Heat Pump - Replace with an AC or Heat Pump?

[A W Warn]

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.

[HiJoeSilver]

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.

[A W Warn]

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?

[HiJoeSilver]

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.

[perryg114]

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

[A W Warn]

Originally Posted by HiJoeSilver

I'm pretty sure you'll need the equivalent of phone jacks ........snip.

I agree with you. That is what is there presently.

[A W Warn]

Originally Posted by perryg114

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.

[HiJoeSilver]

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.

[HiJoeSilver]

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.

[A W Warn]

Originally Posted by HiJoeSilver

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!

[lewster]

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?

[A W Warn]

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.

[HiJoeSilver]

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.

[HiJoeSilver]

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

[A W Warn]

The two Dometic units I've looked at are the Brisk Air 2-15,000 BTU and the Penguin 2-13,500 BTU.

The price of the Brisk Air 2 is substantially less than the Penguin 2. Why?

Are they both "plug and play", with regard to the existing control wiring in my Excella?

Is one unit quieter running than the other?

[nrgtrakr]

Related ...
I had a house in TN with a heat pump. The heat was wimpy, not as good as a regular furnace and needed wood stove backup on the really cold nights; as was the AC not really AC that was serious about cooling in the hottest days of summer.
Are the RV units similar wimpy, or is the AC comparable to an AC only unit that just happens to also make heat?

[A W Warn]

Originally Posted by nrgtrakr

Related ...
I had a house in TN with a heat pump. The heat was wimpy, not as good as a regular furnace and needed wood stove backup on the really cold nights; as was the AC not really AC that was serious about cooling in the hottest days of summer.
Are the RV units similar wimpy, or is the AC comparable to an AC only unit that just happens to also make heat?

Any heat pump, regardless of brand, type, or size, looses its heating efficiency as outside air temperatures drop, the exception being those that draw heat from the earth or ground water. When outside air drops really low those that have the condensate coil that use outside air are pretty much useless. The heat pump at my house is installed so that a natural gas furnace comes at ~30+ degrees F.

[A W Warn]

Originally Posted by lewster

Any other questions?

Thanks for setting me straight on modifying the furnace fan function!

After reading this post several times, one thing that finally sunk into my thick skull. You said "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."

Will there be any modification or additions to the existing thermostat wires, the one with jacks, if I use an AC only unit? Will the CCC-II will control the furnace using these existing wiring to the thermostat?

I really do not understand the bundle of wiring that is in the ceiling of the trailer at the roof unit. I have not studied those wires at all, though I have a basic understanding. I know there is a 12v supply. I know there are two wires from the furnace. Will you clarify/give me more detail of what the other wires are for, and I will have to do something to these wires if I install the AC only unit? Will I just remove the connector and re-wire the new unit using the same wires or will there be some that will not be used?

[lewster]

Originally Posted by A W Warn

Thanks for setting me straight on modifying the furnace fan function!

After reading this post several times, one thing that finally sunk into my thick skull. You said "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."

Will there be any modification or additions to the existing thermostat wires, the one with jacks, if I use an AC only unit? Will the CCC-II will control the furnace using these existing wiring to the thermostat? IIRC, There are about 6 wires that come to the Airstream wire bundle from the A/C unit; those being a 12VDC positive and ground, the 2 furnace wires and 2 yellow wires that are for load shed devices which are not used in Airstream trailers. There will be 4 coming from the Airstream: 12VDC positive and negative and the 2 blue furnace wires. You will also have 2 RJ-11 phone cables from the A/C unit that terminate in plastic unions. These are for the comm. cable that runs to the t/stat (CCC-I or CCC-II). You can use either one. All of the wires from the Airstream should be connected to the mating wires that lead to the A?C relay board. These wires are identical in all Dometic units that use the CCC series of t/stats.

I really do not understand the bundle of wiring that is in the ceiling of the trailer at the roof unit. I have not studied those wires at all, though I have a basic understanding. I know there is a 12v supply. I know there are two wires from the furnace. Will you clarify/give me more detail of what the other wires are for, and I will have to do something to these wires if I install the AC only unit? Will I just remove the connector and re-wire the new unit using the same wires or will there be some that will not be used?

Again, all Dometic units that use the CCC series of t/stats have the same wiring plan. It is a wire-for-wire replacement, and you simply plug in the RJ-11 into the new union from the new A/C unit.

"The two Dometic units I've looked at are the Brisk Air 2-15,000 BTU and the Penguin 2-13,500 BTU.

The price of the Brisk Air 2 is substantially less than the Penguin 2. Why?

Are they both "plug and play", with regard to the existing control wiring in my Excella?

Is one unit quieter running than the other?"

The Brisk Air II is a high profile unit with a smaller roof footprint. It is less expensive because the condenser is vertical instead of horizontal and the fans have more room for placement. The coils are also higher. I have been told that all of these characteristics are less expensive to manufacture. They are not made for use with the aux. drain kit, but you can modify one if you are handy. I have been told that these run much quieter than the Penguin II, but have no direct experience with specific decibel levels of either unit.

Either will work with your existing t/stat but require a retro fit control board. The new units that are ordered for remote t/stat use are designed for the CCC-II, which is a plug and play install with what you now have. They can also be ordered for the single zone t/stat, which will require 18AWG cable for the t/stat connection.

[nrgtrakr]

Originally Posted by A W Warn

Any heat pump, regardless of brand, type, or size, looses its heating efficiency as outside air temperatures drop, the exception being those that draw heat from the earth or ground water. When outside air drops really low those that have the condensate coil that use outside air are pretty much useless. The heat pump at my house is installed so that a natural gas furnace comes at ~30+ degrees F.

Understood ...
and the AC is less efficient as well.
But for an RV heat pump I was curious about the AC being a real AC, capable of making cold, or still just a pump.