Boiler not firing up for hot water but does for central heating

[Marty1979]

Hello folks

I have a Glow Worm Micron boiler (sealed system) and Heatre Sadia Mega Flo storage cylinder. I have just moved into the property, programmed the Honeywell digital stat and find that the boiler fires up for central heating but not hot water. I am having to use the immersion heater which is far from practical and I suspect costly.

There are 2 no Honeywell 22mm zone (2 port) valves - one on the flow and one on the return. I have moved the levers arms on both zone valves and they spring back to auto.

Please can you advise what to do when you have a second or possibly diagnose the issue. I have some plumbing experience but obviously require some time served knowledge from you guys.

Thanks ever so much

Martyn

 

[Mike Jackson]

First step is find the timer for hot water and set that as the digital stat won't affect the water. Failing that get someone in as, from your description, you obviously don't understand the system and could easily do more harm than good.

 

[Unregistered]

Morning Mike

Apologies, I've totally confused things as I was typing this late last night. I meant to say I have a digital Honeywell programmable timer not a digital stat. The stat as you say would have nothing to do with it.

When I turned the central heating on, I manually moved the lever arm across on the 2 port valve on the primary flow. This then allowed the hot water from the central heating to divert through to the coil in the unvented cylinder. That's why I was wondering if the head gear was knackered on the 2 port valve(s).

I have set the programmer to see if it calls for heating and hot water by day and times . If it only kicks in for heating do you think it'd be the port valves?

Again, thanks for your swift response and if nothing else I'll get someone in.

Many thanks

 

[stevetheplumber]

it could be the valve or it could be something else not feeding power to the valve

 

[finchy01]

I know it's not an answer but you mentioned unvented a couple of times and that you have a bit of plumbing experience. Unvented requires an extra qualification called G3. I would recommend you get a g3 plumbing engineer in as these things can become bombs if they go wrong. They have so many safety cut offs that it's extremely unlikely but to be safe, get one of us in. Where abouts are you?

 

[Unregistered]

Hi all

Thanks gents for all your help and advice. The digital programmer is kicking in for the CH but not hot water. I have got a volt detector pen and there is power in both black cables going into each of the respective 2 port zone valves so might be the Honeywell digital programmer? The programmer is a Honeywell ST6400C programmer and the 2 no 2 port zone valves are Honeywell, too.

Finchy01 - mate, I live near Gravesend in Kent - is that your neck of the woods or anyone on here nearby?

Many thanks.

 

[finchy01]

I hate to turn down work but I'm lucky enough not to have to travel too far and that's certainly out my neck of the woods. Maybe try posting in the looking for a plumber forum on here. I'm sure a few of the guys are your way.

 

[Unregistered]

Has the thermal trip on the cylinder activated, if the immersion has been used and set a bit high it can trip the cylinder thermostat. a voltstick wont help as there is a permanent live to both valves (grey wire) you need to test if 240v on the switch wire (brown).