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Boiler w/ millivolt gas valve turned on by itself (no thermostat call for heat).

GCR
GCR Member Posts: 10
Yesterday evening in warm DC area I noticed my boiler was on. The thermostat did not show a call for heat. I removed the thermostat from the wall, this did not fix the issue. Changed the thermostat batteries, set it to call for heat in thermostat, then set it to turn off that call in thermostat. None of these steps turned off the boiler. Turning the gas valve to "pilot" turned off the boiler.

Could a short in the wiring from thermostat to gas valve cause this? That is my next area to check.

Comments

  • mattmia2
    mattmia2 Member Posts: 7,190
    Yes. Did you disconnect the thermostat wire from the valve? Look closely at the wires before you disconnect them, they could be nearly touching and decided today was the day to touch. Depending on the age and design of the valve a bad valve could cause it too.
    HomerJSmith
  • GroundUp
    GroundUp Member Posts: 1,495
    Is it a cold start boiler? Just to point out the obvious, a hot start boiler runs like a water heater and will fire anytime the internal temp drops below setpoint- no regard to the thermostat.
    mattmia2
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,142
    If it is hot water with a tankless coil, it could be a defective flow check bad aqua stat or wiring problem

    If it is steam it could be a bad aquastat, wiring problem.


    But from what the OP posted it sounded like a runaway boiler.
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 7,190
    if it doesn't have a tankless aquastat or some other control keeping it hot without a t-stat call and you can't find a definite cause, I would replace the valve. If the valve is firing without an electrical signal calling for heat there are several very bad things that can happen.
  • mattmia2
    mattmia2 Member Posts: 7,190
    Look for a burned or chaffed wire between the valve and the safeties as well.
  • GCR
    GCR Member Posts: 10
    Thanks for all the helpful comments. Disconnecting the thermostat wire at the valve fixed it. Testing confirmed a short in that wire. Will replace.
    GGrossmattmia2
  • 109A_5
    109A_5 Member Posts: 483
    When replacing the old wire, inspect for damage, so maybe it happening again can be permanently be avoided. Since then the original failure is understood.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022
    GCR said:

    Thanks for all the helpful comments. Disconnecting the thermostat wire at the valve fixed it. Testing confirmed a short in that wire. Will replace.

    I understand what you mean by "Short in the wire" however that is the incorrect term for the condition. A short circuit is when you have a conductor that connects the positive end of a battery to the negative end of a battery without a load. In AC house current is would be like placing a paperclip in a power outlet connecting the source to the return path (the white and black wire) with no load.

    On your Millivolt gas valve circuit, there is very little current and therefor no fire hazard from overheating electricity in the event of an actual short circuit. The powerpile generator may fail if shorted out. In your case there is no short. Just a bad wire that is connected somewhere, where it should not be connected.

    The correct term for your condition is a completed circuit. If a thermostat wire has insulation that is compromised (a staple or nail for example) and completes the circuit before the thermostat switch contacts, there is no short circuit. Here is a simple illustration.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • mattmia2
    mattmia2 Member Posts: 7,190
    edited June 2022
    A short is any unintended connection between 2 parts of a circuit. Many times people incorrectly call an open circuit a "short".

    https://en.wikipedia.org/wiki/Short_circuit

    In this case it is forcing the 2 nodes at the thermostat to be at the same potential even when the thermostat is open.
    STEVEusaPA
  • 109A_5
    109A_5 Member Posts: 483
    OK I can't help myself here.

    I agree with @GCR and @mattmia2 that a 'Short' or 'Short Circuit' is usually an undesired defect in a circuit causing unintentional results by current flowing in an unintended path or at an unintended time or both.

    A 'completed circuit' could be a 'Short Circuit' in the strictest sense. However, it looks like the common usage of 'completed circuit' is with the case that the circuit is functionally normal with no defects and it is simply in the energized state or 'On'.

    An 'Open Circuit' can be normal state when a circuit's control device is in the state that de-energizes the circuit so that no current is flowing and the circuit is considered 'Off'.

    An 'Open Circuit' can also be a defective in a circuit that when the control device is commanded 'Closed' or 'On' and the circuit does not function as expected due to no current flow caused by the defect.

    Open and Closed have the exact opposite definitions in the Plumbing world as compared to the Electrical world.

    Examples:

    A 'Closed' Plumbing valve stops the water from flowing.
    A 'Closed' switch allows the electrical current to flow.

    An 'Open' Plumbing valve lets the water flow.
    An 'Open' switch stops the electrical current flow.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Dave Carpentier
    Dave Carpentier Member Posts: 410
    I always thought of a "short circuit" as just that.. a shortened path. The electricity couldnt get to where it needed to go, it did a u-turn and went back home. (lol)
    In telecom wires, we used terms like dead-short and partial-short. A partial short is a high resistance connection between the wires due to water ingress or some physical damage (many times due to birds trying to peck the wires for nesting). An intermittent-short would randomly dial numbers (via pulse dialing).
    30+ yrs in telecom outside plant.
    Currently in building maintenance.
    EdTheHeaterManmattmia2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977

    I'm sorry @109A_5 but I must disagree with the statement that the initial problem mentioned in this discussion is in no way a short of any kind, Dead Short, Partial Short, or even a pair of Short-Shorts.
    mattmia2 said:

    A short is any unintended connection between 2 parts of a circuit. Many times people incorrectly call an open circuit a "short".

    https://en.wikipedia.org/wiki/Short_circuit

    In this case it is forcing the 2 nodes at the thermostat to be at the same potential even when the thermostat is open.

    There is only 1/2 of the definition of a short circuit in the given problem mentioned above. Therefore it is not technically a short.

    The 1/2 that is missing is the part that states "....with no or very low electrical impedance. This results in an excessive current flowing through the circuit."

    Since the gas valve is included in the circuit, the normal impedance of the circuit is present, operating the gas valve, although not the intended operation, but also not a Short circuit, since there is no "excessive current flowing".

    When your are right, you are right. An I'm Right, and I know it. :p

    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • Jamie Hall
    Jamie Hall Member Posts: 20,467
    Being slightly perverse... I wonder if the original use of the term "short circuit" may not derive from telegraphy (what's a telegraph, grampa?). There, a short circuit was quite literally that: somewhere along the line between East Overshoe and Smith Station there was a defect in the wire which allowed the signal to be cutoff beyond it (in either direction) but which appeared more or less normal at each end. It wasn't an open -- that was obvious enough -- but it allowed current to flow, it just never made it to the receiving set at the other end. I doubt that the distinction between high impedance shorts and low impedance ones ever mattered, since telegraphy was inherently remarkably high impedance anyway (10 miles of iron wire will do that to you...). And it usually wasn't a matter of crossed wires, either (that gave a variety of very strange problems!), since most telegraphy was earth return.

    Just speculating.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EdTheHeaterMan
  • 109A_5
    109A_5 Member Posts: 483

    When your are right, you are right. An I'm Right, and I know it.

    @EdTheHeaterMan Clearly you don't understand. You are wrong and sadly don't know it.

    Go back and read or re-read the link that @mattmia2 provided.

    In the case of @GCR the DESIRED current is 0.000000000 Amps, Zero, No current flow, No electrons moving. Because of the defect, the 'Shorted Circuit', the control device (the thermostat) is rendered inoperative (from a system point of view) and the circuit has excessive current since ANY current above 0.000000000 Amps is 'excessive' as compared to the desired state of 'Off or an 'Open Switch', No current flowing, None, Zero, 0.000000000 Amps.

    In this case it is not about the impedance of the Gas Valve or the impedance of the AC power source, it is about the impedance of the control device, which the desired state was 'Open' or 'Off', an infinite impedance. Since the 'Short' in this case is with the wires going to the thermostat the low impedance 'Short' is commanding the Gas valve to the undesired active state causing the burner to be active in @GCR's case.

    No where does it define the the low impedance path HAS to be directly across the power source. Just between two nodes of an electric circuit intended to be at different voltages, an 'Open Switch' in this case.

    The shorted battery terminals is ONE possible example BUT NOT the only example. You need to better understand Thévenin equivalent resistance.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022
    @109A_5
    You clearly don't understand what the words are saying in the link that @mattmia2 posted. Here is the first and most important section of the link
    "A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit. The opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes.

    In you followup of that post you selected the portion that any good politician would use. the part that reinforces your position. A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current.
    to travel along an unintended path


    The part that of the definition that proves my fact is with no or very low electrical impedance. This results in an excessive current flowing through the circuit.

    In your infinite wisdom can your explain "with no or very low electrical impedance. This results in an excessive current flowing through the circuit" to me? If you believe the unintended path thru the gas valve's solenoid windings is a path with no or low impedance, then you need to read more books on electricity. Just read the remainder of that Wikipedia article. there it mentions over heating, fire, explosion, damage, and all other unwanted scenarios. They also mention that some short circuits are intentional, as in welding, or perhaps the "crowbar circuit protectors."

    If this were to happen on a 24 volt or a 120, 220 or 440 volt circuit, the result would be the same. The operation of load (with the related impedance of the load) when otherwise unwanted. If that same defect in the wire happened between the source and the return path without the load, then it would be a short circuit. The same piece of wire in one location IS a short and in another location IS NOT a short. So don't get your shorts in a bunch and sit back and learn something!

    @GCR's bad wire is completing a circuit, it is not a short!
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • 109A_5
    109A_5 Member Posts: 483
    @EdTheHeaterMan, Go back and read or re-read the link that @mattmia2 provided. It is you that needs the education. Maybe it will sink in, it is simple. @GCR did not want want his boiler running. The desired circuit current in this case IS NONE, ANYTHING BEYOND NONE is EXCESSIVE !!!!!!!!!!!!

    AGAIN !!!!!!!!!!!! In this case it is not about the impedance of the Gas Valve or the impedance of the AC power source, it is about the impedance of the control device, which the desired state was 'Open' or 'Off', an infinite impedance. Since the wires to the control device are 'Shorted' there is a low impedance path bypassing the control device. A SHORT CIRCUIT !!!

    Talk about a good politician, YOU clearly do not understand the Whole of the article that @mattmia2 posted, you probably never will, because you are stuck on an ill conceived theory that does not hold weight in the real world, no wonder folks have such a hard time understanding Electricity with nonsense like this being spewed.

    If that same defect in the wire happened between the source and the return path without the load, then it would be a short circuit. @GCR's bad wire is completing a circuit, it is not a short!

    Again, your amazingly limited definition of Short Circuit is ONLY ONE example, @GCR's bad wire is completing a circuit, is another, like it or not, It is a short circuit !!!

    "A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages." You seem to conveniently IGNORE the FACT that the two nodes DO NOT have to be across the power source. The author's intentionally used the words "two nodes" to avoid nonsense like yours.

    When the thermostat is 'Open' or 'Off' there is different Voltages on each terminal. With the thermostat wires 'Shorted' that is no longer true, it is a 'Short Circuit'.

    Without looking it up can you define "Impedance" as it applies to an Electrical circuit ??? I can.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Jamie Hall
    Jamie Hall Member Posts: 20,467
    @109A_5 . May I respectfully submit that your tone, if not your content, is out of line with the custom of the Wall.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNEGGross
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022
    @109A_5 Again you misunderstand the word you are referring to. Merrion Webster has 5 different definitions of the word node. In the case of wikipedia's use in the definition of a Short Circuit, https://www.merriam-webster.com/dictionary/node, I do not believe that they are referring to a pathological swelling or enlargement, or an entangling complication, or two points where the orbit of a planet or comet intersects the ecliptic, or even a point, line, or surface of a vibrating body or system that is free or relatively free from vibratory motion.

    I believe that their reference to a node is #5: a point at which subsidiary parts originate or center.

    No I do not believe the thermostat of the limit or any other part of the circuit is the Origination or Source of the electrical current.

    In my diagram, the source is a 9volt battery. In @GCK's example the source of the electricity is a 750 mv pilot generator. With house current it is the power company, and in the house current example a node would be where the circuit breaker panel is located and to be more specific, the section of wire between the source and the appliance, another node would be the section of the wire between the appliance and the common or return path to the source. This includes the circuit breaker and the service line connection back to the transformer's secondary on the pole outside.

    Again it is all about opening your mind to a new concept and learning something new today.

    I love it when I'm proven correct!

    BTW... Thanks @Jamie Hall for the support, however this is just a spirited debate over a difference of opinion. Or more like a difference of fact v. opinion

    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022
    I believe it is important to correct misunderstandings when ever possible. This is a case where using the term incorrectly can result in an undesirable outcome. If @109A_5 were to ask me (as his helper on a job site) to short out the thermostat with a jumper wire, I understand now that he wants me to actually Jumper the thermostat in order to eliminate the thermostat from the circuit in order to verify a part of the circuit.

    If however I did not know this, and he wanted to do the same test and I actually short circuited the thermostat wire it would have a different result and we would be installing a new transformer or a new thermostat.

    Why would I do this foolish jump? Perhaps my superior wanted to put a voltage meter on the other ends of the wire to see if there is any unusual resistance in the wire between the second floor thermostat location and the boiler room. How am I supposed to know why he wants it shorted and not jumped. I'm only the helper that was properly "teached" what a short circuit is, in technical school.


    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • gerry gill
    gerry gill Member Posts: 3,047

    GCR said:

    Thanks for all the helpful comments. Disconnecting the thermostat wire at the valve fixed it. Testing confirmed a short in that wire. Will replace.

    I understand what you mean by "Short in the wire" however that is the incorrect term for the condition. A short circuit is when you have a conductor that connects the positive end of a battery to the negative end of a battery without a load. In AC house current is would be like placing a paperclip in a power outlet connecting the source to the return path (the white and black wire) with no load.

    On your Millivolt gas valve circuit, there is very little current and therefor no fire hazard from overheating electricity in the event of an actual short circuit. The powerpile generator may fail if shorted out. In your case there is no short. Just a bad wire that is connected somewhere, where it should not be connected.

    The correct term for your condition is a completed circuit. If a thermostat wire has insulation that is compromised (a staple or nail for example) and completes the circuit before the thermostat switch contacts, there is no short circuit. Here is a simple illustration.
    I love the diagram Ed. you must be a great teacher.
    gwgillplumbingandheating.com
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

    EdTheHeaterMan
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,977
    And this is what's wrong with our country...someone has to be 'right' at any cost.
    Who cares, the problem was solved.
    Terminology differs, but everyone seems to understand.
    steve
    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022

    And this is what's wrong with our country...someone has to be 'right' at any cost.
    Who cares, the problem was solved.
    Terminology differs, but everyone seems to understand.

    And that is why I get banned from facebook. It is too much fun to argue a position that is so controversial as politics that gets people's "SHORTS" in a bunch LOL. But I learned about electricity in an electrical class many many years ago. The teacher pounded that point into the students over and over again.

    I'm sorry if @109A_5 was a little spirited is his reply. I never took offense to his replies. I rather enjoyed them. I was hoping to find his rebuttal to my NODE definition. But perhaps he has given up on his quest and admitted that he may have been mistaken. I understand that, at times, it is difficult to admit ones mistakes, Although I personally have never actually had to do that.

    Respectfully Submitted,
    Mr. Ed
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • JUGHNE
    JUGHNE Member Posts: 10,315
    The gas valve has a power source/circuit and a switching/tstat circuit.

    A "short" in the power circuit would waste the fuse/source.

    A "short" in the switching circuit would energize the gas valve/load with no damage to the source or gas valve.....hopefully the gas was ignited properly.....

    IMO

    The "short" term is used incorrectly by most lay people.
    It is quicker to correct their problem than try to explain that they had a loose connection and not a true "short".
    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    @JUGHNE But it's more fun to win an argument against a colleague. Leaving the consumer out of the equation of course. This would have been the debate in the truck on the way home from the service call.

    Still looking for my Protagonist's point of view on the definition of NODE as it applies to electrical circuitry. He was the one who made a point of the term that makes this discussion clear as mud.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • mattmia2
    mattmia2 Member Posts: 7,190

    Still looking for my Protagonist's point of view on the definition of NODE as it applies to electrical circuitry. He was the one who made a point of the term that makes this discussion clear as mud.

    https://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws#Kirchhoff's_current_law
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,977
    edited June 2022
    That description of Kirchhoff's circuit laws uses the word NODE five times, however it does not actually define the term. I believe this better describes the term NODE as it applies to electrical circuits in the terms of the off topic discussion at hand. https://en.wikipedia.org/wiki/Node_(circuits)

    And the fact that the original post was already resolved, The discussion has gone off topic in a Fun Way! IMO
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • Dave Carpentier
    Dave Carpentier Member Posts: 410
    FWIW, in telecom before we got our own fancy dmm sets, we would "short" the line so the central office guy could check how many ohms he could see from that end. An open circuit from his end would indicate a broken wire somewhere, and a higher than expected ohm reading would indicate a partial open. Problem was, many guys would use their scissors or knife to cut across the wire pair insulation to make that short. It would be a quick way to complete the test but years later would corrode open. Job security ?
    Anyhow, point being that the telecom low voltage pair is current limited. "Shorts" cause an increase in current flow which the telcom switches would detect and act on (draw dial tone, or dial a pulsed number). We could put a dead short across the wire pair right in the central office and it wouldnt blow a fuse.. the switch would just recognize it as an off-hook condition.
    So.. I think I'd like to go with short = an unexpected contact between conductors in a circuit path.

    30+ yrs in telecom outside plant.
    Currently in building maintenance.
  • Jamie Hall
    Jamie Hall Member Posts: 20,467
    I'd go with your definition, too, @Dave Carpentier . Do I recall correctly that one could "dial" a number if one had a good sense of timing by simply manipulating a short?

    Thing that still amazes me is how robust, really, the wire line and central office telephone equipment was. Not only were the bits and pieces (like your telephone) pretty near bullet proof, but the whole system just worked. There have been many times the power went out and I have just picked up the 'phone and called the power company -- and the expectation was that the 'phone would work, and it did.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 7,190

    I'd go with your definition, too, @Dave Carpentier . Do I recall correctly that one could "dial" a number if one had a good sense of timing by simply manipulating a short?

    Thing that still amazes me is how robust, really, the wire line and central office telephone equipment was. Not only were the bits and pieces (like your telephone) pretty near bullet proof, but the whole system just worked. There have been many times the power went out and I have just picked up the 'phone and called the power company -- and the expectation was that the 'phone would work, and it did.

    The dial is just a clockwork that shorts the line the number of times corresponding to the number you dialed.

    A pots line is a copper pair back to the CO and the CO has battery banks and generators to keep it up and your line powered in a power outage.
  • JUGHNE
    JUGHNE Member Posts: 10,315
    But not today with fiber optics.
    We have fiber to the house and we have to furnish power to make it operate.

    There is a battery pack plugged in to carry us thru power outages.
    It might last 1-2 days with limited use.
    If the batteries die we have no landline.
    Fiber does not carry the 48 volts that the copper pair did.

    I do the HVAC for our phone company and did notice that their battery bank is now only a third of what it used to be. It is for in house equipment back up only, to carry them thru the generator start up/transfer switch should they lose power.

    And with the FO systems now installed in the building the cooling load has dropped to about half of previous.

    Brother has AT&T phone thru cable, drop power for modem and phone drops out.
  • Jamie Hall
    Jamie Hall Member Posts: 20,467
    I know, @JUGHNE . We don't have fiber to the house -- maybe someday, they tell us -- but the copper line transitions to fiber 3 miles down the road, and there is a power supply there. Which lasts maybe a day or so. If you're lucky. Not the reliability there once was, but I'm sure it's cheaper and easier to maintain from there, and carries a lot more calls and data.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 7,190
    Being able to communicate in an emergency is overrated. i keep asking this question of those replacing the pots phones with voip phones at work, no one seems to have an answer.