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Topic: Roof-top a/c (Read 1129 times) previous topic - next topic

Roof-top a/c

Over the past couple of years we've replaced both rooftop a/c units. The old front one cycled both compressor and fan together, while the old rear one cycled only the compressor, with the fan running constantly. The new front unit is a relatively inexpensive one (a/c only, no heat), and the fan runs constantly while the compressor cycles on and off as needed. MOT just replaced the rear unit with a fancy one. Heat pump, heat, wall thermostat. I can set it on AUTO, which means that the fan and compressor cycle together, or on LOW or HIGH, which has the fan run constantly at either low or high speed and the compressor cycles on and off.

The new thermostat controls everything on that unit, and it is a capacitive touch device, so it is possible to switch modes without noticing. I suspect that we're going to have to learn to be very careful around it, lest it do things that we hadn't wanted.

Re: Roof-top a/c

Reply #1 –
Any chance you could help us with manufacture & model of each of your new roof air conditioners. And any other details like what the new thermostat controls.

It seems to us that any model that runs fan all the time is not as desirable as one where the fan shuts off with compressor motor.

Thanks

Re: Roof-top a/c

Reply #2 –
Furrion and attwood ac's run the fan all the time cycling the compressor on and off with a second fan.. I know a couple of people that have attwoods and like them.



Keith
The selected media item is not currently available.Keith & Jo
2003 U320T 4025 PBBS Designer series
Build 6203    Cummins 500hp
2000 U320 4010 WTFE / Build 5762 —Sold—
Motorcade #18070   
Pasadena, Texas
2015 Jeep Wrangler Sahara-Sunset Orange pearl coat
Don't argue with a fool, people watching might not be able to tell the difference.

Re: Roof-top a/c

Reply #3 –
Quote from: hdff –
Furrion and Atwood ac's run the fan all the time...I know a couple of people that have Atwood and like them.
We have two Atwood Air Command units and like them.  The constantly running fans are, IMO, both a plus and a minus.  On the plus side, I think the fans keep the temperature much more consistent throughout the whole coach (compared to our old Penguins).  On the minus side, there is the constant noise of the fans.  Depends on how sensitive one is to the fan noise.  Doesn't bother me - I can just ignore it.  Of course, my high frequency hearing is shot, plus I have tinnitus.  My DW thinks it is a very pleasant "white noise" that helps her get to sleep.  Bottom line: fans on all the time, for us, no problem.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Roof-top a/c

Reply #4 –
Furrion AC air circulating fan runs if it is on. 3 speeds or automatic speed based on temp difference. It does not have to be on.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof-top a/c

Reply #5 –
Are there any new/current Roof A/C models that do not have a continuous air movement fan?

Is anyone aware of a mod that we could make to shut off fan when compressor motor stops, similar to our original roof A/C units. Seems like a simple mod could be the answer. Maybe a switch where we could choose.

Surprised manufacturer does not offer us the option to move air for more consistent air flow or turn off fan motor. Home A/C units have a fan switch where we have choice. Seems arrogant or maybe they want earlier wear on fan motor. After all, low energy consumption is a current topic these days and appliance energy ratings are there to reward manufacturers.

We sometimes turn on cooling with a higher temp set point to keep motorhome from overheating, but not necessarily cold, where fan on between long compressor-off times is more wear on unit, more electric usage, and unnecessary sound.

Several of us have been talking about this subject and we could benefit by Forum members thoughts & ideas.

Thanks,

Barry & Cindy

Re: Roof-top a/c

Reply #6 –
Dual attwoods here. At first didn't like the fans on all the time. Now used to it. White noise. Quiet enough. Keeps the air moving. I like them and the price was right.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: Roof-top a/c

Reply #7 –
Two motors on the Furions, Barry. Lots of operation modes including a night setting that raises cooling temps or lowers heat temps as the night goes on.  Automatic modes that heat or cool as needed. Automatic fan speeds tgat lowe the closer you get to set points. Either can be set to cool or heat or fan only or off. One can heat and the other cool. 

No heat pump but you are not a fan of those. Two 15.5 K ACs, two controllers, two air dist inside covers and a thermostat were $1700.

Worth looking at.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof-top a/c

Reply #8 –
With 2 controllers, I assume 1 in bedroom and 1 in the front area? How do you control your aqua hot the old T-stat in the front and remote in the rear? I am looking to replace both of mine very soon, although they are proud of penguin 2s if you can really find them.
99 U320 40
97 Jeep wrangler toad
Now full time 8 months
Starting a new brick and wood home
Chattanooga, Tn

Re: Roof-top a/c

Reply #9 –
There is a controller in each AC unit. DIP switches identify which is which, up to 4 units. The control box has all of the wiring to connect the 120v AC, the +/- 12v DC, the heat zone associated with the AC unit, and 4 wires to connect to the 4 zone thermostat.  I re-used the existing 6 wire control wires, a phone cable, to connect the units together and to the thermostat. Each AC unit has a built in temperature sensor and there are optional remote temperature sensor kits available.  The temp sensor in the bedroom can be connected to the rear AC unit.

The multizone Furrion thermostat is a much more sophisticated device than the 4 or 5 button Dometic that lets you use all of the capabilities of the Furrions. I do not think the older Dometic thermostat controls will work with the Furrions.

The wiring to turn on and off the Aqua Hot is already in each AC space. They connect to the two heater wires coming out of the control unit. When you set the Furrion multizone thermostat to the zone you want, and heat mode and set the temperature the AH will come on if heat is needed.  If you have a furnace it works the same.

Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN
 

Re: Roof-top a/c

Reply #11 –
I dug out the information on the air conditioners. The front one is a Dometic B57915. As I said, it is a pretty basic unit. It does have provision for a small heat strip, but the manual cautions that it is only to be used for a few minutes. This particular unit does not have that.

The rear one is also a Dometic, a 15K white Penguin II heat pump.

Both are noisier than the old units, but that's typical I'm told. The front unit, being a "dumb" one, has a fan that runs constantly. I frequently sit directly below it, and I don't notice the compressor cycling on and off unless I'm paying attention to it. The rear unit, being a "smart" unit, can cycle the fan and compressor together or leave the fan running while the compressor cycles. Again, unless I'm paying attention to it, I can't hear when the cycling happens. The first night with it I put it on AUTO, which cycled the fan and compressor together. That kept waking us up, so I switched it. Now we sleep soundly all night.

As was mentioned above, since these are noisier than older ones, they are a great white noise generator. With then on we don't hear anything outside.