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Revamp HVAC [message #302099]

Mon, 13 June 2016 20:14

pjburt

Messages: 436
Registered: February 2016
Location: Fresno, California

Karma: 1

Senior Member

I took the front off my hvac today to see what condition it was in inside and to clean it. The door "seals" were dust there was a lot of debris in the chambers but, the heater core and evap coils were clean. This is a late 73 recirc system. I've been studying this tutorial by Zay Brand on the GMCWS site: http://gmcws.org/Tech/air_conditioning/air_conditing.html
He suggests you maintain 20% outside air when the recirc door is open. My question is, is there a specific reason for this or can I close the outside air off completely and just use recirc air? I would think there is enough air leakage in the coach to replenish the oxygen supply. At least in ours. Rolling Eyes

Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.

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Re: Revamp HVAC [message #302105 is a reply to message #302099]

Mon, 13 June 2016 21:03

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

You want to keep positive pressure in the coach to force fumes out. Both CO and holding tank odors.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: Revamp HVAC [message #302106 is a reply to message #302099]

Mon, 13 June 2016 21:09

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

You want to keep positive pressure in the coach to force fumes out. Both CO and holding tank odors.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: Revamp HVAC [message #302111 is a reply to message #302099]

Tue, 14 June 2016 06:49

bobby5832708

Messages: 237
Registered: November 2006
Location: Winter Springs FL

Karma: 3

Senior Member

Back in 2007 I did the same thing to my 1974 GMC's air box. I also removed the recirc door and covered the recirc opening with lots of aluminum duct tape to make the system 100% recirculated air. 9 years later and I'm still here.

For a couple of years I had a CO detector running off the inverter and it never made a sound. Like you said, there are plenty of air leaks in these things so the inside air apparently gets changed enough. I also have a top-quality exhaust, Jim K's 2-muffler stainless system and Thorley headers. If you've got a swiss-cheese exhaust system then your results may be different.

The usual disclaimers: JWID, YMMV.

Bob Heller
2017 Winnebago 29VE
Winter Springs FL

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Re: [GMCnet] Revamp HVAC [message #302114 is a reply to message #302099]

Tue, 14 June 2016 08:12

Mr ERFisher

Messages: 7117
Registered: August 2005

Karma: 2

Senior Member

Read here
http://gmcmotorhome.info/heat.html#CONFIG

On Monday, June 13, 2016, Jerry Burt wrote:

> I took the front off my hvac today to see what condition it was in inside
> and to clean it. The door "seals" were dust there was a lot of debris in the
> chambers but, the heater core and evap coils were clean. This is a late 73
> recirc system. I've been studying this tutorial by Zay Brand on the GMCWS
> site: http://gmcws.org/Tech/air_conditioning/air_conditing.html
> He suggests you maintain 20% outside air when the recirc door is open. My
> question is, is there a specific reason for this or can I close the outside
> air off completely and just use recirc air? I would think there is enough
> air leakage in the coach to replenish the oxygen supply. At least in ours.
> :roll:
> --
> Patti & Jerry Burt
> 73 Gmc 26'
> Photos - http://jburt.smugmug.com/GMC-Motorhome
> Lots of upgrades but lots to do to make it ours.
>
> _______________________________________________
> GMCnet mailing list
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>

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
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http://gmcmotorhome.info/APC.html
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Re: Revamp HVAC [message #302118 is a reply to message #302099]

Tue, 14 June 2016 09:18

pjburt

Messages: 436
Registered: February 2016
Location: Fresno, California

Karma: 1

Senior Member

Thanks for all your the info. I think I'll put the 1" diverter in and play with different fresh air covers to see what kind of difference they make.

Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.

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