Erv-
This is great stuff. Your addition to the group is significant and meaningful to
all us information hounds.
Ron and Julie
> I have gotten quite a few questions after my lengthy post last night. I will
> try to answer those I can, and will try to find answers for the others.
> Anyone able to help on sources, etc, fell free to jump in.
>
> I had written in my post:
> compartment, or under a bed, but sales were never very good on these >>
>
> good contact to get additional information? >>
>
> Yes -
www.dometic.com (Duo-Therm is now a division of Dometic). However, I
> didn't find any dimensions listed for these on the website. Be sure to check
> out their low-profile roof-mount unit - Penguin. That is the one that will be
> replacing the Mark IV unit on our GMC. Also, check out their items under
> "Heat Pumps for Heavy Duty Trucks". They are selling a heat pump system that
> runs from batteries, using an inverter. Give anybody any ideas? This also
> brings up the subject of AGM (advanced glass mat) batteries - but that's a
> discussion for a whole other subject line - maybe later.
>
> alternator. Have you tried this approach for any of your truck systems? >>
>
> Dave, I don't believe this will work if you try to run them directly off the
> alternator output. Compressors used in 110vac systems are designed to run at
> a constant RPM, which is controlled by the AC frequency of 60 Hertz. Now, if
> you could figure out how to make the alternator run at a constant speed. . .
>
> Let's go back to the battery system mentioned above - (we have installed some
> of these in our sleepers, and this does work). You are actually running the
> unit off the alternator (indirectly, through an inverter); you can use it
> with the generator, and you can use it when you are plugged in! The best of
> all worlds. One thing to remember - these heat pumps are only 7500 BTU output
> cooling, so you would need a minimum of 2 units on a GMC.
>
> evaporator/blower for the dash air system to the header above and between
> the driver and passenger seats. So far I have not seen anything that looks
> good enough. But the position would be ideal. It would pick up the hot air
> from on high, circulate lots of cool air up front and it would be
> positioned above the compressor so the oil will not accumulate in the
> return lines. >>
>
> Now you're talking, Dave! That is the place to put an air conditioner unit -
> up high. We did this on a sleeper - worked great. It was a blower unit made
> by Acme for conversion van rear units. Only problem was running the
> refrigerant hoses through the wall - and don't forget that you have to get
> rid of the condensate somehow. (Maybe you could keep your glass of Dr. Pepper
> lined up with the drips?) Because of these problems we don't do it anymore.
>
> enter the existing lines from below, lest oil be trapped. Does this mean
> that the new suction line should run at or above the level of the existing
> return line for its entire length, or just at the point of junction? I'm
> trying to design a "slave" or second heater/AC unit to be mounted towards the
> rear and about shoulder-high in the coach. Must I keep the suction line high
> (maybe running over the roof) all the way, or can it be run down under the
> floor? The latter would be preferable for several reasons, but I don't want
> to starve my compressor for oil. Is it possible to change the height of the
> suction line so long as one stays below a certain degree of slope? Any
> hints appreciated. >>
>
> Rick, the suction line can be below the floor (we do all of our sleepers that
> way), and does not have to have any particular slope - just try to avoid dips
> in the line that might form oil traps. The slight amount of oil that normally
> travels through the suction line is swept along with the refrigerant vapor,
> and is returned to the compressor in small amounts. However, if oil is
> allowed to collect in larger amounts, it will sit there until the line
> becomes restricted enough to blow the oil out.
>
> It is the junction where the new suction line enters the original line that
> it is important to enter from above. Otherwise, if the front evaporator is
> working, and the rear is not, it could allow oil to drip into the teed line.
> This junction is usualy quite close to the compressor, and when the rear
> evaporator comes on, it could send a slug of oil to the compressor, and crack
> the reed valves.
>
> I had also written:
> us a prototype unit that appears to be very compact, and they were quite
> interested when I mentioned coming up with a kit for an add-on unit for the
> GMC. >>
>
> I went to see them today, and they seem quite enthused about this project -
> but we need a GMC to look at first. When I get ours home, we will take it
> over to them and see what we can figure out. The have several types of units,
> including one that could be installed in a 6" high space.
>
> I see that we need to find a source for high-pressure cutout switches. Can
> someone tell me if the high pressure service port (where you connect the
> guages) is the same 1/4" size as the low pressure port? Most later model GMC
> cars used a smaller port (3/16" I believe) on the high pressure side.
>
> Thanks for all the other notes I got from y'all too. 'Preciate it.
>
> Well folks, I gotta get some sleep to make up for that 2:30 AM writing spree
> I had this morning.
>
> Later,
> Erv Troyer
> Lagrange, IN
