flushing LST radiators

[markadams]

Hi,

I was called to a job in a care home which was a complaint about poor output from the LST radiators.

I had a look at the system it is a sealed system working on a valiant system boiler with an unvented tank.

The boiler is working fine but all the radiators are a lot cooler than normal.

I took a sample of water and it was rusty and brown so I was going to start by flushing the system with a Magnacleanse and then install a Magnaclean filter.

I have little experience of the LST radiators but it doesn't seem like you can agitate the radiator due to the design, so I wonder if the Magnacleanse is going to be effective?

Mark.

 

[chris watkins]

Who is the LST manufacturer ?

The two most popular (Myson & Stelrad) when I was out there where just standard rads behind a casing with grilles top & bottom, these can be removed to access the rad underneath.

 

[markadams]

They look like JAGA rads, they are just a small finned heat exchanger type element under the cover.

Mark.

 

[joni os]

Have had trouble with fin type LST due to modulating boiler reducing water temp. Increasing flow temp. both increases efficiency of convection and temperature of convected air. Necessary to keep temp at 75 C plus to achieve reasonable output.

 

[markadams]

The system has been in many years and they tell me it has been heating up a lot more until a week ago.

Other than the dirty/rusty water I cant really see any reason for me. The PRV and Expansion vessel has recently been changed by another engineer but this would not effect it, the pressure is fine but it is hard to tell as the rads are low water content so you cant feel them in the same way as a normal rad.

 

[oz-plumber]

Test the pump to see whether it has dropped performance.
Could be a nackered capacitor.

also see if you can see under the elements - cobwebs reduce the performance of the elements dramatically due to restricted airflow.

 

[joni os]

Take temp. of pipes going to and from rad.

 

[markadams]

Hi,

How would you test the pump Oz? it is pumping as the flow and return pipes to the boiler are HOT.

When I check the flow and return to the rad they are luke warm or cold.

Every radiator was effected at the same time so not sure that cobwebs caused it but I will clean all 26 rads.

 

[joni os]

If return at boiler is hotter than pipes at rads. you have a bypass somewhere in the system, either deliberate or through rad close to boiler.
Is there a 3 way valve in the system, stuck open the wrong way.