# Underfloor heating system problems (or how to check a meter)



## Pudsey_Bear (Sep 25, 2008)

I have a little problem (cream won't fix it) one of the pumps on our CH doesn't seem to be working, so I took the top of to see if it was a mechanical or electrical fault.


I get 236 V across live/earth but no Volts across live/neutral, not being a sparky, I'm not sure what this means.

As for the title, a while back I was getting 275 volts at the sockets, the electrical company came out and said it was reading 245 volts and within limits, now I get 236 volts so am wondering if there's a simple (cheap) way to check my multimeter, which is a Alphatek tek255.

Kev.


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## rayc (Jun 3, 2008)

*Re: How do you check a multimeter*



Kev_n_Liz said:


> I have a little problem (cream won't fix it) one of the pumps on our CH doesn't seem to be working, so I took the top of to see if it was a mechanical or electrical fault.
> 
> I get 236 V across live/earth but no Volts across live/neutral, not being a sparky, I'm not sure what this means.
> 
> Kev.


It is telling you that the Neutral leg of the supply is open somewhere.

As for the meter it is propably within it's spec. It is best on ac to use it just as an indicator and not get hung up on the actual voltage.

Ray


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## philoaks (Sep 2, 2008)

*Re: How do you check a multimeter*



Kev_n_Liz said:


> I have a little problem (cream won't fix it) one of the pumps on our CH doesn't seem to be working, so I took the top of to see if it was a mechanical or electrical fault.
> 
> I get 236 V across live/earth but no Volts across live/neutral, not being a sparky, I'm not sure what this means.
> 
> ...


In work we use multimeters that have to be accurate. Once a year they are sent off to a company who "calibrate" them to ensure that they still read within limits.

For normal domestic use, as Ray says, it isn't critical that it is accurate and just an "indication" of a mains voltage should suffice.


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## Pudsey_Bear (Sep 25, 2008)

*Re: How do you check a multimeter*



rayc said:


> It is telling you that the Neutral leg of the supply is open somewhere.
> Ray


Thanks Ray, but what does that mean exactly, is my pump goosed or is it the wiring, we had a sparky in yesterday working on the CH electrics, although he didn't touch the pump itself he was working on the thermostat link to the boiler.

Kev.


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## sallytrafic (Jan 17, 2006)

Well its only an indication, not proof, that the fault lies elsewhere than your pump. It could be a disturbed contact or there might be a relay or switch in the neutral leg that is faulty.


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## davesport (Nov 12, 2006)

If the neutral side is open, the pump won't work. You'll have to find out what's causing the open circuit on the neutral side. So don't write the pump off yet, it may well be OK.

If the leccy's been in about the wiring that would be a good place to start faultfinding.

D.


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## zappy61 (May 1, 2005)

Hi Kev,
As you explain it it sounds like you have 240v going to earth which is not good and if true I am surprised you have not tripped the breaker or blown the fuse. You say one of the pumps, how many have you got? What is the pump and what does it do? Is it on the closed circuit to the radiators or does it do some other job? How is it controlled via room thermostat or the controller?

Graham


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## Pudsey_Bear (Sep 25, 2008)

Hi Graham,

We have 3 pumps altogether, one on the boiler, one upstairs, and one on the ground floor, it's an underfloor system, and it's been the bain of my life for over two years, we just replaced a Baxi Barcelona system boiler for a Ferroli Combi, to try and get it sorted.

I have just put a plug on the pump to get it going, but it seems to be making it worse. IE with the pump off the pipes work around it gets too hot to touch, turn it on and it goes cold, even if I leave it for a while to maybe circulate all the cold out of the system it stays cold, turn it off and it warms up.

I had no part in this set up, but it almost like the pump is pumping the wrong way somehow.

I'm going to Google underfloor flow diagrams to see if it suggests anything.

Kev.

PS the upstairs is nice and toasty warm as it should be.


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## zappy61 (May 1, 2005)

Well if the pipe goes cold when the pump is circulating then it is pulling cold water from somewhere. Do you know what type of central heating system you have? Is it open with a header tank or closed with a filling loop off the cold water main? When you connect the pump to the electrical supply can you tell that it is working? Kevin just a thought, are two of the pumps on the upstairs and downstairs underfloor systems? If so the are probaly controlling the flow & return mix in each circuit and should be controlled by a room stat. If so make sure there is no fault on the stat or that the mixing valve between the flow and return is working ok.



Graham


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## rayc (Jun 3, 2008)

zappy61 said:


> Hi Kev,
> As you explain it it sounds like you have 240v going to earth which is not good and if true I am surprised you have not tripped the breaker or blown the fuse. You say one of the pumps, how many have you got? What is the pump and what does it do? Is it on the closed circuit to the radiators or does it do some other job? How is it controlled via room thermostat or the controller?
> 
> Graham


Kev said he had 240v between Live and Earth not that the Live was at Earth potential . This is normal as Earth and Neutral are connected to the same place back at the power / sub station.


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## zappy61 (May 1, 2005)

rayc said:


> zappy61 said:
> 
> 
> > Hi Kev,
> ...


Thanks Ray, Just interpretation I guess.

Graham


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## rayc (Jun 3, 2008)

*Re: How do you check a multimeter*



Kev_n_Liz said:


> rayc said:
> 
> 
> > It is telling you that the Neutral leg of the supply is open somewhere.
> ...


It means that the Neutral supply is not connected to the pump. On my system, which is very basic and typical of installations in the early 90's, the Neutral is permanently connected to all the components of the system and the Live is switched by the thermostats to switch the pump and boiler on when called for.

It is very difficult to fault find remotely on your system without knowing the "Plan" that it is wired to.


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## rayc (Jun 3, 2008)

Kev_n_Liz said:


> Hi Graham,
> 
> I have just put a plug on the pump to get it going, but it seems to be making it worse. IE with the pump off the pipes work around it gets too hot to touch, turn it on and it goes cold, even if I leave it for a while to maybe circulate all the cold out of the system it stays cold, turn it off and it warms up.Kev.
> 
> PS the upstairs is nice and toasty warm as it should be.


I would guess that without the pump running it is getting hot by conduction through the pipework from the boiler. When you power the pump up through the 13A plug and the water gets cold then obviously it is circulating and you know the pump is ok. My second guess is that a Diverter valve is not being switched and that the water within the ground floor rads is just circulating and with no feed from the boiler.

My first action would be to find out what is happening to the Neutral supply to the pump. Perhaps they are using Neutral switching and there is a problem with the switching of the pump and the diverter valve, which my 3rd guess is from the Thermostat that controls the ground floor.


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## wobby (May 1, 2005)

If your getting a reading between live and earth that is not a sign of a fault., quite the contrary it mean that your live circuit is OK. If your not then getting a reading between live and neutral you have a neutral fault somewhere. You will need to trace back the neutral wire and see if it has become disconnected.

Earth goes as it states straight to earth. Neutral goes via the fuse-board RCB and then to earth. 

Wobby


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## davesport (Nov 12, 2006)

Kev, do you have a solenoid operated valve anywhere or is the system simply controlled by the operation of the pumps ?

Do you know which circuit the pump in question is in ?

Is it possible for the pump to be installed the wrong way, in effect putting the pump in the return side ?

D.


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## Pudsey_Bear (Sep 25, 2008)

Thanks everyone, lots of answers and more questions.

I'll try to explain further, and there is a drawing below of how the downstairs manifold is laid out.

Currently the feed from the boiler gets as far as the bottom manifold, it's too hot to touch almost, certainly to hot to hold, (like me :lol: :lol the vertical pipe to the thermo valve is also hot, as is the return pipe to the left of it, the pipe to the right of the the thermo valve just gets warm.

Almost as soon as the pump is turned on it starts go cold every where, the motorised valve appears not to be working as the normal whirr is missing on booting up the downstairs thermostat, there is only one as money was tight when our lass built the house and the (Richard Cranium) plumber said it would be fine like that, retro fitting a stat to each zone isn't an option right now.

Upstairs as said is running fine, it seems from what I've gleaned from Google and you chaps/esess that there might be a neutral off somewhere.

the job centre beckons, so I'll look when I get back.

Kev


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## zappy61 (May 1, 2005)

*underfloor heating*

Kev, to check if its the motorised valve can you manually open it? there is usually a lever on the side or top depending on the type. If you can then with the room stat calling for heat see if you get circulation i.e the flow and return from the U/F ciruit gets hot. If it does it is the motorised valve sometimes they do go. The reason the pipework gets hot is probably because you are getting partial circulation but not enough when the pump is on. If that doesn't work maybe suspect the mixing valve.

Graham


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## Chudders (Jul 5, 2008)

To me one of your problems certainly sounds like a lost neutral. If you get a reading phase to earth but not phase to neutral then the neutral has a problem. As a word of warning however, don,t be tempted to 'borrow' a neutral from another circuit as an easy option. This does not comply with the wiring regulations and is dangerous. I carry out almost exclusively electrical inspection and testing and have seen this on numerous occasions which will always result in me providing an 'unsatisfactory' report. I think you first of all need to carry out some 'dead' continuity tests to establish where the neutral fault lies.
With regard to the multimeter,s accuracy, I have several bits of test equipment and they all require calibration every 6 months as well as monthly routine checking against a known source. I would not be too concerned about the differing readings on a multimeter unless it is fairly expensive (Megger or Fluke etc for instance) and has been calibrated recently.
Dave


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## Pudsey_Bear (Sep 25, 2008)

*Re: underfloor heating*



zappy61 said:


> Kev, to check if its the motorised valve can you manually open it? there is usually a lever on the side or top depending on the type. If you can then with the room stat calling for heat see if you get circulation i.e the flow and return from the U/F ciruit gets hot. If it does it is the motorised valve sometimes they do go. The reason the pipework gets hot is probably because you are getting partial circulation but not enough when the pump is on. If that doesn't work maybe suspect the mixing valve.
> 
> Graham


Hi Graham,

I eventually managed to get the motorised valve lever to move over to it's flushing mode, and with the pump on plug/socket setup we have loads of heat too much in fact, I'll need to turn the boiler temp down a few degrees.

Whilst I do have a new motorised valve ( a replacement for the pumped HW before we changed to a Combi boiler) I'm a bit loathe to assume the old valve is goosed especially when there is a problem neutral in the same area, so I'll have the sparky check his wiring before getting the plumber back in.

Why don't these people have qualifications in all three areas more often IE gas/plumbing/electrical, it's so easy for them to blame someone elses work and extract even more money, it also breeds distrust.

Kev


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## Pudsey_Bear (Sep 25, 2008)

Chudders said:


> To me one of your problems certainly sounds like a lost neutral. If you get a reading phase to earth but not phase to neutral then the neutral has a problem. As a word of warning however, don,t be tempted to 'borrow' a neutral from another circuit as an easy option. This does not comply with the wiring regulations and is dangerous. I carry out almost exclusively electrical inspection and testing and have seen this on numerous occasions which will always result in me providing an 'unsatisfactory' report. I think you first of all need to carry out some 'dead' continuity tests to establish where the neutral fault lies.
> With regard to the multimeter,s accuracy, I have several bits of test equipment and they all require calibration every 6 months as well as monthly routine checking against a known source. I would not be too concerned about the differing readings on a multimeter unless it is fairly expensive (Megger or Fluke etc for instance) and has been calibrated recently.
> Dave


Thanks Dave, I'll not be going into the valves wiring, I don't have a manual to study and there are too many variables to test without a sound knowledge of both electrickery and how the wiring system is done, so it's going to be the sparky who fixed it to re-fix it so it works properly.

I think it must be the neutrals at fault here it seems to coincidental that two adjacent items should stop working at the same moment, but as I've said, I do have a spare working pump and motorised valve handy, but don't think they'll be needed.

Kev.


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## arh (Dec 8, 2007)

I'm not trying to hi-jack this thread, but on the same theme, how does one find out how many amps you're pulling with a muli-meter


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## zappy61 (May 1, 2005)

*underfloor heating*

Hi Kev,

Sonds like the motorised valve, it just seems unlikely that you would suddenly loose a neutral, it is normally the live that is switched.

Graham


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## Pudsey_Bear (Sep 25, 2008)

Hi,

Volts multiplied by Amps = Watts 
Watts divided by Volts = Amps 
Watts divided by Amps = Volts

does that help

Kev


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## Pudsey_Bear (Sep 25, 2008)

*Re: underfloor heating*



zappy61 said:


> Hi Kev,
> 
> Sonds like the motorised valve, it just seems unlikely that you would suddenly loose a neutral, it is normally the live that is switched.
> 
> Graham


I agree, but the neutral appears to be gone from the pump hence it's on a plug/socket, so it could be related, we're also having a problem upstairs now as the pump isn't going off at the timed off points.

It is fast becoming a nightmare which we just cannot continue to throw money at, unfortunately I don't have any plumbers or sparkys amongst my mates.

Kev.


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## clodhopper2006 (Aug 13, 2006)

arh said:


> I'm not trying to hi-jack this thread, but on the same theme, how does one find out how many amps you're pulling with a muli-meter


you set the multimeter to amps and connect in series with the circuit you want to measure.


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## BJT (Oct 31, 2008)

You should not have a thermostat connected to the boiler control as this should operate on its internal thermostat. If you put a room stat onto the boiler it cannot provide the primary hot water at boiler temperature 'on demand' to the hot water cylinder. It should control the motorised valves, but all the wiring probably goes to a common terminal box/rail. It sounds like a link has been left out or more likely put back after doing some work but is not installed back properly and has the terminal screw against the insulation. Get the bright spark who did the thermostat work back to check that he has not inadvertently cocked up somewhere!


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## Pudsey_Bear (Sep 25, 2008)

BJT said:


> You should not have a thermostat connected to the boiler control as this should operate on its internal thermostat. If you put a room stat onto the boiler it cannot provide the primary hot water at boiler temperature 'on demand' to the hot water cylinder. It should control the motorised valves, but all the wiring probably goes to a common terminal box/rail. It sounds like a link has been left out or more likely put back after doing some work but is not installed back properly and has the terminal screw against the insulation. Get the bright spark who did the thermostat work back to check that he has not inadvertently cocked up somewhere!


Thanks BJT,

I'll answer one part at a time

The thermostats are not connected directly to the boiler, they control (I wish) the motorised valve and pump.

The boiler does indeed have it's own stat.

It's a Combi, so no cylinder.

The wiring at each valve/pump goes into a junction box on each floor (2) then to another box in the boiler room, then on to the boiler (Ferroli Optimax 38C HE) via a non volt relay.

I agree there must be a wiring fault somewhere.

Kev.

PS Download Manual for Ferroli Optimax 38C HE


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## Fatalhud (Mar 3, 2006)

If the pump worked up to the point of the electrician working on the system, then there is a good chance he may have disturbed or cocked something up.
There may also be motorised valves in the system, and without a wiring diagram it is almost impossible to diagnose the problem.

Alan H


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## zappy61 (May 1, 2005)

Hi Kev,
I agree with Alan if the pump and valve was working up to the point the electrian worked on the stat link there is a fair chance he's got something wrong. Get him back in.

Graham


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## Pudsey_Bear (Sep 25, 2008)

Update

Sparky just left, he had missed a neutral wire out of the system, so hopefully it will all work as it is supposed to now.

As an aside do any of you have underfloor heating, as it's all new to me and I was wondering what to set the boiler CH temp at, and also the three way stat, baring in mind a desired ambient of around 20-21 degrees air temp.

It is currently set to 40 on the boiler, and the three way stat is at 30.

Kev.


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## zappy61 (May 1, 2005)

Kev_n_Liz said:


> Update
> 
> Sparky just left, he had missed a neutral wire out of the system, so hopefully it will all work as it is supposed to now.
> 
> ...


Hi Kev,
For maximum efficiency the boiler flow should be 70/80degC and the HW stat (which I am assuming is the 3 way stat) at around 40/50degC. The room stat should control the ambient temperature of the rooms.

Graham


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## Pudsey_Bear (Sep 25, 2008)

Thanks Graham, that's roughly what it was set at, and it was too hot.

Well it's a bit cooler now, and we still have problems, the pump is working, the motorised valve is working, there is no air in the system I've bled everywhere and only got water no air at all.

I couldn't tell before if it was working as the system takes ages to cool down, but it is not working as it should, I'm seriously thinking of just taking the power away from the downstairs pump and motorised valve, and working it manually as it was nice and toasty before he "mended" it, upstairs is colder too for some reason.

If I had any hair I'd pull it out.

Does anyone have a Sunvic SZ2301F 2 port motorised valve instruction sheet, as I'm sure it's working backwards, or is that not possible.

I've attached a pic of the one I have or very similar, the tiny lever end you can see on the extreme left just between the white top and black base, on our this is currently the off position IE not calling for heat, it swings to the other side, I like to know if this is the correct position.

If I appear confused, it's most likely because I am.

Kev.


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## rayc (Jun 3, 2008)

Kev_n_Liz said:


> Thanks Graham, that's roughly what it was set at, and it was too hot.
> 
> Well it's a bit cooler now, and we still have problems, the pump is working, the motorised valve is working, there is no air in the system I've bled everywhere and only got water no air at all.
> 
> ...


Kev, I think the number you have given is for the activator part and not the complete valve assembly;
http://www.sunvic.co.uk/motorised_valves.htm

In any event it is a straight forward two position valve which is either open for flow[powered] or closed to flow [unpowered]. The lever is used to manually open it when filling the system. I don't think it matters which way the valve is plumbed but there may be a direction of flow arrow stamped on the valve body. 
Thats how the equvalent Honeywell works which is a direct replacement.

Could you possibly explain your problem now that you have got the pump and valve fixed as a lot of water has passed under the bridge [though not much round your system] since you first posted.

Ray


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## G2EWS (May 1, 2006)

Hi Kev,

Not got time to read this as I am on my way out, but was a little concerned that some are saying the voltage is not that important!

It most certainly is!

I was in a pub when the lights started going bright and popping. All hell let loose in this very old building. The owners wanted everyone out, but fortunately for them they had a party of electricians in. They got a multimeter out and found something over 300V on the 240V circuit. It turned out there had been a problem locally and they had part of the 3 phase circuit going round the pub! Damn scary, particularly as it was thatched with very old beams! Watching light bulbs go white hot then popping was quite a sight! I was not brave enough to touch the very old wiring to see how hot it was!

So I cannot agree with the voltage not mattering. It is important and if your meter is not reading correctly I would buy another or if it is an expensive one get it checked.

Sorry if this has already been covered, as mentioned I have no time to read any more.

Regards

Chris


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## rayc (Jun 3, 2008)

G2EWS said:


> Hi Kev,
> 
> Not got time to read this as I am on my way out, but was a little concerned that some are saying the voltage is not that important!
> 
> ...


Nobody told Kev that the voltage wasn't important but to use HIS meter only as an indicator. It would be uneconomical for him to get his private meter calibrated, the annual calibration being more expensive than a new meter.


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## zappy61 (May 1, 2005)

The problem with underflor heating Kev, is it is slow to heat up and slow to cool down a bit like a electric storage heater. So, by the time the room stat has sensed the room is up to temp and shuts off the MV, the residual heat in the building fabric will continue to add heat to the room. The trick is to set the stat say a little lower than the norm say 19degC and see how it goes. Many people have this type of heating in consevatories and when the sun suddenly comes out you have all that solar energy plus the residual heat which makes it uncomfortable and diffiucult to control. I know it is said that UF heating heats the lower room zones, it is not very controllable unlike a simple radiator which heats up and cools down much quicker.

So exoperiment but I don't think I would be doing it manually, defeats the object really.

The Sunvic valve is just an open or close 2 port valve normally closed when not nergised by the spring return, so when you energise it if you see the lever move across it is working and open.

Graham


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## Pudsey_Bear (Sep 25, 2008)

zappy61 said:


> The Sunvic valve is just an open or close 2 port valve normally closed when not nergised by the spring return, so when you energise it if you see the lever move across it is working and open.
> 
> Graham


I assume the lever can only move in one direction when heat is called for then, it's looking more like a pump issue then, I wonder if it is pumping the wrong way around the system, have a look at the manifold layout drawing below.

I just double checked the flow arrow on the pump to ensure I'd drawn it correctly, which I have, the internal wiring is correct, so it would point away from the pump being at fault. I even took out the test screw and it is rotating, but I know if I turn the pump off it will work OK, at least it did before he put in the missing neutral wire.

It's a shame I don't know a friendly plumber/sparky, who lives locally

Kev


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## G2EWS (May 1, 2006)

rayc said:


> Nobody told Kev that the voltage wasn't important but to use HIS meter only as an indicator. It would be uneconomical for him to get his private meter calibrated, the annual calibration being more expensive than a new meter.
> 
> It is best on ac to use it just as an indicator and not get hung up on the actual voltage.


Hi Ray,

Couple of points here. Not to get hung up on the actual voltage is tantamount to saying it is not important. It most certainly is as explained.

As to getting a multimeter calibrated being more expensive that a new meter, I suggest you either know little about meters or perhaps about the cost of calibration. I have multimeters that cost over £500 and I also arrange calibrations that cost less than £50. It is all relative to the cost of his meter as I suggested.

But I think I covered that adequately here:



G2EWS said:


> It is important and if your meter is not reading correctly I would buy another or if it is an expensive one get it checked.


Best regards

Chris


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## Pudsey_Bear (Sep 25, 2008)

Can we forget about the meter it was a tenner and not worth the hassle.

Kev.


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## G2EWS (May 1, 2006)

Kev_n_Liz said:


> Can we forget about the meter it was a tenner and not worth the hassle.
> 
> Kev.


Hi Kev,

Sounds like a good idea. Forgotten!

Anyway having not looked through the thread did you solve your problem?

Regards

Chris


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## Pudsey_Bear (Sep 25, 2008)

No, it's no better than before, if you read the thread you might be able to see something no ones thought of.

Kev.


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## G2EWS (May 1, 2006)

Hi Kev,

Will try and read through in my lunch break.

Regards

Chris


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