No Hot Water but got Heating

[help_is_on_its_way_eek]

Can anyone help - this is a wierd one. When timer set for constant hotwater I get hot upstairs radiators and no hot water - downstairs rads stay cold. When I set timer full 24 hour heating and 24 hour hot water - I get hot radiators throughout and still no hot water. The timer is of the older machanical type. There is no option to switch to central heating only.

The hot cylinder tank stays cold and does not have any electrical device or themostatic valve connected to it. Used to work fine upto a week ago.

It is Potterton upright boiler with normal gravity fed cold water to the hot water cylinder. All hot water pipes from the boiler are hot


PS. I was thinking of an air trap - but I have no idea how it got it and how to release the air.

 

[chrishutt]

You're probably running out of system water due to a blocked feed pipe or a stuck float valve. Take a look at the feed and expansion tank.

 

[Mikeyboy]

Do you have a primatic cylinder installed ? Is there one large , and one small storage tank in your loft space ?

 

[help_is_on_its_way_eek]

Yes there is a large storage tank fed by the rising main and a seperate much smaller tank fed by the rising main.

The hot water tank has a 22mm pipe going in the bottom, this comes from the large storage tank - I guess it has two 22mm pipes in the side ( I can not see them) and one 22mm pipe at the top whuch branches of to I guess the hot water taps and to a vent to the storage tank in the loft.