Boiler cuts out after two minutes - please help

[Paul_griff]

I recently drained my system to remove and de sludge a radiator (I know I didn't need to drain system but did for some daft reason). I then struggled to refill which was traced to a blocked cold feed and rectified, now my boiler only runs for about two minutes before cutting out, the restarting after about five minutes.
it is an ideal classic boiler with f/e tank in the loft, I have bled air from the pump, cylinder coil, all radiators and boiler return but am still thinking that there is air somewhere, please help me.

 

[Blake]

I would also assume that you have an air lock somewhere which is causing the boiler to overheat. Have you tried attaching a hose to a drain off and see if opening will help pull any air out?

 

[sam51]

what you need is a good plumber/heating engineer,so you can go to work and earn you money.
then pay a plumber so he can some money,every one happy.
horses for courses.

 

[Paul_griff]

I would also assume that you have an air lock somewhere which is causing the boiler to overheat. Have you tried attaching a hose to a drain off and see if opening will help pull any air out?

where do I attatch the hose to? I have an external drain point that I used to drain the system before, would draining some from that do what you are suggesting

 

[Paul_griff]

what you need is a good plumber/heating engineer,so you can go to work and earn you money.
then pay a plumber so he can some money,every one happy.
horses for courses.

Unfortunatly I'm going to work in the day and coming home to play with my heating system all evening. Tried to get a plumber yesterday but he let me down!

 

[diamondgas]

where do I attatch the hose to? I have an external drain point that I used to drain the system before, would draining some from that do what you are suggesting

Good chance all you'll do is introduce more air IMO!

Is the system fully pumped? Diverter valve fitted? Do you know what i mean by that?

 

[Paul_griff]

Could the airlock be in the boiler itself? would the boiler have any sort of auto air vent on it or would it just be the bleed cap/vent on the return?

 

[Paul_griff]

Good chance all you'll do is introduce more air IMO!

Is the system fully pumped? Diverter valve fitted? Do you know what i mean by that?

i believe it is fully pumped this is the setup, flow from boiler goes to pump, pump to three port valve one side to cylinder coil other side to radiator circuit

 

[diamondgas]

i believe it is fully pumped this is the setup, flow from boiler goes to pump, pump to three port valve one side to cylinder coil other side to radiator circuit

Air lock is less likely on a fully pumped providing there isn't a blockage/restriction anywhere ... You did mention blocked cold feed, did you check to see if the blockage extended into the main circuit where the feed teed into? Usually does in my experience. This then reduces the ability of the pump to remove any air that hit's it! Just guessing mind ... Any chance you could upload a picture of the pump, valve and feed pipe configuration?

Anyhoo's in the mean time, turn the boiler thermostat off, and put the system on HEATING only! That should push any air into your radiators with a bit of luck 🙂

 

[Paul_griff]

Air lock is less likely on a fully pumped providing there isn't a blockage/restriction anywhere ... You did mention blocked cold feed, did you check to see if the blockage extended into the main circuit where the feed teed into? Usually does in my experience. This then reduces the ability of the pump to remove any air that hit's it! Just guessing mind ... Any chance you could upload a picture of the pump, valve and feed pipe configuration?

Anyhoo's in the mean time, turn the boiler thermostat off, and put the system on HEATING only! That should push any air into your radiators with a bit of luck 🙂

There was brown sludge all the way down to the pump, got as much as I coud out (which was quite a lot) don't know what was other side of pump and three port valve, pump and three port valve seem to be doing there job though as when calling for heat or water the relevant pipes quickly warm before the boiler cuts out. If I close water or heating isolator valve I can hear pump start to struggle so I am satisfied there is flow through everything.

will try and upload a picture ASAP, will take an hour of so to boot up old windows pc!

 

[diamondgas]

If your system is cold you wouldn't expect the pipes to get hot quick ... that indicates poor circulation .... Any air that hits the pump will reduce it's ability to move water, the impeller just spins in the air...! Putting the boiler on can add to the problem in my experience ..... Pump pointing downwards is also a contributor, no idea if yours is or not? ... Brown sludge is indicative of active corrosion and pumping over, as is a blocked cold feed, not saying this is your problem but the symptoms you describe would have my probability indicator pointing in that direction 🙂 .... I've seen the bore of a 22mm pipe reduced to half or less with the build up of crud!!!

All this I am assuming of course...... You may just have a knackered pump??? 😀

 

[petercj]

Make sure your pump is set to the highest setting, usually a 3 - if it's a smart pump, put it on manual 3 setting.

What was the header tank like? Worse case scenario could be that muck has been downloaded from the header tank and has restricted the heat-exchanger. Less likely if you have a filter fitted? Try all the other advice before looking into that possibility. If it turns out to be a restricted heat-exchanger, a power flush might help. You can hire out a machine from somewhere like HSS.

 

[Paul_griff]

If your system is cold you wouldn't expect the pipes to get hot quick ... that indicates poor circulation .... Any air that hits the pump will reduce it's ability to move water, the impeller just spins in the air...! Putting the boiler on can add to the problem in my experience ..... Pump pointing downwards is also a contributor, no idea if yours is or not? ... Brown sludge is indicative of active corrosion and pumping over, as is a blocked cold feed, not saying this is your problem but the symptoms you describe would have my probability indicator pointing in that direction 🙂 .... I've seen the bore of a 22mm pipe reduced to half or less with the build up of crud!!!

All this I am assuming of course...... You may just have a knackered pump??? 😀

trying to upload photos but don't know where they are going, anyway the pump is pumping downwards, my 22mm pipes were probably reduced to at least half by the sludge, running the heating with the boiler thermostat off seems to be doing some good as I am getting some air out of a radiator now so there was obviously some in there somewhere (the photo needs rotating)

 

[diamondgas]

Try your pump on a lower setting .... Is the feed and vent above the pump? a picture of that set up may help 🙂 .... As mentioned a power flush sounds like something worth considering, Pipework configuration could do with checking out also IMO.

 

[Paul_griff]

Make sure your pump is set to the highest setting, usually a 3 - if it's a smart pump, put it on manual 3 setting.

What was the header tank like? Worse case scenario could be that muck has been downloaded from the header tank and has restricted the heat-exchanger. Less likely if you have a filter fitted? Try all the other advice before looking into that possibility. If it turns out to be a restricted heat-exchanger, a power flush might help. You can hire out a machine from somewhere like HSS.

pump is on three, header tank was pretty horrible at the bottom got most of it out though , some may have got into the pipes. Things seem to be gradually improving with getting more air out of the radiators, still the boiler will not stay lit yet though.
might have to do a power flush whatever the outcome as there was some serious crap in there.

 

[Paul_griff]

Feed and is above the pump, return vent is above the pump and cylinder coil vent is below the pump. By the way my wife says if I get it working she will get us a Chinese and I can relax and watch football (she can get me some beer to) I asked if you were invited as well and she says you are, so lets get this one cracked and we can eat drink and be merry and warm!

 

[diamondgas]

pump is on three, header tank was pretty horrible at the bottom got most of it out though , some may have got into the pipes. Things seem to be gradually improving with getting more air out of the radiators, still the boiler will not stay lit yet though.
might have to do a power flush whatever the outcome as there was some serious crap in there.

Turn the pump speed down and leave the boiler thermostat off see if things quieten down any? Also run on heating only if you haven't already done so! Get you're pipework set up checked out too. Sounds like it's been pumping over that's down to the way the pipes have been installed usually!

 

[mfgs]

Feed and is above the pump, return vent is above the pump and cylinder coil vent is below the pump. By the way my wife says if I get it working she will get us a Chinese and I can relax and watch football (she can get me some beer to) I asked if you were invited as well and she says you are, so lets get this one cracked and we can eat drink and be merry and warm!

Where do you live? No point me trying to help out if you live 100 miles away because I have no chance of getting any of the Chinese then.

 

[Paul_griff]

Turn the pump speed down and leave the boiler thermostat off see if things quieten down any? Also run on heating only if you haven't already done so! Get you're pipework set up checked out too. Sounds like it's been pumping over that's down to the way the pipes have been installed usually!

What do you mean by pumping over?

 

[Plumbus]

Wonder if the drain down / air is a red herring. I have the ideal classic F250 and similar symptoms to stop / start of the boiler. I checked everything then got the GSR in...turned out to be the circuit board.

 

[Paul_griff]

Wonder if the drain down / air is a red herring. I have the ideal classic F250 and similar symptoms to stop / start of the boiler. I checked everything then got the GSR in...turned out to be the circuit board.

could be but the thought that air coming out is doing some good is keeping me happy so for tonight I'll hold on to that hope

 

[Plumbus]

Fingers crossed for you. Enjoy

 

[diamondgas]

could be but the thought that air coming out is doing some good is keeping me happy so for tonight I'll hold on to that hope

Be good to know how you get on Paul 🙂

 

[REDSAW]

you did turn off the boiler/pump when you drained down?.

 

[Paul_griff]

Be good to know how you get on Paul 🙂

Many thanks for all your help Diamondgas, as it stands I have got upstairs radiators nice and warm and hot water, boiler still cutting out and cooling then restarting but it is creating heat upstairs (allthough i assume this heat takes much longer to create than usual), downstairs radiators still ice cold so possibly an airlock between floors?
also I am wondering if my pump will bleed correctly in the position it is fitted, I guess the best way to fit to get rid of air is horizontal with the bleed screw facing up?

once again many thanks, I will update tomorrow, in the meantime all advice and suggestions gratefully receivedreceived