The precharge of air for the pressure tank is usually recommended to be set 2 PSI below the cut-in for the pressure switch. This allows time for the pump to get pressure to the pressure tank before the pressure tank is out of water. It also allows a little margin for differences in calibration of the water pressure gauge and the air pressure gauge.
I bought a LDR 020 9645 garden hose connector Pressure Gauge. It has a lazy hand AKA tattle-tale hand to record the peak pressure. I found that I could wind that hand around and use the lazy hand to record the minimum pressure.
I recently replaced my pressure switch, and turned the cut-in a couple PSI lower than the original 40 PSI. I raised the precharge on my tank. However when the lazy hand showed that the pressure had dropped momentarily to 20 PSI at some point, I lowered the precharge 1 PSI. Since, the needle is holding near the cut-in point so no big transient yet. However maybe there will be a transient if I have a bigger load. So I will leave the gauge in place for a while. The pressure gauge is located at a spigot very close to the pressure switch. This might not be as useful if the pressure was being monitored closer to a point of use.
It seems to me that with this technique, if you thought the precharge setting was close, and if you saw a low transient recorded, you could just release maybe 1 second of air from the tank without emptying the tank, and without removing the water pressure. It would be for fine tuning. Then set the needle back up and wait for a future downward transient. We know if you get the transient, you must have too much air rather than not enough. I thought somebody might find this method of use, or at least of interest.
I bought a LDR 020 9645 garden hose connector Pressure Gauge. It has a lazy hand AKA tattle-tale hand to record the peak pressure. I found that I could wind that hand around and use the lazy hand to record the minimum pressure.
I recently replaced my pressure switch, and turned the cut-in a couple PSI lower than the original 40 PSI. I raised the precharge on my tank. However when the lazy hand showed that the pressure had dropped momentarily to 20 PSI at some point, I lowered the precharge 1 PSI. Since, the needle is holding near the cut-in point so no big transient yet. However maybe there will be a transient if I have a bigger load. So I will leave the gauge in place for a while. The pressure gauge is located at a spigot very close to the pressure switch. This might not be as useful if the pressure was being monitored closer to a point of use.
It seems to me that with this technique, if you thought the precharge setting was close, and if you saw a low transient recorded, you could just release maybe 1 second of air from the tank without emptying the tank, and without removing the water pressure. It would be for fine tuning. Then set the needle back up and wait for a future downward transient. We know if you get the transient, you must have too much air rather than not enough. I thought somebody might find this method of use, or at least of interest.
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