Central Heating not firing

Hi all
I am a complete amateur trying to get my central heating going again.
I reattached an old radiator, bled it and all seemed fine then I noticed that the downstairs radiators were all cold. Upstairs were lukwarm all of a sudden.
I assumed an airlock but could not find air in any of the rads. Then I looked in the attic and found that header tank was empty (and dry). Fixed valve on stop cock and that seems to be ok now.
I ssumed system airlock. We don't seem to have a bleed valve on the system in this house so I drained it down and refilled it bleeding all downstairs and then upstairs.
Now when switched central heating on again, the water does not seem to flow and boiler does not fully ignite (pilot only).
Can anyone detect anything screamingly obvious that I have neglected to do?
Pump is definitely working by the way.
Jules
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Have you bled the pump? Should be a big (plastic?) screw you loosen to let water out. Air in the pump can prevent water circulating.
HTH Dave R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is not a bleed screw.
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 08 Dec 2003 21:03:34 +0000, geoff wrote:

OK it's an access cover but it serves to let any air that's in the pump out.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

bearings are between the water and the screw cover.
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 09 Dec 2003 00:04:11 +0000, geoff wrote:

Perhaps I should have said it serves to let enough of the air out to get the pump primed.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It's a grundfos selectric.
Can't see any screw except the big one in the middle which I have removed and replaced to no avail.
It spurted out a little water and the pump rotor is visible. Seemed to be spinning happily.
Jules

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

With my pump there is a big black plastic screw in the middle of the cover. If I unscrew this a few turns then jiggle it water comes out. This effectively bleeds the pump. Had to do this last time I drained and refilled because of symptoms like yours - pump running but no heat to radiators. After some jiggling and spurting (plumbing can be fun) the note of the pump changed, there was a 'shoosh' noise, and everything started working again. If your setup is like mine (pump in airing cupboard by hot water tank, higher than highest radiator) then you probably got into the situation where the upstairs radiators had water but the pump was running on air. This can cause an airlock in the feed down from the header tank to the system, and/or in the pump.
(1) Try jiggling that central screw a bit more - from what you said you didn't get a lot of water out so you may still have mainly air in the pump. If the pump was full of water and pumping at presssure I would expect water to come out quite forcefully. Also, if you have a speed switch, try increasing the speed of the pump.
(2) Try to clear out the feed from your header tank to the system. You can do this from the top or the bottom.
(i) from the top: tie up the stop cock and then drain the header tank using whatever drain you have at the bottom of the system. If your header tank will not drain because of an airlock or blockage, then siphon it out into the bath using a hosepipe. This also cleans any crud out of the header tank. Disconnect the feed pipe from the bottom of the tank, and connect a hose pipe to it with a jubilee clip. Other end of the hosepipe on a mains cold tap. This will pressurise the system and then you can bleed all the radiators and hopefully clear all the air out. This is especially effective when gunge has been sucked out of the header tank into the pipework because you let it empty.
(ii) from the bottom: attach a hose pipe between a cold mains tap and your drain tap at the bottom of the central heating. Open the drain tap and turn on the cold tap. This will pressurise your system and should drive water up the filler pipe to the header tank, then out the overflow (check carefully first that your overflow is working). This should shift any air out of the top end of the system above the level of the upstairs radiators.
Do this slowly and carefully! Too much oomph with the cold mains, or a poorly tightened jubilee clip, can rain on your parade.
I would be mildly surprised if you boiler had overheated because the thermostat should shut it off as soon as it is up to temperature, and you haven't been running it dry as far as I can tell because your upstairs radiators were still warm, therfore at least partly full of water.
My (virtual) money is still on an airlock in the pump.
Cheers
Dave R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

Er.. what about the expansion pipe? Unless I'm missing something(!), rather than pressurise the system, mains water will flow up the expansion pipe into the header tank - and will promptly pee out through the (now open) bottom connection!
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Good point - I am now racking my brains to remeber how I did this when I had to clear my system out.
My first guess would be that I put a bung in the hole out of the tank, or a stop end where the copper was disconnected from the tank coupler. However to pressurise the system you would have to close off the expansion pipe as well.
Second thought is that I had my trusty helper working the tap, and once water came out of the expansion pipe then the top end of the system was clear of air and crud. Probably best to put a bucket in the (empty) tank under the expansion pipe to save having to siphon the water out again.
I describd this correctly (I think) a few months back - will have to Google back and find out.
Thinking further, if you attached the hose to the expansion pipe with the down pipe still connected, then this would force water round the system and water should come up the down pipe. This again would clear air and crud out of the top end of the system. However ISTR my expansion pipe is 22mm so would need some adapting to take a hose pipe (which just fits 15mm).
Apologies to the OP for my senior moment :-(
Cheers Dave R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

With little or no flow, the boiler may have overheated and tripped out on its over-heat stat if it has one. This has to be manually reset by pressing a button before the boiler will fire again. Your boiler User Handbook should explain it.
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
No handbook is available. Can't find any info on this boiler actually
Ideal Stelrad W2000
Jules
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

Hvae you tried the manufacturers to see whether they can supply a manual? You can email them at customers snipped-for-privacy@idealboilers.com or phone their Technical Helpline on 01482 498663
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Much obliged.
Have now sorteed this problem though. I ran the system with the drain open and my wife in the attic keeping an eye on the header tank level. Did this for about 20 mins and then ran it as normal.
The return pipe got warm fairly quickly which was a good sign, the boler cut in and cut out when the water got to hot (another good sign) about an hour later the rads started to warm up slowly.
This morning it is back to normal with the extra radiator.
Much obliged to all.
Jules
or phone their

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello Julian

Could be a proper airlock. Hosepipe on the drain and a watchful eye on the header tank can fix that...

...or, more likely, the boiler's locked itself since it overheated when you ran without water. Take cover off and look for an obvious reset button. Failing that, rifle drawers and then google for manuals. Failing that, ask in here giving make and model.
--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Simon
Actually I let it cool down and it started up again but stopped after a while when the water coming out of the boiler was very hot.
Now only the Pilot stays on but the pump keeps pumping.
When you say hosepipe on the drain I suppose you mean run the system with the drain open and somebody in the attic making sure that the header level doesn't get too low?
Jules
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In an earlier contribution to this discussion,

I assumed he meant squirt mains water in through a hosepipe, and make sure that the header doesn't overflow. Perhaps Simon can clarify?
--
Cheers,
Set Square
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello Julian

Nono, the other way around. The method is the same as backflushing a hot water tap.
You connect a hosepipe to the drain connector of the CH, open the drain and turn on the hosepipe's tap. Forces water back through the system (although by the shortest route, so won't get an airlock in a badly designed system).
The reason I say to have someone watching the header tank is indeed to stop it overflowing. It should have an overflow pipe, but quite often these are undersized and/or blocked. Don't trust just this alone!
--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.