Baffled by central heating with a mind of its own......ready to give up!!

[JoseGaf]

Have a combi boiler system in a 1908 house, boiler isn't great, 20yrs old but it is serviced, has new pump and diverter valve...and works. The radiators and pipework however are another story.....firstly as its an old house the pipes are all circa 15mm (not the latest larger dia)....the boiler is downstairs out in the annex away from the main house. In the 4 yrs we've lived there the best we've seen is 6 out of the 8 radiators working......sometimes we are down to none working as we are now. I've had various central heating engineers round and at best they've got warmth into all the radiators which soon dies away. We've bled the rads, balanced them, tried to flush them by adding taps to the ones which don't heat up......there's just no pattern though, you can start draining rads whilst keeping the pressure up and things start to heat up....then for no reason the rads will start to cool after 30 mins or so......also even if you get it all working as soon as the boiler shuts down as its not needed to heat the next time it comes on the following day you are back to square one......its been suggested we either get the system powerflushed or have the whole house pipework stripped and and new boiler.....both are expensive but as I want to move house next year I thought powerflush.....got a guy in yesterday quoting £360 and he said they didn't do the powerflushing I was after...that didn't help. Then he had a look around and said I needed my pipework replacing because nothing was heating up...thanks but no thanks.
I am reaching the end of my tether....has a 10mth old, a 2 1/2 yr old and a wife who just wants me to get the house warm without eating into our house move fund...easier said than done.
Can any of you experts offer any advice......or if theres anyone in the Daventry (Northants) area who'd be willing to have a look I'd be more than happy to compensate for your time....please help!?

 

[newcastle phill]

I presume its a single pipe system based on the powerflush man stating they dont do the flush for your system.
Sounds like severe sludging.

 

[Ermintrude]

Stan was around that area. Sounds like you've got a flow issue. Expect that the one pipe had been modified so that the radiators are no longer directly above the main pipe. Is there good access under the floor? If so get a torch and a roll of 15mm soeedfit and about 8 tees

Power flush won't work on a one pipe. Take one rad off at a time and throughly wash it out with hose pipe.

 

[diamondgas]

Without more info on system type and boiler the issue could be caused by a multitude of possibilities.

 

[JoseGaf]

I presume its a single pipe system based on the powerflush man stating they dont do the flush for your system.
Sounds like severe sludging.

I'm no central heating engineer, have learnt a bit about how it works but have had now 3 different engineers have a go at it. I know the pipework size and routing isn't great, I can see the pipework for the first couple of metres above the boiler in a cupboard, after that it disappears into the ceiling (single storey annex) and towards the main house (3 bed terraced house, is not big). There is only one single pipe feeding hot water and within 1.5m of the boiler it splits into 2 to feed a radiator and towel rail in the bathroom....I imagine this on its own reduces the flow to the rest of the house.
We've had 2 lots of sludge remover in the system over the last 2 years and I can only assume most has been flushed out through one of the many flushing sessions whilst keeping bolier pressure up.....the water is murky.
I think there may be a blockage, sludge or other thats in the return pipes probably not a million miles from the boiler but as I manage to get most of the rads working at some point or other its very confusing....I'd imagine a blockage would be static but seems to move around.....

 

[newcastle phill]

Can be but do move around often

 

[JoseGaf]

Without more info on system type and boiler the issue could be caused by a multitude of possibilities.

Its a Heatline Viso (Vizo) boiler.....yes I know its :nono: but it was in when I bought the house....its fully serviced and does work, pump is 6mths old

 

[JoseGaf]

Can be but do move around often

Any ideas on what I could do to clear it? Thought about draining the system but this won't necessarily cure the problem....

 

[newcastle phill]

Rads off in garden , hose on tap to rad. Flush through and bang each rad with rubber mallet at same time or use percussion drill with special rubber adaptor/pad
Repeat for each rad.
put all back on and powerflush full system. (Providing it can be flushed)
Then Chemically clean and power flush full system. Test only then add inhibitors once satisfactory.
If satisfactory. Invest in magnaclean

 

[diamondgas]

Its a Heatline Viso (Vizo) boiler.....yes I know its sh*te but it was in when I bought the house....its fully serviced and does work, pump is 6mths old

The vizo has a filter on the return pipe under the boiler (behind the big silver nut). As you are not interfering with the boiler case you can remove this nut and check see if the filter is blocked! That's if it hasn't already been checked? Word of caution here!! If you put too much pressure on these nuts you can cause leaks internally on the boiler! Hold against yourself when undooing

Otherwise you can determine circulation issues with pipe thermometers.

Does the boiler fire up, flow from it get MAD HOT then switch off and flow cool right down ... repeating the same thing over and over?

 

[Millsy 82]

If you have 8 rads off a 15mm pipe it will need repiping. If you have pulled a lot of water out of the system then I would very much doubt it will be sludge. I would imagine that the rads have been fiddled with and balanced and balanced until they are virtually shut.

I know you said you are hoping to move but I would rather be warm for the time that I'm there.

 

[JoseGaf]

The vizo has a filter on the return pipe under the boiler (behind the big silver nut). As you are not interfering with the boiler case you can remove this nut and check see if the filter is blocked! That's if it hasn't already been checked? Word of caution here!! If you put too much pressure on these nuts you can cause leaks internally on the boiler! Hold against yourself when undooing

Otherwise you can determine circulation issues with pipe thermometers.

Does the boiler fire up, flow from it get MAD HOT then switch off and flow cool right down ... repeating the same thing over and over?

boiler fires up and feed pipe gets red hot, can sometimes get warmth in the return but takes a bit of fiddling with the system.

is the nut covering the filter about 30mm diameter? If so i think ive located it...will need some grips to undo as its more than finger tight....will try carefully tomorrow....there is a blue tap to stop flow just before it....should i turn off boiler and this flow via blue tap prior to removing nut....i imagine i need to?
thanks

 

[JoseGaf]

Rads off in garden , hose on tap to rad. Flush through and bang each rad with rubber mallet at same time or use percussion drill with special rubber adaptor/pad
Repeat for each rad.
put all back on and powerflush full system. (Providing it can be flushed)
Then Chemically clean and power flush full system. Test only then add inhibitors once satisfactory.
If satisfactory. Invest in magnaclean

Am going to take one of the downstairs rads off tomorrow, one with a tap thats never worked....will clean it out......if easy enough ill try and get another 1 or 2 done tomorrow.....thanks

question.....if there is sludge in the system, what happens if it makes its way to the boiler via the return...does it hit a filter or recirculate and go out via the feed?

 

[JoseGaf]

If you have 8 rads off a 15mm pipe it will need repiping. If you have pulled a lot of water out of the system then I would very much doubt it will be sludge. I would imagine that the rads have been fiddled with and balanced and balanced until they are virtually shut.

I know you said you are hoping to move but I would rather be warm for the time that I'm there.

The frustration i have is that all bar one radiator got hot yesterday whilst i was trying to get things going....ive watched all the youtube videos on bleeding and balancing so am reasonably confident in what ive done. Am sure if i can get the system clean it will run fine.....hopefully cleaning out the rads will improve flow........am definitely looking at getting the pipes out of the boiler changed to larger diameter, repiping the bathroom loop and removing the rad behind the towel rail in the bathroom....engineer rightly pointed out that this is probably draining a lot of flow very early in the system

 

[newcastle phill]

Will line heat exchanger and reduce efficiency.
Whacking with a mallet is helpful.
But if you can get hold of special attachement for percussion drill set to hammer mode - the micro vibrations are so much more effective

 

[goz666]

Have you got TRV's on ??? If you have, take all the heads off spray the pin at the top with WD40 and press up n down a few times with a pair of grips or a spanner. I've been to loads of cold rads, even when other 'plumbers' have been there first and all I've found is Sticking TRV's.

 

[JoseGaf]

Will line heat exchanger and reduce efficiency.
Whacking with a mallet is helpful.
But if you can get hold of special attachement for percussion drill set to hammer mode - the micro vibrations are so much more effective

Is this something i need to do with the heat exchanger removed or in situ on the boiler?

 

[JoseGaf]

Have you got TRV's on ??? If you have, take all the heads off spray the pin at the top with WD40 and press up n down a few times with a pair of grips or a spanner. I've been to loads of cold rads, even when other 'plumbers' have been there first and all I've found is Sticking TRV's.

2 of the 3 regular problem rads have trvs......have checked the pins and are functioning ok, pins arent stuck, ta

 

[goz666]

2 of the 3 regular problem rads have trvs......have checked the pins and are functioning ok, pins arent stuck, ta

In that case mate, I would try running without the TRV heads on. If no different I would take them off and see if any debris is blocking them. Been to one once that someone had previously had the rad off to decorate and plugged with tissue, forgot to remove tissue and it was stuck inside the TRV causing no circulation.

 

[JoseGaf]

In that case mate, I would try running without the TRV heads on. If no different I would take them off and see if any debris is blocking them. Been to one once that someone had previously had the rad off to decorate and plugged with tissue, forgot to remove tissue and it was stuck inside the TRV causing no circulation.

Will try that tomorrow, thank you

 

[tamz]

Start with swapping the pump head.
Filter would be a permanent problem and air locks or sludge doesn't float about a system in the manner you describe.
Best if you can get someone who knows what they are doing on the job to see what is actually happening.
Stan (safegasinstall) on here is in your area and knows his stuff but hasn't been on for a wee while. PM him.

 

[jase158]

I am in Aylesbury, I usually book in for powerflush and survey on the day, If i don't think it will need it then I quote on the day then we quote for what it does need.

Does sound like you need to take the rads off and flush out outside, only thing that has been forgotten is that you open the valves a little into a bucket to ensure you are getting flow to each side.

Make sure boiler is off and system is pressurised!! If it is a pressurised system, you could connect hose to radiator valve and flush it through, using the filling loop, so pipework gets a clean as well as rads!!

 

[Ollieg]

You have a heatline viso, which is a combi as far as i know.
If you had a sludge problem the dhw heat exchanger would have been blocked long ago (no hot water). I dont think you have a sludge problem.
Fundamental pipework problem is where I think the issue is.

 

[diamondgas]

boiler fires up and feed pipe gets red hot, can sometimes get warmth in the return but takes a bit of fiddling with the system.

is the nut covering the filter about 30mm diameter? If so i think ive located it...will need some grips to undo as its more than finger tight....will try carefully tomorrow....there is a blue tap to stop flow just before it....should i turn off boiler and this flow via blue tap prior to removing nut....i imagine i need to?
thanks

You have to remove the pressure from the system before you remove the nut. Yes it's a 'blanking cap nut' If you can get the valve turned off then it doesn't hard to do so, likewise with the flow valve opposite side! They do seize however so don't force them too much!

Have a bucket ready to catch any residual water once you've taken the pressure off/drained down.... If you're at all not sure get someone in to do it!!

Feed pipe red hot and return warm is definitely restricted flow. If the hot water heats okay then you can rule out the pump

 

[JoseGaf]

Well i found time to get a couple of rads off to clean out......first radiator which has never worked had lots of black water inside....checked the feed and return taps had pressure and they did. Then took off bathroom rad and towel rail which are closest to the boiler and are the rads that i can normally get working.....again these were black inside. Plan tomorrow to get the final 2 downstairs rads cleaned out......1 which has never really worked but i managed to get hot the other day for a while for the first time....the other which used to work last winter.
my plan is to get all of the remaining rads done next wknd then stick some de-sludge solution in......then flush through the following day......hopefully this will all help.....im not running the central heating again until ive cleaned all the rads