What is a pressuretrol?

[thebatman]

I am fairly new in HVAC. I was hoping someone could explain to me what a pressuretrol is. Also are they usually available in 4-20 signal?

[CDNtech]

Pressuretrol controllers are often found on steam boilers. Steam boilers operate off these controllers as opposed to temperature conrtrollers found on a water boiler. For example when boiler pressure drops below 9psi the burner comes on, turns off at 15psi, all through a mercury bulb. The set points are adjustable between the controllers range. They are usually available in 2 to 15psi, 5 to 10psi, 10 to 150psi, and 20 to 300psi. I know they are usually rated for 24V ac to 120V ac. Don't see why you couldn't use them with DC voltage, if that's what you mean when you say 4 to 20 signal. If you log onto honeywell.com I'm sure they have all kinds of info for you.

[HVACJOEK]

If you are new to HVAC maybe this link to a Kele page will answer some of your questions about pressuretrols... and 4-20 is a pressure transmiter:cool:

http://www.kele.com/webservices/index/index.aspx?section=5

[CDNtech]

I see, I automatically assumed HoneyWell Pressuretrol, my mistake. Now the 4 - 10 makes more sense

[thebatman]

If you are new to HVAC maybe this link to a Kele page will answer some of your questions about pressuretrols... and 4-20 is a pressure transmiter:cool:

http://www.kele.com/webservices/index/index.aspx?section=5

Thanks I'll check it out.

[Jerry Condiff]

A pressuretrol [ pressure controller ] typifies a Honeywell product. It is an electric switch, controlled by pressure. In the case of a steam boiler, for example, the steam pressure you can live with would be the low setting on the pressuretrol, and the highest pressure you require would be the pressure setting at the high end of the switch. The adjusting screws on the top of the pressuretrol are for adjusting the low side of the switch with one of the screws, and the high side of the switch with the other screw. You may be adjusting the differential between the high side of the switch and the low side. The High pressure setting, when reached, would shut down the Boiler, by opening a contact in the switch. The boiler will stay off until the pressure drops to the low pressure setting which will result in the contacts closing, allowing current to flow to the boiler start circut.:)