Central Heating pipework

[Des Jennings]

They are discharges for expansion.
Need to get the UV serviced.

Cheers.

 

[Des Jennings]

Cheers.

Is it the larger or the smaller of the pipes? If you do have an unvented HW cylinder and it's the larger of the pipes that's dripping/running then get the cylinder serviced.

If it's the smaller pipe then you need the boiler serviced.

It is the larger of the two pipes that is dripping but, surprisingly, there is no dripping of water into the tundish by the cylinder which also indicates servicing of the air gap in the cylinder according to instructions fixed to the cylinder.

 

[Johntheo5]

You may also have a expansion relief valve installed as part of a group set which comprises a PRV set to 3bar, a NRV and then the expansion valve set to 6bar, can you check this, if installed.

 

[Des Jennings]

You may also have a expansion relief valve installed as part of a group set which comprises a PRV set to 3bar, a NRV and then the expansion valve set to 6bar, can you check this, if installed.

Attached are two relief valves connected to the cylinder.

 

[Johntheo5]

That 8 bar expansion valve?? should also discharge into a tunings or some visible method of checking it, if not leaking then possibly boiler PRV but system pressure should start falling except that you have auto filling & top up

 

[dilalio]

Easiest thing to do is undo the connection where inlet group connects to the discharge and see if the outlet is wet/dripping.
It should be teed in above the tundish for the TPRV but they're often not.

 

[Madrab]

Get them both serviced, point out the dripping.

 

[Johntheo5]

Have only seen 3 or 4 unvented cylinders but these were all 7bar/6bar PRV's.

 

[Des Jennings]

Thanks. A service is required.

 

[Madrab]

there is no dripping of water into the tundish by the cylinder which also indicates servicing of the air gap in the cylinder according to instructions fixed to the cylinder.

If it's installed correctly, both the cold water expansion PRV (on the control set) and the T&PRV should discharge into the same tundish, that then provides a localised visual indicator that the UV needs looked at.

The other smaller blow off would be for the boiler and it is typically hard piped outside without an air break and the indicator is that it drips proving that the boiler PRV has/is lifted and either the EV in the boiler needs serviced or the service and the PRV needs replaced, as the valve isn't closing back down porperly.