Strangely enough, I swapped the stat with 2 other stats and still had the same problem but when I jumped the stat completely, I would get heat. After soaping all the fittings and finding no leaks, I rigged a test squeeze bulb to pressurize the actuator to find that it was leaking enough pressure...
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...
