Patrick --
> The one that came on mine looks like it belongs in a
> well-house.
Penn controls, Goshen, IN probably had 90% of the market share for these
types of controls. They also made water pump switches. My aunt probably made
or inspected the one you've got. She worked that line for 30 years. Also,
Mrs. Penn was my Sunday school teacher.
> I found a small pressure switch(looks like a gauge sending
> unit) which is set for 80psi on and 115 psi off for $19.
{snip} Looks cool, and the price is right.
>I like the fact the the switch is small and sealed, but the one
>disadvantage I see is the lack of an unloader. Is this really a
>necessity?
I'm not an air systems engineer, so just for what it's worth... air pressure
controls like this were targeted for AC cap start split phase motors that
have low starting torque. The control would unload the residual head
pressure and let the motor start will less of a static load.
The GMC uses a DC brush style motor with nearly constant torque
characteristics. Shouldn't be a problem. The motor pulls the load at 120#
steady state, so starting at 80 is a breeze.
Also, think about this scenario:
You get in your coach, turn on the key. If the EL control is in 'auto', the
compressor starts running, building head pressure. You turn the key to
start, and the ignition switch cuts power to the compressor. The pressure
switch on the EL system doesn't unload the head pressure.
You crank the engine, then release the ignition key to the run position. The
compressor motor starts right back up under full head pressure. This isn't
any different a condition than your new switch with no unload capability.
If you're still concerned, make sure you've got a good one way valve to hold
pressure in the air storage tank and put (or make) a small leak in the line
between the compressor and the one way valve. It will "weep' some pressure
when the compressor is running, but will also unload the residual head
pressure when it stops. The one way valve holds the pressure in the storage
tank.
Just some thoughts.
Mark Grady
'77 K
N Webster, IN
mgrady
> The one that came on mine looks like it belongs in a
> well-house.
Penn controls, Goshen, IN probably had 90% of the market share for these
types of controls. They also made water pump switches. My aunt probably made
or inspected the one you've got. She worked that line for 30 years. Also,
Mrs. Penn was my Sunday school teacher.
> I found a small pressure switch(looks like a gauge sending
> unit) which is set for 80psi on and 115 psi off for $19.
{snip} Looks cool, and the price is right.
>I like the fact the the switch is small and sealed, but the one
>disadvantage I see is the lack of an unloader. Is this really a
>necessity?
I'm not an air systems engineer, so just for what it's worth... air pressure
controls like this were targeted for AC cap start split phase motors that
have low starting torque. The control would unload the residual head
pressure and let the motor start will less of a static load.
The GMC uses a DC brush style motor with nearly constant torque
characteristics. Shouldn't be a problem. The motor pulls the load at 120#
steady state, so starting at 80 is a breeze.
Also, think about this scenario:
You get in your coach, turn on the key. If the EL control is in 'auto', the
compressor starts running, building head pressure. You turn the key to
start, and the ignition switch cuts power to the compressor. The pressure
switch on the EL system doesn't unload the head pressure.
You crank the engine, then release the ignition key to the run position. The
compressor motor starts right back up under full head pressure. This isn't
any different a condition than your new switch with no unload capability.
If you're still concerned, make sure you've got a good one way valve to hold
pressure in the air storage tank and put (or make) a small leak in the line
between the compressor and the one way valve. It will "weep' some pressure
when the compressor is running, but will also unload the residual head
pressure when it stops. The one way valve holds the pressure in the storage
tank.
Just some thoughts.
Mark Grady
'77 K
N Webster, IN
mgrady
atri63
