Air Conditioning Thermostat

[Ken Juul]

My boat has a two unit AC system, the old unit has a capaliary tube analog thermostat.  It has bit the dust.  New one is $120, probably only have a couple years  of life left in the unit, would prefer to switch to a less expensive digital thermostat.  The unit is manufactured by Eastern Marine Corp,now Quorum Marine, sold under the Ocean Breeze name.  Anybody know how to change from the 7 wire analog to the 4 wire digital?  Because of liability issues the company won't help with the conversion.  He did say that Red was common, compressor was yellow, fan was green, heat is Brown.  Also have purple, Black and white wires to do something with.  Have a couple of pretty worthless wiring diagrams I can share.  Don't need the electric element heat function if it makes wiring any simplier. 

[KWKloeber]

post them and would be glad to see what I can tell...

[Ken Juul]

Link to the Quorum site, may be of use:  http://www.oceanbreezeac.com/thermostat_setup.php

Three schematics  ac2 came cutoff from the factory.

[KWKloeber]

post them and would be glad to see what I can tell...

Ken when I download the JPGs and try to read/zoom in on them, they are just all pixilated/crappy images, and can't read a word.  Maybe a higher resolution or scan to pdf?
I presume those were all analog? Is there a schematic of the digital unit?

Ken

[Ken Juul]

because of the picture size limitation can't do much more.  I guess I should have put them in seperate posts.  I'll rescan and try that.  Schematics for the digital versions are on the Quorum web site.

[KWKloeber]

because of the picture size limitation can't do much more.  I guess I should have put them in seperate posts.  I'll rescan and try that.  Schematics for the digital versions are on the Quorum web site.

High resolution, email directly. 
KWKloeber@aol.com

Which t-stat are you wanting - there's several on there?  The one I looked at didn't really have a schematic, just a wire-terminal list.  Maybe I missed it.

Ken

[Ken Juul]

I was planning on using a Honeywell purchased at Lowes.  Connections are labeled B, O, G, Y, W, R, Rc  But no explanation what each of those mean, standard colors used in the house application.

Email on the way

[KWKloeber]

I was planning on using a Honeywell purchased at Lowes.  Connections are labeled B, O, G, Y, W, R, Rc  But no explanation what each of those mean, standard colors used in the house application.

Email on the way

Ahhhh ha.  Maybe with the HW model number you can find a schematic or a an HVAC guy would know the colors/use?

I'll look at the new scans but w/o a schematic of the HW unit, kinda blind.

Ken

[KWKloeber]

Ok, of the 7 conductors on the AC, we have the below functions.

Can you find find out anything on the honeywell t-stat connections? Model number?

A/C:
Brown - heater element so we can discount
Blue   - ditto

green - obviously earth ground

red -  compressor ON
white - neutral to compressor

yellow -  Fan (possibly neutral?)
orange - ditto (possibly power?)

The pump is wired to the thermostat (white/purple), separate from the harness connections.


Ken

[KWKloeber]

I was planning on using a Honeywell purchased at Lowes.  Connections are labeled B, O, G, Y, W, R, Rc  But no explanation what each of those mean, standard colors used in the house application.

Email on the way

Ken,

Is the Lowes T-stat you're looking at a low voltage or household voltage?

Ken

[Ken Juul]

page 5 of this manual may be helpful. 

https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-2448ES.pdf

I could not find the operating voltage.  Beleive it is the standard 24vdc that most thermostats operate at.

[KWKloeber]

ken,

1st I am at a loss because I don't have AC and am not familiar with your control unit, so I may be off base on some things... but here goes..


The 7 wires from your control to the AC, are 120-volt, and I don't see any relays on the schematic.  And two of the three connections to the thermostat part itself of the control unit are 120-v; can't tell what the 3rd is.  So it appears?? that the actual thermostat is high voltage.

The household A/C-heat TStats are, as you say, low voltage @ 24-v , and they turn on and off relays for the high voltage fan, compressor, etc. that are located inside the AC/furnace.  There are high voltage thermostats, but only for heat not A/C, as far as I know. 

I don't know if the Honeywell TStats will work on 12 volt, rather than 24-v.  It probably will, but you'd need to install 12-v relays for the Tstst to turn on the fan, compressor, pump - or maybe it could be done with one relay.  The 120-v power runs to the control, not to the AC, so the relays would need to be near the control/thermostat.  or the 120-v power could be re-routed to the A/C, and the relays installed there (so the wires from the control to the A/C would then become low voltage and simply trip the relays.

I notice that the Ocean Breeze QU311 digital control contains relays right at the TStat, bso would appear to be a replacement for you current analog control   Again I don't see any evidence of relays on the info that you scanned to me for your current control.  The QU500 digital control doesn't show any relays -- they must be on the A/C unit.

I hope this helps some at this point.

ken

[KWKloeber]

Ken,

Here's another thought. 

If you kept the 120-v power going to the control location, you could use a simple high voltage heating-only thermostat w/ one feed (+ neutral and earth) to power everything at the AC (pump, compressor, fan.)   

Connect the TStat to a normally-closed relay

-- When the temp goes below "X", the TStat powers the relay to trip open, and shuts off the AC. 

-- When the temp goes above "X", the TStat powers down and the relay goes dead (back to normally closed,) and powers up the AC.  The relay would just need to be sized for the 120-v load of the compressor + fan + pump.

Ken

[Ken Juul]

Thanks for trying.  Think I'll just bit the bullet and buy the expensive thermostat.  In the end it is better than botching the installation and having to replace the entire unit.