Hot Water not switching on from timer

[Lennom]

We have a very basic timer that intermittently fails. The heating always comes on, but the hot water sometimes doesn't; tends to be when there is a sudden change in air temperature outside. Do any of you helpful, clever people know why that might be?

Many thanks in advance.

 

[D_Hailsham]

Possibly the timer is faulty, but need more info about your system.

Boiler make/model
Any motorized valves? How many?
Is there a thermostat on the side of the HW cylinder?
Make/ model of timer?
How old is it?

 

[Lennom]

Possibly the timer is faulty, but need more info about your system.

Boiler make/model
Any motorized valves? How many?
Is there a thermostat on the side of the HW cylinder?
Make/ model of timer?
How old is it?

Thanks for your response. In answer to your questions:

Boiler is a Potterton Kingfisher (very old)
Not sure about the valves - where are they?
There is a thermostat on the side of the cylinder
The timer is only two years old, and is a Siemens RWB2E

Hope you can help, as even when I switch it to the 'On' position, it won't work, but the CH still does.

 

[Hugh Jaleak]

Motorised valve or valves will be somewhere after the pump, usually in the airing cupboard for ease of installation although dont have to be. (Silver or plastic box, on a brass body with 2 or 3 pipes connected, and a cable going to a junction box.)

From what you have said, I suspect either you have a valve sticking shut or there is a blocked primary (pipe) on the HW side. Could you post a pic of your setup? Will help diagnose type of system and possible faults.

 

[D_Hailsham]

Boiler is a Potterton Kingfisher (very old)

Had one at my last house.
How many water pipes connect to the boiler - two or more?

If only two pipes, you have a fully pumped system and will have either one valve (left pic) or two (right pic).

If more than two pipes, you have a pumped heating/gravity HW system. This will have just one valve (right pic) near the cylinder

View media item 5946 View media item 11762

 

[Lennom]

Boiler is a Potterton Kingfisher (very old)

Had one at my last house.
How many water pipes connect to the boiler - two or more?

If only two pipes, you have a fully pumped system and will have either one valve (left pic) or two (right pic).

If more than two pipes, you have a pumped heating/gravity HW system. This will have just one valve (right pic) near the cylinder

View media item 5946 View media item 11762

Thank you (and to you, Hugh). We have two pipes connected to the boiler.

 

[D_Hailsham]

We have two pipes connected to the boiler.

Good. Now tell us how many valves.

 

[Lennom]

We have two pipes connected to the boiler.

Good. Now tell us how many valves.

Oh, forgot, sorry. It has two valves.

 

[Hugh Jaleak]

For a temporary fix to get you some hot water you need to find the valve on the pipe from the pump to the cylinder. There should be a lever or switch marked Man and Auto. Move this to Man, it will wedge the valve open. Now switch the HW side on, boiler and pump should fire and check hot water from the boiler is passing through this valve into the cylinder.

 

[twgas]

Not all valves will switch the boiler on when in the manual position, if yours doesn't you need to turn the heating on and this will get you going.

 

[Lennom]

Not all valves will switch the boiler on when in the manual position, if yours doesn't you need to turn the heating on and this will get you going.

Many thanks to all who have responded to this query - much appreciated.