Cold radiators upstairs

[b33zo]

Hope someone will be kind enough to give some advice on this ongoing problem. Though I've done lots of plumbing and a fair bit of heating this has got me stuck.
Ideal Mexico HE30 (floorstanding) boiler about 3 years old, Grunfos pump 2-3 years old and Honeywell 3port valve 1 year old. Honeywell room stat - new.
Rads throughout (balanced) reach reasonable temp when programmer set for CH but when set for CH and HW the upstairs rads go cold.
I've had all the rads off and flushed with a hose so feel that they should be okay and run de-sludger through for a week. Now wondering if there could be a section of pipework upstairs clogged.
Any suggestions would be most welcome.
B33zo

 

[keithkar]

Have you checked to see if there is a cylinder balancing valve.

 

[b33zo]

Have you checked to see if there is a cylinder balancing valve.

Thanks KeithKar. No cylinder balancing valve fitted.
The system is vented and the cyclinder is about 25 years old.
Everything worked fine for 20+ years untill the 3 port valve became sluggish three of years ago.
I took out a bit of associated pipework when I replaced it and found quite a build-up of 'compressed' sludge in the 22mm tube.
Cleaned everything up and the system CH and HW worked fine.
Tired old boiler 'retired' a couple of years ago after magnificent service and replaced with new Ideal Mexico (apparently not highly regarded). Problems ever since...

 

[keithkar]

Check the pump speed it may be set too low, it may be worth fitting a balancing valve on the return from the cylinder, however if the heating works on heating only it should work just as well when the hot water demand is satisfied and the mid position valve returns to heating only.

 

[b33zo]

Check the pump speed it may be set too low, it may be worth fitting a balancing valve on the return from the cylinder, however if the heating works on heating only it should work just as well when the hot water demand is satisfied and the mid position valve returns to heating only.

Thanks again Keithkar, Pump set high. As you say if the heating works okay on CH it should continue working okay on CH and HW - but it doesnt!
With programmer set to CH only all the rads get hot. When it's set to CH and HW the water is very hot, the downstairs rads are hot but the upstairs rads are luke warm.
Cheers

 

[danhiltonplumbingservices]

sounds like to much demand on the hw when in hw/ch mode could be bad pipework or undersized pump/boiler.

 

[b33zo]

sounds like to much demand on the hw when in hw/ch mode could be bad pipework or undersized pump/boiler.

Thanks Dan. I turned the cylinder stat down to see if that made any difference but as far as I can tell there is no difference.

 

[picasso]

The comprssed sludge you found was probably acting as a balancing valve for the hot water cylinder, water takes the path of least resistance, its easier to go through the cylinder coil that the upstair rads, do as keithkar suggested and fit a valve on the return as it leaves the cylinder.

 

[b33zo]

The comprssed sludge you found was probably acting as a balancing valve for the hot water cylinder, water takes the path of least resistance, its easier to go through the cylinder coil that the upstair rads, do as keithkar suggested and fit a valve on the return as it leaves the cylinder.

Thanks Picasso. I'll fit a balancing valve as suggested and see what happens. As the HW can get very hot it suggests that the boiler is booting out enough heat but when the programmer is set for both HW and CH the water is circulating the easiest way possible which is through the cylinder coil. If that is true then I figure there must be some restriction in the pipework somewhere...