luke warm water from indirect cylander

[1807mick]

Hello, system - gas fired back boiler heating indirect cylinder, no zone valves, gravity fed.
Problem - Hot water barely gets warm.
I have checked pipes to cylinder and both flow and return are hot but cylinder is only warmish.
Checked header tank and it is full.
Boilers fires up stays on for a few minutes then switches off, it fires up again after several minutes then switches off. This cycle repeats but the boiler stays on for less time and switches off quicker than at first.
You might have gathered I'm a competent DIYer but cant fathom this, help from any of you professional guys would be much appreciated as had views of a plumber who could only suggest a blockage in the cylinder coil. Thank you - Mick

 

[lame plumber]

get in a plumber who knows his stuff could be a boiler issue, airlock all depends if you have been diying, re boiler issue, we wont advice on that area.

 

[mountainman]

I had a similar problem today, the customer thought that it would be a good idea to turn the boiler 'stat to minimum "as it is now summer", not realising that the hot water would only come out Luke warm.
A costly error on his part.

 

[HackneyHeating]

what you probably have is a scaled up/blocked coil, why is there no zone valve or temperature control??

 

[Killy Bing]

what you probably have is a scaled up/blocked coil, why is there no zone valve or temperature control??

Gravity.........its not even a c plan. very basic

 

[lame plumber]

if your in a hard water area its probably all scaled up from years of use, best advice, invest to save, new system needed

 

[1807mick]

thanks for all the advice, it is my daughters rented home and the landlord wont do anything. The stat is full up. As for DYOG Im daft enough to mess with gas but basic plumbing I can do. I think scaling up might the problem or maybe a blockage by something than can be flushed out sludge etc.
Anyway, thank you all again.

 

[1807mick]

Oops missed a 'not' between Im and daft, but Im sure you all know what I meant