Problem with Diverter Valve?

djp64

I'd be grateful for some insight / advice before I call a central heating engineer / plumber:

I have a traditional heating system with a boiler and immersion heater / storage tank.

I have an old sliding Honeywell programmer. I don't used the timer function on this - I just slide the relevant switch for HW / CH to continuous when I want them. For the HW once it's been on for an hour or so I slide it back to off.

When the CH is on it can take 10 or more attempts for the HW 'heating' to kick in. When the CH is off it usually kicks in first time.

From googling this would appear to be a diverter valve issue. I have checked in the airing cupboard and I have two of these valves. Is it usual to have 2?

Does my diagnosis of the problem appear to be reasonable?

Thanks in advance

Debbie

garethgas

My first suspicion would be the timer. Notorious for their poor quality switching mechanism.

plumb1_2

you need to put a electric test on it, so see if the valve/stat is getting power.

happybiker

You do not have a diverter valve fitted. you have 2 Zone valves.

When the heating is on, the boiler will be hot and possibly up to temperature. When switching the hot water on, cold water will have to circulate throught the boiler before it will fire up. When no heating is on, the boiler should fire up as soon as the zone valve has opened ( probably about 15 seconds)

Are you sure there is a fault and it's not that you are impatient?

Leave the C/H on for a while to get hot.
Feel the pipe between the hot water tank and the zone valve that controls it.
Then turn on the hot water, go back to the zone valve that feeds the cylinder and feel the pipe again. If it is hotter, all should be ok ( the boiler will only fire back up when it's temperature falls sufficient to need heat input.)

djp64

Thank you for all your replies.
Plumb1 - I'm not confident in my ability to do this. I'm OK with mechanical things but don't touch electrics etc :-)
happybiker - thank you for your detailed explanation of why I have two valves and what their purpose is. I did not have the hot water on yesterday. I have a 'modern' immersion tank that is coated in foam so one tank of water lasts 2 days (there's only me). I felt the two pipes leading into / out of the two valves that I have. From one valve the pipe goes down and into the base of the immersion / storage tank. That was warm. For the other which runs vertical and down through the floorboards (and presumably to the boiler etc) I have assumed this is the CH feed. This was actually cooler than the HW one but the heating hadn't fired up for a while.

When I put the heating on today I will leave it to run and warm as you suggest and then try the hot water. I do leave a reasonable amount of time before assuming the hot water isn't going to kick in but perhaps not enough. I will leave a longer time period and see what happens and report back.

Thanks once again.

Debbie x

happybiker

You are correct in assuming 1 valve controls the heating circuit and 1 controls the DHW (domestic hot water)

From your discription of the controls, I would suggest you have an early 'Honeywell sundial S plan' control system.

Google that and you should find technical details(not really needed though) and an explanation of how it works.

There is another simple check that you can do but it requires 2 people to carry out. Post back if you still don't think the system is right or you are unsure.

Cheers
H

zaax

Here's a nice video http://youtu.be/Yyn_fBEH90U