What is this valve?

[diynoob]

Anyone know what is valve is and what the nut is for? It says Pegler England on it.

I have gravity HW and this valve is on the flow side just after the boiler. I guess it's a non-return valve?

The HW is not working well and the temperature before the valve is currently 60C but after the valve its 40C so I think the valve is sludged up. I turned the nut a bit and it can turn either direction. It makes a pinging/springing noise when turned.

 

[cross thread]

Pressure relief valve ,leave it

 

[cross thread]

Show a photo of the pipes as they enter the cylinder

 

[diynoob]

Its a regular boiler on an open vented system (2 tanks in loft). The CH has a pump but the HW is gravity only. The cylinder is in the room above.

It doesn't make sense to have a pressure release valve on an open vented set up does it? Gravity systems need a non-return valve usually.

 

[diynoob]

This is the cylinder. The system has worked fine for years. The gravity HW has always been a bit slow, but not as bad as it currently is. The problem started after I removed an old radiator so it's highly likely there is air or sludge in the HW circuit. The boiler fires up but there is a big temperature drop in the flow pipe. By the time it gets near the cylinder it's cold.

The biggest temp drop occurs at the valve, hence the question. Probably got air in the system near the valve. I'll drain and refill the HW circuit once the boiler cools down.

 

[Exedon]

Old spring loaded safety valve.

 

[Hugh Jaleak]

Safety Valve, used to be common with old back boilers, in properties years ago, where there was a risk of the pipes freezing.

It is not unknown for both Vent and Cold Feed to freeze on an open system, then should boiler thermostat fail, (or in the case of solid fuel), and the water in the system boils, then if it cannot safely vent to atmosphere it becomes superheated, and in a split second turns to steam. This increases it's volume by about 365, so the weakest point goes, usually the cast iron water jacket of the boiler, with the effect of a bomb. Have known them to blow a Fireplace/Chimney Breast to bits.

My Tutor told me at College 35 years ago, if you fit a Safety Valve, you will ensure the Boiler cannot explode.

 

[diynoob]

Thanks all. I think it’s a red herring then. There is an air lock in the HW circuit and I think it’s near that valve but the valve is not related to the problem. I will drain and refill HW.

The valve was 5 quarter turns open so I have left it at that.

 

[cross thread]

Check the header tank is full , check with a magnet where the cold feed and expansion tee into the flow/ return pipes

 

[diynoob]

I emailed the manufacturer before posting here and they got back to me:

The valve pictured in your email below is a pressure safety valve which was offered by Pegler prior to 2010, before it was discontinued due to changes in legislation which required safety valves to discharge to a drain and not to the environment. As a result, we are no longer able to offer an alternative to this product.

It would spray over the boiler and electrics so it does seem like a bad idea. My vents and water tanks are in heated space anyway so they aren't going to freeze.

The lack of a non return valve means water can get sucked out of the HW circuit into the CH and creates airlocks. I see a lot of threads with the same setup have the same problem: https://www.diynot.com/diy/threads/gravity-fed-water-system-problem.120986/

I have a boiler service booked this month so will ask the engineer if he'll fit a NRV.

 

[jj4091]

Give him notice so that he can bring parts and allow extra time or you may end up paying for a seperate visit on top of the service.

 

[diynoob]

I let him know about the airlock problem and absent NRV so he's going to work on that instead of the service.