I have just fitted a Techflow QT120 twin shower pump in the loft. Before anyone tells me I know Techflow dont recomend it and its not the best place for shower pumps.
Initially I thought the problem of poor pressure on the pumped hot side side was down to the pump being installed in the loft and air getting into the pump. After chasing my tail on this theory and fitting an ESSEX type flange (techflange from Techflow), an Anti gravity loop, manual vents on the hot inlet to the pump and a bottle vent on the hot output of the pump I came to the conclusion this wasnt the problem.
To prove this I purged the shower pump and pipe work of air when the hot water cyslinder was full of cold water and then tried the shower on full hot. With this I had good pressure on the hot side of the pump - same as on the cold side.
I therefore decide the problem could be down to the hot water being do hot causing cavitation in the pump. The cylinder stat was set at 60degrees but to be honest the water has always been too hot. I emptied the hot water tank and then turned the stat down to 50 degrees to try the pump at this temperature. The problem was the water remained just as hot.
Before people start suggesting the thermosat is faulty or the mid position valve is faulty they are not. I have changed them both as a precautionary measure and checked the mid position valve and thermostat operate (as per a Y plan system). They oprate as they should, but the cyslinder thermostat seems to register a much lower temperature than the water in the cylinder. The cylinder thermostat is a Honeywell strap on type that is mounted 1/3 the way up the cylinder as is normal. It has good contact with the cylinder which is nice and shiny copper. Through tweaking the thermostat, I have found that setting it to 40-45 degrees yeilds a water temperature in the range of 60-65 degrees. This is acheived when the boiler thermostat is set on 4 (approx 71 degress according to the manual).
I have wondered if it is worth moving the thermostat further up the cylinder, but then I wont get a call for heat until the water at that level is 'cool' an so coudl end up with less hot water capacity?
I have also wondered if the issue is because the cylinder thermostat is located between the coil inlet/outlets on the cylinder?
Is it normal for the cylinder stat to be so far out compared to the water temperature?
The only option I can see is to set the water temp by trial and error - ignoring the actual temp on the thermostat scale. Or fit a thermostat probe that takes the water temp directly - that is if you can retrofit them somehow to a cylinder without a suitable boss?
Any suggestions are welcome. This is driving me insane.
Initially I thought the problem of poor pressure on the pumped hot side side was down to the pump being installed in the loft and air getting into the pump. After chasing my tail on this theory and fitting an ESSEX type flange (techflange from Techflow), an Anti gravity loop, manual vents on the hot inlet to the pump and a bottle vent on the hot output of the pump I came to the conclusion this wasnt the problem.
To prove this I purged the shower pump and pipe work of air when the hot water cyslinder was full of cold water and then tried the shower on full hot. With this I had good pressure on the hot side of the pump - same as on the cold side.
I therefore decide the problem could be down to the hot water being do hot causing cavitation in the pump. The cylinder stat was set at 60degrees but to be honest the water has always been too hot. I emptied the hot water tank and then turned the stat down to 50 degrees to try the pump at this temperature. The problem was the water remained just as hot.
Before people start suggesting the thermosat is faulty or the mid position valve is faulty they are not. I have changed them both as a precautionary measure and checked the mid position valve and thermostat operate (as per a Y plan system). They oprate as they should, but the cyslinder thermostat seems to register a much lower temperature than the water in the cylinder. The cylinder thermostat is a Honeywell strap on type that is mounted 1/3 the way up the cylinder as is normal. It has good contact with the cylinder which is nice and shiny copper. Through tweaking the thermostat, I have found that setting it to 40-45 degrees yeilds a water temperature in the range of 60-65 degrees. This is acheived when the boiler thermostat is set on 4 (approx 71 degress according to the manual).
I have wondered if it is worth moving the thermostat further up the cylinder, but then I wont get a call for heat until the water at that level is 'cool' an so coudl end up with less hot water capacity?
I have also wondered if the issue is because the cylinder thermostat is located between the coil inlet/outlets on the cylinder?
Is it normal for the cylinder stat to be so far out compared to the water temperature?
The only option I can see is to set the water temp by trial and error - ignoring the actual temp on the thermostat scale. Or fit a thermostat probe that takes the water temp directly - that is if you can retrofit them somehow to a cylinder without a suitable boss?
Any suggestions are welcome. This is driving me insane.
