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Old 10-10-2015, 02:18 PM   #1
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Heat Pump - Replace with an AC or Heat Pump?

The heat pump fan motor recently burned out in my 99 Excella. For this reason and a few other things on the unit that need repair, I have decided to replace the 16 year old unit with new. I have looked at the Dometic units and will choose one of that brand.

My questions are:
(1) Since we hardly ever use the heat pump for heating, we would be happy with a AC only unit. The thermostat that is in the trailer now controls both the roof top unit and the furnace. If I purchase the AC only unit, I will need a new/separate thermostat for the furnace. What is involved in modifying the wiring for the additional thermostat. (I think the furnace thermostat wires now terminate at the opening through the roof.

(2) If I decide to replace the old heat pump with a new heat pump, I know that I need to order:
(a) roof top unit (which kind Penguin II low profile or ???)
(b) thermostat
(c) drain kit
(d) additional foam gasket
(e) air distribution box for inside

Is their anything else I'll need?
Your advice is welcomed!

add edit:
(3) If I add a thermostat for the furnace, I am considering modifying the thermostat wiring to allow me to run the furnace fan continuously while letting the thermostat control the furnace. Is their any reason I should not? Has anyone done this in their RV.
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Old 10-10-2015, 05:20 PM   #2
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User cp not working do I can't get to a previous post that I did a long write up on but if you go with heat pump you'll need to use a CCCII to control it. This means having 4 wires available to put RJ phone jacks(existing wire may be to big to fit in an RJ jack though you could probably splice ends) on each end or running new wire from ac to thermostat. Non heat pump needs either 3 wires or ADB control, no phone jacks. SZLCD can run furnace and ac keeping one thermostat.
Not sure you can change thermostat wiring to do what you want as it's controlled by the circuit board in the furnace.
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Old 10-10-2015, 05:44 PM   #3
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In my 99 Excella the existing control wiring between the existing thermostat and the existing rooftop unit is the same wiring/jack as is used in the present day Dometic heat pumps, I think. Am I wrong?
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Old 10-10-2015, 05:54 PM   #4
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I'm pretty sure you'll need the equivalent of phone jacks and CCCII for a heat pump unit. As long as you have 4 wires, besides the blue furnace wires you should be able to splice on RJ jacks to the existing wires. The CCCII requires phone jack terminal wires to connect. The blue furnace wires are run somewhat independently so you'd be able to use the furnace there.
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Old 10-10-2015, 05:58 PM   #5
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You can get an AC with a heater strip that will keep the trailer warm till about 40F then you will need the furnace but you probably will be in the same boat with the heat pump. The heater strip does not cycle the compressor on and off or put wear and tear on the compressor. A heat pump might be marginally cheaper to run but you paid for the camp sight either way.

Perry
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Old 10-10-2015, 06:02 PM   #6
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Originally Posted by HiJoeSilver View Post
I'm pretty sure you'll need the equivalent of phone jacks ........snip.
I agree with you. That is what is there presently.
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Old 10-10-2015, 06:04 PM   #7
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Originally Posted by perryg114 View Post
You can get an AC with a heater strip that will keep the trailer warm till about 40F then you will need the furnace but you probably will be in the same boat with the heat pump. The heater strip does not cycle the compressor on and off or put wear and tear on the compressor. A heat pump might be marginally cheaper to run but you paid for the camp sight either way.

Perry
We never use the heat pump in our Excella or the heat strips in our Safari for heating. The roof top units makes to much noise.
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Old 10-10-2015, 06:15 PM   #8
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Disregard my previous , I just got on my computer and pulled up the dometic product guide. You can get penguin II that will work with either the ADB controls or CCCII or SZLCD. The SZLCD and CCCII have different wiring requirements though. SZLCD uses 3 normal wires plus the furnace wires. CCCII uses 4 wire phone wire plus furnace wires. ADB controls control hp and ac, furnace gets controlled by separate thermostat.
You can't use a house thermostat for the ac and/or heat pump because dometic uses their own signals.
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Old 10-10-2015, 06:31 PM   #9
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Here's a link to the dometic product guide, if you go to the AC section close to the end, they have tables for the available units, there's a section for ac only and another section on the next page for the heat pump units, the right column tells you what they can be controlled with, thermostat means either CCCII or SZLCD not just any thermostat. The units that list thermostat need to have a control kit ordered separately. if the model lists the CCCII or SZLCD in the right column then it comes with the control already installed, but you still have to buy the CCCII or SZLCD separate.
http://www.dometic.com/QBankFiles3/E...2014_22709.pdf


If you call dometic and talk to them they are very helpful. I talked to them several times about technical items when trying to figure this out and they were very helpful.

Sorry for any confusion.
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Old 10-10-2015, 07:12 PM   #10
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Quote:
Originally Posted by HiJoeSilver View Post
Here's a link to the dometic product guide, if you go to the AC section close to the end, they have tables for the available units, there's a section for ac only and another section on the next page for the heat pump units, the right column tells you what they can be controlled with, thermostat means either CCCII or SZLCD not just any thermostat. The units that list thermostat need to have a control kit ordered separately. if the model lists the CCCII or SZLCD in the right column then it comes with the control already installed, but you still have to buy the CCCII or SZLCD separate.
http://www.dometic.com/QBankFiles3/E...2014_22709.pdf


If you call dometic and talk to them they are very helpful. I talked to them several times about technical items when trying to figure this out and they were very helpful.

Sorry for any confusion.
Thanks for the link and advice!
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Old 10-10-2015, 08:39 PM   #11
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My questions are:
(1) Since we hardly ever use the heat pump for heating, we would be happy with a AC only unit. The thermostat that is in the trailer now controls both the roof top unit and the furnace. If I purchase the AC only unit, I will need a new/separate thermostat for the furnace. What is involved in modifying the wiring for the additional thermostat. (I think the furnace thermostat wires now terminate at the opening through the roof.

(2) If I decide to replace the old heat pump with a new heat pump, I know that I need to order:
(a) roof top unit (which kind Penguin II low profile or ???)
(b) thermostat
(c) drain kit
(d) additional foam gasket
(e) air distribution box for inside

Is their anything else I'll need?
Your advice is welcomed!

add edit:
(3) If I add a thermostat for the furnace, I am considering modifying the thermostat wiring to allow me to run the furnace fan continuously while letting the thermostat control the furnace. Is their any reason I should not? Has anyone done this in their RV.Single zone t/stats are not compatible with the CCC-I or CCC-II communication cables (RJ-11 cable). They require separate, heavier cabling that IIRC, needs to be a minimum 18AWG.


If you order either a new heat pump OR a new A/C only, you will need either a new CCC-II (which is a plug and play from your older CCC-I), a single zone t/stat kit (which requires new control wiring) or a retrofit relay control board to make your present CCC-I reverse compatible with your new unit. I would use the new unit in it's entirety and replace the t/stat with present technology.

The Penguin II is the low profile replacement for your existing unit. You will also need an aux. drain kit so you can connect the unit to your existing interior drain line and a new interior ADB (air distribution box).

Your furnace wires presently terminate at the A/C under the existing unit. You can use them to control your furnace with either the CCC-II or the single zone t/stat.

I would NOT order a heat strip, as they are essentially worthless for any other purpose other than removing the chill from the air. I have personally had several of these in various RVs (diesel pushers and a 19 Bambi CCD) and if you need heat, either a heat pump or furnace is definitely the option to use.

Finally, why would you want to modify the fan control of the furnace? First, you will have to bypass the blower control function of the furnace igniter board, as it is constructed to follow a set sequence after setting the t/stat: operate the fan for 15-30 seconds to purge the chamber and verify if the blower is producing sufficient exhaust air (sail switch), ignites the burner with the blower still operating, extinguished the burner when the t/stat setting is satisfied and continues to run the blower for a 3 minute cool down and purge cycle.

Any modification to this process is extremely unwise!!!!! You are dealing with a listed LP appliance and modifying the listed operational sequence will have unwanted consequences IF you have an incendiary event (specifically, your insurance company will DENY any claim arising from the modification)!!!!

Any other questions?
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Old 10-10-2015, 09:56 PM   #12
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Thanks Lewster,
Your advice is always great.

At first I thought I wanted the AC only. But, after considering the modification to the existing thermostat wiring and having to add wire for a separate new thermostat location, I have been having second thoughts. I'm still considering options.
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Old 10-10-2015, 09:57 PM   #13
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It would be nice if dometic could program a dehumidify mode where it would run the AC and heat strips at the same time to cool and dehumidify the air then warm it back up before it was blown back into the living space.
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Old 10-10-2015, 10:02 PM   #14
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It all comes pretty much separate.

(2) If I decide to replace the old heat pump with a new heat pump, I know that I need to order:
(a) roof top unit (which kind Penguin II low profile or ???) comes as the rooftop unit with new gasket and control module that goes with the model ordered. There are different models for ADB control, SZLCD, and CCCII.
(b) thermostat, you do need to order separately, depending on your choice and matched with the rooftop model you order.
(c) drain kit, the drin cup kit comes with an extra gasket
(d) additional foam gasket, see above
(e) air distribution box for inside, ordered separate, there are 2 models, one for ADB control and one for control with a separate thermostat. also includes the bolts for holding the ac down.


Those are the parts you'll need
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