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two pressures with NTI tx-151c combi unit
I am new to this house, and it has a NTI tx-151 combi unit. There is a digital pressure monitor on the front panel of the main display, and a normal round one by the overpressure release valve.
I think I have some air in the system, and maybe a bad watts ext-30 expansion tank.
The round gauge is almost always at 30 (some times a little less) sometimes a little more after the system has bee running for quite a while. When it is over 30, it releases a little water (table spoons).
The digital gauge varies from 13 to 20 lbs when the system is running, and with a pressure tester on the expansion tank, the digital gauge seems to follow the tank pressure... which is a little wierd because it moves so much and so fast. (it will move a pound every second or two)
The User guide shows both gauges but doesn't explain their function. I not about to dig into it too far until the weather warms up a bit.
I need to understand it, because I don't have faith in the installer. After reading some forums, the plumbing seems way off. Also it is a replacement (5 years old) for another system that failed. A few of the oddities;
1) no way to descale, they never installed a hose fitting/tap on the cold side of the hot water heater side of the unit
2) they never installed the screen filter to keep particulates out of the boiler on the cold side of the unit.
3) they connected the hot side of hydronic floor to the return side of the hydronic floor with a 1 inch pipe (almost no flow thru the floors)
4) there is an H pipe supplied with the unit, and with this added to the existing piping, there is very little flow of floor water to the boiler. (there is a mainly stagnant loop between the boiler H pipe, and the circulation pump (which has it's own loop..
... I can fix it all, but I would like to understand the meaning of the two different pressure gauges before I start.