Unvented over heat stay tripping intermittently.

[Fireboy24]

Hi there,
Third call back today. Bit of help please. Installed Telford easy fit unvented cylinder 3 weeks ago. Over heat stat has started tripping on cylinder leading to no hot water. Primary circuit for the coil set at 73*C so no where near manufacturers cut out temp of 83*C.

When I'm there and have the hot water on if I turn the cylinder stat down it closes the 2 port valve and turns the boiler off so it's wired in correctly and that side of it is ok.

Presuming it's a faulty stat but just wondering if there's anything I might be missing???

Cheers

 

[ShaunCorbs]

You set the hot water temp to 73 ?

 

[Fireboy24]

Not the cylinder stat. That's set at 65*C. I'm taking about the temp for the flow on the boiler being set at 73*C. The cylinder stat sits next to the coil in the cylinder.

 

[ShaunCorbs]

Bring the cylinder stat down to 60 should sort it

 

[Gasmk1]

My thoughts also too high a temp lower it to 60 and try that go to 65 max

 

[snowhead]

What's the temperature of the water at a tap, assuming it doesn't have TMV at cylinder?

If the stat is low down in the cylinder even 60 is too high.

 

[Fireboy24]

Thanks guys,

No TMV fitted. I'll try nudging the cylinder stat down and making sure the DHW outlets are achieving 60*C minimum.

I think I'm over thinking this one a bit. Either a faulty stat or cylinder temp set to high.

 

[Fireboy24]

Yes SNOW HEAD. Stat is low down located near the coil.

 

[Chuck]

Thanks guys,

No TMV fitted. I'll try nudging the cylinder stat down and making sure the DHW outlets are achieving 60*C minimum.

I think I'm over thinking this one a bit. Either a faulty stat or cylinder temp set to high.

Store temperature should be 60°C. Outlet temperatures (assuming you mean taps) need to be 50°C within one minute. See:

HSE - Legionnaires' disease - Risk systems - Hot and cold water systems

for the details.

If you have G3 ticket, you should know this stuff in detail already. If you don't have a G3 ticket you're breaking the law by working on unvented systems.

 

[Fireboy24]

Chuck everyone here knows the basics of what temp stored hot water should be at. The thread is about the problem with the stat.