Saturday, March 3, 2012

Progress with Sunbox pump

3 Mar 2012: I am slowly stirring myself to look into this, there is the time and daylight, and it's a matter of remembering how all this works, then to tackle each part using logic, multimeter, guesswork and deduction.

Facts:
  1. Fuse hasn't blown, as the Thermostat comes on when you switch on the socket.
  2. The Thermostat correctly reacts when there is a real-T or a delta-T and it sends a signal to the 2-way Valve.
  3. The 2-way Valve is opening, because when the circulating pump in the heat pump is driving the loop, the glycol goes up to the Sunbox, and through the old Energy Meter and the Volume meter on the way back. But it is running more slowly than it should be.
  4. There is NO AC power to the pump in the loft. So I don't think it is a pump failure. 
  5. When the heat pump is sleeping, the thermostat says that it is sending liquid to the loft, but there is no circulation.
I need to put the loft pump onto a 13amp plug to make sure that is working, because if I am going to bother to replace the energy meter, I should seriously consider replacing the pump with a new one, guaranteed to work to -10ºC working fluid. This one is probably only rated down to +2ºC, and it is an ancient second hand one.

More to follow. Time for a tea, and then continue with investigation.
This is the actuator that was sticking. The metal lever to the left was a way to unstick it,
but I didn't realise until I had taken if off. But the spring needed lubricating, anyway. 
 Problem Solved
  1. I discovered that the 2-way solenoid valve was opening only partially, and if it does that, it allows some liquid up to the panels only when the GSHP is running. One can tell this by the noise it makes when closing. If it closes correctly, you can hear the spring working from the other end of the house.
  2. There was no power being returned from the Solenoid valve. If it is fully opened, it sends 240vAC to the pump in the loft. 
  3. The actuator is removable, and has a lever you can push to free the actuator if it is stuck. I added some cycle lubricant to the spring, and checked that it worked, then replaced.
  4. Everything is now working as it should be.
The actuator back in place on the 2-way valve, to the left of the vertical insulated pipe.
Pity, we lost all the lovely solar heat from last Thursday! I am kind of surprised, as I would expect these valves to have a longer service life between repairs. They only have a 12 month warranty which seems a short time for something that becomes part of a heating system in which you would not expect such early failure.

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