Loosing a lot of hot water. Pressure release valve ????

[Collectors]

Hi, we fitted a pressurised hot water tank in the loft & the last few months we have been loosing about 1lt of water every hour through the night. Its now got a lot worse & as its intermittent & in the loft its not easy to catch when its leaking.as i got a bad back, so to check, last night i put a jug under the tundish waste pipe outside by the drain & this morning it was full.
Few things i noticed was 1. its more often at night. 2. the emersions is on around these times. 3. Our water pressure has gone up on the mains side from 4.5 to 6 bar, but still 3.2B on the cylinder side. Water temp always around 125F/52c, so i dont think its the stat & over heating.
Is it more likely to be the tank PRV or the incoming main water PR control. A or B, & is it common?

 

[dilalio]

Have you had it serviced?
Also, it looks like you have a tundish alarm... Has that not been activating?

 

[Collectors]

Was only fitted 9 months ago & the tundish alarm is not set very well, bit of an experiment. My fault. lol
I am going to put the emersion on for an hour & see if somthing happens, but i have temp sensors everywhere & the tanks not gone over 52'ish C.
PS:
Just updated the alarm. Water only has to touch one wire now.

 

[Johntheo5]

You say its still 3.2bar on the cylinder side, does it rise at night or if you reheat the cylinder during the day with no HW draw off?, if the PRV (pressure reducing valve) is not drop tight then the pressure can rise due to leakage past the PRV, especially at night with no HW draw off.
There should also be another PRV, a ERV, expansion relief valve, on the cold inlet to the cylinder, normally incorporated in a valve combination set that has the PRV, ERV and a NRV, the ERV is set lower than the cylinder PRV, maybe 6bar or lower vs 8bar, it will be stamped on the end(s) of the PRVs, if this is not lifting but the cylinder one is then looks like a faulty cylinder PRV.
Has the cylinder got a external expansion vessel?.

 

[dilalio]

Was only fitted 9 months ago & the tundish alarm is not set very well, bit of an experiment. My fault. lol
I am going to put the emersion on for an hour & see if somthing happens, but i have temp sensors everywhere & the tanks not gone over 52'ish C.

So, just to confirm...
This is a direct cylinder and is electric heating only? No gas boiler and cylinder coil?

First thing to check would be expansion vessel... Can't see it in the photo.