WE ALL NEED MORE AIR

Jim,

Agreed!

The problem with the GMC AC is the pressure drop through the whole system which is caused by the number of turns the air flow has to make. IIRC from my Hamilton Standard field rep days each 90° turn is like adding 5 - 7 feet of ducting. I can't remember how many turns it makes. This subject has been addressed here before as I vaguely remember stating this earlier.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Jim Kanomata
Sent: Friday, August 4, 2017 5:48 AM
To: gmclist
Subject: Re: [GMCnet] WE ALL NEED MORE AIR

We need to determin feet per min. velocity through the Coil, as we know
anything over 500 ft/min face volocity can cause the condensate to blow
into the ducts and water droplets will be a problem. Having a 3-4 speed can
help avoid that to some degree.
If there is a way to find the data of our origional blower , it might guide
one to avoid problems.
We can take data off all the outlets and try to get approximate cfm it
produces at MAX.
Average Vel times the area of each and add them up. We have the
instruments, but now for me to do it.

On Thu, Aug 3, 2017 at 11:47 AM, John Phillips
wrote:

> To bad it does not list a 17-39-22
> There are 3 blowers listing that I think could work
> http://www.spalautomotive.com/eng/products/view_centrifugal.
> aspx?id=017-A40-73
> http://www.spalautomotive.com/eng/products/view_centrifugal.
> aspx?id=017-A46-73
> http://www.spalautomotive.com/eng/products/view_centrifugal.
> aspx?id=017-A54-73
>
>

>

> > > ​I did see some specs for the 15-1556 before I found it on Amazon. As I
> > > recall it was 14 amps max and 800 CFM at 1 inch of water. I will see if
> > I can find the data again. ​
> >
> >
> > That would be awesome. FWIW, here's a really good page I found for the
> > SPAL blower models:
> > http://www.spalautomotive.com/eng/products/centrifugal_12D.aspx
> >
> > We're trying to figure out what the oem blower runs in terms of amps.
> The
> > fusible link is 30 amps,
> > so has to run much less than that.
> >
> > Also, what size is the oem blower wheel? I'm having trouble finding
> that
> > info.
> > I think a double blower would be more efficient, but not if its wheels
> are
> > too small.
> > Lots of trade offs here.
> >
> > thanks,
> >
> > Karen
> > 1975 26'
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
>
>
>
> --
>
> *John Phillips*
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
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Tom,

Your mod is quite clever, I was wondering why you didn't attach the blower directly to the back of the A/C plenum?

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Thomas Pryor
Sent: Friday, August 4, 2017 7:48 AM
To: gmclist
Subject: Re: [GMCnet] WE ALL NEED MORE AIR

The MCC Centrifugal Fan assembly (15-1561 )that I purchased some 2Yrs ago
was about $80. It is rated at 650 CFM with a static resistance of 3" H20.

I located a dealer that sells them for 80.57 plus shipping. See http://www.
buspartswarehouse.com/Products/A-C-Blower-Assemblies/2619902.html?whence=
Phone 800) 635-5567

*I AM TRYING TO GET A MORE RECOGNIZED SOURCE FOR THIS FAN.*.........DON'T
BE AFRAID OF SPAL OR OTHER RECOGNIZED NAMES THAT HAVE INTEGRAL RESISTORS.

FYI..................... THE MCC PART NO 15-1556 ON AMAZON IS A 24V
FAN.............DON'T DISAPPOINT YOUR YOUR SELF.

--
Regards,

Tom Pryor
4188 Limerick Dr
Lake Wales, Fl 33859
Cell 248 470 9186

Living on a waterfront is not a matter of life or death. Its more
important than that.
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I'll answer that, based on my complete redesign & construction: First off,
in Tom's case, he didn't want to build a new HVAC box, which would be
required to provide room in front of the existing box for the blower.
He might, of course, have hung the blower below the box and only had one
bend in the air flow, but that would have partially obstructed the radiator.

Most importantly, for Tom's and My mods: The problem of providing supply
air to the blower. With the blower out front, where we'd really like it to
be for most-linear air flow, one would have to provide ducting from the
cockpit out to and completely surrounding the blower. A BIG fabrication
job.

If you look at all of the dual blowers, you'll see that they all induct air
to the wheels from both sides -- the outside and around the center-mounted
motor. I seriously consider closing the motor side and using round ducts
into each side, but finally figured out that the wheels would be seriously
starved for supply air.
Among other strikes against the idea.

Tom, feel free to supply your own reasons if this doesn't cover it.

Ken H.

> Tom,
>
> Your mod is quite clever, I was wondering why you didn't attach the blower
> directly to the back of the A/C plenum?
 
Ken,

I may be confused but doesn't Tom's design connect ducts from the floor to the BACK of the HVAC box?

My question meant to find out why not just bolt the blower directly to the back of the HVAC box?

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken Henderson
Sent: Friday, August 4, 2017 9:24 AM
To: GMC Mail List
Subject: Re: [GMCnet] WE ALL NEED MORE AIR

I'll answer that, based on my complete redesign & construction: First off,
in Tom's case, he didn't want to build a new HVAC box, which would be
required to provide room in front of the existing box for the blower.
He might, of course, have hung the blower below the box and only had one
bend in the air flow, but that would have partially obstructed the radiator.

Most importantly, for Tom's and My mods: The problem of providing supply
air to the blower. With the blower out front, where we'd really like it to
be for most-linear air flow, one would have to provide ducting from the
cockpit out to and completely surrounding the blower. A BIG fabrication
job.

If you look at all of the dual blowers, you'll see that they all induct air
to the wheels from both sides -- the outside and around the center-mounted
motor. I seriously consider closing the motor side and using round ducts
into each side, but finally figured out that the wheels would be seriously
starved for supply air.
Among other strikes against the idea.

Tom, feel free to supply your own reasons if this doesn't cover it.

Ken H.

> Tom,
>
> Your mod is quite clever, I was wondering why you didn't attach the blower
> directly to the back of the A/C plenum?
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We may be referring to different "backs" -- to me, that means the forward,
outside, surface of the HVAC box -- in other words, nearest the front of
the coach.

The blower is inside the cockpit, so it's inducting air from there rather
than having to have it ducted to a location on the outside of the HVAC box.

Ken H.

> Ken,
>
> I may be confused but doesn't Tom's design connect ducts from the floor to
> the BACK of the HVAC box?
>
> My question meant to find out why not just bolt the blower directly to the
> back of the HVAC box?
>
>
 
Ken,

Let's use aircraft terms.

I think Tom's blower mod feeds air to the tail end of the HVAC box.

http://www.gmcmhphotos.com/photos/i-need-more-air/p63444-ab-thumb-img-0955-1024.html

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken Henderson
Sent: Friday, August 4, 2017 11:02 AM
To: GMC Mail List
Subject: Re: [GMCnet] WE ALL NEED MORE AIR

We may be referring to different "backs" -- to me, that means the forward,
outside, surface of the HVAC box -- in other words, nearest the front of
the coach.

The blower is inside the cockpit, so it's inducting air from there rather
than having to have it ducted to a location on the outside of the HVAC box.

Ken H.
 
We need someone to get some data on how well this works. Air flow and
temperature differential temperature. If the evaporator is not cold it does
not matter how much air you push if you are counting on cooling. If you are
counting and having fast moving 100-degree air, well that is a different
story.

> Ken,
>
> I may be confused but doesn't Tom's design connect ducts from the floor to
> the BACK of the HVAC box?
>
> My question meant to find out why not just bolt the blower directly to the
> back of the HVAC box?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken
> Henderson
> Sent: Friday, August 4, 2017 9:24 AM
> To: GMC Mail List
> Subject: Re: [GMCnet] WE ALL NEED MORE AIR
>
> I'll answer that, based on my complete redesign & construction: First off,
> in Tom's case, he didn't want to build a new HVAC box, which would be
> required to provide room in front of the existing box for the blower.
> He might, of course, have hung the blower below the box and only had one
> bend in the air flow, but that would have partially obstructed the
> radiator.
>
> Most importantly, for Tom's and My mods: The problem of providing supply
> air to the blower. With the blower out front, where we'd really like it to
> be for most-linear air flow, one would have to provide ducting from the
> cockpit out to and completely surrounding the blower. A BIG fabrication
> job.
>
> If you look at all of the dual blowers, you'll see that they all induct air
> to the wheels from both sides -- the outside and around the center-mounted
> motor. I seriously consider closing the motor side and using round ducts
> into each side, but finally figured out that the wheels would be seriously
> starved for supply air.
> Among other strikes against the idea.
>
> Tom, feel free to supply your own reasons if this doesn't cover it.
>
> Ken H.
>
>
> On Thu, Aug 3, 2017 at 6:35 PM, Rob Mueller

>
> > Tom,
> >
> > Your mod is quite clever, I was wondering why you didn't attach the
> blower
> > directly to the back of the A/C plenum?
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
John,

The compressor / evaporator have more than enough capacity. The problem is air flow.

What year GMC do you have?

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of John Phillips
Sent: Friday, August 4, 2017 11:29 AM
To: gmclist
Subject: Re: [GMCnet] WE ALL NEED MORE AIR

We need someone to get some data on how well this works. Air flow and
temperature differential temperature. If the evaporator is not cold it does
not matter how much air you push if you are counting on cooling. If you are
counting and having fast moving 100-degree air, well that is a different
story.

*John Phillips*
 
So OKAY, just occurred to me that the modification also has a significant
increase in Square inches of inlet size.

The opening on the side of the HVAC box has an effective size 5" X 3.5" or
17.5 Sq inches.

Cutouts for the double centrifugal into 4" X 3.5" X two or 28 square
inches.

I believe that works out to be about a 35% increase, just say'n

____________________________________________________________
________________________________________________

FOR GENERAL COMPARISON ........BUT CERTAINLY NOT SCIENTIFIC..........ORDER
OF MAGNITUDE COMPARISON:

SPAL makes a 3 speed single impeller (PN SPAL 064 A42 28 D 12V 3 SPEED
BLOWER) SEE (http://www.spalautomotive.com/eng/products/centrifugal_12S.aspx
)

I think itis comparable to our OEM SINGLE IMPELLER BLOWER.............. IT
IS RATED AT 455 CFM

SPAL INLET is 4 3/4" or 19 SQ INCHES GMC INLET is 4
1/2 " 17.3 SQ INCHES

SPAL OULET IS 5 3/4" X 2 5/8" or 15 SQ INCHES GMC OUTLET IS 5" X 3.5"
OR 17.5 SQ INCHES

SPAL IMPELLER IS 4.8 INCHES DIA GMC IMPELLER IS
5.0 INCHES DIA

SPAL IMPELLER IS 3.9 INCHES WIDTH GMC IMPELLER IS 3.25
INCHES WIDTH

I THINK WE COULD MAKE THE STATEMENT THAT OUR GMC BLOWER EFFECTIVELY
DEVELOPS 450 TO 500 CFM.
THAT SAID THE MCC 15-1561 DOUBLE BLOWER IS RATED AT 650 CFM PER MY CONTACT
AT MCC, JOSH.

THAT IS A 23 % IMPROVEMENT, EH?

_______________________________________________________________________________________________________________

IT WOULD APPEAR THAT THIS MODIFICATION INCREASES HVAC INLET SIZE BY 35%
AND A 23 % CFM INCREASE........JUST SAY'N

__________________________________________________________________________________________________________________

BTW Just found one more source on Bay for the MCC 151561 blower at $89.00
http://www.ebay.com.sg/itm/MCC-12V-Dual-Squirrel-Cage-Twin-Blower-Fan-Motor-
Assy-15-1561/250875055779
--
--
Regards,

Tom Pryor
4188 Limerick Dr
Lake Wales, Fl 33859
Cell 248 470 9186

Living on a waterfront is not a matter of life or death. Its more
important than that.
 
Yep, I agree. And so do I. Simply because its too difficult to route
"return air" to a blower at the nose end of the HVAC box.

Ken H.

> Ken,
>
> Let's use aircraft terms.
>
> I think Tom's blower mod feeds air to the tail end of the HVAC box.
>
> http://www.gmcmhphotos.com/photos/i-need-more-air/p63444-
> ab-thumb-img-0955-1024.html
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken
> Henderson
> Sent: Friday, August 4, 2017 11:02 AM
> To: GMC Mail List
> Subject: Re: [GMCnet] WE ALL NEED MORE AIR
>
> We may be referring to different "backs" -- to me, that means the forward,
> outside, surface of the HVAC box -- in other words, nearest the front of
> the coach.
>
> The blower is inside the cockpit, so it's inducting air from there rather
> than having to have it ducted to a location on the outside of the HVAC box.
>
> Ken H.
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Adding a resistor package is a trivial obstacle. Probably be able to acquire one easily at any men's mall. Nothing special.
More fun would be a PWM module and really control the speed to exactly what you need.
Doing the 'pin out' on the cable would be interesting, but I think you would want to roll your own design.
Tom, MS II
1975 Avion sale
--
1975 GMC Avion
KA4CSG
 
I knew it was something....

Since Tom and I first talked about this, something kicked up a parity error flag and it has taken me a while to track it down...

Where Tom put blowers is where 73&4 have the MAX AIR outlet part tacked on. That piece it essential if one is to have any A/C performance at all in
the older coaches.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> I knew it was something....
>
> Since Tom and I first talked about this, something kicked up a parity error flag and it has taken me a while to track it down...
>
> Where Tom put blowers is where 73&4 have the MAX AIR outlet part tacked on. That piece it essential if one is to have any A/C performance at all
> in the older coaches.
>
> Matt

We have a 75 with the 'max air' opening and the goofy scoop thing to direct it upwards from the floor.
Since that's what we use 99% of the time, it was a concern for me too.
There seems to be enough room between the scoop and the engine hatch opening, and I was also considering partially recessing
the blower into the floor to make it less of a giant lump. If you don't have the scoop though,
you'd risk having all your AC output being sucked back into the intake of the new blower.

Looks like it's still workable to me.

I was just comparing this to the other modification, where you mount the OEM blower on the front side of the case.
The problem with that is it's sucking air through the evap instead of blowing it, and we were concerned about
the water/vapor going through the blower motor. Short of a major rework or replacement of the enormous OEM box,
Tom's idea looks like a good improvement.

Karen
1975 26'
 
Has anyone finished and tested this mod?

> > I knew it was something....
> >
> > Since Tom and I first talked about this, something kicked up a parity
> error flag and it has taken me a while to track it down...
> >
> > Where Tom put blowers is where 73&4 have the MAX AIR outlet part tacked
> on. That piece it essential if one is to have any A/C performance at all
> > in the older coaches.
> >
> > Matt
>
>
> We have a 75 with the 'max air' opening and the goofy scoop thing to
> direct it upwards from the floor.
> Since that's what we use 99% of the time, it was a concern for me too.
> There seems to be enough room between the scoop and the engine hatch
> opening, and I was also considering partially recessing
> the blower into the floor to make it less of a giant lump. If you don't
> have the scoop though,
> you'd risk having all your AC output being sucked back into the intake of
> the new blower.
>
> Looks like it's still workable to me.
>
> I was just comparing this to the other modification, where you mount the
> OEM blower on the front side of the case.
> The problem with that is it's sucking air through the evap instead of
> blowing it, and we were concerned about
> the water/vapor going through the blower motor. Short of a major rework
> or replacement of the enormous OEM box,
> Tom's idea looks like a good improvement.
>
> Karen
> 1975 26'
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
> Has anyone finished and tested this mod?

Just got my blower in the mail today and hope to try the mod in the next few days.

Karen
1975 26'
 
> > Has anyone finished and tested this mod?
>
>
> Just got my blower in the mail today and hope to try the mod in the next few days.
>
> Karen
> 1975 26'


Well, not as good as I hoped. I chose to try abandoning the max air vent, so mounted the new blower
directly on the back of the AC box. I thought about mounting it further back and keeping the max air vent "snorkel",
but I didn't want that much protrusion into the cockpit. Without the max air slot open, it's basically the
same as the 73/74 box

We have an anemometer for measuring wind speed, so for lack of a better tool, I used that. All measurements
were taken with AC blower set to "high". The stock system with the max air vent closed got about 2 meters
per second (mps) out of the center dash vents. With the new blower, they got 3mps. The stock max air duct vents with
the oem blower got about 6mps, so double even the improved center vents. With no duct in front of the max air slot, it's 9+mps.

So, with the new blower, there was a definite improvement out of the center dash vents, though still nothing out of
the passenger side vent. However, it was nowhere near as good as the max air vent with the stock blower. There's also
the issue of the blower noise, though that could likely be improved upon with a baffle.

I think Mark Wall pretty well summed it up in his presentation, when he said
it wouldn't matter how much air you push through it, the oem (pre-77) ducts are the problem.
He did quite an interesting bunch of modifications, if you haven't seen them:
http://www.gmcmi.com/wp-content/uploads/2013/02/HVAC-Systems.pdf

FWIW, I was able to use the stock resistor pack with the new blower. Slightly easier
than modifying the wiring to use the new resistors, though that's not bad either.
The oem resistors are about half the ohms of the new pack.
Since I was only measuring "high", it didn't matter.

I'll probably play with this more later, but for now I'm out of time.
If I can get the heater core out, I think I could do Mark Wall's vent modifications
without removing the whole AC box.


Karen
1975 26'
 
I'll point out for those of us attending the December in Orlando Pet The Puppy And Spend Money rally at Wekiwa Springs, they day trip to SkyCraft
should produce workable blowers for this mod. The have an aisle of them in various configurations.
Ten sites left in the favored loop, 21 total available out of 60 total. Book early or be left out.
--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
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