New Pump in Combi - but CH still not working ?

[letmedoit]

He's behind you.

Sh*t he made me jump, thanks for that

OK if you guys have got that out of your sytems - can I ask you to concentrate on mine and let me remind you of my very first post: -

I have flushed the system using the fill loop at the boiler.

By closing the CH flow isolation valve under the boiler I can get a good flush down the return pipe, through the rads (5 mins each in turn) and out the drain-valve which is next to the TRV on the kitchen rad.

However, closing the CH return and opening the CH flow means the water is now going through the main heat exchanger etc before going down the flow pipe and out the drain. Result is a much smaller amount out of the end of the drain hose.

Do I really need to take a radiator off to do it again !!!?

 

[letmedoit]

Just been thinking some more about my post above^^^^.

If I assume the return pipework and the rads are not blocked due to the good flow out the drain hose when back-flushing with the flow pipe isolated, would the following also be likely: -

1. With all the rads turned off except the one nearest the boiler (bathroom - Ts off before the pipes go into the floor), then the flow pipe below this rad through the first floor, down to ground floor and out the drain hose must also be clear (because when back-flushing thats the waters route when it comes out of the rad) ?

2. When I have the return isolated and flush via the flow pipe, would the reduced flow out of the drain hose be caused by the restrictions in the bore of the pipes in the main heat exchanger, or possibly a partial blockage in the flow pipe between the boiler in the attic and first floor (where bath rad Ts off) which might also help explain why the auto by-pass is opening fully ?

 

[spraggo]

,

Do I really need to take a radiator off to do it again !!!?

There was no need to close the flow and return valves under the boiler to carry out the flushing as I suggested and obviously there would have been a reduction in flow with the water going through the heat exchanger. However if you want to eliminate the flow through the boiler as a problem then carry out the flushing on the last rad as suggested and then do the same on the first radiator in the circuit and note the difference in the amount of water coming out from the flow and return pipes of both rads, is the kitchen radiator the last one in the circuit?.

If there is a noticable difference then use another hose and fittings on the first or nearest rad and connect to incoming cold water mains tap, with the boiler isolating valves turned off
It is all very well for you to pick us up on things like reminding us of your first post but you must realize that we can only imagine what your problems are as we are not there on site.

spraggo

 

[letmedoit]

It is all very well for you to pick us up on things like reminding us of your first post but you must realize that we can only imagine what your problems are as we are not there on site.

Only mentioned cause it was 3 pages ago and I am sure you guys are reading and answering lots of strange enquiries (thanks).

There was no need to close the flow and return valves under the boiler to carry out the flushing as I suggested

I know you weren't suggesting this. I only did this to try to determine the location of any possible blockage - but as you know, I am really still none the wiser !

is the kitchen radiator the last one in the circuit?.

Yes, the drain valve is in the flow pipe just next to the TRV.

 

[letmedoit]

Just an update for those interested: -

I removed the isolation valve from the flow underneath the boiler which was in a 6" section of horizontal pipe and found it chocablock with black stuff. This stuff extended from the valve into the pipe for about 2" solid.

After scrapping the black muck out and putting everything back we now have our CH working again.

I guess as the pump gradually failed it allowed a build-up ?

Main thing is we are now warm and Her-indoors is happy again !
Thanks to those who helped with various suggestions. At least I know the the different bits of the system have now been checked out.

 

[JohnD]

it would be a good idea to use a cleaning chemical now to remove the scale and sediment that must be present in other parts of the system that you have not taken apart yet. Black iron oxide is usually soft sludge, but hard limescale can appear black where it is stained by iron oxide in the water. Try dropping a bit of that scale in vinegar and see if it fizzes.

If you can afford an extra £100 or so, a Magnaclean or Spirovent is amazingly good at trapping particles of scale and sediment that are floating round or have been loosened by the cleaner, and preventing them forming a new blockage.

 

[letmedoit]

Thanks for your suggestion.

Having flushed the whole sytem repeatedly within an inch of its life, I have added X400 sytem restorer which I will leave to go round for a month. When I flush the system then, I will get a Magnaclean fitted to the return pipe (convenient location in a cupd under the boiler) before adding X100 inhibitor and refilling.