| Powerpile vs. thermocouple
A Powerpile ( I think that is a registered Honeywell name) consists of several thermocouples contained in a single housing. The thermocouples are wired in series to produce the higher voltage of the Powerpile. A single thermocouple produces about 30 to 40 millivolts whereas a Powerpile produces about 750 millivolts.
A thermocouple cannot produce enough voltage to operate a gas valve although it can hold the gas valve open. The Powerpile CAN produce enough voltage to open the gas valve.
It is extremely unlikely that you have a pressure sensor on your system, that connecting "pipe" on the aquastat is merely a means of mounting the chassis of the aquastat and holding the thermal bulb in a closed-end tube in contact with the boiler water. |