Pressurised Cylinder with 3 port

[newcomers]

Saw an ariston cylinder today with a 3 port, and not a 2 port, is this ok? Somebody said that it should have 2 2 ports, cant see why

Thanks

 

[gas4you]

If an unvented mains cylinder has a 3 port valve in the heating system it ALSO HAS TO HAVE a 2 port as supplied by the manufacturer between the 3 port and the cylinder in the flow, as this is the safety device to stop the cylinder overheating if boiler does not shut off,

Most 3 ports rest with DHW open.

 

[Dan Robinson]

The two Johns and I saw a Electric boiler, Unvented cylinder and Air-Water heat recovery system supplied by the manufactuer as a pack - with only a three-port valve at the Kent Ag show the other day.

Sales guy/smart ar*e wasn't too happy when we pointed it out to him.

Plank... Company's soldering bods were'nt that hot either.

Shame though 'cos I was asking honourable father-in-law about the Recovery unit and aparently the company is considered the dog's whatsits in Japan.

 

[Onetap]

If an unvented mains cylinder has a 3 port valve in the heating system it ALSO HAS TO HAVE a 2 port as supplied by the manufacturer between the 3 port and the cylinder in the flow, as this is the safety device to stop the cylinder overheating if boiler does not shut off,

Most 3 ports rest with DHW open.

True.

Also, the 2-port spring-returns shut in the event fo a power failure, preventing the unvented cylinder from overheating.
3-ports usually spring return open to the DHW side.
You can get 2-ports that spring return open, for use on solid fuel boilers.

You often see batches of Honeywell 2-port valves, in unvented manufacturers' packaging, being sold on E-Bay, so I think some unvented installers haven't grasped the reasoning for using the 2-port valve, nor the fact that they have to use ALL the parts that they get in the kit.

 

[newcomers]

so is it safe or not?

How hard would it be (from a wiring point) to add the 2 port?

 

[gas4you]

so is it safe or not?

How hard would it be (from a wiring point) to add the 2 port?

It is not safe. easy job to add in terms of wiring and plumbing.

 

[doitall]

The two Johns and I saw a Electric boiler, Unvented cylinder and Air-Water heat recovery system supplied by the manufactuer as a pack - with only a three-port valve at the Kent Ag show the other day.

Sales guy/smart ar*e wasn't too happy when we pointed it out to him.

Plank... Company's soldering bods were'nt that hot either.

Shame though 'cos I was asking honourable father-in-law about the Recovery unit and aparently the company is considered the dog's whatsits in Japan.

Would that be the same johns that blagged 3 tape meassures from the enviroment agency, and was last seen heading towards the car park with a Cow under his arm

 

[Dan Robinson]

Armed and dangerous with a marksman about their number