Heating system with only one two port valve. Is this dangerous ...

[egginyourface]

Came across a heating system which had only 1x 2 port valve which was used only for the heating. There was another valve which had been disconnected from the mains but set in open position. I assume this was for the hot water.

Then From the junction box there's one three core going up to 2 x cylinders in the loft. Am i correct in thinking this is dangerous?

Shouldnt there be a valve to control hot water to cylinders

 

[Knobhead]

The water tank can’t get any hotter than the temperature set on the boiler. So it’s a bit basic but nothing wrong with it.

 

[egginyourface]

I haven't seen the cylinder but think its a megaflo. Doesn't the valve act as safety device, ie shut down the boiler etc

 

[RmBo_0]

Sounds like its been changed from s plan to c plan for some reason. But don't think it's dangerous myself.

 

[egginyourface]

Thank u both for replies

So what's the point of having a valve for hot water if its not needed?

 

[Knobhead]

The H/W valve diverts all the boiler output to the heating. No other reason.

 

[Deleted member 9648]

I haven't seen the cylinder but think its a megaflo. Doesn't the valve act as safety device, ie shut down the boiler etc

....all it does is switch off the HW when the tanks are up to temp.....sounds to me like it has failed,been locked open to get the system working,and never got changed.

 

[egginyourface]

Sorry If this sounds daft, but whats the point in having 2 port valve for hot water if its not needed?

 

[londonlec]

You need a G3 qualified plumber to work on these, as you say, I am 90% sure this unvented cylinder needs a 2 port zone valve as part of its safety mechanism.

 

[snowhead]

In the past it was common to have no valves.
The Hot water temp relied on the boiler setting and the heating was controlled by pump on or off.

However if it's an unvented, which Megaflows are, it MUST have a normally closed 2 port valve on the boiler flow to the cylinder controlled by a safety over-temp stat on the cylinder.

It needs someone with G.3 to sort it out.
Plumbers aren't the only one's with G.3

 

[egginyourface]

Your right. It's a in unvented cylinder. Had a look at it today. I'm not involved with the system myself but out of curiosity opened the junction box and noticed the hot water 2 port valve has been disconnected. Theres a 3 core whicj leaves the jb and goes upto cylinder in the loft. I asked the plumber why he hasn't re instated it and he said it works fine with out it.

Now I'm interested in learning how these systems work and have feeling this is unsafe.

 

[londonlec]

I personally (as a spark!) think it is unsafe and contravenes G3.

The 2 port valve is often supplied by the manufacturer of the cylinder, they wouldn't hand you a £50 zone valve for nowt ;-)

 

[SYKRAPS]

If it is a megaflow unvented cylinder you DO need a 2 port valve for the DHW connected as a safety cutout to stop the cylinder overheating, I have been lead to believe that these systems can be like a ticking time bomb waiting to go off without it.

http://www.plumbcenter.co.uk/wcssto...l/ti/on/HeatraeSadia_Megaflo_Installation.pdf

 

[egginyourface]

Sorted it with client. Have arranged for engineer to go round tomorrow

 

[Spark1979]

Its definitely needed how can you shut heat off to cylinder if central heating is turned on the water in the tank will boil without the valve to shut it off