pressure settings

[Mick Irish]

Hi All
First time poster here.
can anyone tell me should there always be a pressure reading above zero on a solar pumping station pressure guage.?  My panels read zero bar at night time when cold but this rises during the day to approx. 4 bar if really hot. panels are heating water fine and pump kicks in and out correctly per solar controller set up. I am living in Ireland if that has any bearing on things. Solar expansion vessel working and precharged to 3 bar
thanks in advance
 
Mick

[Iain]

Hi
Welcome.
My system is pressurised to 1 bar and the precharge is 0.8 bar in the expansion vessel.
So you either need to charge your system to a pressure of 3.2 bar when cold.
Or
Reduce the EV precharge pressure to a lower setting and run at a lower pressure.

The EV precharge should always be 0.2 bar below the system pressure when cold.
Otherwise you get 0 pressure at night/ or when cold and the pressure rises when hot.

Might be worth checking if you have a small leak as your pressure is low, unless you are loosing from the pressure relief valve.
Normally the PRV is 3 bar, if yours is 3 bar you will need to run at a lower system pressure to keep the working pressure lower than the relief pressure.

If your PRV is higher, as long as your EV and system pressure is lower you should be ok.
On mine for reference.
System pressure =charged to 1 bar
EV pre charge =0.8 bar
PRV = 3 bar

Iain

[desperate]

I reckon if you are going from 0 to 4 bar your expansion vessel might be knackered, my system fluctuates from 1ish bar cold to 1.75ish hot.

Desp

[Iain]

Hi

I reckon if you are going from 0 to 4 bar your expansion vessel might be knackered,

But it might do that with an EV precharge of 3 bar. If the system is starting at 0 bar. The EV won't be able to absorb any pressure until it reaches 3 bar. So the pressure rises quickly.

Iain

[Mick Irish]

the expansion vessel was replaced only a week ago , the pressure release valve on my system  only operates when pressure hits 6bar.
 so am I ok with the settings I have
 
out of interest does lowering the precharge pressure of an expansion vessel when cold increase the system pressure?

[Iain]

Hi

out of interest does lowering the precharge pressure of an expansion vessel when cold increase the system pressure

The system pressure needs to be set slightly higher than the precharge pressure in the EV.
Your EV is set to 3 bar and your PRV is set to 6 bar.
I would think you need to charge your system to about 3.2 bar when cold.
Have you any documentation for the system.? Does it say what the system pressure should be?

Was the system recharged after the EV was changed?
It should have been. The system pressure when cold needs to be just above the EV precharge pressure.
Is there a filling loop fitted for pressurising the system? Similar to a boiler filling loop. Or does it get repressurised with a garden sprayer type pump?


Iain

[desperate]

Hi

I reckon if you are going from 0 to 4 bar your expansion vessel might be knackered,

But it might do that with an EV precharge of 3 bar. If the system is starting at 0 bar. The EV won't be able to absorb any pressure until it reaches 3 bar. So the pressure rises quickly.

Iain

Iain, of course you are right, I failed to take into account the precharge pressure.

Desp

[knighty]

^^

isn't that only true if you're using the total volume of the expansion vessel?   so it's totally empty for the 0psi reading?

I've always read that a pressure vessel should be filled to 70% of final system pressure

[Mick Irish]

Thanks for all info Iain
The system is filled manually usually with a electric pump cart type thing
 When the system was charged it definitely wasn’t above ev precharge it was charged slightly lower
I will look into this now myself
 Thanks for all replies much appreciated
Mick

[Iain]

Hi

I've always read that a pressure vessel should be filled to 70% of final system pressure

Similar ball park, to my understanding, mine is 0.8 bar on a 1 bar system.

As long as the system pressure is higher than the EV pressure when the system is cold. I have always used 0.2 bar but 70% would cover greater system pressure ranges.
So with a 3 bar precharge the system pressure would need to be 4.3 bar.
Seems quite high for a system.
I might  be tempted to drop the EV precharge to something like 1 bar and run the system at  1.2 / 1.4 bar(cold)
Iain

[rogeriko]

The precharge pressure is always set high from the manufacturers so that it is easy to release some air to get the pressure your system requires without having to faff about with air pumps. On a level system the pressure should be set to 0.8 bar and the system run at 1.2 bar. As you go up into 2nd and 3rd stories high you must increase all pressures by 0.2 bar for each story of height. If your pressure vessel still has 3.0 bar air pressure then it was installed by a bunch of cowboys.

[Mick Irish]

Thanks for all the replies on another note capsule someone send me a pic/photo of a garden sprayer adapted to pump fluid into panels
Thanks
Mick

[Mick Irish]

Hi all could someone enlighten me as to how a garden sprayer is adapted to pump solar fluid into the pumping pics would be good if anyone has any
Thanks in advance
Mick

[Antman]

Hi Mick
See http://www.handyantman.co.uk/Hozelock.JPG from my Navitron support page
Hoselock spray uses 3/8" bsp to 15mm compression adaptor on wand to take filling loop.
Antman

[Mick Irish]

Thank you ant man much appreciated
Mick