"Little David" Pressure Switch? What is this guy?

[ElectronicEric]

This is on a compressor in a central rack refrig system. Does anyone know what this guy does?

http://picasaweb.google.com/ericjhwi...36540619706690

[refrigman22]

Looks like a cheap pressure activated anti short cycle switch to me.

[IceMonster]

it is time delay controller for the startup of the compressor. it allows the unit to have sufficent static pressure before the compressor can start up. It is mostly used as safety device to prevent overloading of compressor startup amps.

[Trublshter]

I've seen some simular to those used on small tonnage yorks for a lo-pressure bypass timer to allow time to build back pressure on start up in lo ambient conditions for units cooling computer rooms. Basically added to them in the field ar some point.

[wkfldal]

its an anti short cycle switch -- as long as the pressure switch is closed and the jumper time is satisfied, comp should run -- cuts out comp at contactor

[hvacmd2002]

I worked for a company in the '80's that installed some here and there.
They were marketed as a way for the stores to save energy. We installed a new LP control to control the compressor, and set it so the compressor would maintain a higher back pressure, so when it ran, it was under full load. Then the timer would keep it from short cycling.

We would also install a clock to record compressor run time. I'm not sure if any customers ever saved anything by using them.

[Biblepoet]

I worked for a company in the '80's that installed some here and there.
They were marketed as a way for the stores to save energy. We installed a new LP control to control the compressor, and set it so the compressor would maintain a higher back pressure, so when it ran, it was under full load. Then the timer would keep it from short cycling.

We would also install a clock to record compressor run time. I'm not sure if any customers ever saved anything by using them.

Yup. Nailed it. My Dad was in a position to sell some to some local Mickey D's and had one installed on on of their W/I units. Just a shame one of the regional directors came along even after he had showed them I believe about $200 month savings and said -"Nope not corporate approved - take it off!!"


Coulda made a mint -<sigh>

B-