Blending valves on a open vented cylinder...

[lambchop]

Joined a firm who does solar thermal & PV, so a newbie at the green stuff

As above it was an oppen vented cylinder + solar therm + boiler. The experienced Installer who Im working under wanted me to fit the TMV on the hot outlet of the cylinder before the open vent pipe. I was confused at first thinkig it was some sort of test, I pointed out that the TMV needs to be on the other side of the open vent otherwise it becomes a sealed system.

He went a bit pale then, Am I right, I think I am. I done a post before about system working pressure and the charge on the expansion vessel being different. Will pay for the BPEC course myself if I have to as I dont mind working under someone but Im getting conflicting info all the time

 

[ecowarm]

A TMV should be fitted after the open vent as you say, did it not have instructions? A typical installation can be seen on page 2 here

 

[SimonG]

Sounds like there may be a few dodgy installs out there if he went a bit pale when you pointed out the error in his ways

 

[mountainman]

On the plus side tho, at least a vented cylinder will prob only take a wall out if it bursts; unvented takes much much more.

 

[lambchop]

no mate, I always take a little time out to read m.i's while having a coffee. The guy I was working under took the mick that he could tell that I was trained up by reading books!!!! wtf! I know a little but I dont know everything so always keen to learn. Installer = trained to install products, whereas Plumber = Installs but knows the science behind the installation

 

[mountainman]

Agree. As is often said, if all else fails read the instructions.
The person that reckons they know it all knows *** all.

 

[lambchop]

My fave RTFB = Read The F'ing Book, got to go missus is getting irate, time for a beer, a bit of face stroking and watch True Blood

 

[blakeecotec]

If the valve is in the wrong place on the vent pipe it wouldn't blow up, the cold feed to the cylinder is also effectively open vented, so the expansion would go up this pipe instead.

 

[eaton]

Or it will implode, I've seen it

 

[chris watkins]

If the valve is in the wrong place on the vent pipe it wouldn't blow up, the cold feed to the cylinder is also effectively open vented, so the expansion would go up this pipe instead.

Ar' but without an effective "safety open vent pipe" you are required under Building Regs G to install a Temperature relief safety valve !!!! just like an un-vented.