Blocked Pipe?

[SparkyUK]

Hi,
I have a problem with my central heating. I have a Vaillant Combi Boiler which is 12 years old and 8mm micro bore pipes!
I recently converted the upstairs radiators so they now have a TRV fitted in them.This involved changing the threaded insert in the rad and to resolder a new piece of tail to the TRV. All has been ok until I decided to add some "fernox superconcentrate Protector" to the last one.This stuff is like glue. Since then the rad is always stone cold, The rad has pressure to it and cold water comes out of the bleeder etc.
I have tried everything, bleeding, making sure PTE tape isn`t blocking anything etc etc. It seems that one of the pipes to the rad is blocked. surely fernox products shouldnt block pipes etc ?
If anyone has has any ideas on how to sort this out id be very happy.

 

[SparkyUK]

Bump

 

[SparkyUK]

its a reversible flow TRV

 

[ChrisR]

Try turning off other radiators to get the flow through this one. Or it may be that the trv has stuck shut, see FAQ section above.

It's irrelevant which end the trv is

 

[SparkyUK]

Ive tried that and Ive had the TRV off to make sure its ok.
Any other ideas? [/quote]

 

[ChrisR]

Do you mean you've had the valve off or just the head?? I mean is the rubber bit free of the seat?

That stuff is fearsome gloopy but should go through OK if you turn all the other potential routes off, so it sounds like there's a flake of something, or worse, blocking things up. Time for the mains hose on the rad union?? DO check your header tank overflow is ok first!

 

[SparkyUK]

Ive had the TRV completely off and blown through it and its ok. Im sure it must be this Fernox stuff
Whats a header tank over flow? I have a combi boiler...........

 

[ChrisR]

I have a combi boiler

so you have.

Ok so remove the rad, put a garden hose on the rad unions, other end to a drain. Same size connection if you're lucky, or you may need one of those black plastic 1/2" to 3/4" inserts you get on garden hose kits for the trv union. Open the rad valve you've connected to, and the filling loop. That should clear the lines, if the mains can't get out you have a problem!

 

[SparkyUK]

ok thanks, ill give that a go.

 

[croydoncorgi]

Fernox concentrate CAN block microbore! It IS (obviously) water-soluble but the water has to get in contact with it! If undiluted concentrate flowed into a section of 8mm microbore there may be a bit of a problem!

My suggestion for a quick fix, FWIW, and PROVIDING you're CERTAIN that the problem is due to concentrate blocking the microbore:

- turn of boiler
- turn off both rad valves on the rad you put the concentrate into
- loosen the airvent (if it leaks a lot of water, you need another solution - one of the valves lets by),
- slacken one of the tail nuts between rad and valve, and drain out a couple of litres of water,
- re-tighten tail nut
- re-tighten airvent and using filling loop on boiler carefully raise pressure on boiler gauge to about 2.5 Bar
- open one of the rad valves slightly. If you can hear water + air running into the rad, close the valve.
- open the other valve and listen for water / air.
If you can hear flow through both ends, the pipes are not / no longer blocked.

Check pressure and return it to 1 Bar if necessary by letting more water out of a rad.

Re-start the system and make sure ALL rads run hot for a while to fully dilute and distribute inhibitor.

2.5Bar of pressure pushing against such a blockage WILL clear it if it's only gooey stuff!

 

[SparkyUK]

Thanks for the advice, I shall give this a try too.