Central heating continuously runs

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Hi
We have a Potterton Suprema boiler, a Potterton EP3002 wall timer and a Wickes wall thermostat.
The heating switches on OK according to the timer schedule but fails to switch off when it reaches the right room temp set on the thermostat so we just get hotter.
I had to have a new thermostat for some reason but I seem to remember there being 3 wires into the stat but there appears to be only 2.
Is that right? And would the missing wire be the one to turn off the heat?
(Pictures attached)
Thanks
Daren
+-------------------------------------------------------------------+ |Filename: Boiler.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf06 | |Filename: Stat.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf07 | |Filename: Timer.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf08 | +-------------------------------------------------------------------+
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Daren Friday


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Most likely, two wires is how it was designed. Third wire could be anything, but probably a common.
It's possible the thermostat isn't the problem. I'll copy in the alt hvac group, they field this question often.
Christopher A. Young Learn more about Jesus www.lds.org .
Hi We have a Potterton Suprema boiler, a Potterton EP3002 wall timer and a Wickes wall thermostat.
The heating switches on OK according to the timer schedule but fails to switch off when it reaches the right room temp set on the thermostat so we just get hotter.
I had to have a new thermostat for some reason but I seem to remember there being 3 wires into the stat but there appears to be only 2.
Is that right? And would the missing wire be the one to turn off the heat?
(Pictures attached)
Thanks
Daren
+-------------------------------------------------------------------+ |Filename: Boiler.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf06 | |Filename: Stat.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf07 | |Filename: Timer.JPG | |Download: http://www.diybanter.com/attachment.php?attachmentidf08 | +-------------------------------------------------------------------+
--
Daren Friday



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The stat should only need 2 wires if its got batteries in it. The pictures are of such small size and poor quality, I can't tell much else. Its possible that you have been having this problem since you put the new stat in.... most likely because the anticipator setting isn't correct, or the temperature delta isn't set correctly, or both.
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I'm sure the professionals on alt havoc will help.
Christopher A. Young Learn more about Jesus www.lds.org .
I've tried 2 other types of stats and all have the same result, the heating ignores them when room reaches temp. I've just changed the stat for a Honeywell CM900 and again I get exactly the same result. If I move the slider to off on the EP3002 everything closes fine.
I thought maybe I'd wired the stat wrong so I rewired it and now I've popped the motorised valve (Myson Power Extra MPE228).
I've ordered a replacement valve and EP3002. See how we go?
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Daren Friday



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Keep playing with it, keep breaking and changing parts... you'll eventually change something and accitentally "fix" it, *OR* you can call you local Master Tech and get the problem corrected the first time and be done with it.
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Steve wrote:

Not everyone has an instant-gratification fixation. I'm sure you could troubleshoot it faster, but as long as he is being safe, give the man a little credit for trying! I do!
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He changed something, and now its not working.... then while trying to "fix" it, he fried a motorized valve... Whats he going to fry next?? How much more is his attempts going to cost in time and money to replace componants that he destroys in the process?? He's already in way over his head if he can't figure out simple controls.
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Steve wrote:

Probably not much compared to the cost of an hour or two of a techs time. If the owner can swap a few components and it works half of the time, the owner is probably way ahead--at least financially, and surely from the point of view of understanding his or her system.
I think I am way ahead because I have made the effort to learn more about how these systems. The industry would seem to prefer for people to be scared and ignorant. The outlook seems good. I would just caution those that will try to "work safe", and to make sure to know what that means in any context in which one is working--for instance in operating a table saw.

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Learning how the system works and then correctly diagnosing what's wrong is different than just buying and changing parts without knowing what you're doing. I think that is what he was referring to.
If the thing was heating when the thermstat should not be calling for heat, wouldn't you just disconnect the thermostat wires first and see if it stopped?
The industry would seem to prefer for people to

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snipped-for-privacy@optonline.net wrote:

Maybe, but many of his posts seem to share the same ring of "union guidelines". Of course, this right is granted to him by the Bill of Rights...

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Does anyone use AC Meter or Amp-probe????
&gt;&gt;&gt;&gt; I've tried 2 other types of stats and all have the same result, the<BR>&gt; &gt;&gt;&gt;&gt; heating ignores them when room reaches temp.<BR>&gt; &gt;&gt;&gt;&gt; I've just changed the stat for a Honeywell CM900 and again I get exactly<BR>&gt; &gt;&gt;&gt;&gt; the same result. If I move the slider to off on the EP3002 everything<BR>&gt; &gt;&gt;&gt;&gt; closes fine.<BR>&gt;<BR>&gt; &gt;&gt;&gt;&gt; I thought maybe I'd wired the stat wrong so I rewired it and now I've<BR>&gt; &gt;&gt;&gt;&gt; popped the motorised valve (Myson Power Extra MPE228).<BR>&gt;<BR>&gt; &gt;&gt;&gt;&gt; I've ordered a replacement valve and EP3002. See how we go?<BR>&gt;<BR>&gt; &gt;&gt;&gt; Keep playing with it, keep breaking and changing parts... you'll<BR>&gt; &gt;&gt;&gt; eventually<BR>&gt; &gt;&gt;&gt; change something and accitentally "fix" it, *OR* you can call you local<BR>&gt; &gt;&gt;&gt; Master Tech and get the problem corrected the first time and be done with<BR>&gt; &gt;&gt;&gt; it.<BR>&gt;<BR>&gt; &gt;&gt; Not everyone has an instant-gratification fixation. I'm sure you could<BR>&gt; &gt;&gt; troubleshoot it faster, but as long as he is being safe, give the man a<BR>&gt; &gt;&gt; little credit for trying! I do!<BR>&gt;<BR>&gt; &gt; He changed something, and now its not working.... then while trying to "fix"<BR>&gt; &gt; it, he fried a motorized valve... Whats he going to fry next?? How much more<BR>&gt; &gt; is his attempts going to cost in time and money to replace componants that<BR>&gt; &gt; he destroys in the process??<BR>&gt;<BR>&gt; Probably not much compared to the cost of an hour or two of a techs<BR>&gt; time. If the owner can swap a few components and it works half of the<BR>&gt; time, the owner is probably way ahead--at least financially, and surely<BR>&gt; from the point of view of understanding his or her system.<BR>&gt;<BR>&gt; I think I am way ahead because I have made the effort to learn more<BR>&gt; about how these systems.<BR><BR>Learning how the system works and then correctly<BR>diagnosing what's wrong is different than just buying and<BR>changing parts without knowing what you're doing.<BR>I think that is what he was referring to.<BR><BR>If the thing was heating when the thermstat should not<BR>be calling for heat, wouldn't you just disconnect = the<BR>thermostat wires first and see if it stopped?<BR><BR><BR><BR><BR><BR>The industry would seem to prefer for people to<BR>&gt; be scared and ignorant. The outlook seems good. I would just caution<BR>&gt; those that will try to "work safe", and to make sure to know what that<BR>&gt; means in any context in which one is working--for instance in operating<BR>&gt; a table saw.<BR>&gt;<BR>&gt;<BR>&gt;<BR>&gt; &gt; He's already in way over his head if he can't figure out simple controls.- Hide quoted text -<BR>&gt;<BR>&gt; - Show quoted text -- Hide quoted text -<BR>&gt;<BR>&gt; - Show quoted text -<BR></FONT></BODY></HTML> ------=
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I do.
Christopher A. Young Learn more about Jesus www.lds.org .
Does anyone use AC Meter or Amp-probe????
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On 8/7/2012 12:21 PM, Bill wrote:

I am not sure, but I think the flamethrower was invented by screw ups trying to fix something. Or maybe it was the Hand Grenade!

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On 8/6/2012 7:15 AM, Steve wrote:

Years ago in the TV repair business we called them "Tube Changers". ^_^
TDD
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The Daring Dufas wrote:

I recall a tube tester at my local drug store, but I am a little young to remember the big picture. Was "Tube Changing" frowned upon back then (mid-late 60's?)? We always wore out the dials--we were quick! : )

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A good repairman would, given the schematics and a VOM, be able to determine _which_ tube to change a priori, rather than just swapping out tubes until the TV works again.
(although I will admit to using the swap technique to fix a mainframe once in Brussels).
scott
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Thats been my point all along for HVAC systems... A good tech can diagnose the system, show you what the problem(s) is/are, correct those problems with parts from his well stocked service truck, and warranty those repairs ..... usually for 1 year.

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wrote:

I worked TV repair in the late 50's. My recollections:
People tried to save money fixing their own TV sets by using those drug store tube testers. Trouble was those tube testers often said a good tube was bad thus wasting the money the customer was trying to save by not calling a TV repairman.

Tube changing (that is trying a new tube in place of a suspected bad tube in a working TV) was the quickest and most reliable way to see if that was the problem. There were specific tubes that did specific things so you didn't have to change out the whole TV's tube set. For example if the vertical hold wasn't locking there were just a few tubes that could cause that and you tried only them.

We didn't carry schematics for all TV models in the shop. They came in a packet with other info on the particular set and were expensive. A good tech could fix most TV problems without one. Tube TV's were incredibly simple and easy to work on compared to today's electronics. If we couldn't fix it without a schematic, then of course we ordered one (at the customers expense of course) and then put it in our library for future use.

We mostly used a VTVM (vacuum tube voltmeter) and a scope in the shop. For service calls we carried VOMs (volt ohm meter) and a picture tube tester along with a case of replacement tubes.

The majority of sets were fixed in the customers house. (Most TVs were very large and heavy in those days so we usually went to the customers house.) If the set couldn't be fixed by tube swapping then it went to the shop to fix. When repaired we delivered it back to the home.

Yes we swapped boards in mainframes at GE in the 60s also. Like tubes swapping out was a quick method of troubleshooting.
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Hmm. A number of sets that I worked on in the 70's had the schematics glued to the inside of the case.

In this case it was past midnight, testing a completely new firmware and OS on a working customer mainframe and the FE had gone home hours ago. Given the failure was in a Load Index Register instruction, which was handled by the Fetch module, I tried to swap the two (20"x30") fetch cards with the on-site spares kit. The new OS still faulted. Tried the two Execute Module cards. Still faulted. Eventually got around to swapping out the MCW (Memory Controller Write) card which fixed the problem. All night, alone in the datacenter of one of Belgiums larger banks. Probably wouldn't happen nowadays.
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On 08 Aug 2012 19:07:06 GMT, snipped-for-privacy@slp53.sl.home (Scott Lurndal) wrote:

You may be remembering the chassis tube location diagrams that were glued inside the cabinets of most sets. Very handy since many tubes required some physical contortion on the tech's part just to reach them in an inaccessible part of the cabinet (when in the customers home). Also they gave the tube type (6AU6, 6V6, ect) by which you could locate and swap the tubes you suspected of causing the problem.
Further a schematic *glued* inside a cabinet would be of little use in the shop since after removing the chassis it was put on the bench to work on and the cabinet was stored in the back of the shop.
But I can only speak for my 50's experience. Your 70's experience may very well be a YMMV.
As an aside I occasionally lost some skin when trying to reach an inaccessible tube and getting my arm too close to the picture tube's high voltage wire. Getting zapped was uncomfortable, but worse it caused my arm to involuntarily jerk back and often (with my luck) it connected with a sharp protrusion of the chassis on the way out.

In the middle 60s I worked testing newly manufactured GE mainframes. You would have thought board testing would have caught all board problems but often when a machine had a problem it was caused by a (new) bad board. So board swapping was a still valid troubleshooting method even when testing at the new system level.
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