A.C. temperature controllers.

[Chris Patterson]

In the house, it's referred to as the thermostat, which in reality I suppose is simply a controller. Bear in mind that I know VERY little about refrigerant situations as a whole, but I gotta tackle mine. As it is, I have a Mermaid 16,000 btu I took out to access some thru-hulls, and I wanted to bench test it before I go to the struggles of re-installing it, and then find out it needs servicing. I think, THINK, that the difference in a home unit, and a boat unit is the home version is static, whereas the boat leans, maybe throwing off the mercury switch? I wanted to get an off the shelf cheapo to try it with, and I think it may work on the bench, but how to wire it? The ones I pick up off of the shelf says, "Unhook the old thermostat, and rewire the new one the same".
Well, that DOES sound awfully good, but completely irrelevant. For the exception of them both having four wires, the resemblance ends there.

So throw something at me here. Good info, and the usuals..

(I know, I know, A.C.'s in go fasters, but I'm spoiled).

 

[reworb]

If I were you I would contact the manufacturer, they are here in Florida not in some offshore location. Here is their contact info:
U.S. Toll Free: 800.330.3553
Fax: 239.418.0538
Email: info@mmair.com
2651 Park Windsor Drive
Suite 203
Fort Myers, FL 33901

By the way do you like your Mermaid unit? I'm considering replacing my failing Cruisaire unit with a Mermaid unit as I'm told they are a lot less expensive.

 

[Doc_holiday]

A residential thermostat, if digital is 24V but one with batteries may function at any voltage. I never tried. Mercury wouldn't work and besides they are illegal now.

I would look for a bi-metal snap acting thermostat but don't go with the cheapest on the shelf. It needs to pop open and closed quickly and smoothly. You may find a motor home thermostat would be ideal and less cost than anything marked "marine".

 

[Chris Patterson]

O my God! I had no idea they were illegal. I actually picked one up at the hardware store that the mercury switch was visible inside, which was my first clue about how it may not work. Probably very old stock I guess.

Hmm, good thoughts though.

And yes, the last boat I got on with a Mermaid, you could hang meat in there. Longevity? Not sure at all. The guys here on the hill like them though..

 

[Tim R.]

In the house, it's referred to as the thermostat, which in reality I suppose is simply a controller. Bear in mind that I know VERY little about refrigerant situations as a whole, but I gotta tackle mine. As it is, I have a Mermaid 16,000 btu I took out to access some thru-hulls, and I wanted to bench test it before I go to the struggles of re-installing it, and then find out it needs servicing. I think, THINK, that the difference in a home unit, and a boat unit is the home version is static, whereas the boat leans, maybe throwing off the mercury switch? I wanted to get an off the shelf cheapo to try it with, and I think it may work on the bench, but how to wire it? The ones I pick up off of the shelf says, "Unhook the old thermostat, and rewire the new one the same".
Well, that DOES sound awfully good, but completely irrelevant. For the exception of them both having four wires, the resemblance ends there.

So throw something at me here. Good info, and the usuals..

(I know, I know, A.C.'s in go fasters, but I'm spoiled).

Your Mermaid should have 4 wires; green, black, white and red. You need to get a thermostat with heat/AC/fan control. A cheap digital Honeywell from any HW store will do. Connect the green wire to G, black wire to Y, white wire to W and the red wire to R. Make sure the R and RC on the thermostat are jumper together.

 

[Chris Patterson]

Tim, I think that is exactly the information I was looking for. I'll give it a go.

 

[DeniseO30]

If it's reverse cycle it may have a 5th wire. O or orange that activates the reversing valve for cooling cycle. this would call for a heat pump thermostat

 

[chuckwayne]

ditto on what Tim said! the digitals actually run on several AA cells, they just switch the home 24vdc power-should work fine.
Our Mermaid 16K btu unit has run flawlessly for 10 years (knock on wood!)

 

[Tim R.]

If it's reverse cycle it may have a 5th wire. O or orange that activates the reversing valve for cooling cycle. this would call for a heat pump thermostat

Denise, our Mermaid unit is reverse cycle but dos not have the orange wire, just the 4 mentioned above.

 

[Chris Patterson]

Hmm, then I am to assume that when I put batteries in the controller, and the A.C. is not wired up, the controller wires just hanging loose, that the digitals will not "light up"?
When I put the two double A's in it, I got nothing, and thought at that time my controller may be kaput. Not so maybe?

 

[Tim R.]

What exactly are you referring to as your "controller"?

A digital thermostat should come to life regardless of system connection. Just inserting the batteries should llight up the clock and temp.

Here is the one I use and it continues to act as a clock and thermometer even when power to my Mermaid AC unit is disconnected.

http://www.homedepot.com/p/Honeywel...ith-Backlight-RTH2410B/202024250#.Ucgzs9iDl8E

 

[Bonzai]

Just replaced both cabin thermostats...recommend you stay away from the 30 day programables . I got ones that are set and forget, on and off...lol. I don't remember if the new ones required batteries but the old programables did.....maybe for memory when breakers for A/C are off?

 

[DeniseO30]

Denise, our Mermaid unit is reverse cycle but dos not have the orange wire, just the 4 mentioned above.

That's interesting Tim! I'd like to look up the wiring and schematics on that. I'd never assume marine anything would be the same as land based things.

Oh then there's the 6th wire for elelctric heat.... 7th for the fault light.. It can get crazy

 

[Chris Patterson]

Yes, the thermostat is what I was referring to. I don't know why I didn't call it that in the first place. I guess maybe I was thinking thermostat like goes on the coils and senses temperatures. Anyway..
So mine must be dead. Because I put two new double
A's in it, and got nothing. Looks like Home Depot is getting a visit. The one of several things I was confused on is if there was any difference much in the "genuine marine" version, or if I could get one off the shelf.
Plan "F", or "G", something, I forget.
Not really a plan at all. More like a scheme, or a plot..

 

[Tim R.]

Yes, the thermostat is what I was referring to. I don't know why I didn't call it that in the first place. I guess maybe I was thinking thermostat like goes on the coils and senses temperatures. Anyway..
So mine must be dead. Because I put two new double
A's in it, and got nothing. Looks like Home Depot is getting a visit. The one of several things I was confused on is if there was any difference much in the "genuine marine" version, or if I could get one off the shelf.
Plan "F", or "G", something, I forget.
Not really a plan at all. More like a scheme, or a plot..

Chris, the original programmable thermostats that Mermaid supplied with their units were and still are LUX home thermostats with a Mermaid decal covering the LUX name. This is a little disappointing as LUX are crap. The non-marinized Honeywell units from Home Depot I use are much better and less expensive.

They also sell a thermostat which they call a "controller". Check out the page below to see what you may have.

http://www.mmair.com/marine_division/marine_thermostats

 

[Tim R.]

That's interesting Tim! I'd like to look up the wiring and schematics on that. I'd never assume marine anything would be the same as land based things.

Oh then there's the 6th wire for electric heat.... 7th for the fault light.. It can get crazy

I should mention that we have the reverse cycle heat, not electric heat option.

Here is a link to their manual: http://www.google.com/url?sa=t&rct=...=TFsUKnDJzyN2jJJNXNoDEA&bvm=bv.48293060,d.dmg

 

[Chris Patterson]

Yepper, I've got the 43103, as they call it, the "old style". While that name suits me, I'm afraid after all that the Lord has called it home. Of course I've not tried the special tool yet, hmmm..

Denise is scaring me to death with the 6 and 7 wire thing. I've only got four, I'm sure of it. And it is reverse cycle heat as well.

Thank you Tim, I've got something firm to work with now. Ignorance is tough, man. Tomorrow I'm going down to the Mary Celeste with my hatchet, whoops, I meant special tool, and see if that thermostat and I can come to terms.

Maybe I'll just stop by the hardware store instead..

 

[DeniseO30]

Many Heat pump (rev cycle) Tstats that wall mount also have a common wire so it would be possible to burn out the power transformer. Fortunately your units don't have that. Tstats no matter how "scary" really are just switches

 

[Chris Patterson]

Well, at the very least, I'm getting a short education in these things. In my travels this morning, I ended up at Lowes, where I found a Hunter brand thermostat on sale for $14.95 thereabouts. That's me, this is just a bench test anyway. Four simple wires, with a relatively decent little wiring diagram of sorts. And the damn thing started up. I was really more than surprised, as this unit has been decommissioned for a while.
But it's not getting very cold. It was 85 degrees where I was standing, and my lazer thermostat shot down in the hole only hit about 65 at best. And the very bottom tubes on the condenser were frosting, which in my limited experience with A.C.'s tells me that it needs refrigerant. I'm pretty sure that the unit uses R22, which I think is everyday auto refrigerant, but the service ports are the old style, like R12 Schrader type connections.
So if I'm right here so far, my question is how do I get the R22 in the unit with this old connection? It can't be that big of a deal, huh?
Thanks so far everybody, I've slowly getting it...

 

[Tim R.]

Good job Chris. Now it is time to call Mermaid. They have a great service dept and will be very helpfull.