Back boiler CH issues

[Tosh]

Hi guys and gals,
Hope everyone's well, I've not been on since before christmas just been way too busy. Hope you're all as busy as I am and 09 is good year for you all.

Just done a job for a mate of swapping some old rad valves for new TRV's and lockshields, but on re-commisioning the system we can't seem to get rid of the air from the system.

A couple of the rads don;yt even seem to have any water in still, we've blead a shed load of air out but still no joy. A couple of the flow pipes start to get hot but then that soon dies out.

I've never worked on a system using a back boiler before, are these just gravity fed from the FE tank as there is no filling loop like on a combi boiler system.

Any ideas for getting the air out and water running round the system again?

Many Thanks

Tosh

 

[Mike Jackson]

I'd suggest you go to [DLMURL="http://astore.amazon.co.uk/tilfor-21?_encoding=UTF8&node=12"]Dave's Amazon Store - Plumbing books[/DLMURL] and get yourself a copy of Central heating fault finding and repair by John Reginald.

In the meantime how did you isolate the system to drain it? It could be a blocked cold feed, an airlock, seized float operated valve.

Mike

 

[buffy27]

whats the craic.
had same issue a while back.dual heating system.oil and solid fuel.duel coil .open vented.if i was right or wrong , i don t know, but what i did was i drove in 2 .5 bar mains water. until it was completely full. venting as i went. listen it worked. that was actually the end of november. popped back recently. every thing grand. buffy

 

[Tosh]

Ran around bleeding every rad and the vent on the HWSC hot feed for the heating for bloody hours.

Tried opening the drain cock on the lowest rad and leaving the supply 'on' to try and purge the system.

Ran the pump to push water through, water comes through lovely for ages, lots of gurgles in pipes so air obviously moving, water feeding in the cold supply from F/E tank lovely, float valve operating fine.

Closed down the drain cock, turn on heating and same thing again. Started from scratch and re-balanced system but still can't get rads hot and air out of system.

Turning pump on/off/on/off certainly moves the air along and you can bleed a little more air out of the system but not enough to get system running properly again.

Any ideas other than "go buy a central heating repair book" will be appreciated.

 

[pnhsolutions]

If it was me i would back fill it from a mains supply i.e the outside tap with a hose!
Make sure you are venting with the pump off as well mate!

 

[Mike Jackson]

The buy a book comment was constructive. You've obviously not come across many older systems and a decent repair book will help you recognise what you are looking at.


That book is what I recommend to any new starters on the firm that I work for when they haven't got much experience of older systems. There are a lot of older systems about and a good understanding of how they work saves a lot of grief.

Mike

 

[John Flower]

E

The buy a book comment was constructive. You've obviously not come across many older systems and a decent repair book will help you recognise what you are looking at.


That book is what I recommend to any new starters on the firm that I work for when they haven't got much experience of older systems. There are a lot of older systems about and a good understanding of how they work saves a lot of grief.

Mike

Good call Mike !#

Have you checked the cold feed and open vent configuration have you checked for blockages ? Is there an air seperator fitted and has it been fitted correctly? Is it a fully pumped or gravity hot water ,pumped heating?
Is it a one pipe system ? Are there motorised valves on the system ,are they fully open ? Is the open vent the specified distance over the F/E tank? Is the F/E tank sized correctly to the size of the system?
Without knowing these answers then you wont have much luck by asking for a quick cure to the problem. Back filling the system will not help in the long run as it will only mask the problem.

Cold Feed and vent should be in 22mm with no valves between the f/e tank and the boiler and with a continual rise to the f/e tank.
The cold feed and vent should not be teed in to the primary coil of the hot water cylinder,especially if the system has been converted to fully pumped( issues with valves in between cold feed and vent and boiler)and should ideally connect either to tappings on the back boiler itself on into the primary flow/return. Normally on flow between boiler and circulator 150mm centres. Check manufacturers details for the correct spec.
Does the system require flushing ? Is there sludge in the F/E tank.

 

[Tosh]

Sorry Mike thought it was a sarcastic comment.
Been on Amazon and looked into as yes I am still a newbie at this and learning all the time.

Pain in the arse with the current economic climate no company will touch a newly qualified with a barge pole so just doing what I can picking up smaller jobs to get the experience so than you very much for your patience on here guys.

Struggling to see all pipe work as a lot of it is run down through the cavity wall.
Think we've just dislodged a load of sludge in system. the F/E tank has a load of kak in it and my mate tried to flush through the system again and is getting tonns of black crap. going to take off the rads one by one and flush them through and see what happens.

Will let you know.

Thanks again.

 

[leakylea]

Ah the joys of plumbing!, the quickest way to sort this may be to back fill off the cold main, put hosepipe on to lowest rad drain off, or the one usually near or on back boiler and let the system fill at a reasonable rate, i would put a push fit blank on the vent pipe so you know all the air or blockage wll come into the tank through the feed pipe, even let it over flow. let water back out of system to a point that f&e tank is at its usual level if you have bled the air out during this filling procedure the system is now full of water and it should work correctly as before,
As mentioned previously the type of system is inportant,DO NOT carry out the above procedure on a "Primatic" sngle feed self venting cylinder you will blow the air bubble and mix your domestic and heating waters, this is where the reality kicks in, Once you start on a job its your job you own it
and the customer expects that you know everything about everything connected to the trade, which of course no one does you,ll sort it mate it may just cost you a fewworry linesand acouple of grey hairs good luck pal