3rd heat zone issue with 2 air conditioners.

[Preston Nash]

I had a local RV shop replace both original Dometic AC units with new Penguin AC only 15K BTU units and a new Dometic CCC2 thermostat.  The original thermostat was a Dometic 4 button model.  When I picked up the RV, the Hurricane heater would not come on.  He quickly figured out how to set dip switches to make the Hurricane come on.  The problem though is that the 3rd heater zone which is in the bathroom, will not come on.  The RV tech is baffled as to how I can have three heater zones with only two AC units.  Can anyone give me any insight as to how this is set up and how I may be able to get this new thermostat to connect to the third zone on the Hurricane?  Since the original thermostat was able to do this, I'm sure the needed wiring is there.  I have a aquastat issue also that I have parts ordered for, so it may be a while before I can try any suggested fixes.  Any ideas are appreciated.   

[Bill Lampkin]

Our 05 PT has three zones w/ 2 AC units; its all in the dip switches on the boards of the AC units. We have zone 1 (living rm, kitchen) zone 2 (lav/bath) zone 3, bdrm). Zones 2,3 show up on the CCC2 tstat in the bedroom. 

[Fred Brooks]

   Preston,
As I recall, there is a third control box somewhere (similar to the PC board inside each air conditioner). That control box has an RG-8 phone connector that is plugged into either the original rear or front air conditioner. That is how the original 4 button t-stat knew there was an additional zone. The issue you are going to have is this: The new air conditioners are only compatible with the new CCC3 thermostat. It will not recognize the original 3rd zone control box. Here is your choices: locate the original 3rd zone control box and replace the PC board inside with the same one that you have in the new air conditioners and turn on the "dip switch" that says: gas heat, then do a "reset" on the CCC-3 so it recognizes the 3rd zone, or install a dedicated "heat thermostat" in the bathroom at run new wires down to the hurricane and attach to the respective zone on the Hurricane control box that turns on that heat exchanger. Hope this helps, Fred

[Preston Nash]

Thanks Fred.  I think that is it.  I did buy two conversion boxes, one for each AC unit.  Those were replacement circuit boards like you mentioned.  From what you are saying, I probably need to buy a third conversion box to replace that old unit, if I can find it.  In the Dometic material I read that each odd zone needs a dedicated 12V power supply.  I wonder if that is something that will already be there or if I need to buy something for that too.  Thank you for the info.  That clears it up for me.  If anyone knows where that third zone box is located, please let us know.   

If I decide to run a new thermostat to the bathroom, it seems like it may be hard to find a route to the bay containing the Hurricane.  That seems to be in a  sealed bay and I don't see an obvious pass through to get from the bathroom to the Hurricane bay. If that proves to be easier than I think it may be, that could be a more simple solution. 

[Fred Brooks]

    Preston,
 I would imagine that the hidden third control box is some where in the bedroom or closet. After posting my reply, I remembered that the 3rd box plugs into the back air conditioner and the back plugs into the front air along with the t-stat RG-8 plug. The 3rd box already has 12 volt going to it because it worked previously. It will be the same procedure that you did on the air conditioners. If you have an issue, you may have to remove the cover of the Hurricane control box and check the 3- 10 amp fuses or the 30 amp fuse. Blessings, Fred

[William Jordan]

Mine has zone one heat and ac in the front thermostat. The bedroom tstat has has zone 2 the bathroom heater only ( no ac even thought you could select air but it does nothing ) and zone 3 the ac and the bedroom heater.
The wiring was there to do this I would suggest the t stat is wired wrong esp since your tech is confused . I think it’s common to be wired that way. control boxes for the ac and heater are in the ceiling ac mounted in the return air behind the grate and filter.
Of course it certainly could be different I’m just familiar with my 03 Marquis and the 5 button t stats.

[Bill Lampkin]

Each control box can be programmed (dip switches) for the functions contolled by each tstat (CCC2). Example, my Zone 2 (bath/lav) has AC, Heat pump, Furnace (Aqua Hot) and Fan functions.

[Preston Nash]

Thanks for the info.  This gives me enough to dive into it when I get time.

[Preston Nash]

I haven't been able to locate the 3rd zone control box.  This brings me to another question.  The bathroom (original zone 3) which does not work now, has one heat exchanger.  The bedroom (original and still zone 2) has one heat exchanger.  We don't use the heater all that much, so combining the bathroom and bedroom into one zone will not be a problem for us.  Can any of you see any issue if I were to run a jumper wire between connection T2 and T3 on the Hurricane control box?  The way I see it, when zone 2 calls for heat, then zone 3 (bathroom) would also receive the command and allow the heat exchanger in the bathroom to work.  Am I missing anything here?  Thank you very much for any ideas and/or input. 

[Fred Brooks]

   Preston,
 I don't see why that wouldn't work. I would isolate the former wire identified as "zone 3" at the hurricane. The only other thing you need to be advised is that there is one more heat exchanger on that original zone 3 configuration. That is the heat exchanger that is located inside the holding tanks enclosed area. When the bathroom circuit is activated, it also supplies power to the holding tanks exchanger. It has its own internal thermostat that calls for heat below 40 degrees. I think when you jump zone 3 to zone 2 you will have to monitor the amperage draw on that respective fuse because you are adding 2 more exchangers to the zone 2 circuit. If the 10 amp fuse can't handle the increase, you may have to change it to a 15 amp fuse. Hope this helps, Fred

[Preston Nash]

Very nice!  I didn't know about the holding tank heat exchanger so that is valuable information.  The way we camp, I doubt that would activate very often at all.  If it does, it's nice to know about keeping an eye on that fuse.  Fred, I appreciate the always expert information.  Thank you.

UPDATE:  I installed the jumper between T2 and T3 and everything works as expected.  This gave me back the bathroom heat exchanger.  Thanks again.