Cruisair heat pump control system problem…I think

[Nick in Manitou]

1984 53’ Extended Deckhouse

Using the old mechanical Honeywell T6052B thermostats.

Previous owner modified the boat pretty extensively and in the process removed the thermostat that I BELIEVE would have been in the galley. The galley and the v-berth systems run off of one compressor.

Current situation is that the thermostat in the v-berth is quite a mess with corrosion and is shot. When the system is turned on, it fires up the compressor and the seawater pump and delivers heat until it is turned off no matter what the thermostat is set to.

So I took the thermostat (Honeywell T6052B) from the master stateroom (where it controls heat and cooling as it should) and installed it in the v-berth to see if it would function there. In the v-berth it would turn on the compressor and seawater pump and supply heat when the thermostat was set to demand it, but when the setting was lowered so that it should call for cooling, no compressor or seawater pump came on. Shouldn’t it just be calling the same units to be turned on with the reversing valve not being called for?

The previous owner had a timer somehow replace the thermostat in the galley and perhaps that wiring there (which looks pretty sketchy and difficult to access) is the culprit. But I figured that I would ask the forum for any ideas of what to check next. I can understand a schematic to a certain extent, but since I don’t really know where to start looking, perhaps one of you folks can use the symptoms to come up with an educated guess as to what the problem might be.

I believe I read somewhere on the forum that the reversing valve is only powered in the heating mode, and we get heat out of the system when it is called for…so between that and the fact that the seawater pump is coming on in the heat mode but not the cooling mode, makes me think that there is a wire somewhere in the control circuitry that the previous owner probably cut. (I should mention that we live in San Francisco Bay and most people never need air conditioning. But if it is on the boat I want it to work if possible!)

I know that folks think the newer controls are great, but for now I am watching my wallet and would rather make sure that the system can work before I spend the money for the fancy digital controls.

If anyone has one of the old Honeywell T6052B thermostats around that they don’t need, I am looking for one! (Even if it is just to control the heat in the winter!)

Thanks!
Nick

[miboatnutz]

I have same boat same year.

The thermostat in the v berth controls forward cabin and galley. I just had a Honeywell thermostat go bad in the master stateroom. Purchased two brand new thermostats on eBay for $35.00 each. They were new old stock from some HVAC company.

There were actually several more listed so you might get lucky. I just did a search on Honeywell and the model number and about a half dozen were listed for sale. That was four months ago.

[miboatnutz]

Only HVAC controls in the galley are fan blower speed rotary switch (low to high) located just below the vent grille.

[Nick in Manitou]

Brian (Miboatnutz),

Thanks a lot for the suggestion about eBay for the thermostat. I thought I had looked on the web a few months ago and not found any replacements at a reasonable cost, but at your suggestion I tried again and found a seller on eBay who had 2 new thermostats for $30 each including priority mail shipping!

I ordered one - although I was tempted to pick up the other one too at that price!

Re my thought that there might have been a thermostat in the galley originally: The system drawing for the air conditioning (Figure 3,10) that is in the manual that came with the boat shows a thermostat in the galley...although the schematic ("Air Conditioning Wiring Diagram" CN130-ED) does not show one in the galley.

But if no one else has a thermostat in the galley along with one in the v-berth, that should make figuring out what my problem is a bit easier...maybe.

So now, why would the compressor and seawater pump come on when calling for heat but not when calling for cooling?

Nick

[SKYCHENEY]

I don't know why you mess with this old stuff. I replaced my themostats and PWX control boxes years ago with Coastal Climate Control FX1 and have not had a single problem ever since. They are cheap and the temperature swing between cycling on and off is much tighter. That Honeywell thermostat setup was not used for too long before they came up with something better.

[Nick in Manitou]

Sky,

The newer controls (FX-1, FX-2) look to cost $399 to $597, and before I venture into that sort of expenditure I would want to make sure that the system is completely functional.

I would hate to spend the money for new controls and find out that it is time to replace the entire unit!

Nick