Hot water not hitting top temperatures

[speedo555666@googlem]

Hope I am posting in the correct forum for this. I work on a large commercial site in London a dn we have 2 stored water calorifiers that feed some areas of the building. They are heated via a primary loop from a CHP with boiler back ups. The primary is reading 78 Degrees on the flow and 69 on the return. At 10.30pm we have a pasteurisation program that should raise the temperature to 70 until 12.00am but we never can get the hot water higher than 61 on one and 58 on the other. Anyone got any ideas? Please see pics. I was wondering if it could be a balancing issue ‍ the 3 port valve is at 100% all day and I'm at a bit of a loss. Also we had it opened and inspected in August and they said they were clear.

 

[mcmoby69]

It could be tmv's installed have a non return valve stuck open, causing cold mains water to push through into the hot supply back to the calorifiers. Won't be noticeable during the day with everything being used. Only when demand stops.
Had similar in a pathology lab where storage tank would over flow in the evenings when the lab was shut.
Check all the tmv's for signs of condensation on the body.

 

[speedo555666@googlem]

It could be tmv's installed have a non return valve stuck open, causing cold mains water to push through into the hot supply back to the calorifiers. Won't be noticeable during the day with everything being used. Only when demand stops.
Had similar in a pathology lab where storage tank would over flow in the evenings when the lab was shut.
Check all the tmv's for signs of condensation on the body.

Will look into the possibility. We have 3 blocks of showers on the system so wonder if it could be those. 5 showers in one block and 3 in each of the others. It's on boosted cold water so if that's at a higher pressure it could be feeding back I guess. Might need to fit some check valves. Didn't think of that. Nice one thanks.

 

[mcmoby69]

All of the showers will have nrv's built in. If they are bar showers it's easy to find which are passing. Run the shower on fully hot, feel the left inlet pipe (usually hot feed) it will get hot. Turn shower off. If the nrv is faulty it will go cold pretty quick. Repeat with all of them.