No hot water (kinda) after system drain?

[matmushroom]

Hi all,

looking for some advice..

I had to drain my central heating system to change some valves on some rads - all went fine, the rads are all heating up fine after I refilled the system.

But now heres the thing....

When I turn on hot water the boiler does nothing, and does not kick in, and as a result we have no hot water.

But heres the other thing....

If I turn on both heating and hot water, we get hot water.

Any idea whats happed

ps....there are 5 valves in the loft/by the boiler/tank. I assume these are valves that need draining once in a while to let out air, I have done this several times and there seems to be no more air comming out of them. All rads also seem to be air free too.

 

[dcawkwell]

There is an electrical fault between the timer and the boiler.
You need to trace if there is 240v from the timer all the way to the boiler
when the hot water at the timer is switched on.
Somewhere in the circuit is a fault.

 

[matmushroom]

There is an electrical fault between the timer and the boiler.
You need to trace if there is 240v from the timer all the way to the boiler
when the hot water at the timer is switched on.
Somewhere in the circuit is a fault.

Could you explain that a little more...

whats/where can I find the timer, and would a faulty timer still explain why we have hot water only when the heating is turned on?

cheers!

 

[dcawkwell]

Could you explain that a little more...

whats/where can I find the timer, and would a faulty timer still explain why we have hot water only when the heating is turned on?

cheers!

There will be a 3 port valve in the system that diverts hot water, hot water and central heating, central heating.
If you are switching to central heating the valve is in the mid position so it will do the central heating and hot water until the cylinder gets hot at which point is switches to central heating. (assuming you have a cylinder thermostat)
When you switch the timer on ( I assume you have a timer to control central heating and hot water) 240v is sent via thermostats and 3 port valve to the pump and boiler. Since it is working for central heating there is a fault with the 240v getting from the timer to the boiler went the switch is set to hot water.

 

[matmushroom]

ah, ok....

Iv had a look, and we have a Honeywell valve/box thing.

Could you confirm something... am I correct in thinking that when I only have the hot water this valve should do something?
I notice theres a little notch/lever on the front - that I can adjust with my finger, when I do this is reverts back to its original position (all the way to the left)?

Is this something a layman can replace, or are we looking to getting a plumber in?

Will I need to drain the system again?

cheers., really apresiate it!

 

[dcawkwell]

ah, ok....

Iv had a look, and we have a Honeywell valve/box thing.

Could you confirm something... am I correct in thinking that when I only have the hot water this valve should do something?
I notice theres a little notch/lever on the front - that I can adjust with my finger, when I do this is reverts back to its original position (all the way to the left)?

Is this something a layman can replace, or are we looking to getting a plumber in?

Will I need to drain the system again?

cheers., really apresiate it!

When you switch to central heating you should see this valve lever move across. As default the valve allows heating hot water.
You can replace the valve as a whole that would be preferred or just the head can be replaced. The fault could be at the valve or could be from the programmer/timer. A fault here would mean that there isn't 240v even getting to this valve. Best left to someone who knows and can identify the fault and where it is before randomly replacing parts.
Ensure you get a heating engineer that has part L electrical.