Boiler cuts out after two minutes - please help

[Paul_griff]

If your boiler was working OK before you drained down, and the hardware hasn't been altered, then you can rule out much of what has been suggested in relation to the immediate problem of the boiler stopping and starting due to pipe configuration, pump fitting, etc.

Unless there is a good explanation why just one radiator was full of sludge, you can safely assume that the rest of the system is also sludged up too.

If I was you, I would put some X400 (or similar cleaner) in, and run it for a week, and then powerflush the system. HSS have an offer on at the moment, and you can hire a powerflush machine for 50 pounds. Clean out the header-tank too.

If muck is causing a restriction in the heat-exchanger, or elswhere, your boiler will close down to protect itself.

If that doesn't fix things, the power flush will be money well invested anyway - a clean system is an efficient system. If it was me, I would also fit a filter at the same time, if there isn't one already that is.

In the event that the boiler still cuts out, then call in a GSR.

If the powerflush fixes things, you can check for pumping over by monitoring the temperature of the water in the header tank when the system is running. If it is pumping over and causing accelerated sludgeing, then get a plumber to advise on modifying the pipe work.

Boiler was fine before I started messing, so as you say I should be able to rule a few things out.

i would imagine the rest of the system is smudged up going on what I have seen so far, the sludged up radiator was the largest of two downstairs radiators and was cold at the bottom and warm at the top.

I have cleaned out the header tank and intent to run some cleaner through it and might just have to hire a power flusher too at that price.

i am concerned as some have suggested that the pump may be failing as the heat the boiler produces in its couple of minute bursts gets round the upstairs radiators but not the downstairs ones.

thanks for your help.

 

[diamondgas]

water is lazy Paul .. it wants to make a complete circuit quickest way possible. As your system cloggs up, like arteries, the extremities start to get left out and the pump struggles on best it can. It's finding the easiest path which sounds like it's your upstairs. I'd imagine even that is slow... Mad hot flow and cold returns? The Introduction of air pockets and aerated water slows the ability of a pump to 'move' water around ... There could be issues with the pump too if it's been subject to all this crud ... Less likely if it worked okay before the draining down but you never know 🙂

Regards flushing ... Unless you know what you're doing I'd get a pro in! There's a potential to make a real mess of your house...!!! Regards x400 or the like, you need circulation for that to do its job, something by the sounds of it your system is lacking!

You're always going to get differing advice on here from real experienced guys down to have a go hero's. I do not know how experienced you are in plumbing Paul but what you're describing could be erring on the realms beyond a great deal of plumbers experience, in my opinion! Not many these days get to mess about with open systems 🙂


Good luck ... 😀

 

[petercj]

I think there's a very good chance the problem has been caused by muck coming down from the header tank, and maybe sludge having been disturbed generally when you drained down.If you treat with cleaning chemical first, and then powerflush thoroughly, it should clean the whole system, including the heat exchanger.You will need to cap off the vent (a Speedfit end-cap will do the job, and be reusable) and you will need to plug the outlet in the header tank - otherwise when you powerflush the loft will get a soaking. With the price of gas these days, it's false economy not to have your system clean and running efficiently, so it will be money well spent whatever the outcome.HSS use Proflush machines, and if you want to read through the powerflushing instructions before you hire, you can download chapter and verse from their website...
[DLMURL="http://proflush.co.uk/powerflush/machine/proflush-professional"]
Proflush | Proflush Professional | State of the art Powerflushing Machine[/DLMURL]

The offer is on through February, and you can get the machine for a weekend for an extra tenner.

 

[Paul_griff]

water is lazy Paul .. it wants to make a complete circuit quickest way possible. As your system cloggs up, like arteries, the extremities start to get left out and the pump struggles on best it can. It's finding the easiest path which sounds like it's your upstairs. I'd imagine even that is slow... Mad hot flow and cold returns? The Introduction of air pockets and aerated water slows the ability of a pump to 'move' water around ... There could be issues with the pump too if it's been subject to all this crud ... Less likely if it worked okay before the draining down but you never know 🙂

Regards flushing ... Unless you know what you're doing I'd get a pro in! There's a potential to make a real mess of your house...!!! Regards x400 or the like, you need circulation for that to do its job, something by the sounds of it your system is lacking!

You're always going to get differing advice on here from real experienced guys down to have a go hero's. I do not know how experienced you are in plumbing Paul but what you're describing could be erring on the realms beyond a great deal of plumbers experience, in my opinion! Not many these days get to mess about with open systems 🙂


Good luck ... 😀

Diamondgas,

i am not experienced in plumbing apart from removing the odd radiator, I am an electrician so am quite practical,but I think I will take your advice regards flushing its probably getting out of my depth.
I am thinking it is an airlock in the pump now because even if I try to heat water only it takes forever for the cylinder coil return to gain any heat, this being a very small circuit compared to heating and allowing for heat exchange to the water in the cylinder I would expect the return pipe temp to rise reasonably quickly. Might change the orientation of the pump at the weekend to allow proper bleeding.
Seems I am a bit of a have a go hero when it comes to plumbing but I am learning all the time and actually quite enjoying it in a perverse way, my family are not freezing as we have an immersion for water and upstairs radiators that get hot eventually so I will battle on for now!

 

[petercj]

"Have a go heros!" lol

Ex BG of course!

 

[diamondgas]

Diamondgas,

i am not experienced in plumbing apart from removing the odd radiator, I am an electrician so am quite practical,but I think I will take your advice regards flushing its probably getting out of my depth.
I am thinking it is an airlock in the pump now because even if I try to heat water only it takes forever for the cylinder coil return to gain any heat, this being a very small circuit compared to heating and allowing for heat exchange to the water in the cylinder I would expect the return pipe temp to rise reasonably quickly. Might change the orientation of the pump at the weekend to allow proper bleeding.
Seems I am a bit of a have a go hero when it comes to plumbing but I am learning all the time and actually quite enjoying it in a perverse way, my family are not freezing as we have an immersion for water and upstairs radiators that get hot eventually so I will battle on for now!

It's good to know when you've reached the limits of your ability mate 🙂 I've changed the odd socket here and there and even wired up systems but wouldn't say I'm in anyway a sparky!!! :lol: Nothing wrong with giving it a go but when it comes to flushing, so many haven't got a clue what they're getting into in my experience! If you're moving the pump then vertical (flow up through) will guarantee air will not stay for long in the pump providing there's an easy and adequate path for the air to 'bubble' up the vent.. saying that though it's best to have the feed and vent before the pump to reduce the amount of the system potentially subject to negative pressures, that may take some doing with your configuration... If you're messing with the pump what's the harm in getting your hands on a new one and putting it in it's place. At least then you'll eliminate the 'heart' of the system and save yourself a few quid as it'll be most likely the first suggestion a pro would make before delving into flushing.

When you mentioned the bore of the pipe being reduced, I've known of the issue to travel a good few meters up and down from the feed and vent position before resuming normal bore. It can turn out to be a nightmare to resolve to be honest, lets hope you've caught it in it's infancy 🙂

It'd be good to find out how you get on 😀

 

[petercj]

To the OP

If you can remove and replace a radiator competently, follow written instructions, and get up into the loft, then you can powerflush a central heating system - don't be put off by the self-delusion and protectionism of anyone on here.

 

[diamondgas]

"Have a go heros!" lol

Ex BG of course!

I worked for 25yrs installation, repair and maintenance for BG, petercj! In was only in the last 10 or so years of being there that we actually considered system design and what occurred when the pump was running. Before that we'd just replace what was faulty! When you get into the workings of a heating system and what happens to water under the differing forces, how it gets from A to B etc. its an eye opener and a great asset of knowledge to have if you're going to make a 'professional' repair engineer, in my opinion! Doesn't matter who you work for in my books, it's more about who you are and what level of professionalism you want to achieve in your career 🙂


To me a "have a go hero" is a competent DIYer or professional in any field who gets out of their depth but isn't aware of it!!

 

[Paul_griff]

It's good to know when you've reached the limits of your ability mate 🙂 I've changed the odd socket here and there and even wired up systems but wouldn't say I'm in anyway a sparky!!! :lol: Nothing wrong with giving it a go but when it comes to flushing, so many haven't got a clue what they're getting into in my experience! If you're moving the pump then vertical (flow up through) will guarantee air will not stay for long in the pump providing there's an easy and adequate path for the air to 'bubble' up the vent.. saying that though it's best to have the feed and vent before the pump to reduce the amount of the system potentially subject to negative pressures, that may take some doing with your configuration... If you're messing with the pump what's the harm in getting your hands on a new one and putting it in it's place. At least then you'll eliminate the 'heart' of the system and save yourself a few quid as it'll be most likely the first suggestion a pro would make before delving into flushing.

When you mentioned the bore of the pipe being reduced, I've known of the issue to travel a good few meters up and down from the feed and vent position before resuming normal bore. It can turn out to be a nightmare to resolve to be honest, lets hope you've caught it in it's infancy 🙂

It'd be good to find out how you get on 😀

New pump arrived today , fitted it in about an hour when I got home from work, didn't change position and all is now working well! Still a lot of bubbling and gushing sounds all round the system but will run it for a while then start bleeding air.
Got some cleaner to put in and hopefully get rid of some of the remaining crap that is in there.
I'm very pleased with myself, don't like getting beat and thought this was going to beat me,but will leave it at that and not bother messing with a powerflush.
Going to post some pictures of the state of the pump ports and possibly take it apart and get some pics of inside too.

Thank you for all you help Diamondgas and everyone else it's very much appreciated

 

[Paul_griff]

Pictures of old pump, not loads of crap in it but obviously enough to cause a big problem

 

[Paul_griff]

Pump taken apart

 

[diamondgas]

Lets hope that's resolved the flow issue ... You'd still benefit from having the system checked over as to why it's caused so much grief paul .... If you've managed to get most of the restriction out you may even get away with some sludge remover? Pop your head in the loft now and again and check that the water in the header tank is staying cold and there's no water coming out of the open vent! 😀

 

[Paul_griff]

Lets hope that's resolved the flow issue ... You'd still benefit from having the system checked over as to why it's caused so much grief paul .... If you've managed to get most of the restriction out you may even get away with some sludge remover? Pop your head in the loft now and again and check that the water in the header tank is staying cold and there's no water coming out of the open vent! 😀

Got sludge remover in as we speak, everything looking good, all warm, water heating quickly as are radiators, loads of sludge taken out when I dealt with the blocked cold feed plus new pump means its loads clearer already, I appreciate that there is probably a load of sludge elsewhere still but hopefully the cleaner will do some work on that.