Internal A/C system (Other ideas)

[dave1]

I am curious about other possibilities for keeping GMC's cool while on the
road.

My experience is that the in-dash AC system is pretty much useless after
the outside air temp gets above 75-80 degrees, especially on a sunny day.
Therefore I end up putting a lot of hours on my Onan while I am on the road.

What I am wondering is... Would it be possible to set up a second
evaporator coil and blower to aid in keeping the inside cool while driving?
I was thinking that there may be enough space above the refrigerator for a
blower/coil assembly. The exhaust could be directed forward to cool the
main living area.

Questions:

- - Does the engine mounted compressor/condenser have enough capacity to
supply two evaporator coils?

- - Has anyone on the list tried this? Care to share your experiences?

- - Any experienced mobile HVAC men out there?

I have some experience in AC repair (enough to give it a try anyway) but no
experience in cooling system design.

Dave
73 Sequoia

 

[mr.c]

Jim Ansett from Colorado showed my his coach one day and had a second coil
under the passenger seat. He used it for cooling. You might look him up and
call. He writes all sort of stuff on the GMC and has made lots of
improvements.
Al Chernoff

> I am curious about other possibilities for keeping GMC's cool while on the
> road.
>
> My experience is that the in-dash AC system is pretty much useless after
> the outside air temp gets above 75-80 degrees, especially on a sunny day.
> Therefore I end up putting a lot of hours on my Onan while I am on the road.
>
> What I am wondering is... Would it be possible to set up a second
> evaporator coil and blower to aid in keeping the inside cool while driving?
> I was thinking that there may be enough space above the refrigerator for a
> blower/coil assembly. The exhaust could be directed forward to cool the
> main living area.
>
> Questions:
>
> - Does the engine mounted compressor/condenser have enough capacity to
> supply two evaporator coils?
>
> - Has anyone on the list tried this? Care to share your experiences?
>
> - Any experienced mobile HVAC men out there?
>
> I have some experience in AC repair (enough to give it a try anyway) but no
> experience in cooling system design.
>
> Dave
> 73 Sequoia

 

[donald w. miller]

Arch,

My goal is 24,000 btu from a dual system with engine idling in neutral.

Several others including Jim Bounds have done these dual systems. Seems
they work well if done properly.

Would you have any data on the OEM Delco evaporator's btu capacity vs. air
flow ? It looks plenty adequate for 24,000 btu if you put enough air
through it, but hard data is better than my usual SWAGs.

As you point out the 12.5 cu. in. compressor is a big one and has plenty of
capacity for two evaporators. It probably pumps enough Freon12 for 30,000
btu with engine idling in neutral.

I would know for certain if I could find the Volumetric Efficiency of this
particular compressor. Would you or anyone happen to know this value or
where to find it ?

Also I am curious to hear why your condenser is headed for your roof top
instead of in front of the radiator.

Is it because you are worried about engine cooling ?

In this HVAC area, GM should have done better. I think they took a
convenient quick easy route instead of putting their engineers to work.

Some AC theory would be timely for me.

Cheers,

Don Miller
75 Glennbrook
Shenandoah Valley of Virginia

Arch said :

>I too would like some answers along the lines you are pursuing. Can
>the compressor handle 2 evaporators----yes this thing has the capacity
>of a 60,000 Btu AC. Thats 5 tons of AC. Can the evaporator handle it?
>Yes, it can----thats not the problem. Can the radiator handle it? That is
the
>problem. I ask about roof mounted condensers in here some time back. I
>was told there was no problem. There is a problem if you want to push
>the limits of AC. The largest roof mounted condenser I found was 29,000
>BTUs. You would have to put two on top to get the job done.
>
>The real problem with the dash air is that the intake for the system is
>down low. You need an intake at the top of the ceiling. Hot air balloons
rise
>so does hot air. The Second Design AC tried to take care of this by
mounting
>the output ducts pointing up. It helps but it does not solve the problem
>of hot air trapped on the ceiling. Any changes you make should include
>an air intake on the ceiling. The other thing you need to do is make sure
>the various doors seal well in the heating/AC box out front. Mine did not.
>
>Would be glad to discuss the theory more if anybody wants to hear it.

 

[richard bachert]

This may sound Mickey Mouse, but when we ran our '75 PB years ago, I put two
small 12V fans on the table off the center of the dash, directing them
straight up into our faces. The evaporative cooling effect was enough to
take the edge off the radiation to which the driver and right seater were
subjected. Those behind the front of the coach were kept pretty comfortable
by running the genny and the roof air under way. There's NO WAY the front
A/C could keep up with the load in these 1248 cubic foot boxes in the
Georgia sun in July or August.
Dick 75 PB in Atlanta

>Dave
>
>I too would like some answers along the lines you are pursuing. Can
>the compressor handle 2 evaporators----yes this thing has the capacity
>of a 60,000 Btu AC. Thats 5 tons of AC. Can the evaporator handle it?
>Yes, it can----thats not the problem. Can the radiator handle it? That is the
>problem. I ask about roof mounted condensers in here some time back. I
>was told there was no problem. There is a problem if you want to push
>the limits of AC. The largest roof mounted condenser I found was 29,000
>BTUs. You would have to put two on top to get the job done.
>
>The real problem with the dash air is that the intake for the system is
>down low. You need an intake at the top of the ceiling. Hot air balloons rise
>so does hot air. The Second Design AC tried to take care of this by mounting
>the output ducts pointing up. It helps but it does not solve the problem
>of hot air trapped on the ceiling. Any changes you make should include
>an air intake on the ceiling. The other thing you need to do is make sure
>the various doors seal well in the heating/AC box out front. Mine did not.
>
>Would be glad to discuss the theory more if anybody wants to hear it.
>
>Take Care
>Arch
>
>In a message dated 3/19/99 2:23:01 PM Central Standard Time, DGMDGM
>writes:
>
>>
>> My experience is that the in-dash AC system is pretty much useless after
>> the outside air temp gets above 75-80 degrees, especially on a sunny day.
>> Therefore I end up putting a lot of hours on my Onan while I am on the
>road.
>>
>>
>> What I am wondering is... Would it be possible to set up a second
>> evaporator coil and blower to aid in keeping the inside cool while driving?
>> I was thinking that there may be enough space above the refrigerator for a
>> blower/coil assembly. The exhaust could be directed forward to cool the
>> main living area.
>>
>

 

[richard bachert]

And your web site URL is...? Want to check them out. My lovely and
talented wife has a faulty hypothalamus gland (her only fault) who requires
- -- no, DEMANDS -- efficient cooling at all times. Came close to human
spontaneous combustion several times just this past summer. Fortunately, we
threw her into the pool in the nick of time.
Dick 75 PB in soggy Hotlanta

>-- [ From: chief evaluator * EMC.Ver #2.5.3 ] --
>
>Don;t forget the fresh air vents I show on my web page, I used them all
>the way into and out of Mexico and only used the air cond once. Most of
>the folks who have put these vents in think they are a great additon to
>the cooling of the GMC.
>gene
>
>-------- REPLY, Original message follows --------
>
>Date: Saturday, 20-Mar-99 12:08 AM
>
>From: Richard Bachert \ Internet: (bachert)
>To: gmclist \ Internet: (gmcmotorhome
>.org)
>
>Subject: Re: GMC: Internal A/C system (Other ideas)
>
>This may sound Mickey Mouse, but when we ran our '75 PB years ago, I put
>two small 12V fans on the table off the center of the dash, directing
>them straight up into our faces. The evaporative cooling effect was
>enough to take the edge off the radiation to which the driver and right
>seater were subjected. Those behind the front of the coach were kept
>pretty comfortable by running the genny and the roof air under way.
>There's NO WAY the front A/C could keep up with the load in these 1248
>cubic foot boxes in the Georgia sun in July or August. Dick 75 PB in
>Atlanta
>

>>Dave
>>
>>I too would like some answers along the lines you are pursuing. Can
>>the compressor handle 2 evaporators----yes this thing has the capacity
>>of a 60,000 Btu AC. Thats 5 tons of AC. Can the evaporator handle it?
>>Yes, it can----thats not the problem. Can the radiator handle it? That
>is the
>>problem. I ask about roof mounted condensers in here some time back. I
>>was told there was no problem. There is a problem if you want to push
>>the limits of AC. The largest roof mounted condenser I found was 29,000
>>BTUs. You would have to put two on top to get the job done.
>>
>>The real problem with the dash air is that the intake for the system is
>>down low. You need an intake at the top of the ceiling. Hot air
>balloons rise
>>so does hot air. The Second Design AC tried to take care of this by
>mounting
>>the output ducts pointing up. It helps but it does not solve the
>problem
>>of hot air trapped on the ceiling. Any changes you make should include
>>an air intake on the ceiling. The other thing you need to do is make
>sure
>>the various doors seal well in the heating/AC box out front. Mine did
>not.
>>
>>Would be glad to discuss the theory more if anybody wants to hear it.
>>
>>Take Care
>>Arch
>>
>>In a message dated 3/19/99 2:23:01 PM Central Standard Time,
>DGMDGM
>>writes:
>>
>>>
>>> My experience is that the in-dash AC system is pretty much useless
>after
>>> the outside air temp gets above 75-80 degrees, especially on a sunny
>day.
>>> Therefore I end up putting a lot of hours on my Onan while I am on
>the
>>road.
>>>
>>>
>>> What I am wondering is... Would it be possible to set up a second
>>> evaporator coil and blower to aid in keeping the inside cool while
>driving?
>>> I was thinking that there may be enough space above the refrigerator
>for a
>>> blower/coil assembly. The exhaust could be directed forward to cool
>the
>>> main living area.
>>>
>>
>
>
>
>-------- REPLY, End of original message --------
>
>
>

 

[dave lowry]

We found another way to supplement cooling up front; installed a couple 12V
fans onto the bracket which holds the mirror and secures the ends of the
visors. There's just enough flat surface on eithr side of the mirror mount.
Each fan is fixed (oscillation off) to point toward its occupant and
controlled by a long handled toggle switch installed in the hard ceiling
cap just ahead of the dome light/speaker panel. Power for each fan is
available from the dome light. This is similar to what Richard B. did, but
the fans are up & out of the way.

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-O------OO--*