Pressurtrol Question

superMARKet

"B" controls make contact on pressure rise, and then open again whent he pressure falls. This is usually the opposite of what you want on a boiler where you're using the pressuretrol to control the burner. You want the burner to run when the pressure is low, and break contact when the pressure rises past the setpoint. That's what the "A" controls do.

The "B" is more suited to maintaining a minimum, the "A" is for maintaining a maximum.

Bernard Smith

What is the differnce between a Honeywell PA404A and a PA404B?

superMARKet

The difference

"B" controls make contact on pressure rise, and then open again whent he pressure falls. This is usually the opposite of what you want on a boiler where you're using the pressuretrol to control the burner. You want the burner to run when the pressure is low, and break contact when the pressure rises past the setpoint. That's what the "A" controls do.

The "B" is more suited to maintaining a minimum, the "A" is for maintaining a maximum.