ModCon Temperature Pressure Gauge Location

ced48

Maybe another dumb question, but, what is the best way to install a P&T gauge on a modcon? I know it should be close to the boiler, but will placing a gauge with the probe in the direct flow path mess with the flow, causing turbulence?

Jean-David Beyer

Temperature Pressure Gauge Location

My mod-con has a pressure-temperature gauge that comes with it. The gauge dial is on the control panel at the top of the boiler, along with the buttons. The main problem with it is that it is too small to read accurately. The pressure and temperature sensors are in the pipe that comes out the top of the heat exchanger and goes out the top of the unit (the supply pipe). My guess is that they cause a little turbulence, but I have no idea if the turbulence matters. After all, for heating the house, the water flows through some 1 1/4 inch steel pipe, a Flow Check valve and the two closely spaced Ts to get up to the system loop. Up there, it goes through an air eliminator and then Ts where the water turns up to go to the circulator for the upstairs zone and the water turns down to go through the circulator for the downstairs slab. So unless the turbulence is too close to the air eliminator, who cares?



One thing wrong with my installation is that the pressure gauge varies when the indirect fired domestic hot water heater is running. That circulator pulls so much water that the pressure gauge reading drops a coupla psi. And it no doubt does where the pressure sensor actually is. And if there were a pressure gauge on the return side, I imagine it would go up by the same amount. It puzzled me for a while. But I do not think it matters.



As far as the temperature gauge sensor, I suggest putting one at each point where you want to measure the temperature. I have one (already discussed) at the output of the heat exchanger. There is another one at the beginning of the system loop showing the temperature of the water supplied to the system and another one at the end of the system loop showing the return tempreature from the system loop.  I wish I had another temperature sensor at the return to the boiler, but I don't.