Air pressure switch

A

alan bredbury

New member
Aug 5, 1999
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There was a post earlier about air pressure switches I use
a switch that I bought from McMaster-Carr industrial supply
and it cycles on and off in about a 7 pound range and is
infinately adjustable to 250 psi. I have one season on it
so far and it has held up so far. I may be exceeding the
amperage rating on the switch I believe that it is a
standard "Micro switch". I love having my pressure held
between 115 and 122 psi. I posted the info at the bottom of
my GMC page,

http://www.finesttool.com/index.html/gmc.htm

For anyone that may be interested.

=====
Alan Bredbury
Clinton, Ct.
1974 GMC 26' Classic Motorhome
http://www.finesttool.com/index.html/special.htm

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Alan,

Your Pressure switch is very interesting! You brought up a valid point.
Having a turn on pressure at 85 or so could present a problem.

I use a pressure switch from Firestone that cuts on at @ 85-90, sometimes
the air pressure in the bag stabilizes the pressure in the tank above 85
but below the pressure I want. I have to "blow" the tank below the
threshold of the pressure switch to get the system to pump up the bag!

Granted, my coach does not have anything resembling a stock set up, in fact
all the original system was stolen before I got the coach. When I conjured
up a rig, I did some unusual stuff but I have found this problem to be most
annoying.

If the pressure switch is marginal on the load, wire it to a relay that
will handle it. I for one am going to trace the set up you have & see if
it solves my problem. Another side benefit I hope to have with keeping
more pressure in the tank is the ability to move up & down a bit quicker.
I not only use one of the one lung Thomas compressors, I have a 110 volt
airless portable compressor on board so when I have plenty of "pump power"
when my generator is on. Yea, it's a bit noisy but I blew my ears out
years ago!

Thanks for the info.

Jim Bounds
- -----------------

>There was a post earlier about air pressure switches I use
>a switch that I bought from McMaster-Carr industrial supply
>and it cycles on and off in about a 7 pound range and is
>infinately adjustable to 250 psi. I have one season on it
>so far and it has held up so far. I may be exceeding the
>amperage rating on the switch I believe that it is a
>standard "Micro switch". I love having my pressure held
>between 115 and 122 psi. I posted the info at the bottom of
>my GMC page,
>
>http://www.finesttool.com/index.html/gmc.htm
>
>For anyone that may be interested.
>
>
>=====
>Alan Bredbury
>Clinton, Ct.
>1974 GMC 26' Classic Motorhome
>http://www.finesttool.com/index.html/special.htm
>
>__________________________________________________
>Do You Yahoo!?
>Send instant messages & get email alerts with Yahoo! Messenger.
>http://im.yahoo.com/
>
>
 
Jim,
Having to tickle the system for more pressure sometimes
with the old pressure switch is exactly why I like this
switch so much. As far as the AMP rating 10 amps at 120 =
(more amps) at 12V but DC arcs more so it wrecks the
contacts. One thing has occured to me and that is that by
starting the compressor at a higher pressure I may be
straining the motor more but you never get something for
nothing and the motor seems to handle it OK. another down
side is that as you may have noticed the new switch is not
exactly cheap.

See the switch at the bottom of this page for those who got
on board late.
http://www.finesttool.com/index.html/gmc.htm

>Your Pressure switch is very interesting! You brought up
>a valid point. Having a turn on pressure at 85 or so could
>present a problem. I use a pressure switch from Firestone
>that cuts on at @ 85-90,sometimes the air pressure in the
>bag stabilizes the pressure in the tank above 85 but below
>the pressure I want. I have to "blow" the tank below the
>threshold of the pressure switch to get the system to pump
>up the bag!

=====
Alan Bredbury
Clinton, Ct.
1974 GMC 26' Classic Motorhome
http://www.finesttool.com/index.html/special.htm

__________________________________________________
Do You Yahoo!?
Send instant messages & get email alerts with Yahoo! Messenger.
http://im.yahoo.com/
 
>Jim,
>Having to tickle the system for more pressure sometimes
>with the old pressure switch is exactly why I like this
>switch so much. As far as the AMP rating 10 amps at 120 =
>(more amps) at 12V but DC arcs more so it wrecks the
contacts.

Could you put a capacitor across the terminals so as to stop the
arcing? Perhaps Henry or one of the other electrical knowledgable
guys could comment?

Emery Stora
77 Kingsley
Santa Fe, NM
 
I just used a driving light relay from AutoZone and wired the switch to
control the relay.

Patrick

>
> >Jim,
> >Having to tickle the system for more pressure sometimes
> >with the old pressure switch is exactly why I like this
> >switch so much. As far as the AMP rating 10 amps at 120 =
> >(more amps) at 12V but DC arcs more so it wrecks the
> contacts.
>
> Could you put a capacitor across the terminals so as to stop the
> arcing? Perhaps Henry or one of the other electrical knowledgable
> guys could comment?
 
I have two dana pumps. Each of them have a power relay to start the
pump.. this way, the load on the pressure switch is just enough to operate
the relays. This has been recommended for some time since the pumps draw
a lot of power on start up.

gene

>>Jim,
>>Having to tickle the system for more pressure sometimes
>>with the old pressure switch is exactly why I like this
>>switch so much. As far as the AMP rating 10 amps at 120 =
>>(more amps) at 12V but DC arcs more so it wrecks the
>contacts.
>
>Could you put a capacitor across the terminals so as to stop the
>arcing? Perhaps Henry or one of the other electrical knowledgable
>guys could comment?
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
>I have two dana pumps. Each of them have a power relay to start the
>pump.. this way, the load on the pressure switch is just enough to operate
>the relays. This has been recommended for some time since the pumps draw
>a lot of power on start up.
>
>gene
>

>>>Jim,
>>>Having to tickle the system for more pressure sometimes
>>>with the old pressure switch is exactly why I like this
>>>switch so much. As far as the AMP rating 10 amps at 120 =
>>>(more amps) at 12V but DC arcs more so it wrecks the
>>contacts.
>>
>>Could you put a capacitor across the terminals so as to stop the
>>arcing? Perhaps Henry or one of the other electrical knowledgable
>>guys could comment?
>>
>>Emery Stora
>>77 Kingsley
>>Santa Fe, NM
>>
>Genef -- 77PB/ore/ca
>GMC MOTORHOME INFORMATION
>mr.erf
>http://www.california.com/~eagle/
 
>I have two dana pumps. Each of them have a power relay to start the
>pump.. this way, the load on the pressure switch is just enough to operate
>the relays. This has been recommended for some time since the pumps draw
>a lot of power on start up.
>
>gene
>

>>>Jim,
>>>Having to tickle the system for more pressure sometimes
>>>with the old pressure switch is exactly why I like this
>>>switch so much. As far as the AMP rating 10 amps at 120 =
>>>(more amps) at 12V but DC arcs more so it wrecks the
>>contacts.
>>
>>Could you put a capacitor across the terminals so as to stop the
>>arcing? Perhaps Henry or one of the other electrical knowledgable
>>guys could comment?
>>
>>Emery Stora
>>77 Kingsley
>>Santa Fe, NM
>>
>Genef -- 77PB/ore/ca
>GMC MOTORHOME INFORMATION
>mr.erf
>http://www.california.com/~eagle/
 
>I have two dana pumps. Each of them have a power relay to start the
>pump.. this way, the load on the pressure switch is just enough to operate
>the relays. This has been recommended for some time since the pumps draw
>a lot of power on start up.
>
>gene

Very good point Gene. In fact, on my 1977 there is already a relay.
I had forgotten that I had switched the power lead from the front
battery to the house battery a long time back.

A relay would draw very little current so there would be not pitting
of contacts it one is installed on the older units. Obviously, there
would then be no need to put on a capacitor.

Emery Stora
77 Kingsley
Santa Fe, NM
 
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