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

 

[ShaunCorbs]

How long do you have hot water on its own for ?

And heating is fine ?

 

[Chris68]

How long do you have hot water on its own for ?

And heating is fine ?

Hot water only lasts for 20 seconds maybe, heating for both areas, Downstairs and upstairs both fine.

 

[Basher]

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

Take the case when the cylinder is cold, and you haven't had the immersion on.
The pipe that feeds the primary coil is "jumping hot"
At that instant, is the return out of the cylinder coil also pretty hot?

It should be a bit cooler, but if it's the same temperature as that area of the tank, I was wondering if there's a circulation problem in the cylinder coil circuit - poor flow leading to a lack of energy transfer?

 

[Chris68]

Take the case when the cylinder is cold, and you haven't had the immersion on.
The pipe that feeds the primary coil is "jumping hot"
At that instant, is the return out of the cylinder coil also pretty hot?

It should be a bit cooler, but if it's the same temperature as that area of the tank, I was wondering if there's a circulation problem in the cylinder coil circuit - poor flow leading to a lack of energy transfer?

Had a plumber out today, he said that maybe there’s a build up of limescale or whatever in the tank. 13 years installed. Is this even possible? He said new tank needed

 

[Basher]

Had a plumber out today, he said that maybe there’s a build up of limescale or whatever in the tank. 13 years installed. Is this even possible? He said new tank needed

Not really my area of expertise. But I will say I had a house in a very lime scale rich area of the country, the old fortic tank immersion heater went, and when I removed it I found the bottom of the tank was inches deep in limescale 'platelets'.
I dug it all out, fitted a new immersion, and all worked fine.

I'm assuming your plumber is inferring there's a build-up of limescale on the coil, rather than just in the bottom of the tank, because surely the latter could be rectified without changing the cylinder!
I'm not clear if your mystery lack of H/W is something that suddenly happened, or if it's been inherited. If it's happened suddenly, I don't think the limescale theory "holds water"🤪.

I'd be wary of changing things before understanding what is causing the problem.

 

[Chris68]

Not really my area of expertise. But I will say I had a house in a very lime scale rich area of the country, the old fortic tank immersion heater went, and when I removed it I found the bottom of the tank was inches deep in limescale 'platelets'.
I dug it all out, fitted a new immersion, and all worked fine.

I'm assuming your plumber is inferring there's a build-up of limescale on the coil, rather than just in the bottom of the tank, because surely the latter could be rectified without changing the cylinder!
I'm not clear if your mystery lack of H/W is something that suddenly happened, or if it's been inherited. If it's happened suddenly, I don't think the limescale theory "holds water"🤪.

I'd be wary of changing things before understanding what is causing the problem.

I would agree with you. This system was nee 13 year ago, can’t think we live in a high lime scale build up area, I’m trying to speak to Baxi re the cylinder, was on hold too long today. I’ve messaged them, hopefully they call back, I would also want to find out the issue rather than just replace