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.

 

[dilalio]

So, both your tprv and prv combine above the tundish.
You need to recreate the fault whilst you are present (as you say... Put immersions on while you're awake).

If it starts discharging into the tundish and d2 termination - check if the water is cold or hot. That will tell you which release valve is passing.

But check air charge on EV... Needs cold feed isolating and hot taps open.

 

[Collectors]

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?.

The gauge that was there leaked, so will replace today. But i put on a temporary gauge to test, but have removed that now. New drawing showing more below.

 

[dilalio]

B is your TPRV.

 

[Collectors]

So, both your tprv and prv combine above the tundish.
You need to recreate the fault whilst you are present (as you say... Put immersions on while you're awake).

If it starts discharging into the tundish and d2 termination - check if the water is cold or hot. That will tell you which release valve is passing.

But check air charge on EV... Needs cold feed isolating and hot taps open.

The system is all electric & the emersion stat is working as its around 52c temp & not drawing electric, so thats switched off as it should do & the prv should go up to at least 70C in temp before any release. For the sake of it i will change the pressure gauge this morning & the pvr. Any recommendations on pvr makes?. The one fitted was a Gledhill.

 

[Collectors]

B is your TPRV.

Sorry, forgot the Temp T. lol
This is a direct cylinder and is electric heating only? No gas boiler and cylinder coil. "Correct"
EV is a bit hidden in the photo.

 

[Johntheo5]

The gauge that was there leaked, so will replace today. But i put on a temporary gauge to test, but have removed that now. New drawing showing more below.
View attachment 420293

You have a common tundish for the ERV and the T&PRV, establish which one is discharging, also post the setting of each, its stamped on the ends.