Loss of hot water pressure in vented cylinder thermal store system

[[spokes]]

Hi everyone,

Got a bit of a head scratcher that I'd really appreciate some help with. I have an Advance TSDC140 thermal store in my home. We went with this kit to compensate for some low hot water pressure issues around the house, and it has worked well until recently.

Every single hot water outlet in the house now has very poor water pressure and flow. The cold pressure at every single outlet is unchanged, and is at a good level.

We have confirmed that good water pressure is reaching at last as far as past the pressure regulating valve on the system. Which makes me believe the blending valve is faulty. When I turn the welding valve's dial I can feel the temperature of the water change, but the overall pressure is still dire.

Would anyone who knows more than me know how to fault-find these valves please?

 

[ianmcd]

Photos please

 

[[spokes]]

Photos please

 

[ianmcd]

on the cold main inlet the valve with the guage on it is a pressure reducing valve, open two hot taps and tell us what the guage reads with the hot taps open full

 

[[spokes]]

on the cold main inlet the valve with the guage on it is a pressure reducing valve, open two hot taps and tell us what the guage reads with the hot taps open full

Thanks for your reply Ian, appreciate it! Without the hot taps on the PRV reads about 2.75 Bar. With the two hot taps on it reads a touch above 2 Bar, as per pics.

 

[ianmcd]

That should be fine, you have a restriction somewhere and it is usually that Pressure reducing valve, but I would have expected the dynamic (taps open) pressure to have dropped a lot lower than that if it was faulty

 

[ianmcd]

The valve half way up the cylinder is a blending valve try that at max and see if the HW flow rate increases, beware though the HW might be really hot, just as a test

 

[[spokes]]

The valve half way up the cylinder is a blending valve try that at max and see if the HW flow rate increases, beware though the HW might be really hot, just as a test

Hi Ian,

spent a good 5 mins varying the blending valve today to see what impact it had on flow rate. It had absolutely no impact whatsoever. I'm guessing this means there's a blockage before the TRV itself?

The Caleffi valve is mounted by two threaded connections with fibre washers. Those connectors are mounted to the copper piping via compression fittings. I'd like to remove these compression fittings and look for a sediment screen, but am concerned that I won't be able to reconnect the compression fitting without damage to the piping.

Would you remove the commissions?

 

[Johntheo5]

If you post the model and size of the PRV then its easy to calculate if that pressure drop is normal by measuring the hot water flowrate and compensating, knowing the store temperature and the mixed water temperature (and mains temperature).

 

[ianmcd]

Hi Ian,

spent a good 5 mins varying the blending valve today to see what impact it had on flow rate. It had absolutely no impact whatsoever. I'm guessing this means there's a blockage before the TRV itself?

The Caleffi valve is mounted by two threaded connections with fibre washers. Those connectors are mounted to the copper piping via compression fittings. I'd like to remove these compression fittings and look for a sediment screen, but am concerned that I won't be able to reconnect the compression fitting without damage to the piping.

Would you remove the commissions?

I think your blending valve is the problem, some do have filter screens, dont know that make but wouldnt do any harm to check, just close the blue handled valve and open a hot tap till the water stops and remove it and chech it to see