Problem with heating water and lots of air in Radiators


Postby andrew-webber » Thu Dec 27, 2007 5:22 pm

Hi There I wonder if somebody could please give me some advise / guidance on how to cure a problem that I am having with the central heating system in a property that I have recently moved into.

I am not very up on these things , but I am very interested to find out more.

I think that I have an open vented, fully pumped system. I have a Baxi Solo RS boiler that is mounted downstairs and an indirect hot water cylinder in the upstairs airing cupboard. In the attic there are two tanks, one a (small) feed and expansion tank and the other a large cold water storage tank for the hot water cylinder. Also in the airing cupboard is a pump and also a silver box with Honeywell stamped on it, which I think is an electrically operated dirverter valve, for diverting the heated water to either the cylinder, radiators or both? I hope that I have worked that out OK?

The main problem that I have is that when the system is heating up just the water in the morning (6-7AM), it is very very noisy (like rushing and gurgling sounds) from within the airing cupboard. The central heating then comes on at 7AM but the hot water does not seem that hot to me (thermostat on the cylinder is set to 60 degrees)

I have just done a test and I initially blead all of the radiators and then switched on the hot water only. Again I got a lot of noise but I noticed that all radiators were getting warm (both upstairs and downstairs) which I think should not be happening as the diverter valve should be stopping the heated water from flowing around the radiators and only allow it to enter the hot water cylinder. Is that correct?

I then turned off the hot water and checked the upstairs radiators for air and even though the system had only been switched on for 20 minutes, one radiator had absolutely loads of air in it!!

Could air be being allowed to enter the system via the diverter valve, which I think must be stuck open as it seems to allow water to flow into both the cylinder and radiators, even though only the hot water was switched on? Would changing this valve be a job that someone like me with limited experience / knowledge could handle, do you think? Or maybe air is being let in via the pump?

Maybe I should just take out a maintenance plan with British Gas and get them to sort it!!

Any help / guidance that anyone can give me would be much appreciated

Thanks very much
Best Regards
Andrew Webber
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Postby marrtin » Fri Dec 28, 2007 10:15 am

Check this topic out.

[url]http://www.diydoctor.org.uk/forums/viewtopic.php?t=7283[/url]

This is probably caused by a badly designed system and needs sorting sooner rather that later. Firstly, try turning down the pump speed setting which may be all you need to do.

On the end where the cable enters your three port valve, you will see a small lever in a long slot. When hot water only is called for, this lever will require reasonable pressure to push it along the slot to the manual position. When CH is called for, this lever should be loose and move freely about.
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Postby andrew-webber » Fri Dec 28, 2007 1:11 pm

Hi Marrtin - many thanks for the quick reply.

I have checked the movement of the lever at the bottom of the valve and it is free and easy to move along to the manual position all of the time, regardless of whether the hot water is on or not.

From browsing the web, I see that you can buy new motors for only £13, which can be fitted (if I understand correctly) without draining the system. From what I can see it is just a simple none polarised motor which switches the valve across. I think that I might be capable of doing this as I qualified in electrical and electronic engineering some years ago.

I realise that it is difficult for you to comment without actually seeing the offending system / parts but would you suggest replacing the complete head (about £100 I think) instead of just the motor.

As an aside, if the lever is in the manual postion, is it supplying both hot water and central heating. I did not want to leave it in the manual position until I knew what the implications are.

I have spoken to the previous occupants of the property and they say the system has always been a bit 'noisy' (for about 13 years!!) but it was working properly when they where last living in the property - which was about 3 - 4 months ago.

So maybe the valve has just seized? - I was thinking about removing the cover on the diverter to see what I find, but I am not sure that I could do anything with it at the moment anyway.

Sorry to be a pain but I have read the post that you suggested and it seems that it is saying that noise within the hot water cylinder is due to the filler pipe from the header tank being in a different place in the circuit to the expansion pipe.
I am not quite sure that I understand what you mean, are you saying that they both need to be on the same side of the pump? Maybe I am not clear on the actual operation of the pipes that connect up to the cylinder.

I assume that there is a pipe going into the top of the cylinder, which is the feed from the cold water storage tank in the loft and that when you mention the expansion pipe, that is a pipe that lets out any excess water / steam from the cylinder and this would just return the excess to the cold water storage tank?

Thanks again for your knowledge and assistance - I find all of this quite interesting to be honest!! (Yes I am sad!!)

Andrew
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Postby andrew-webber » Fri Dec 28, 2007 1:36 pm

I have now turned the pump speed down to setting 2, instead of 3 and the slushing / rushing water noises are a lot quieter - I will see what difference it makes to the heating of the radiators later today.

One point that I forgot to mention, that may reinforce the thinking that there is a problem with the diverter, is that when I switch the programmer to hot water only, I can hear a continuous light clicking from the valve.

Thanks again for your time and assistance.

Andrew
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Postby marrtin » Fri Dec 28, 2007 11:45 pm

Firstly, you could try speed one on the pump. The only problem you may have is that some radiators may not reach full temperature.

Just to confirm try the valve lever with the power to the system turned off at the fused spur. Only then will you be sure the valve is in the DHW only position.

If you remove the cover to the valve, you will see the gearing and electrical assembly is fixed to the valve body by two captive screws. If these are removed the assy will lift clear of the body (it may need gentle persuasion). To ensure the valve is not seized, using a pair of pliers, you should be able to turn the valve mechanism through it's three positions. "A" only open, Both open and "B" only open.

If you decide to replace the motor assy ensure you get the same type (either 5 wire or 3 wire).

Check this topic for information about this valve.

[url]http://www.diydoctor.org.uk/forums/viewtopic.php?t=6443[/url]

(Wish the URL's worked on this site!!!)
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Postby marrtin » Sat Dec 29, 2007 12:14 am

As far as the air being drawn in, the feed from the header tank and the expansion pipe need to be as close to each other as possible. The further they are apart, the greater the possibility that there will be a pressure difference between the two causing either air to enter the expansion or water to be ejected into the header tank.

This is most likely to happen when the pump starts as all the water in the system is stationary and therefore the highest pressures occur.

Imagine the worst case scenario where the expansion is placed slightly ahead of the pump and the feed just behind it. It would not be unreasonable to expect when the pump started, water would be pushed up into the the expansion in to the header tank and drawn down the feed. Yours is in effect the reverse.

In my system here, the two were placed on either side of the boiler in the airing cupboard. That was sufficiently far apart to cause a differential and air to be drawn in, and boy did it do just that. Now it's re-plumbed, it is as quiet as a mouse!!!!
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Postby andrew-webber » Sat Dec 29, 2007 3:19 pm

Many thanks again Marrtin - it is much appreciated. I think that I will take the cover of the diverter valve and have a look later today to verify that it is just the motor that is the problem.

I have switched off the power to the pump and the valve and the lever is still free to move along, wihtout any resistance at all, so I think it must be the valve motor, is that correct?

I understand what you are saying about the proximity of the feed from the header tank and the expansion pipe - thinking about it that is just basic physics, I suppose (I knew that Physics O level would come in handy one day!!).

Today was the first time that the water being heated did not wake me up with 'those noises', although I did have a few beers last night!! I will see how it is over the next few days and then maybe try the pump on speed setting 1.

Many thanks yet again, you obviously have a great deal of knowledge and experience - are you a heating engineer by trade?
andrew-webber
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Postby ndfranklin » Sat Dec 29, 2007 10:58 pm

Hi there

I'm having a very similar problem myself but without the noise and would really appreciate some help with it.

My system is a Potterton Flamingo 50s boiler, not sure of the make of the time controller, a room thermostat downstairs set to 68 (boilers upstairs vented outside, with hot water tank/immersion heater mounted above) a thermostat on the hot water cylinder set to 80 and a honeywell valve.

I've read through this thread and it's made me think it may be the valve although it does sound like it works when I move the little lever on top backwards and forwards from auto to manual. The problem is, whilst the central heating works fine, as does the room thermostat as does the timer/controller, I'm only getting lukewarm water from the hot taps and then it takes some time to warm up, but never gets hot. I've fiddled with that lever before, althogh not really knowing what it did and it didn't seem to make any difference.

So if I'm understanding this thread correctly, if I switch it over to manual and get hot water out tommorow, that means the valve is not auto-switching properly. If I still don't get any hot water, the valve is seized and probably needs replacing?

Thanks in advance

Nigel
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Postby andrew-webber » Sun Dec 30, 2007 9:19 am

Hi Again – just a quick update, as I finally had some time to get the cover off the diverter valve yesterday and study it’s operation.

When I first started looking at this problem and you mentioned the lever at the bottom of the valve to me, I noticed that the valve lever was about in the middle of the long slot. I am not sure why it was there, but I think it should be at the auto position, for normal operation. Is that correct?

When I turn on the DHW only, the lever is actually free to move along to the manual position, except for the last 5mm or so, which does actually require some pressure to move it to the end of the slot. If I then let go of the lever, it moves back to about a central position!!


If I turn the central heating on and the DHW off, I can see that the spring in the valve is stretched (the lever if free to move along the complete length of the slot). So it appears that the valve is actually working and is not seized??

If I turn the central heating off and only switch on the DHW, with the level in the auto position, I can just hear a lot of clicking from the motor and I can see the spring trying to be stretched, but it is moving straight back and thus not actually changing is length/position.

Thus I think that I still have a problem with the operation of the diverter valve, as I am still getting the radiators being heated when DHW is only being called for and I suppose thinking about it logically, it is only this valve that is responsible for that. I can only assume that the wiring etc is ok, as I am told by the previous occupants of the house that the system was working ok before they moved out ( the properly was left empty for about 3 months or so before I moved in). I think that when I am feeling a bit brave, I will remove the motor, as suggested, and check the actual operation of the valve.

Thanks
Andrew
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Postby marrtin » Sun Dec 30, 2007 11:05 am

Aw shucks, your making me go red! Thanks for the compliments.

Although it is not my main job now, I have been installing heating systems for over thirty years. I only work on heating now once or twice a month when a Corgi colleague gets stuck with a big installation.


The motor assy incorporates spring return gearing, and assuming the lever is free, as soon as the power is removed, you will hear the valve returning to the rest position with only the DHW port open. So if this is not happening, either the valve is seized or the gearing assy is worn out.
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Postby andrew-webber » Sun Dec 30, 2007 2:25 pm

Thanks again Marrtin - I really do find this stuff quite interesting, for some reason.

As you say, when I remove the power to the diverter, the spring returns to the 'closed' position and I can hear a slight whurr, which must be the motor returning to it's home position.

If I then re-apply the power, the position of the motor / spring does not change initialy, but if I understand you correctly this should be ok as it is in the DHW position.

Now, if I switch just the hot water on, the motor turns and the spring is stretched by a few mm but then the clicking occurs where is seems that the motor is trying to turn the valve a but more but the spring is holding it in position - or more likely the actual valve will not move any further.

I suppose that I really need to get the motor off and see if I can turn the valve manually. I just do not want to remove the motor and then not be able to run the central heating - I am not bothered about the DHW as I can heat that via the immersion heater.

Thanks again Marrtin. I think that you have inspired me to maybe go on a basic central heating course and try to get some basic background knowledge and get more confident with this stuff.

Best Regards,
Andrew
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Joined: Thu Dec 27, 2007 5:01 pm


Postby marrtin » Mon Dec 31, 2007 12:02 am

Removing the motor is a simple task, and you will not have any problem running the heating whilst it is removed (assuming the wiring is connected).

From how you describe, the valve appears to be working correctly except for the noise. When both CH an DHW are called for, the valve needs to be held in the centre position with both ports open. This is achieved by supplying 230v to the motor until it reaches the centre point. At that point it operates a microswitch which reduces the voltage down to 100v, sufficient to hold the gearing stationary against the spring return. If part of this mechanism fails, the motor will constantly hunt back and forth in an attempt to maintain the centre position.
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Postby andrew-webber » Mon Dec 31, 2007 1:01 pm

Thanks again for the additional information Marrtin.

I am away for the new year period and so will get brave in the new year and get the motor off and see what is happening exactly.

I will report back on progress.

Andrew.
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Postby andrew-webber » Tue Jan 22, 2008 2:13 pm

Well I have replaced the mid position / diverter valve and all is now working fine.

Thanks again for you help Marrtin
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Joined: Thu Dec 27, 2007 5:01 pm


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