerant over pressure.

The wiring of the Taco AVM valve (or different designation for a Zone Sentry valve) for a unit with Climadry thus should not be as shown in Figure 21 "AVM Valve Wiring" on page 244 of IOM:A, intercepting the Y1 signal from the thermostat. Instead, Y1 should be routed directly to Y1 on the ECM board (tab 2 on the terminal block). DXM outputs NO2 on connector block P3 (page 517, IOM:K) and either terminal block 6 (C) at the ECM board or C on connector block P1 on the DXM board may be used for 24 VAC hot and common for the Taco valve. DIP switches 2.4, 2.5, and 2.6 for Accessory Relay 2 would be set ON/OFF/ON. Also (see NOTE at top/right of page 525, IOM:K), DIP switch 1.5 should be ON and DIP switch 2.7 OFF.

The only thing that is not clear is whether or not the Accessory relays remain on during unit lockout and whether water must remain on in that condition.

I cannot verify that the above suggestion to drive the appropriate slow-open/close water valve from Accessory Relay 2 actually works, although DXM board documentation indicates that this would work. The problem in my installation was realized only after the installation was completed using a heat motor zone valve, with Y1 routed through the valve and DH going directly to the DXM board. Last summer, the humidity setting at the thermostat was left very high, to keep the thermostat from trying to signal on DH without Y1 also activated. Careful use of the system allowed normal but infrequent cooling operation to provide adequate dehumification without overcooling most of the time, but not always. The house is new and superinsulated. The gross conditioned space is about 4,000 sq.ft., and the heat pump is your smallest, TTV026 (two-ton). Over the winter, which wasn't particularly severe, the unit kept the house at temperature easily, without going into second stage. Last summer also was not severe either, which resulted in the classic problem of overcooling with insufficient dehumidification due to a grossly oversized unit.

Everything considered, I really ought to have replaced the water valve and wired it through Accessory Relay 2. However, my brother designed and built for me a small and inexpensive custom circuit board for use with the existing (and very slow) valve. It activates the valve when either Y1 or DH from the thermostat is active; when the valve end switch is closed, indicating an open valve, both Y1 and DH are connected through to the heat pump in their respective states. It works, but it isn't elegant and is not the way an installation with Climadry using ground water ought to be done.

It occurs to me that your newly announced Trilogy line, with its ability to ramp down to 30% of capacity according to need, may be able to avoid the problem of oversize in cooling mode much of the time, but perhaps not all the time. If Climadry is to be an option for Trilogy, then my comments above about water valve selection and wiring will apply to that line as well.

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Climatemaster did respond to the email, saying (without confirming my wiring proposal):

"Thank you again for your detailed feedback. The wiring diagram does need modification as you mentioned below. We are also working on an improved ClimaDry, on communicating units, which should reduce the complexity and errors.

 We are still considering some of the options on Trilogy – as you guessed, it may not have ClimaDry, as the refrigerant will be measured and controlled much better, for higher humidity control using the air coil.

 Thank you again for your feedback.

 

I appreciate you sharing your experience

Good information.

Dick

ClimaDry documentation states that it is inappropriate for open loop systems (especially with EWTs below 70F). I would like to know how it works for you.

As to slow opening valves, I always send CC off the control board to the Valve and the end switch circuit turns on the compressor. I found early on with open loop that using Y1 to operate the valve, wastes water during time outs and lockouts. Wired this way the valve is tied to compressor operation.

I believe this method would work well in your situation.

G.O. Joe

G.O., can you give me a reference in CM's documentation that says Climadry is inappropriate for open loop? I never saw that. I wonder what the reasoning on that would be.

Actually, with the custom board that turns on the water when either Y1 or DH is signaled installed, the thing seems to work just fine. With the recent weather being quite humid without really high temperatures, the tstat has occasionally shown "CLIMADRY" on the display, with temperature satisfied but not the humidity setting. The system runs without dropping temperature any further and the humidity comes down.

I wondered about wiring as you suggested, running the CC line through the valve first, as a solution. I was reluctant to try that, suspecting that there might be something in the DXM board logic that might be expecting some measurement to change within X seconds of activating the CC line, resulting in a fault if it was taking too long. The custom board my brother and I put together is not an elegant solution, for sure, although it works. Philosophically, the heat pump, and not the thermostat, ought to control the water. I'll keep your solution in mind, in case the custom board conks out.

Dick

http://www.climatemaster.com/downloads/97B0051N01.pdf

Page 3 Notes 2+6  ***EDIT*** See Bottom Correction

Although, Note 2 does not specifically exclude open loop (and contains a generic reference to open loop that I believe is intended for non-ClimaDry units), the unavailability of a Cu-Ni coax with a ClimaDry unit infers to me the exclusion.

Note 6 specifically states the required minimum of 70F EWT, a temperature I would never expect with open loop in the NH (unless you are rejecting to a standing column that has climbed to that temperature during the cooling season). ***EDIT*** See Bottom Correction

The seaside community that I live in often has OS temps near and below dewpoints (think fog). Our requirement for dehumidification, more often than not, exceeds that for cooling. I have been more than curious about what ClimaDry could do for us but was turned away by the specifications and requirements documented above. After much research I believe I have more than a basic understanding how it works.

However, with great interest, I will defer to your hands on experience and ask if you might be able to quantify ClimaDry performance in your application?

Thanks,
G.O. Joe

***EDIT Correction*** Follows
Note 6 in the above documentation was misread and misinterpreted by me. There is not a minimum requirement for EWT. The 70F minimum requirement is for entering air. My Note 6 comments are invalid. My apologies to all.

Dick

See corrections in my previous post.

So, with even greater interest, I would like to know how ClimaDry works for you.


G.O. Joe

Resurrecting an old thread, I thought I'd report on a change to my system.

In January of this year, the original heat motor zone valve for the water flow (Taco) failed. Rather than replace the actuator, I went with the newer, faster acting Geo Zone Sentry valve, also by Taco. In addition to that, I think through by my own error while diagnosing the system failure, the custom board my brother had built for me failed. That board had been designed to turn on the water valve when either cooling or dehumidification without cooling was needed. Following advice earlier in this thread, I simply disconnected the custom board, and returned wiring to the original configuration (but with Y1 from zone board going directly to the DXM board, and not through the valve). Then I cut into the wire from the DXM board on the heat pump, sending that signal through the new zone valve. Wire from CC into the valve, wire from the end switch continuing on to the compressor contactor. This works just fine. I see no reason it won't work this summer when the Climadry feature likely will be needed at times. The compressor can't start until water is flowing.