Pressure loss
Pressure loss
(OP)
I’ve got a pneumatically controlled PIU in a VAV system that will not energize. The pneumatic thermostat builds enough pressure to close the VAV when calling for heat but will not provide enough pressure to activate the fan switch and heat strip switch. I’ve replaced both switches with known good devices but the results are the same. All of the other PIU’s in the system are still functioning properly. Any suggestions?





RE: Pressure loss
To verify the stat:
Start at the stat-is supply pressure sufficient to close the switches, if not problem is in the pneumatic supply not the stat.
Next check the stat output-disconnect the branch and connect an accurate gage. Turn setpoint to full cooling(on DA stat temp up pressure up)- gage should read supply pressure.
Next,if not, depends on the type of stat but most brands have replaceable arms. Old school actually... today most would just try a new stat.
If yes then verify tubing to VAV controller. Disconnect branch line at controller and repeat above steps....
Enough steps for now, Reply with how you make out.
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RE: Pressure loss
RE: Pressure loss
My question now is should a properly functioning pneumatic stat (TK-1101-404-2) always bleed off a little air pressure???
Thanks for everyone’s help.