Unvented Center cylinder no hot water

[Chris68]

Hi all, I’ve got an issue with no hot water from Center 300L unvented Cylinder on S Plan plus system. All Electrical controls working fine. Only way to get hot water to the taps is by using immersion heater. Any ideas what could be up? Thanks in advance.

 

[ShaunCorbs]

Is the port valve working / opening ?

 

[Chris68]

Is the port valve working / opening ?

Hi, yes. I’ve even swapped over zone valves from Heating and wired it to Hot water, the electrical part anyway. I’ve left the body I. Place though.

 

[ShaunCorbs]

And you could open the body via the spindle easily ?

 

[Chris68]

And you could open the body via the spindle easily ?

Do you mean can I turn the mechanical part on the pipe part of the zone valve? I tried to turn it by hand but really doesn’t feel like it moves that much, I’m not sure what’s normal. I suppose I could try the heating zone valve to compare.

 

[ShaunCorbs]

Should move easily 12- 2

 

[Chris68]

Should move easily 12- 2

Yeah, just took 2 heads off and both the same. Turn pretty easy with finger and thumb. I tried opening the hot water zone valve yesterday and I could hear the water passing the valve into the cylinder.

 

[ShaunCorbs]

Need to check when you turn hw on via your controls the brown from the hw two port has 240v with a multi meter

 

[Chris68]

Need to check when you turn hw on via your controls the brown from the hw two port has 240v with a multi meter

I’m a Spark, I’ve checked that it all switches right. I confirmed that if the cylinder stat is calling for heat on the cylinder, the zone valve fires and gas on boiler ignites. All working fine. Just no hot water at taps unless like I say, I put the separate immersion heater switch on for a few hours.

 

[ShaunCorbs]

Do you have hot water going through the port valve ?

 

[Chris68]

It sounds like it is. There’s a little gushing noise for sure.

Do you have hot water

 

[ShaunCorbs]

But does the pipe get red hot ?

 

[Chris68]

But does the pipe get red hot ?

Yes, the pipe that goes to the primary into the cylinder is jumping hot.

 

[ShaunCorbs]

And it heats for a good hour eg the flow pipe stays hot ?

 

[Chris68]

And it heats for a good hour eg the flow pipe stays hot ?

Yes it seems to, the boiler gets right up to about 85 degrees and then the gas light goes off, I’m guessing that’s the boiler doing it’s job, even if the cylinder is still calling for heat. Only literally a bowl full of hot water, then runs cold again