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Electronics Advice, Please

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  • Kent L. Aldershof
    Here s a challenge for you electronics tech experts. My Vermont vacation home has two-zone heating, with rather unconventional zone valves. These are
    Message 1 of 4 , Apr 5 7:08 AM
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      Here's a challenge for you electronics tech experts.

      My Vermont vacation home has two-zone heating, with rather unconventional
      zone valves. These are three-wire valves, which are both powered open
      and powered closed (rather than powered open and spring-return closed,
      the more common way). The main zone valve I keep on a programmable
      thermostat.

      The old thermostat, which died at the end of last winter, was set up for
      either two-wire or three-wire control. Now, I find that the new
      programmable thermostats all seem to be for two-wire systems only. So,
      at the advice of the heating expert at my local plumbing supply house, I
      added an isolating relay. This is a DPDT 24 Volts AC relay, one side
      wired to power the zone valve open, the other wired to power it closed.
      Power is supplied to the zone valves by the furnace transformer. The
      relay coil is connected to a separate 24 V. transformer secondary and to
      the thermostat switch (with the relay coil substituting for the coil of a
      conventional zone valve).

      Works elegantly, as it should. But only for a short time, and therein
      lies the problem.

      The new programmable thermostat lasted about three weeks; then it blew
      out, locking up in the Call For Heat position. Hence, my furnace ran
      almost steadily, day and night, consuming vast amounts of $2 per gallon
      heating oil and keeping the house above 80 degrees day and night. This I
      discovered after being away from the house for a couple of weeks.

      The heating guy assured me that it had to be a relay problem; but
      installing a new relay did no good at all. Replacing the programmable
      thermostat with an old-fashioned mercury switch thermostat worked just
      fine. The furnace shuts on and off as it should, and the house stays at
      the pre-set temperature, but of course the old-style thermostat is not
      programmable.

      In any case, the plumbing shop replaced the programmable unit (BTW, a
      White-Rodgers model) with a new one, stating that such a situation had
      never before been seen. The replacement thermostat also worked fine, for
      a couple of weeks; then, upon returning to the house after another
      absence, I found exactly the same burnout in the new thermostat.

      This time, the plumbing shop guy gave up. Kindly, they refunded my
      money, with dire statements that I must have done something wrong.
      However, I do careful work especially with electrical devices, and there
      are no mis-wirings nor accidental shorts nor bad connections. Just a
      system that burns out $80 thermostats one after another.

      I can think of only two possible causes -- but perhaps you experts can
      come up with something else. First, there may be a large inductive kick
      when the relay energizes or de-energizes, and the thermostat's switching
      circuitry cannot handle that spike. Or alternately, the notoriously
      unreliable electric power in Vermont gets interrupted fairly often during
      the winter months, and the restoration of power may send some kind of
      transient voltage spike down the line.

      I don't know how to deal with this, if some kind of spiking is the
      problem, except perhaps to hook a capacitor across the primary (or
      secondary) of the 24 V. transformer -- or, perhaps, to a grounded line.
      But I do not know what size capacitor would be appropriate, if that is at
      all a useful fix.

      I think this is not an over-current situation, because the heating guy
      even checked with the engineering department at White-Rodgers, and the
      engineer assured him that the thermostat would easily handle the current
      drawn by the relay coil. Moreover, the heating guy insists that he has
      exactly this arrangement in his own home, using the same components, and
      he has had no problem. Hence the slurs on my ability to do a simple
      wiring job.

      In any case, my frustration tolerance has long since been exceeded. I
      don't want the inconvenience of a non-programmable thermostat, I don't
      want to have to replace the zone valves with two-wire units, and I don't
      want to keep replacing thermostats and burning vast amounts of heating
      oil.

      I will be grateful for your expressions of sympathy. I will be even more
      grateful for your guidance as to how I can fix the problem, once and for
      all, and safely install a new programmable thermostat.

      Thoughts and suggestions?

      Kent
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    • Mike Passerotti
      Kent, As best as I can figure, there is some sort of discrepency in the wiring. My sympathy for heating. My normal heating cost me $120 one month this winter
      Message 2 of 4 , Apr 5 10:27 AM
      • 0 Attachment
        RE: [TeslaTurbine] Electronics Advice, Please

        Kent, As best as I can figure, there is some sort of discrepency in the wiring.  My sympathy for heating.  My normal heating cost me $120 one month this winter when everything worked correctly.

        The manufacturer has a web site with more information:  http://www.white-rodgers.com

        What we know:
        three-wire valves, which are both powered open and powered closed
        DPDT 24 Volts AC relay
        Two 24 VAC transformers to power the relay and valve
        thermostat switch outputs for 24VAC systems

        What we don't know:
        Is the thermostat a battery supplied or 24VAC supplied type?  What is the model number?

        This attached diagram is what we would expect to see.  Please correct me if I'm wrong.
        If you can draw a diagram of what you do have, then that might clear up my conception.

        Modern devices are polarized AC so be careful how things are wired with respect to polarity if its marked.

        If you hooked up the 24VAC on the output of the thermostat that is powered by 24VAC, then you are connecting power to power and that could blow the output switch.

        Another possibility is the DPDT 24 Volts AC relay is drawing too much power during operation. That would draw a higher than normal current through the thermostat output switch and possibly damage it.  The solution there would be to add a resistor in series with the relay coil.  The resistor would drop the power running through the relay and thermostat output switch.  Check the power rating requirement (voltage and current) for the thermostat and the relay.


        Mike Passerotti - Software Engineer
        MedPlus Web Development Team
        8805 Governor's Hill Drive, Suite 100
        Cincinnati, OH 45249
        (513) 697-3200 xt 350
        (513) 583-8885 Fax
        mpasserotti@...


        -----Original Message-----
        From: Kent L. Aldershof [mailto:Aldershof-MSI@...]
        Sent: Thursday, April 05, 2001 10:08 AM
        To: USA-Tesla@...
        Cc: TeslaTurbine@...
        Subject: [TeslaTurbine] Electronics Advice, Please



        Here's a challenge for you electronics tech experts.

        My Vermont vacation home has two-zone heating, with rather unconventional
        zone valves.  These are three-wire valves, which are both powered open
        and powered closed (rather than powered open and spring-return closed,
        the more common way).  The main zone valve I keep on a programmable
        thermostat.

        The old thermostat, which died at the end of last winter, was set up for
        either two-wire or three-wire control.  Now, I find that the new
        programmable thermostats all seem to be for two-wire systems only.  So,
        at the advice of the heating expert at my local plumbing supply house, I
        added an isolating relay.  This is a DPDT 24 Volts AC relay, one side
        wired to power the zone valve open, the other wired to power it closed.
        Power is supplied to the zone valves by the furnace transformer.  The
        relay coil is connected to a separate 24 V.  transformer secondary and to
        the thermostat switch (with the relay coil substituting for the coil of a
        conventional zone valve).

        Works elegantly, as it should.  But only for a short time, and therein
        lies the problem.

        The new programmable thermostat lasted about three weeks; then it blew
        out, locking up in the Call For Heat position.  Hence, my furnace ran
        almost steadily, day and night, consuming vast amounts of $2 per gallon
        heating oil and keeping the house above 80 degrees day and night.  This I
        discovered after being away from the house for a couple of weeks.

        The heating guy assured me that it had to be a relay problem; but
        installing a new relay did no good at all.  Replacing the programmable
        thermostat with an old-fashioned mercury switch thermostat worked just
        fine.  The furnace shuts on and off as it should, and the house stays at
        the pre-set temperature, but of course the old-style thermostat is not
        programmable.

        In any case, the plumbing shop replaced the programmable unit (BTW, a
        White-Rodgers model) with a new one, stating that such a situation had
        never before been seen.  The replacement thermostat also worked fine, for
         a couple of weeks; then, upon returning to the house after another
        absence, I found exactly the same burnout in the new thermostat.

        This time, the plumbing shop guy gave up.  Kindly, they refunded my
        money, with dire statements that I must have done something wrong.
        However, I do careful work especially with electrical devices, and there
        are no mis-wirings nor accidental shorts nor bad connections.  Just a
        system that burns out $80 thermostats one after another.

        I can think of only two possible causes -- but perhaps you experts can
        come up with something else.  First, there may be a large inductive kick
        when the relay energizes or de-energizes, and the thermostat's switching
        circuitry cannot handle that spike.  Or alternately, the notoriously
        unreliable electric power in Vermont gets interrupted fairly often during
        the winter months, and the restoration of power may send some kind of
        transient voltage spike down the line.

        I don't know how to deal with this, if some kind of spiking is the
        problem, except perhaps to hook a capacitor across the primary (or
        secondary) of the 24 V. transformer -- or, perhaps, to a grounded line.
        But I do not know what size capacitor would be appropriate, if that is at
        all a useful fix.

        I think this is not an over-current situation, because the heating guy
        even checked with the engineering department at White-Rodgers, and the
        engineer assured him that the thermostat would easily handle the current
        drawn by the relay coil.  Moreover, the heating guy insists that he has
        exactly this arrangement in his own home, using the same components, and
        he has had no problem.  Hence the slurs on my ability to do a simple
        wiring job.

        In any case, my frustration tolerance has long since been exceeded.  I
        don't want the inconvenience of a non-programmable thermostat, I don't
        want to have to replace the zone valves with two-wire units, and I don't
        want to keep replacing thermostats and burning vast amounts of heating
        oil.

        I will be grateful for your expressions of sympathy.  I will be even more
        grateful for your guidance as to how I can fix the problem, once and for
        all, and safely install a new programmable thermostat.

        Thoughts and suggestions?

        Kent
        ________________________________________________________________
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        Juno offers FREE or PREMIUM Internet access for less!
        Join Juno today!  For your FREE software, visit:
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      • Fred McGalliard
        Two suggestions, sort of. First, it is probably a kick when the solenoid is turned off. This would be easily resolved with a free wheeling diode at the
        Message 3 of 4 , Apr 9 2:30 PM
        • 0 Attachment
          Two suggestions, sort of. First, it is probably a kick when the solenoid is
          turned off. This would be easily resolved with a free wheeling diode at the
          controller. If the solenoid relay is generating a kick from the power system
          relay coils, this could spark across the solenoid relay and might get back
          to the controller. This would take a pair of free wheeling diodes to dump
          these spikes as well. A capacitor would cause a small spark in the contacts
          on closure, wearing the relays out faster, but would reduce the voltage
          reached by the flyback inductive kick. The diode would eliminate this spark
          and almost all of the kick. Probably the better solution.

          The AC voltage at the input would have to be pretty high to cause failure.
          This controller probably has a small transformer to drop the voltage to
          12-24V. The voltage regulator at this step can probably take a 30-60%
          overvoltage without damage. This is a bit higher than the transformer can
          take probably. So is the transformer toast? Can you look inside it to see?
          (It should be easy to take apart.)

          If the output is permanently connected to 24V, or ground, but the 60hz power
          input does not cause smoke, then the output has probably been damaged by
          either a static electric surge, or an over voltage condition such as you
          might get from turning the relay off without a place to dump the coil
          energy. Since you were, both times, out of house, the natural question is
          was there an ESD event, like a local lightening strike or a flyback spike.
          What do you know about the circuit? Does the output consist of a small SCR
          and is it open or "on" with 24V 60Hz, or is it DC? Some of these small
          output SCRs are really small, and it may be possible to blast them with a
          relatively small overload. Any way your wiring could twist and short out
          briefly, or perhaps long periods of driving the "on" state into a bit too
          large a load would over heat it. I would check the load current and the peak
          voltage with a VOM to first order. If there are no signs of smoke or heat
          damage, but the part is shorted, it was probably an ESD type of spike. If
          there is smoke damage, you may be able to tell if the power input did the
          deed.

          ----- Original Message -----
          From: "Kent L. Aldershof" <Aldershof-MSI@...>
          To: <USA-Tesla@...>
          Cc: <TeslaTurbine@...>
          Sent: Thursday, April 05, 2001 7:08 AM
          Subject: [TeslaTurbine] Electronics Advice, Please


          >
          > Here's a challenge for you electronics tech experts.
          >
          > My Vermont vacation home has two-zone heating, with rather unconventional
          > zone valves. These are three-wire valves, which are both powered open
          > and powered closed (rather than powered open and spring-return closed,
          > the more common way). The main zone valve I keep on a programmable
          > thermostat.
          >
          > The old thermostat, which died at the end of last winter, was set up for
          > either two-wire or three-wire control. Now, I find that the new
          > programmable thermostats all seem to be for two-wire systems only. So,
          > at the advice of the heating expert at my local plumbing supply house, I
          > added an isolating relay. This is a DPDT 24 Volts AC relay, one side
          > wired to power the zone valve open, the other wired to power it closed.
          > Power is supplied to the zone valves by the furnace transformer. The
          > relay coil is connected to a separate 24 V. transformer secondary and to
          > the thermostat switch (with the relay coil substituting for the coil of a
          > conventional zone valve).
          >
          > Works elegantly, as it should. But only for a short time, and therein
          > lies the problem.
          >
          > The new programmable thermostat lasted about three weeks; then it blew
          > out, locking up in the Call For Heat position. Hence, my furnace ran
          > almost steadily, day and night, consuming vast amounts of $2 per gallon
          > heating oil and keeping the house above 80 degrees day and night. This I
          > discovered after being away from the house for a couple of weeks.
          >
          > The heating guy assured me that it had to be a relay problem; but
          > installing a new relay did no good at all. Replacing the programmable
          > thermostat with an old-fashioned mercury switch thermostat worked just
          > fine. The furnace shuts on and off as it should, and the house stays at
          > the pre-set temperature, but of course the old-style thermostat is not
          > programmable.
          >
          > In any case, the plumbing shop replaced the programmable unit (BTW, a
          > White-Rodgers model) with a new one, stating that such a situation had
          > never before been seen. The replacement thermostat also worked fine, for
          > a couple of weeks; then, upon returning to the house after another
          > absence, I found exactly the same burnout in the new thermostat.
          >
          > This time, the plumbing shop guy gave up. Kindly, they refunded my
          > money, with dire statements that I must have done something wrong.
          > However, I do careful work especially with electrical devices, and there
          > are no mis-wirings nor accidental shorts nor bad connections. Just a
          > system that burns out $80 thermostats one after another.
          >
          > I can think of only two possible causes -- but perhaps you experts can
          > come up with something else. First, there may be a large inductive kick
          > when the relay energizes or de-energizes, and the thermostat's switching
          > circuitry cannot handle that spike. Or alternately, the notoriously
          > unreliable electric power in Vermont gets interrupted fairly often during
          > the winter months, and the restoration of power may send some kind of
          > transient voltage spike down the line.
          >
          > I don't know how to deal with this, if some kind of spiking is the
          > problem, except perhaps to hook a capacitor across the primary (or
          > secondary) of the 24 V. transformer -- or, perhaps, to a grounded line.
          > But I do not know what size capacitor would be appropriate, if that is at
          > all a useful fix.
          >
          > I think this is not an over-current situation, because the heating guy
          > even checked with the engineering department at White-Rodgers, and the
          > engineer assured him that the thermostat would easily handle the current
          > drawn by the relay coil. Moreover, the heating guy insists that he has
          > exactly this arrangement in his own home, using the same components, and
          > he has had no problem. Hence the slurs on my ability to do a simple
          > wiring job.
          >
          > In any case, my frustration tolerance has long since been exceeded. I
          > don't want the inconvenience of a non-programmable thermostat, I don't
          > want to have to replace the zone valves with two-wire units, and I don't
          > want to keep replacing thermostats and burning vast amounts of heating
          > oil.
          >
          > I will be grateful for your expressions of sympathy. I will be even more
          > grateful for your guidance as to how I can fix the problem, once and for
          > all, and safely install a new programmable thermostat.
          >
          > Thoughts and suggestions?
          >
          > Kent
          > ________________________________________________________________
          > GET INTERNET ACCESS FROM JUNO!
          > Juno offers FREE or PREMIUM Internet access for less!
          > Join Juno today! For your FREE software, visit:
          > http://dl.www.juno.com/get/tagj.
          >
          >
          >
          >
          > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
          >
          >
          >
        • Eddy De Wolf
          What the fuck is going on with this list EDW ... From: Fred McGalliard [mailto:frederick.b.mcgalliard@BOEING.COM] Sent: maandag 9 april 2001 23:30 To:
          Message 4 of 4 , Apr 11 12:19 PM
          • 0 Attachment
            What the fuck is going on with this list
             
            EDW
            -----Original Message-----
            From: Fred McGalliard [mailto:frederick.b.mcgalliard@...]
            Sent: maandag 9 april 2001 23:30
            To: TeslaTurbine@yahoogroups.com
            Subject: Re: [TeslaTurbine] Electronics Advice, Please

            Two suggestions, sort of. First, it is probably a kick when the solenoid is
            turned off. This would be easily resolved with a free wheeling diode at the
            controller. If the solenoid relay is generating a kick from the power system
            relay coils, this could spark across the solenoid relay and might get back
            to the controller. This would take a pair of free wheeling diodes to dump
            these spikes as well. A capacitor would cause a small spark in the contacts
            on closure, wearing the relays out faster, but would reduce the voltage
            reached by the flyback inductive kick. The diode would eliminate this spark
            and almost all of the kick. Probably the better solution.

            The AC voltage at the input would have to be pretty high to cause failure.
            This controller probably has a small transformer to drop the voltage to
            12-24V. The voltage regulator at this step can probably take a 30-60%
            overvoltage without damage. This is a bit higher than the transformer can
            take probably. So is the transformer toast? Can you look inside it to see?
            (It should be easy to take apart.)

            If the output is permanently connected to 24V, or ground, but the 60hz power
            input does not cause smoke, then the output has probably been damaged by
            either a static electric surge, or an over voltage condition such as you
            might get from turning the relay off without a place to dump the coil
            energy. Since you were, both times, out of house, the natural question is
            was there an ESD event, like a local lightening strike or a flyback spike.
            What do you know about the circuit? Does the output consist of a small SCR
            and is it open or "on" with 24V 60Hz, or is it DC? Some of these small
            output SCRs are really small, and it may be possible to blast them with a
            relatively small overload. Any way your wiring could twist and short out
            briefly, or perhaps long periods of driving the "on" state into a bit too
            large a load would over heat it. I would check the load current and the peak
            voltage with a VOM to first order. If there are no signs of smoke or heat
            damage, but the part is shorted, it was probably an ESD type of spike. If
            there is smoke damage, you may be able to tell if the power input did the
            deed.

            ----- Original Message -----
            From: "Kent L. Aldershof" <Aldershof-MSI@...>
            To: <USA-Tesla@...>
            Cc: <TeslaTurbine@...>
            Sent: Thursday, April 05, 2001 7:08 AM
            Subject: [TeslaTurbine] Electronics Advice, Please


            >
            > Here's a challenge for you electronics tech experts.
            >
            > My Vermont vacation home has two-zone heating, with rather unconventional
            > zone valves.  These are three-wire valves, which are both powered open
            > and powered closed (rather than powered open and spring-return closed,
            > the more common way).  The main zone valve I keep on a programmable
            > thermostat.
            >
            > The old thermostat, which died at the end of last winter, was set up for
            > either two-wire or three-wire control.  Now, I find that the new
            > programmable thermostats all seem to be for two-wire systems only.  So,
            > at the advice of the heating expert at my local plumbing supply house, I
            > added an isolating relay.  This is a DPDT 24 Volts AC relay, one side
            > wired to power the zone valve open, the other wired to power it closed.
            > Power is supplied to the zone valves by the furnace transformer.  The
            > relay coil is connected to a separate 24 V.  transformer secondary and to
            > the thermostat switch (with the relay coil substituting for the coil of a
            > conventional zone valve).
            >
            > Works elegantly, as it should.  But only for a short time, and therein
            > lies the problem.
            >
            > The new programmable thermostat lasted about three weeks; then it blew
            > out, locking up in the Call For Heat position.  Hence, my furnace ran
            > almost steadily, day and night, consuming vast amounts of $2 per gallon
            > heating oil and keeping the house above 80 degrees day and night.  This I
            > discovered after being away from the house for a couple of weeks.
            >
            > The heating guy assured me that it had to be a relay problem; but
            > installing a new relay did no good at all.  Replacing the programmable
            > thermostat with an old-fashioned mercury switch thermostat worked just
            > fine.  The furnace shuts on and off as it should, and the house stays at
            > the pre-set temperature, but of course the old-style thermostat is not
            > programmable.
            >
            > In any case, the plumbing shop replaced the programmable unit (BTW, a
            > White-Rodgers model) with a new one, stating that such a situation had
            > never before been seen.  The replacement thermostat also worked fine, for
            >  a couple of weeks; then, upon returning to the house after another
            > absence, I found exactly the same burnout in the new thermostat.
            >
            > This time, the plumbing shop guy gave up.  Kindly, they refunded my
            > money, with dire statements that I must have done something wrong.
            > However, I do careful work especially with electrical devices, and there
            > are no mis-wirings nor accidental shorts nor bad connections.  Just a
            > system that burns out $80 thermostats one after another.
            >
            > I can think of only two possible causes -- but perhaps you experts can
            > come up with something else.  First, there may be a large inductive kick
            > when the relay energizes or de-energizes, and the thermostat's switching
            > circuitry cannot handle that spike.  Or alternately, the notoriously
            > unreliable electric power in Vermont gets interrupted fairly often during
            > the winter months, and the restoration of power may send some kind of
            > transient voltage spike down the line.
            >
            > I don't know how to deal with this, if some kind of spiking is the
            > problem, except perhaps to hook a capacitor across the primary (or
            > secondary) of the 24 V. transformer -- or, perhaps, to a grounded line.
            > But I do not know what size capacitor would be appropriate, if that is at
            > all a useful fix.
            >
            > I think this is not an over-current situation, because the heating guy
            > even checked with the engineering department at White-Rodgers, and the
            > engineer assured him that the thermostat would easily handle the current
            > drawn by the relay coil.  Moreover, the heating guy insists that he has
            > exactly this arrangement in his own home, using the same components, and
            > he has had no problem.  Hence the slurs on my ability to do a simple
            > wiring job.
            >
            > In any case, my frustration tolerance has long since been exceeded.  I
            > don't want the inconvenience of a non-programmable thermostat, I don't
            > want to have to replace the zone valves with two-wire units, and I don't
            > want to keep replacing thermostats and burning vast amounts of heating
            > oil.
            >
            > I will be grateful for your expressions of sympathy.  I will be even more
            > grateful for your guidance as to how I can fix the problem, once and for
            > all, and safely install a new programmable thermostat.
            >
            > Thoughts and suggestions?
            >
            > Kent
            > ________________________________________________________________
            > GET INTERNET ACCESS FROM JUNO!
            > Juno offers FREE or PREMIUM Internet access for less!
            > Join Juno today!  For your FREE software, visit:
            > http://dl.www.juno.com/get/tagj.
            >
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
            >



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