central heating not working after new radiators fitted

pinkllama

hi all,

i have just replaced 2 radiators with larger ones in my flat as it took hours to heat the flat up.

it's an open system, ie there is a header tank in the loft.

i refilled the system and bled all the radiators.

the problem now is that the boiler fires up for a few minutes and then switches off - not heating any of the radiators.

prior to fitting the new radiators, it worked fine.

i understand that the boiler is switching itself off as a safety measure as it is too hot.

i think that there could be an air lock in the boiler that is preventing it from working/ pumping the water around the radiators.

its currently -5c outside and i desperately need some help!!

one thing that could be a clue as to why it's not working is, when i refilled the system the header tank let loads of water in for a few seconds then it just trickled in for the next hour or so before all the radiators were full of water.


any advice?

thanks

update - when i turn the boiler on, it sounds 'hollow' as if there is no water in it

keystone

I'm pterry sure you still have air in the system. You have to get it out. Just because the rads produce water when you operate the bleed vaves doesn't mean that the whole system has water in it.

Also if its a flat I'm not totally convinced that replacing the radiators was necessarily the right thing to do. There could be all sorts of reasons for poor circulation. But you would need someone to look at it for you. In the meantime you need to make sure all the air is out.

Sorry but theres no more to say really.

Cheers

keystone

pinkllama wrote: »

one thing that could be a clue as to why it's not working is, when i refilled the system the header tank let loads of water in for a few seconds then it just trickled in for the next hour or so before all the radiators were full of water.

This para definitely says airlock to me.

Cheers

pinkllama

thanks for the reply.

how can i get the air out, other than by bleeding the radiators?

keystone

Keep letting water out of the bottom of the system until the air settles in radiators then it can be easily bled.

If you have a HW cylinder you can crack one of the joints where the primary joins the cylinder - that usually lets some air out.

As long as you don't run it dry cycle pump speed through the three speed settings. That alters the pressure in the pipework and helps to move the air along. You've just got to keep with it really. Eventually there will be enough water in the system for circulation to start occuring. Then it will get easier as the pump starts to move it around and the boiler heats it up.

It could all resolve itself in an hour - you could be doing it all day.

Best of luck.

Cheers

Canucklehead

Hi

You might also try venting the pump.
Pink Grundfos has a large silver screw in the middle,undo it (not all the way )
Myson has a large black nut, same idea though.

Any other air vents on the pipework? Follow the pipe up to the cylinder top connection on the side ,any tees ? Small brass knurled nut? Maybe even an auto air vent with the cap screwed down.
Try venting under all conditions ie heating on /off, hot water on /off in all combinations.
The ultimate problem will most lkely be a blocking cold feed and/or the pump is full of gunge .

GSR

pinkllama

bit of success.

there are 4 rads in the flat.

2 ( in the kitchen and bathroom) are now getting hot water to them. i keep bleeding the one in the kitchen (closest to the boiler) every few mins.

the rad in kitchen is 50% hot
the rad in bathroom (towel rad) is 100% hot

on looking at the pipework, the 2 rads that aren't working at all, are on separate pipework, which goes up from the boiler into the loft, then back down into the bedroom and lounge. all this pipework is completely cold. there is another bleed valve on one of these pipes, i've opened it but only water comes out.

should i open this valve for a while, feeding into a bucket to see if any air comes out?

thanks for any help - i seem to be half way there!

really trying to avoid calling out a plumber, would love to complete it on my own seeing as i've made it this far.

bitemebankers

One thing you can try - not strictly best practice - is to attach a length of hose to your drain !!!!, and attach the other end to a mains cold water tap. Open the drain !!!! then open the tap - this will force water back up though the system. You will need a friend / partner to keep an eye on the feed/expansion tank upstairs to make sure it doesn't get too full. This procedure will clear pretty much any airlock. However, if you apply too much pressure for too long, you could damage your system, so please be careful.

pinkllama

Officer_Dibble wrote: »

Turn off the two with heat as you've got circulation to them. Turn off one of the cold rads and run the system with only one until you get some heat at the rad then swich and get the other one warm. Once you get the two cold ones running open each of the others until you get heat at all the rads.

Once you have circulation to all of the system, you may need to install a cleaner into the system.

When you bleed the rads is the water black?

the water is rust coloured

i've already put some cleaner into the system as one of the rads that i replaced was blocked in the middle.

i'll try turning off the 2 that work and see what happens.

Canucklehead,

i did find 2 knurled brass bleed valves in the loft, one of lets out a tiny bit of air if a open it every half hour.

pinkllama

is it a good idea to bleed the 2 rads that aren't working, of some water. hoping that air will eventually come out?

keystone

pinkllama wrote: »

the water is rust coloured

Not good. As well as air you prolly have a blockage as well. If the F&E tank gets hot when/if you get it working then its pumping over and all you are doing is reintroducing aerated water which is contributing nicely to corrosion = rust.

i've already put some cleaner into the system as one of the rads that i replaced was blocked in the middle.

Before or after you changed the rads and is it still in there?

TBH you really do need to get someone in to look at the whole system for you. I'd suggest today if at all poss.

Cheers