We moved house before Christmas and boiler started playing up. It's since had a full service, all parts changed that could be changed, by the boiler companies engineers. So we know the boiler is working properly.

Central heating is as follows:

Basement - under floor heating, working fine Ground floor - under floor heating, working fine 1st floor - 3 radiators (2 in bedrooms, with thermostatic valves, 1 heated towel rail in bathroom) Attic 4 radiators (2 long but not very tall radiators, these run along the floor where the eaves meet the floor, 1 radiator with thermostatic valve, 1 heated towel rail)

The problem we are having is this, all first floor radiators only get hot some of the time, sometimes hot at the top, cold at the bottom, sometimes they come on and are OK, sometimes they come on and are luke warm, sometimes they come on, are OK for a bit then turn off.

Very, very annoying. We've bled them but this doesn't seem to have made any difference. We've had plumbers out (cost a fortune) we've had the whole system flushed, but it's still the same. Also the two long radiators in the attic are doing the same thing, although the other 2 radiators in the attic are really hot. The plumbers said it's air in the system and it will keep happening, but how long are you supposed to wait until it clears. And does it just clear itself? When we bleed the rads no air comes out! Finally, sometimes the pipes leading to the problem rads up through the floor are warm and sometimes freezing. Should these pipes not be hot all the time (if heating is set to be on)?

Oh and we know that these radiators work, cos before the boiler problem they were really hot.

Any help appreciated :(

The problem we are having is this, all first floor radiators only get hot some of the time, sometimes hot at the top, cold at the bottom

Thats very odd, it's usually the other way round.

Perhaps the bottom of the radiators are full of "silt" (or whatever).

It is usually one of two things: air-lock or silted up radiators. But as you have bled the system and also had it flushed out this seems quite strange.

The only other thing that springs to mind is the width of tubing that carries the water from the boiler to the radiators. On some older houses, this tube is microbore, that is, narrower than the more standard widths of copper tubing (15mm, 22mm and 28mm). It could be as thin as 8mm (or 10mm).

With more powerful and reliable boilers (which now have to be condensing type boilers) the narrower gauge pipes might struggle to carry the water through the system. This happened to us some years back when we had a new boiler fitted. The thought of having to replace the microbore pipe with standard 15mm and 22mm hastened our decision to sell the house.

If the problem doesn't remedy itself, PM me and I'll forward details of plumbers who can give you advice (we being plumbers merchants ourselves although I know nothing about plumbing personally, being the company's 'number cruncher').

Finally, if you're the real Jarvis Cocker, can I have signed photograph please?

Do you have a combi boiler or a conventional tank fed system? You also mentioned thermostatic rad valves...are these fitted to all the radiators or just some? When you bleed the radiators, do you get water spurting out? Just a few elementary questions to give us a better idea as to what the problem could be.

Is the boiler actually big enough to cope with that many rads?

Sometimes, if a system is added to - eg when a loft is converted - the boiler can no longer cope.

It does sound like air in the system though, which would be why you get random cold spots. The trick is to bleed the rads that are cold at the top whenever that situation arises - so keep your key to hand ;)

To answer a few questions:

It is a combi boiler, the whole system is only 2 years old. Prior to that there was no heating in the house. The boiler, accoring to the engineer is big enought to heat our house and the two ajoining house.

Thermostatic valves are fitted to all the radiators, except the two towel rails. Yes I get water coming out when I bleed the radiators. And it doesn't help them to heat up after it's been done. They just heat up when they fell like it.

OK. on the front of your boiler, you should be able to see a pressure gauge and the needle should be showing approx 1-2 bar pressure. Go and take a look and report back with the pressure reading.

You may also be having a problem with your pump. If there's air in the system then the pump doesn't work as efficiently as it should.

I'm not at home at the moment but I've checked the pressure and it's fine, what it should be about 1 1/2 bars. Plumber showed me how to top it up when water has come out of the radiators.

If it was the pump wouldn't the bolier engineer have checked this out?

Presumably, you have got all the Thermostatic Rad Valves ( TRV's ) fully opened ie set at MAX ?

I can only tell you what happened with my system in a previous house. Everything was checked out and working but we got air in the system. When this happens there is little or no resistance in the pump as it's working against air rather than water. There should be a cut out mechanism to prevent the motor burning out and this was what was happening. After bleeding the system and sealing it we eventually sorted the problem out.

Yes all the TVR's are set to fully open. The little radiators in the attic, pipes are hot, radiator has no heat at all!

The problem we are having is this, all first floor radiators only get hot some of the time, sometimes hot at the top, cold at the bottom, sometimes they come on and are OK, sometimes they come on and are luke warm, sometimes they come on, are OK for a bit then turn off.

:(

Could it be that the TRV's are simply doing their job by turning off the radiators as the room reaches temperature? Do the rads get hot when the boiler first fires up, and then start to close down as the house warms up?
Sorry if I seem to be over simplfying this, but you need to check the obvious things first before you start getting expensive items like diverter valves and circuit boards replaced.

I had this exact problem in my house. The system wasn't working properly so any heat that was transferred upwards was done by gravity rather than the pump. Solved it by having the pipework that comes directly off the boiler replaced with thicker pipes and a new pump.

No it's not that because even when the heating first comes on they don't get hot.

Does the boiler deliver all the hot water ok, or is that problematic as well?
On a combi system, the pump is used to generate the hot water via a diverter valve and as such you would be experiencing problems with the hot water as well as the c. heating.

No the hot water is fine, the diverter valve was also replaced by the boiler engineer.

In that case, we seem to have exhausted all the obvious possibilities, but, if it was me ,I would be tempted to remove a couple of the TRV heads from the valves ( just unscrew them or slacken the retaining clip and pull off ) to see if it allows circulation. After that mmmmm.... may have to start looking at the control board, modulation etc (costly).
BTW.... Did you actually see the old diverter valve which the enginner says he changed?

If the divertor valve was replaced this may be the problem. Is there an external indicator on the valve to show which way the water is being diverted? If, after using the hot water, this doesn't re-set to ch then it's broken.

2 circuit boards were also replaced by the engineer and yes I saw the diverter valuve that was replaced, infact he left all the parts that he took out.

I agree with Max at this point, it's maybe worth looking a little closer at the operation of the diverter valve. This item tends to be the usual suspect in these cases. You can buy a seal replacement kit for these for about £10-15 which would be far cheaper than changing the whole thing if you are going to DIY. A plumber is more likely to want to change the whole valve as it's easier and more profitable. I'd still have a go at removing one of the TRV heads, you never know, the whole batch could be calibrated wrongly and therefore closing down much too early, it's got to be worth a try especially as all the main boiler parts have been changed to no avail.

If it's the diverter valve the not working why are the other radiators upstairs and the under floor heating all working OK? Wouldnlt the whole CH system be affected if this was the case?

The diverter valve could be sticking, ie only partly open and so limiting the flow to the heating circuit

So I guess that means getting a plumber to come and look again, more expencehttp://www.sheffieldforum.co.uk/images/smilies/frown.gif

Oh and thanks for all the help and suggestions everyone.

Jarvis, do come back and let us know what the problem was when you eventually get it sorted.....just to satisfy our curiosity! Cheers.

Stopmessing about with plumbers etc. You need a good diagnostic heating engineer. Anyone who tells you it is the circuit board , without checking all possibilities is a cowboy. You are putting good money after bad as any heating engineer will tell you

I had a similar problem when I moved a rad for someone. After re-filling the system and bleeding all the rads, they weren't working properly.
I sorted it by turning off all the rad valves at both ends of the rad, stating the pump going, then opening each rads valves to move the airlock round the system and into a rad. The air was trapped in a section of pipework so no amount of normal bleeding would have shifted it.
It was a real pain to solve, but it worked eventually.
Hope this helps

Well touch wood we seem to have sloved it this weekend. We turned off the radiators that were working OK, just left on the ones that were being temperamental, left heating running for a couple of hours, radiators seemed OK, then we gradually turned on the others that we knew were OK before and it seems to have done the trick. Up to now anyway! Thanks again for all the help.

It’s my turn with a problem now :rolleyes:

The other morning when the heating came on, it made a weird noise like a bubbling type of noise. I rang me dad and told him what it sounded like, he said your radiators need bleeding. So we did that, the last radiator we bled, all the air came out but no water dripped from it.

We closed it back up and put the heating on, we heard no weird sounds so we thought job done. We checked the radiators after an hour or so and they were all stone cold. :(

I checked the pump and that was running ok, I looked at my boiler and only the pilot light was lit but it was only a small flame, I took the panel off and as soon as I did the pilot light went out!

I haven’t been able to light it since, as soon as I release the button it goes out? Are to two things related??

Any help will be much appreciated :)

hi owlsman
it sounds like your thermocouple has packed in, you should be able to get a replacement easily enough, when the pilot won't stay lit this is usually the culprit-as for your other problem, sorry dunno:(

john.

Is it a combi boiler? If so, the pilot light won't light the burners unless your water pressure is correct. Once the pilot goes out then you may also have a problem re-lighting it until your pressure is back up.

Is it a combi boiler? If so, the pilot light won't light the burners unless your water pressure is correct. Once the pilot goes out then you may also have a problem re-lighting it until your pressure is back up.

No it isnt a combi boiler, a bit more info for you, we still have hot water as we have a seperate water heater in the bathroom.

Thanks for your replys :)

when u bleed the rads u need to do it until water comes out otherwise there is still air in the system if water dosnt come out then the ballcock in the loft tank may be stuck, its the small tank and it should have about 5 to 6 inches of water in it this could be the cause of the noise also check it out because you will burn the pump out if it runs dry. as for the pilot u may have disturbed something when u removed the case and probably not related.

when u bleed the rads u need to do it until water comes out otherwise there is still air in the system if water dosnt come out then the ballcock in the loft tank may be stuck, its the small tank and it should have about 5 to 6 inches of water in it this could be the cause of the noise also check it out because you will burn the pump out if it runs dry. as for the pilot u may have disturbed something when u removed the case and probably not related.


I did bleed them all, just the last one, i left it open for ages and nothing came out :confused:

Ive checked the tank in the loft and that seems to be fine.:huh:

Ive got someone coming to have a look on Thurs, hopefully the mystery will be solved.... Thats if i havent froze to death :(

Thanks for your reply :thumbsup:

That Magneteer chappy seems to be confusing the issue it sounds like he may be more suited to the telephone system (BT). PS As a plumber I would be turning the pump onto full, make sure all rad valves are open. When each radiator gets hot turn rad valves down to half open.

Well I had a chap come yesterday and the boiler had overheated and me being a bit :huh: didnt reset it!

Everything was running ok, that is until this morning.

The heating went off at 11pm last night, and was set to come on at 4.30am.

Got up at 5.30am and the rads were ice cold!!

Looked at the boiler and it gone out again (overheated).

The pump was making a rather loud noise, he said if it overheats again there is a problem with air getting in.

Got to give them a ring now and see if they can come out and sort it for me.

Any sugestions to what could be wrong??

Thanks again.

Well the problem is back! It's gradually got worse over the week. So my next question is does anyone know a heating engineer? Please PM me if you do. Thanks

You have already proved that this problem has nothing to do with the boiler or any of its components and that the fault lies with the circulation of water around the heating system. You can cure this easliy yourelf by BALANCING the system. Firstly, get the boiler running at its normal operating temperature, and then as Rogdodge rightly points out, make sure all radiator valves are fully open, including the lockshield valves which are on the opposite end to the TRV's. To open the lockshield valves you will need to remove the plastic cap with a screwdriver, and then using pliers or grips, turn the square drive open (anti clockwise) until it stops. Now, on the radiators which are fully hot, turn the locksheild valve to half open. This should throttle down the volume of water entering the radiator and force it into the ones which are sluggish. After a few minutes you should notice some improvement in the cold radiators. If not throttle the lockshield valve down a bit more and so on until all the rads are of an even temperature, ie balanced.
Give it a try before forking out.

thanks Magneteer, I'll give that a go this weekend. Cheers again

Well the engineer ran out of time on friday!!

Ive got to wait until monday now, he seems to think their is some kind of blockage in the header tank.

I hope its a quick job and is fairly cheap :confused: :help:

Well, the mystery has finally been solved!! :rolleyes: *wipes sweat from brow*

There was a blockage in the pipe that the water runs down.. Problem solved???? No ... he took the boiler apart, and hey presto... the controler PCB had burnt out...

So, they have ordered another one....But i will still be freezing my threpney's off till they get the part fitted...:rolleyes:

EDIT: Heating got sorted last friday :thumbsup:
ahhhhhh warmth......... :)

Hi, well it seems we may be getting somewhere with the mystery if the cold radiators. I've balanced and bled and still nothing. We've now noticed that the radiators don't start to get warm until the hot water is running ie having a shower in the morning. Once I've been in the shower the radiators kick in and get nice and warm. Can anyone offer any suggestions, is it the boiler? Don't want to waste any more money getting someone in til I have an idea what's wrong. Any help would be greatly appriciated.

Cheers

Sorry to hijack the thread, but I've got a question that's been bugging me for some time. A lot of houses I've seen in Sheffield have no main thermostat. Is this 'normal'?

A house I've been looking at has a combi boiler, and TRVs on the radiators (I've yet to find out if they've left one without). In the absence of a room thermostat, would the boiler still know when to stop heating the system? Or would the heating bills be astronomical because the boiler wouldn't stop heating? Should I steer clear of a system like this?

EDIT: There is a programmer so I can set what times it comes on and off at, but in winter that will be a lot of the time. I just don't want it permanently blazing away. Also, there's no hot water tank by the look of it, so any hot water would be instant from the boiler I presume. Why then, does the programmer allow me to turn hot water on and off at given times?

Sorry to hijack the thread, but I've got a question that's been bugging me for some time. A lot of houses I've seen in Sheffield have no main thermostat. Is this 'normal'?

A house I've been looking at has a combi boiler, and TRVs on the radiators (I've yet to find out if they've left one without). In the absence of a room thermostat, would the boiler still know when to stop heating the system? Or would the heating bills be astronomical because the boiler wouldn't stop heating? Should I steer clear of a system like this?

EDIT: There is a programmer so I can set what times it comes on and off at, but in winter that will be a lot of the time. I just don't want it permanently blazing away. Also, there's no hot water tank by the look of it, so any hot water would be instant from the boiler I presume. Why then, does the programmer allow me to turn hot water on and off at given times?

My house is exactly like this, i dont have a main thermostat. I thought it was a bit strange at first,but it seems to run ok (when you have got a blockage in your pipes *see above*).

I dont have a clue how it works, but it hasnt caused any problems with high heating bills. :)

If you have TRV's fitted to all your rads, then you are controlling the temperature of each room individually and don't require a room stat ( which will switch the heating in the whole house on and off as the temperature varies). TRV's are a far more efficient way of controlling the heating. The combi boiler is fitted with an internal bypass so that if all the TRV's are closed, there will still be circulation within the boiler itself. A modern combi will also modulate to meet the demands of the heating load ie. it will turn itself down to simmer, once the heating is running at it's optimum temperature, or increase if it drops. Far more efficient than older boilers which would just keep batting away regardless.
Jarvis, your problem now seems to point once more in the direction of the diverter valve, although this is by no means certain.

A common mistake is to bleed the system when the heating is on. Only bleed them when the heating is off. Start at the top and work down , ten bottom up. other wise turn the bottom radiators off and force the sysytem.

I wonder if anyone can help me, please!
I have Worcester Bosch 240 LPG boiler, heating works fine, and water gets hot. When it feels like it, thats is! water is hot all day, and then it becomes very tempremental as of a night time! :confused: