URGENT pressure relief valve

[proview1122]

Hi
I am having a pellet boiler installed in spain and the instruction manual says "maximum working pressure of boiler is 2 Bar"
the plumber is installing a saftey group which has a prv of 4 bar so I'm just wondering should the pvr be 2 bar or is that working pressure and 4 bar release if things go wrong.

cheers

 

[ShaunCorbs]

Safety should be below boiler maximum and above working pressure

tbh 2 bar seems low (max pressure) as you would be looking at a working pressure of around 0.5-0.75 bar to increase when hot to around 1.5 bar

 

[Chuck]

I am having a pellet boiler installed in spain and the instruction manual says "maximum working pressure of boiler is 2 Bar"

It's not really possible to answer this without the model of boiler and photos and/or a diagram of the installation. Most boilers are protected by their own PRV installed by the manufacturer. If you were in the UK, my guess would be the PRV you are enquring about is on the domestic hot water side of the system, which is unrelated to the working pressre of the boiler because there is a heat exchanger separating the two.

 

[Stu-B]

Give the manufacturers tech guys a call, in my experience they’re always more than happy to help.

 

[John.g]

IF the maximum working pressure of the boiler is 2 bar then the safety valve (PRV) on the boiler will and must be set to 2 bar.

 

[snowhead]

What Chuck said.
2 separate systems, which never mix, each with their own pressure setting.
They'll be a thermal store separating them.

 

[proview1122]

the boiler is a spanish make cant remember the name off hand (im in uk) it goes to a 800lt thermal store the prv is above the boiler the potable water has its own system so I guess that the prv should be 2bar ill have to send one over, why I asked is that at 2bar max working pressure you would run at say 1.5bar so not a lot of head room for expansion 2 floor house with rads

 

[John.g]

The person designing this system shouldn't have a problem with running at 1.5 bar vs say 2.5 bar for the more normal 3.0 bar boiler, it will require a expansion vessel ~ x 1.75 vol of the 2.5 bar system.

 

[proview1122]

yes I think its 80lt or 100lt floor standing pressure tank

 

[John.g]

If the boiler is heating the 800 Litre thermal store directly then my basic calcs would show that a 100 litre E.vessel will give a final pressure of 1.47 bar from a pre charge pressure of 0.5 bar & filling pressure of 0.75 bar & store temp of 85C. A 80 litre would result in a final pressure of 1.76 bar for the same conditions or 1.46 bar @ store temp of 75C.

 

[proview1122]

wow, thanks for the calcs, its good to know the supplier / plumber got it right apart from prv which i'll get them to change before commissioning

cheers all