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]

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