Adjusting the PRV to go to 4 bar..?

Post new thread

Currently reading:
Adjusting the PRV to go to 4 bar..?

Discuss Adjusting the PRV to go to 4 bar..? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

D

dblvkrb

Messages
25
We've installed a new 25mm water mains in to replace a led mains in and the pressure is so high we've had to put pressure reducing valve on and cap at 3 bar.

The flowrate from the tap is about 10 litres per minute but we're expecting at least 15l/m. The taps/showers are rated to 3bar but I want to find out if anyone thinks there is a great risk in adjusting the PRV to 4bar to increase the flow.

For info, the combi storage boiler is rated for 18l/m and the current Plumbing has been power flushed, no issues. Any advice appreciated?
 
Sort by date Sort by votes
Riley said:
You will not increase the flow by increasing the pressure. If that’s what you’re intent on doing you might as well remove the PRV. The PRV could be defective. In terms of what does it reduce to I meant what pipesize is it coming out of the stopcock. Do you notice this reduced flow at all outlets
Click to expand...

15mm coming off the stopcock - the flow rate is the same on the 1st floor and in the loft conversion, almost no loss the further up the house you go.

It might be a defective PRV - would this definitely not reduce the flow rate if it were working effectively?
 
Upvote 0 Downvote
Riley said:
Yes boiler pic
Click to expand...

Not the greatest pic, but hopefully gives you an idea of the boiler - the hot flow is only 2 l/m less than off the cold mains, I doubt it is the issue.

boiler1.jpg
 
Upvote 0 Downvote
Pickwickpick said:
As Riley and others have said pressure and flow are not the same thing. A PRV could have sorted out the splashing tap but will not have affected flow.

As an example:

If we have two taps both with a flow rate of 15 lpm where tap no1 has 6bar pressure and tap no2 has 3 bar pressure, both will fill the sink up in the same amount of time. But when taps are turned on tap no1 will splash much more violently off the surface of the sink due to the much greater pressure than tap no2. i.e. its the same amount of water but coming out with more force, turn the pressure down and water hits the sink with less force so doesn't splash/bounce but its exact same amount of water per minute hitting the sink.
Click to expand...

I understand this, and I'll caveat by saying I didn't personally test the flow rate before the PRV installation but it's obvious it has reduced both the flow rate and the pressure. I'm guessing where we may be getting to is possibly a defective/clogged PRV?
 
Upvote 0 Downvote
As much as i appreciate why everyone is saying increasing the pressure of the prv won't do anything, turning it up and seeing if it improves isn't going to hurt, even by half a bar, the boiler is rated up to 5bar anyway so it's not going to hurt. And if it doesn't work atleast you've ruled it out.
 
Upvote 0 Downvote
dblvkrb said:
Not the greatest pic, but hopefully gives you an idea of the boiler - the hot flow is only 2 l/m less than off the cold mains, I doubt it is the issue.

View attachment 36032
Click to expand...
dblvkrb said:
Not the greatest pic, but hopefully gives you an idea of the boiler - the hot flow is only 2 l/m less than off the cold mains, I doubt it is the issue.

View attachment 36032
Click to expand...
dblvkrb said:
Not the greatest pic, but hopefully gives you an idea of the boiler - the hot flow is only 2 l/m less than off the cold mains, I doubt it is the issue.

View attachment 36032
Click to expand...
Those valves supposed to be closed guys?
 
Upvote 0 Downvote
rpm said:
Those valves supposed to be closed guys?
Click to expand...

So.. I could test increasing the static (PRV) pressure to see if the dynamic pressure improves the flow, have I understood this right?

I'll pass on whether the valves should be closed (I did not install the boiler) - but it is working as expected and the hot flow is similar to the cold mains flow.
 
Upvote 0 Downvote
Yes you can increase the pressure, as I said your boiler is rated at 5 bar, stick below that and you'll be fine.

And no those valves aren't supposed to be closed, but then the hot feed coming from the top of the heat store should also feed the boiler through a blending valve mixed with the cold main. Whoever installed the boiler hasn't finished it.
 
Upvote 0 Downvote
Craig Watson said:
Yes you can increase the pressure, as I said your boiler is rated at 5 bar, stick below that and you'll be fine.

And no those valves aren't supposed to be closed, but then the hot feed coming from the top of the heat store should also feed the boiler through a blending valve mixed with the cold main. Whoever installed the boiler hasn't finished it.
Click to expand...

Thanks - I will definitely check out the boiler setup with the installer, the blending valve should be somewhere. The boiler is rated to 5 bar, just worried about the taps being rated to 3, but I think I may have to test this anyway to see exactly how much the flow rate is effected.
 
Upvote 0 Downvote
Riley said:
If that’s a heat store then what pressure is that safe up to??
Click to expand...
It's rated upto 5 bar, the boiler, flue gas recovery and heat store all come together. The heat store is pressurised by the heating water not the mains, it has a coil going through it which comes off the flue gas and back into the cold feed to the boiler, at least it should do but as I said, it's not finished. And I just want to point out to you again that I don't disagree with anything your saying and op has gone the wrong way about reducing his flow rate but for the sake of adjusting the pressure and how long it will take it's worth a try.
 
Upvote 0 Downvote
Craig Watson said:
It's rated upto 5 bar, the boiler, flue gas recovery and heat store all come together. The heat store is pressurised by the heating water not the mains, it has a coil going through it which comes off the flue gas and back into the cold feed to the boiler, at least it should do but as I said, it's not finished. And I just want to point out to you again that I don't disagree with anything your saying and op has gone the wrong way about reducing his flow rate but for the sake of adjusting the pressure and how long it will take it's worth a try.
Click to expand...

Just want to add that the picture uploaded was about a month ago and probably was mid installation, but I am definitely going to double check it (and take some more pics).
 
Upvote 0 Downvote
To be honest, I know we're going off track here but the whole system seems pointless to me, why run cold mains through heat recovery, then through a heat store only to blend it down to 30°. Why not just have the heat recovery?
 
Upvote 0 Downvote
Sorry im with you it’s a set ok that makes more sense but my argument still remains. I’m not arguing with the logic of what you’re saying but that still looks like it’s piped in 22 under the boiler for cold and dhw and op has said it comes in in 15mm so obviously it upsized too which is going to further affect flow
 
Upvote 0 Downvote
New posts

Reply to Adjusting the PRV to go to 4 bar..? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Back
Top