Author Topic: Roof Top Heat Pumps  (Read 5220 times)

Offline scanzel

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Roof Top Heat Pumps
« on: December 11, 2007, 11:46:28 AM »
Do roof top air heat pump units really provide good heat when needed or are they not worth the added expense when buying. I will have a Proheat, but thought the heat pumps might be good until the Proheat needs to take over.
Steve Canzellarini
Berlin, CT
1989 Prevost XL

Offline DavidInWilmNC

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Re: Roof Top Heat Pumps
« Reply #1 on: December 11, 2007, 11:53:11 AM »
My 15K Btu Carrier puts out a lot of heat above 38° or so.  Below that, the 1500 watt heat strips come on (and don't do much).  I think the heat pump option was around $90 or so more than straight cooling on my unit.  It seemed like a good deal to me.  If you're on park power, and it's above 38°, it makes a lot more sense than using $3.50/ gallon diesel for heating.

David

Offline Nick Badame Refrig/ACC

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Re: Roof Top Heat Pumps
« Reply #2 on: December 11, 2007, 11:59:42 AM »
Hi Steve,

David has givin you good advice.  The HP option is also a good back-up to your Proheat. ..you never know??

Good Luck
Nick-
Whatever it takes!-GITIT DONE! 
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Offline ChuckMC9

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Re: Roof Top Heat Pumps
« Reply #3 on: December 11, 2007, 01:27:20 PM »
Best decision I ever made. Unless you are in a region where it's *always* freezing, where they won't do you any good.

This season, I've used propane about four hours, and the HPs hundreds. And one of them does the job all the time. I don't think I've ever had to turn on both at once. I use one in the daytime and the other at nite. These are 15K Carriers, but most brands probably perform about the same.

Do it, and don't look back.

Offline NJT5047

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Re: Roof Top Heat Pumps
« Reply #4 on: December 11, 2007, 06:47:53 PM »
My 15K Btu Carrier puts out a lot of heat above 38° or so.  Below that, the 1500 watt heat strips come on (and don't do much).  I think the heat pump option was around $90 or so more than straight cooling on my unit.  It seemed like a good deal to me.  If you're on park power, and it's above 38°, it makes a lot more sense than using $3.50/ gallon diesel for heating.

David

Ditto.  I have two Dometic heat pumps (15K cool/12K heat) that work great down to about 40*.  One unit, the front easily warms the bus 95% of the time.    Below about 38*, no good.   We have an LP RV Hydroflame and a little Pelonis plug in heater for backup.  I've never used the Hydroflame.  We have rarely encountered freezing conditions.   
Mine are about 6 years old, and have been problem free....so far!
Separate wall thermostats allow maintaining a stable temp in the coach. 
Another thing to think about is insulation.  The Pelonis will maintain heat in my bus in below freezing weather...'cause I got foam, dual pane windows, and heavy windshield drapes.   This would be different with standard insulation and windows.
While you are building, insulate what you can...payback will be appreciated. 
As David sez, operating a ProHeat with today's diesel prices could be expensive.  However, your ProHeat is a nice heating unit...nice engine heater too.   
Regards,  JR

 
JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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Offline GM0406

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Re: Roof Top Heat Pumps
« Reply #5 on: December 12, 2007, 10:33:36 AM »
Heat pumps have a secret that some don't know about.  Reduce the air to the indoor section and you can operate at a lower outside temperature.  Think about it.  Bill T.

cody

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Re: Roof Top Heat Pumps
« Reply #6 on: December 12, 2007, 11:12:20 AM »
We have 2 carrier 15K heat pumps on the roof and like the others said, they work great down to about 40F.  One thing that hasn't been mentioned is how loud they are, the fans are quite powerful and the noise level is fairly high, at night we use the front one and during the daytime when we're in the front section of the bus, we use the rear one so it's workable.  One at a time works well when we're hooked up to 30 amp service but to use both at the same time we would be better off with a 50 amp set up.

Offline ChuckMC9

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Re: Roof Top Heat Pumps
« Reply #7 on: December 12, 2007, 11:50:31 AM »
One thing that hasn't been mentioned is how loud they are, the fans are quite powerful and the noise level is fairly high

You are right about that one, buddy. But the hidden benefit is that you don't hear nuthin' of those scalawag neighbors and all their shenanagans and goings on. It's actually a feature, not a bug! (as they say in the computer world) And it's no worse than summertime, so I'm used to it by now.

Offline NJT5047

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Re: Roof Top Heat Pumps
« Reply #8 on: December 12, 2007, 07:16:06 PM »
One thing that hasn't been mentioned is how loud they are, the fans are quite powerful and the noise level is fairly high

You are right about that one, buddy. But the hidden benefit is that you don't hear nuthin' of those scalawag neighbors and all their shenanagans and goings on. It's actually a feature, not a bug! (as they say in the computer world) And it's no worse than summertime, so I'm used to it by now.

Yep.  You'll know when they are running.  Dometics (other may too) offer a choice of function...fan on all the time, fan on with heat or cool, hi or low, etc. 
Terri and I like the noise at night.  Don't find it a bother during the day either...after so many years in RVs, reckon we're used to the noise.   
Obviously, we use a lot more cool than heat.  They are great on hot days.  You can FEEL the cool when rooftops are running.  And, you'll feel the heat too.  They put out hot air.  Unlike home style heat pumps that I'm aquainted with.  Above 45* or so, they make good heat. 
As Cody says, we only use one unit for the most of our needs.  One unit will heat the bus until it gets too cold to use.   Generally one unit will cool the bus too.  We almost never run the rear unit. 
Only after driving a long way on  100* day.  Then it gets a little time.   Once cooled down, one unit will maintain the coach. 
I'd go with the heat pump for the small difference in price. 
JR
JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand

Offline ChuckMC9

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Re: Roof Top Heat Pumps
« Reply #9 on: December 15, 2007, 08:31:12 PM »
Reporting in:

31° outside, 69° inside. That's with ONE HP running. Almost 40° differential. I didn't know that was possible.

One HP only, with the heating element that comes on at freezing or so.

But I don't expect to wake up to 69° - we'll see!



Offline Busted Knuckle

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Re: Roof Top Heat Pumps
« Reply #10 on: December 15, 2007, 08:47:22 PM »
Quote from: ChuckMC9
You are right about that one, buddy. But the hidden benefit is that you don't hear nuthin' of those scalawag neighbors and all their shenanagans and goings on. It's actually a feature, not a bug! (as they say in the computer world) And it's no worse than summertime, so I'm used to it by now.

HEY we resemble that remark! LOL! Opps! Maybe that's we resent that remark! LOL! ;D
;D  BK  ;D
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Offline ChuckMC9

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Re: Roof Top Heat Pumps
« Reply #11 on: December 16, 2007, 07:09:11 AM »
Yeah, it depends on where you are. To some of the occupants, I'm the strange person in an old bus who's always working on that old pile all the time. To others who are in old beat-up 5ers and TT's, I'm the guy with the big comfortable bus. One man's ceiling, another's floor, etc...

This morning, 25° out / 55° in, with just the heatstrip from one unit all nite long. I can live with that. A quick blast of propane and all's toasty again.
« Last Edit: December 16, 2007, 07:57:06 AM by ChuckMC9 »

Dallas

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Re: Roof Top Heat Pumps
« Reply #12 on: December 16, 2007, 07:39:26 AM »
Here in NW TN, the temp this morning is around 30° and our 2 1500W space heaters are keeping the inside of our 4103 a toasty 76°.

One is on low and the other is on high. We also have 3 fans running to distribute the air throughout the bus, otherwise the floor gets somewhat less than comfortable.

We've been in temps as low as -8°F and the two heaters will keep the interior in the 50° to 60° range, depending on the wind. As Chuck says, a blast of heat from the propane cook stove while fixing breakfast brings it all back up to comfy levels again.

Keep Warm!

Dallas

Offline ChuckMC9

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Re: Roof Top Heat Pumps
« Reply #13 on: December 16, 2007, 08:10:34 AM »
Update: the compressor just cut back in this morning, at 34°, after a nite of declaring itself off-duty.

cody

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Re: Roof Top Heat Pumps
« Reply #14 on: December 16, 2007, 08:16:23 AM »
I spend a fair amount of time in dallases bus and it is really quite warm in there, but I notice dallas does a lot of talking, unlike BK who is very quiet and shy, I'm wondering if the two electric heaters would really be needed when the BS sesssions get going hot and heavy. lol Libby just told me I may want to watch my step now, dallas will be out for revenge lol.