Halstead finest gold - Two problems, possibly related?

[piggoy]

We've recently moved into a house that has a rather old Halstead 'Finest' Gold boiler. After what our plumber told us about the boiler I suspect the 'Finest' part is a bit of an overstatement

Anyhow, the boiler has two problems -

Firstly the boiler makes a high pitch wining sound the moment a H/W tap is switched off. This wining sound seems to resonate through the pipes all around the house but most definitely originates at the boiler. To make the wining stop you have to quickly blast the H/W tap on and off. I suspect the diverter valve is faulty?

Secondly the closed system will not keep its pressure. If I top up the system to 1 bar (cold) the pressure will be near zero after a few days. The water pressure is being lost from the pressure relief valve. The PRV is working correctly since it will not vent water until >3bar. When the C/H is switched on the pressure does not anywhere near exceed 3 bar. So the loss of water from the PRV doesn't seem to be a classic overpressure scenario related to expansion vessel etc. The pressure DOES exceed 3 bar when the C/H is on and the H/W is pulsed on and off. The pressure guage pulses above 3 bar the moment the H/W is turned off and some pressure is vented from the PRV. Could this be the diverter valve causing this as well?

I have not checked the pressure in the expansion vessel - would this be a place to start?

Thanks in advance

 

[Gasguru]

Nothing really wrong with these boilers apart from a poor quality outer casing. All plumbers/heating installers like to slag off Halstead but most of the boilers parts are found in other boilers too.

Pop down the front controls panel and check the diverter valve at the front lower right hand side. Unclip the switch box on the left end of the diverter. Open/close the hot tap several times and check the pin retracts quickly. It sounds as though the pin is slow to retract keeping the boiler firing. This would be due to a faulty diverter or trapped air in the hot pipework (dead leg).

If the water is starting to boil the pressure increase could result in the PRV opening....you would normally see the gauge jumping all over the place.

 

[piggoy]

Nothing really wrong with these boilers apart from a poor quality outer casing. All plumbers/heating installers like to slag off Halstead but most of the boilers parts are found in other boilers too.

Pop down the front controls panel and check the diverter valve at the front lower right hand side. Unclip the switch box on the left end of the diverter. Open/close the hot tap several times and check the pin retracts quickly. It sounds as though the pin is slow to retract keeping the boiler firing. This would be due to a faulty diverter or trapped air in the hot pipework (dead leg).

If the water is starting to boil the pressure increase could result in the PRV opening....you would normally see the gauge jumping all over the place.

Thanks. After opening the control panel I can provide an update on the issue. The hot water demand pin moves in and out with ease and activates the microswitch. No probems are apparent there. The annoying wining sound starts when the hot water demand pin retracts and the pump is still running. Once the pump finishes its overrun the wining stops. I cannot work out where the wining sound comes from but it sounds like its coming from the pump.

 

[J_N30]

If the pressure is going over 3 bar on demand then the expansion vessel is flat.