Adding 3rd a/c to garage

[Fire Marshal Bill]

The Texas heat is coming! We have a Momentum 320G. Has anyone had a third a/c successfully added to their garage on a unit that came prepped for it from the factory? What all is involved? The more research I do, the more confused I get. The more answers i get, the more questions I have. According to the build sheet the unit is prepped for a 3rd a/c but apparently that doesn’t include the EMS. Some are of the opinion it’s no longer necessary on 2020 models. Hearing also that if the existing 2 units are wired to one leg of the breaker panel, that the 3rd unit should be pre-wired on the opposite leg and that you can plug and play if so. Have also heard the added unit will have its own EMS built in. Need expert advice here as this needs to be done sooner than later. Just can’t get a straight answer on how it needs to be done. The how determines the cost. Was told by dealer to add EMS system to make everything work correctly could cost upwards of $5K 😳. There has to be an easier way, especially if I’m prepped for it already. Right?

[howson]

The Texas heat is coming! We have a Momentum 320G. Has anyone had a third a/c successfully added to their garage on a unit that came prepped for it from the factory? What all is involved? The more research I do, the more confused I get. The more answers i get, the more questions I have. According to the build sheet the unit is prepped for a 3rd a/c but apparently that doesn’t include the EMS. Some are of the opinion it’s no longer necessary on 2020 models. Hearing also that if the existing 2 units are wired to one leg of the breaker panel, that the 3rd unit should be pre-wired on the opposite leg and that you can plug and play if so. Have also heard the added unit will have its own EMS built in. Need expert advice here as this needs to be done sooner than later. Just can’t get a straight answer on how it needs to be done. The how determines the cost. Was told by dealer to add EMS system to make everything work correctly could cost upwards of $5K 😳. There has to be an easier way, especially if I’m prepped for it already. Right?

Welcome to Grand Design's Technical Forum, Fire Marshall Bill. I'm sure we can get an accurate answer to you, even if we have to get our GD representative involved. (But I think there will be someone here who can answer.)

For clarification, are you using the acronym "EMS" for "Electrical Management System"? To (most of) us here, that is a component like a Progressive Industries EMS-HW50C:


If "EMS" means something else, can you please clarify?

Again, welcome!

Howard

[Fire Marshal Bill]

Sorry, the Power Control System. I am prepped for third a/c but do not have the panel that comes in the cabinet with my main controls. I’m not sure that adding a 3rd a/c will work without this. There is much confusion surrounding this. I was assuming that since my unit is prepped for a 3rd a/c unit that it would be a fairly straightforward process to add one.

[howson]

Sorry, the Power Control System. I am prepped for third a/c but do not have the panel that comes in the cabinet with my main controls. I’m not sure that adding a 3rd a/c will work without this. There is much confusion surrounding this. I was assuming that since my unit is prepped for a 3rd a/c unit that it would be a fairly straightforward process to add one.

I found the schematic below at http://precisioncircuitsinc.com/wp-c...n-Momentum.pdf



I do not know if it specifically applies to your Momentum, but the diagram does give a clue as to it's purpose. Specifically, the Power Control System (PCS) is a load-shedding device, meaning that when it senses too much simultaneous demand it will "shed" one of the loads to keep from overwhelming the capability of the trailer's electrical capacity.


GDRV-Megan or GDRV-Emily:

1) Does GD consider the PCS a required piece of equipment in conjunction with the installation of the third air conditioner in a 320G?
2) What is the PCS model used in the 320G? http://precisioncircuitsinc.com/category/all-products/ has "Midi PCS", and "Midi-Power Control System" that all look similar to Fire Marshal Bill's picture.

TIA!

Howard

[GDRV-Emily]

howson GDRV-Megan Fire Marshal Bill



I would recommend contact our support team to get the most accurate info in regard to this question. They would be best suited to find an immediate answer. You can email them at customerservice@granddesignrv.com or you may call t hem at 574-825-9679 Mon thru Fri 8-5 EDT

I would encourage you to post the info here that they provide so that others can have access to the info!

[Fire Marshal Bill]

I called Grand Design as suggested. We double checked by VIN that my 320G was prepped at the factory for a third a/c. It was. I was told by the tech that I would need to use a dump type a/c as a stand alone unit which won’t be tied into the 320G’s ductwork. It would be controlled at the unit itself, by way of a step stool in my case. Was told a prepped unit has wiring up in ceiling at the location of the garage power fan. Removal of this fan will leave a 14”x14” opening which is standard for rv air conditioners. There is also a breaker already installed in the panel for a third unit (see pic). So the good news is it’s basically a plug and play deal! If I can locate an a/c unit with a remote control I’ll be set 😂.

[howson]

I was told by the tech that I would need to use a dump type a/c as a stand alone unit which won’t be tied into the 320G’s ductwork.

Kind of befuddling as the "racetrack" is literally right there where the 3rd ac is going to be installed. Looking at the ROOF plan, though, it confirms what you were told. The third ac shown in the diagram is not tied into the "racetrack". If you call Customer Service again ask them to email you a ROOF plan for your unit and you'll see what I am referencing. (I'm not authorized to post the diagram here--sorry!)

[Fire Marshal Bill]

So, they didn't mention that as part of the "prep" package that it had a thermostat cable already pulled in and ready to hook up at both ends? It seems to me that any A/C prep package should also include that multi-conductor cable from where the unit goes, to a location on a wall for the thermostat. With my Keystone trailer, it did.....maybe not so much with Grand Design. It might be worthwhile to check with them again or see if Emily can find out for you. Having to climb up on a stool or short ladder would be unacceptable to me.

I called back and was told there was a thermostat wire in the wall. I will have to investigate to confirm. I hope so!

[Country Campers]

I called back and was told there was a thermostat wire in the wall. I will have to investigate to confirm. I hope so!

I will guess if you remove the light switch beside the door the wires should be behind it. The floor plan video on GD's website shows a thermostat right above the light switch.

Brian