Sorting out expansion vessel and overtemperature valve

[jack]

4 hours ago, John Carroll said:

You said the EV was flat, what pressure was it recharged to?, it should also have been done at the very least with the cold mains to the cylinder shut off and a HW tap opened, if its located above the cylinder then that should be OK.

 

Originally 3 bar and it's located above the cylinder. I'll make sure I do what you say when I recharge it (didn't manage to do it over the weekend). I've turned off my immersion diverter for the moment, so the temperature in the tank won't exceed ~50° C until I've got all of this sorted out. 

 

4 hours ago, John Carroll said:

I would also suggest checking that there is a pressure reducing valve (PRV) installed (which there should be) on the cold water valve set and most/more important that its setting is checked.

 

There's a 3 bar pressure reducing valve on the incoming mains. I already have a pressure gauge on its way so I can test it.

 

4 hours ago, John Carroll said:

Even with your 22L EV and assuming that you will rarely if ever be reheating a full cylinder, more likely say 80% or 200L then a final pressure of 3.12bar at 60C & 3.25bar at 65C with a cyl prepressure of 2.3bar, 2.5bar (if available) will still give over 90% flowrate of a 3.0bar cylinder.

 

Okay, thanks. I'm going to have a think about the setup as a whole. Currently considering adding an additional expension vessel to the cold feed near the tank, as there's more space there than where the current one is near the ceiling.

 

4 hours ago, John Carroll said:

Is the blue PRV next to the (red) TPR also stamped as set to 4.5bar?

 

There are two valves: 3.5 bar pressure relief, and 90-95°/4.5 bar temperature/pressure relief.

Thanks again, I appreciate the feedback.

[John Carroll]

From the horse's (McDonald Water Storage) mouth, the MI's show, below, the expansion relief valve mounted on the cylinder as yours is and none on the valve set (again like yours), the PRV should be set to 2.1bar, likewise the EV charge pressure....set to 2.1bar  and that's why a 22L EV is perfectly acceptable under those conditions, a full reheat to 60C then gives a final pressure of 2.8bar, 65C gives 2.91bar & 70C gives 3.12bar. all comfortably below the expansion relief valve's 3.5bar setting.

 

 

 

 

 

ECOFlow-Installation-Manual.pdf

Edited Monday at 18:53 by John Carroll

[jack]

13 hours ago, John Carroll said:

From the horse's (McDonald Water Storage) mouth ...

 

Thanks John. I found that document a couple of days ago. It was one of the triggers for my comment about rethinking the setup as a whole. It's frustrating the original plumber apparently didn't read the manual before installing a 3 bar PVR on the incoming mains 10 years ago! 

 

While it's been fine operating at 3 bar for 10 years, I'm going to lower the incoming PRV to the recommended pressure. I'll also install another expansion vessel to help keep the pressure low.

 

While static pressure is fine, it does drop noticeably if a couple of showers or taps are in use. I suspect the most likely culprit is the water softener, but I'll be doing some pressure tests on the weekend to see what I can learn.

 

Either way, I'd like to do what I can (within reason) to avoid making the crappy dynamic pressure any worse when I change to the lower pressure PRV on the incoming main.

[Nickfromwales]

43 minutes ago, jack said:

 

Thanks John. I found that document a couple of days ago. It was one of the triggers for my comment about rethinking the setup as a whole. It's frustrating the original plumber apparently didn't read the manual before installing a 3 bar PVR on the incoming mains 10 years ago! 

 

While it's been fine operating at 3 bar for 10 years, I'm going to lower the incoming PRV to the recommended pressure. I'll also install another expansion vessel to help keep the pressure low.

 

While static pressure is fine, it does drop noticeably if a couple of showers or taps are in use. I suspect the most likely culprit is the water softener, but I'll be doing some pressure tests on the weekend to see what I can learn.

 

Either way, I'd like to do what I can (within reason) to avoid making the crappy dynamic pressure any worse when I change to the lower pressure PRV on the incoming main.

If you can leave a 5bar PEV feeding the softener, and only drop to 2.1 at the cylinder group then that would help. 
 

If your incoming cold mains will never see 5 bar then just leave a raw feed to the softener. 
 

Can you install a 150 or 200L accumulator anywhere, as this would make a big difference. 

[Nickfromwales]

Ps kudos to @John Carroll as I am guilty of skim reading, and assumed stainless cylinder and 3 or 3.5bar at the control group.

 

Many heads always better than one.

[John Carroll]

If, (which it probably has been) the EV precharge pressure has/had been set to 3.0bar and even assuming that the cold water pressure after the PRV (set to 3.0bar) never went higher than 2.0bar before reheating then the expansion relief valve would still have lifted if ~ 150L or more of the UV cylinder required reheating to 60C.

 

My ancient spreadsheet, below, may be of interst and be a help in sizing calculations for either HW or CH.

EV CalcsJK Rev0.xlsx