DIY Doctor

hot water to expansion

Postby clairville2003 » Thu Mar 18, 2010 1:00 pm

Hi All, This is the symptoms of the problem i have and any comments are greatly appreciated.

I have a gas fired central heating system for radiators and hot water and is fully pumped via pump and 3 way valve. Seperate stats on heating and water.

No issues when system is off.
When switched on it heats up fine and the valve changes over ok between the water and heating etc. I have already changed the vakve and pump. When either the heating or the hot water has reached temperature the pump cuts off, boiler shuts down and valve returns to normal mid position so all looks as though it is working fine. But red hot water is being vented back into the header tank and causing loud banging.

I have checked all the stats and they work ok. Could it be the boiler stat??? I have a myson orion and ive turned the boiler stat down to -1- and it still happens. I cant understand how the water can get so hot when the boiler stat is on minimum. It used to be that the boiler needed to be on 5 to allow enogh heat to get through the system.
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Postby htg engineer » Thu Mar 18, 2010 5:06 pm

yes it probably is the boiler stat at fault.

htg engineer
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Postby tytherington » Fri Apr 02, 2010 2:51 pm

probaly boiler stat or pummp fitted wrong way round if boiler stat you should employ a gas safe engineer
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