3 port valve problems

[paulie1970]

The return on the cylinder should be the last tee before it goes back to boiler to avoid reverse circulation when just DHW is called for.

I hope the cylinder is vented and not unvented if its coming off that 3 port valve...post some pictures up if you want.

Sure. For what it is worth here are pictures. Hopefully it makes sense to someone....

 

[Chalked]

It will never work properly with a three port. There is always a way through the valve. It should be done with multiple two port valves.
One for cyl, one for rads and one for underfloor .

 

[Chalked]

Oh dear! Overflow on prv discharge.
Back to main prob.
Cylinder stat will turn off three way and two way valve ( lazy buggers for not replacing three way) three way shuts hot water port, underfloor calls and water goes round heating circuit too.

Just replace the three port with one zone valve on the heating.
Oh and advise they get a G3 engineer to sort the cylinder.

 

[paulie1970]

Oh dear! Overflow on prv discharge.
Back to main prob.
Cylinder stat will turn off three way and two way valve ( lazy buggers for not replacing three way) three way shuts hot water port, underfloor calls and water goes round heating circuit too.

Just replace the three port with one zone valve on the heating.
Oh and advise they get a G3 engineer to sort the cylinder.

Thank you for the thoughts on the system engineering. There may well be a correlation with the UFH and rad heat. I will monitor this

What is G3 non-compliant about the system that you can see?

 

[paulie1970]

It will never work properly with a three port. There is always a way through the valve. It should be done with multiple two port valves.
One for cyl, one for rads and one for underfloor .

Many thanks. Does this suggest reverse circulation or simply poor control? Would the three port save effort installing at expense of fine control? The pumber initially thought everything would be controlled via TRV and did not supply thermostat. Presumably it would "work" under such circumstances but not well?

 

[Riley]

Not a great install. Would doubt installer was G3

 

[paulie1970]

Not a great install. Would doubt installer was G3

Possibly not, I didn't have a choice. Is the system non-compliant or just not best practice? In any event it doesn't work...

 

[Riley]

It's really a different issue. Without going into too much depth the safety discharges on the cylinder are not piped correctly. It's actually illegal for a non-G3 engineer to work on one of these cylinders. And you always have a choice. The installers should be upfront with their qualifications.

 

[paulie1970]

Deal came as part of a package under a main contractor. I had assumed that he would be diligent in selecting sub contractor. The subbie may indeed be G3, it wasn't my concern. My main interest is in getting it working rather than detecting and punishing possible illegality. There would seem to be some pointers on how to proceed here...
Thanks

 

[Riley]

Ok that's your perogitive however when these things aren't plumbed in properly it sets alarm bells ringing. Not to sound too drama queen but unvented cylinders are literally a bomb which can take out your roof/house wall if they aren't installed correctly. I'm not necessarily saying to raise the illegality but rather concerns about yours and your families safety. Up to you though if course