Johnson controls All Range

[Iceneck]

I was given one of these http://cgproducts.johnsoncontrols.co...PDF/125454.PDF by a refrigeration mechanic that I know and was told in so many words to "learn it inside and out, take it apart, screw with it, break it, fix it, but learn how it works." I read the online manual, but am still a little confused. I'm going to ohm the contacts as I adjust the pressure settings, but i'm not sure the switch will close since there's no pressure on the capillary tube (it's just sitting on my bench, not installed on a system). He asked me what I thought it did, and I asked him what it was connected to and he said "liquid line of a small rooftop condensing unit". At first I thought it was a condenser fan cycling control...ie., head pressure control. In other words, when the pressure is above a certain point the condenser fan kicks on. But I also see there is a high pressure control that opens the circuit above a certain pressure...which would lead me to believe that it somehow switches (cuts out) the compressor above a certain head pressure. I realize it can't do both. Can anyone lead me in the right direction here? I know they're widely used in one on one systems and want to learn more about them...

[Phase Loss]

You're going to technical school right?

I'm just curious, what book is the course being taught from?

[powell]

The manual you have is for the Johnson Controls P70, P72, and P170 series controls, not just one control.

Look at the back of the control, or inside the cover, and get the model number. Then go to page 9 of the manual.

[jpsmith1cm]

I was given one of these http://cgproducts.johnsoncontrols.co...PDF/125454.PDF by a refrigeration mechanic that I know and was told in so many words to "learn it inside and out, take it apart, screw with it, break it, fix it, but learn how it works." I read the online manual, but am still a little confused. I'm going to ohm the contacts as I adjust the pressure settings, but i'm not sure the switch will close since there's no pressure on the capillary tube (it's just sitting on my bench, not installed on a system). He asked me what I thought it did, and I asked him what it was connected to and he said "liquid line of a small rooftop condensing unit". At first I thought it was a condenser fan cycling control...ie., head pressure control. In other words, when the pressure is above a certain point the condenser fan kicks on. But I also see there is a high pressure control that opens the circuit above a certain pressure...which would lead me to believe that it somehow switches (cuts out) the compressor above a certain head pressure. I realize it can't do both. Can anyone lead me in the right direction here? I know they're widely used in one on one systems and want to learn more about them...

Do you have access to nitrogen and a set of manifold gauges?

That's a GREAT way to set and test pressure controls.

[Iceneck]

You're going to technical school right?

I'm just curious, what book is the course being taught from?

Refrigeration and Air conditioning Technology. I have the 2009 ed. (at least I think it's 2009 ed).

[Iceneck]

Do you have access to nitrogen and a set of manifold gauges?

That's a GREAT way to set and test pressure controls.

I have both at work...I'm home now. But, I'd have to find the male fitting for the flare connection...not sure what size it is. That's a great idea, though! Once I find the fitting, I could solder it onto a pipe, then solder on a T with a schrader valve for my guages, then cap both ends and use the nitrogen regulator to adjust pressure and check for continuity between the two terminals at various pressures...

I adjusted the high pressure side all the way down (to what I think is atmospheric pressure, the scale didn't go that far), heard a "click", and got continuity between the two terminals.

[jpsmith1cm]

I have both at work...I'm home now. But, I'd have to find the male fitting for the flare connection...not sure what size it is. That's a great idea, though! Once I find the fitting, I could solder it onto a pipe, then solder on a T with a schrader valve for my guages, then cap both ends and use the nitrogen regulator to adjust pressure and check for continuity between the two terminals at various pressures...

I adjusted the high pressure side all the way down (to what I think is atmospheric pressure, the scale didn't go that far), heard a "click", and got continuity between the two terminals.

You could just wrench it onto the manifold.

a 1/4" male x 1/4" male fitting is pretty common.

[Iceneck]

The manual you have is for the Johnson Controls P70, P72, and P170 series controls, not just one control.

Look at the back of the control, or inside the cover, and get the model number. Then go to page 9 of the manual.

It says P70AA-118...damn, i shoulda figured that before i posted.

[Iceneck]

You could just wrench it onto the manifold.

a 1/4" male x 1/4" male fitting is pretty common.

Just did so and it fits....

[DLZ Dan]

If you screw it onto the low side of the manifold, you can pressurize and see where the contacts open and close.

[jpsmith1cm]

If you screw it onto the low side of the manifold, you can pressurize and see where the contacts open and close.

Might be a high side control....

[Iceneck]

I thought it was a fan cycling control, but now realize it's not. Also thought it might be a high pressure control...i.e., it would open the circuit when a high pressure setpoint was acheived. But it would have to be normally closed below that setpoint, and it's not when I ohm it with my meter.

[pairman]

P70AA-118 opens when pressure drops. You have a fan cycling control. When then pressure rises the switch closes to energize the condenser fan. As the pressure drops then the switch opens and the condenser fan shuts off.

[Iceneck]

Now it's time to put it on my AC! I figure I'll wrench it onto my manifold then connect the hose to the high side of the AC system. Take the c fan wire off the load side of the contactor and make it cut in at...hmm, it's 70 degrees out and I have R22...need to figure that one out.

[Phase Loss]

I like to set them close to the minimum and maximum design conditions.

[Iceneck]

Is the "differential" sort of like a deadband setting, to keep the cond. fan motor from short cycling?

[crackertech]

Is the "differential" sort of like a deadband setting, to keep the cond. fan motor from short cycling?

Yes.

[Phase Loss]

You will run into several variations of terminology.

Deadband

Differential

Neutral Zone

Hysteresis

All basically mean the same thing...for the most part, but not always