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Trianco Heatmaker HW-series

XJMan
XJMan Member Posts: 14
OK, here goes.



I have a Trianco Heatmaker HW-series (pre-MarkII).  Everything electronic seems to be functioning properly, but It keeps locking out.  The end result is the unit runs itself cold.  Once this happens, she leaks a bit.

If I leave the 2 heating Zones off, it seems to be happy and will maintain above 160 degree temp (as shown on the temp guage). 



Things I've noticed:

1. When the unit ignites, it runs for approx. 15 sec then shuts down the flame (even when the zones are calling)

2. When #1 occurs, there is a faint click (not the stacked switch) then the flame turns off.

3. Occasionally, the relay on the Gas Valve "double clutches, toggles" also causing the flame to go out.



 The low limit switch and S89C controller have been replaced recently.  The gas valve toggling would seem to indicate some type of intermittent voltage drop.  I've checked everything twice and can't seem to find the root cause.  I've been fighting this thing for a week and need some ideas.
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Comments

  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Look for the following

    1. Cross contamination of the vented flue gases with the intake air. This can easily be tested with a combustion analyzer, any CO2 above 1% in the air intake side is cross contamination.



    2. Moisture in the Combustion chamber, backed up condensation



    3. Poor combustion CO2 reading should be between 8.0 to 8.5 O2 between 7 and 6



    4. Gas valve malfunction



    5. Boiler integrated control malfunction



    6. Stack switch or operating control



    7. Igniter failure



    If the temperature will not rise above 160 degrees F look for moisture in the chamber affecting the flame signal. This could also be the result of a defective thermostat in the thermostatic union.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    leak

    Where is it leaking from???
  • XJMan
    XJMan Member Posts: 14
    edited February 2011
    Thanks!! Seems to be a common theme within your answer.

    Here are my questions, generated by your answer.



    1. Cross contamination.  When measuring the CO2, where is it measured??



    2. I've checked the flue (concentric pipe) and it seems to be OK. 



    3. Poor Combustion:  This measurement is taken at the exhaust?? 



    4. There is an awful lot happening at that relay.  You can here it cycle (clicking) it also occasionally buzzes.   I was wondering whether it had something to do with feedback from the (what I suspect is) a differential pressure valve ???

    5. Boiler integrated control ?  The controller is an Honeywell S89C1095 which has been replaced.  It's new.  It ran for a day or so after the swap out.  Then reacted the same as the original controller.

    6. Stack Switch or operating control.  I've looked, electrically at these, and both seems sound.  The Stack Switch and TCO are tied into the operation of the Gas Valve, which during operation will draw between .2A to .56A so I was wondering whether one of the switches impedance is fluctuating to cause the Gas Valve relay to toggle.

    7.  The igniter is igniting %98 of the time.  Though I did notice a few fails.  I was told that if it wasn't working, it was an "all or nothing" scenario.



    Other observations:  I did notice that when the system isn't operating (i.e. the burner is not ignited) the blower will shutdown but the internal circulator pump seems to run continually.  It will shutdown completely at times (both blower and internal circulator are OFF) but for the most part the internal circulator is ON.



    Thanks for the help, it is appreciated. 
  • XJMan
    XJMan Member Posts: 14
    leak

    From the seal where the DHW coil enters the tank.  ONly when the temp / pressure drops.  It seeps, more than anything else.  It's a nuisance, that will have to wait until warmer temperatures.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Do you have the manual for

    Heatmaker? Or do you have Technical Bulletin 92-05 of May 16, 1997? That bulletin illustrates location for cross contamination testing and combustion testing.

    If you e-mail me with your e-mail address I can send it to you or I can FAX it to you if you have a FAX number.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    You can also get in touch with

    Tech Service Department at Laars, they now handle Heatmaker issue. The phone number is 800-900-9276 Ext 4 for George Peteya or e-mail [email protected]
  • XJMan
    XJMan Member Posts: 14
    Heatmaker manual

    I do have the manual.  Though it's quite ambiguous ( it mentions flame/vent lights etc) my unit has no indicator lights to speak of. 



    The tech bull, I do not have. 



    I do not have an available fax number.  I'm also not sure what the rules are on posting an e-mail address.    I think you can add a file to the posts though.



    Thanks I do appreciate everyone's input. 
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    My e-mail address

    is [email protected]
  • XJMan
    XJMan Member Posts: 14
    Makes no earthly sense.

    OK, so my configuration is 2 zone controls that run to a relay that powers a single circulator.   When I was running the system, I would manually engage Zone 1 and things would seem to run fine for awhile.  I would engage Zone 2 (both zones enabled and calling) and then the gas valve relay would engage, but would toggle OFF and ON (during the toggling, you can hear the flame go out and reignite.)   Zone 2 would not start the circulator when enabled on it's own. 

    SO....I pulled the zone controller for Zone 2.  Leaving only zone 1 wired.  Turned the system back ON, and everything was happy.  The system ran all night and into yesterday without an issue.  Brought the house up to the thermostat set point (68 degrees) and ran fine until about 5pm.  Then the Gas Valves relay started buzzing and toggling again.  

    I shutdown the system for 15 minutes, and restarted.  The unit powered up, blower came ON, nothing at the Gas valve.  No relay engage.  No ignition in the chamber.  Fini.  Tried this a few times, with the same result.  So I pulled the wires to the Gas valve, threw a Volt meter inline, and started the system.  Unit powered up, blower came ON, 24V shows on the meter (so the Gas Valve should have engaged if it was connected).  System then shuts down, because it didn't ignite.  Turn all power to the system OFF.  Reconnect the Gas valve.  Power ON.  Gas Valve does not engage.  System shuts down.  I cycled the power several times, and finally, the Gas Valve relay engaged.  Through you can hear it buzzing and toggling ON and OFF. 



    I truly think my Gas valves relay has called it quits.  Is there something else that would cause the Gas Valve relay to toggle???  I've called a local plumber,  to see if he can verify the CO2 levels as suggested, in previous replies.    If the CO2 levels are off, why would it run for almost a full day without issue ??  HELP??? 
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    I meant to ask you this before

    the HW provides domestic hot water. Is you r unit working to provide hot water?



    Also the gas valve on this unit is a negative pressure gas valve. The outlet pressure should be between negative .05" W.C. and negative .35" W.C. (water column) as measured with a digital manometer. This assumes an inlet pressure of 4" W.C. up to 14" W.C. Have your plumber check that as that could cause the solenoid in the gas valve to do what you say it is doing.
  • XJMan
    XJMan Member Posts: 14
    Hot water

    The system will, as long as the temperature is sufficient, provide hot water.   



    I'll have the plumber check out the orifice to insure the operating setup of the Gas Valve.



    Thanks again.
  • Tony_23
    Tony_23 Member Posts: 1,033
    heatmaker

    You should be checking voltage to the gas control with the wiring still connected. Also, just because it gets voltage and doesn't fire doesn't mean its not opening.



    When was the last time the combustion coil / chamber cleaned ?  If the ignitor gets a buildup around it it will overheat and short, shutting down the flame.



    There are limits in the gas valve circuit that may be weak, especially if they've been wet.



    Sounds like you need experienced, professional eyes on site.
  • XJMan
    XJMan Member Posts: 14
    Updates

    Just to keep everyone apprised and for future searches of Heatmaker issues.



    Yesterday I talked to George at Laars.  He gave me a few things to check.  One of which requires a manometer which, unfortunately is not something I have in my tool box. 



    The plumber I've been dealing with told me, ignitors are either bad or good.  This information is erroneous.  Ignitors should be between 50 Ohms and 80 Ohms for proper ignition.  I checked mine, and it's running at about 110 Ohms.  It will be replaced post haste. 

    Another thing observed is:  The Gas Valve relay starts toggling around 170 degrees and above. 



    Tony,

    I've been looking for experienced eyes, and well, seems hard to come by with regards to this generation of system.  As far as the internal plumbing of the system is concerned, they handle that quite well.  Once into the "nitty gritty" of the electrical side, that is where experience seems to deteriorate. 

    To your point of checking voltages while connected.  This has been done. 

    When energized, the Gas Valve is receiving 25V @ .2 to .5A.  The current definitely sags, then climbs to almost .6A when the Gas Valve relays starts buzzing. 



    Neither the gas valve, nor any other electrical component has seen water of any type.  Although, I stated above, the system does leak a bit when the temp/pressure drops, it's more seeping than anything else.  

    You stated,   "There are limits in the gas valve circuit that may be weak".   Could you clarify those limits ??  Electrically, I'm capable of checking pretty much anything.   I do think it's quite interesting the Gas Valve toggles only above a certain temp (~~170degrees).  I've also checked the impedance of the TCO while the unit is fired and only saw marginal fluctuations.  The TCO was maybe 10 Ohms +/- 2Ohms when the system was fired. 



    Again, thanks to everyone for your input.  
  • Tony_23
    Tony_23 Member Posts: 1,033
    Limits and voltage

    Does the voltage at the gas control drop at all when this "toggling" occurs ? If it does, that indicates a component in the circuit that is opening. If not, then I think its the gas valve coil going bad. It may not be temp related, but time related and just seems like temp related.



    If you trace back through the wiring from the gas control you'll find temperature limit controls in that circuit. Check those while in operation.
  • haventseenenough
    haventseenenough Member Posts: 61
    heatmakers

    Are u running with the old style snap disc aquastats or retro fitted honeywell 4006 aquastats? Troublemakers will run with an ignitor with upto 130 ohms of restiance, but still should be replaced.Gotta love Troublemakers. Hire a qualified tech,get satifaction with a job well done.It will waste less of your time and get the problem solved.
  • XJMan
    XJMan Member Posts: 14
    Weekend Updates

    I replaced the ignitor Friday evening when I returned from work.  



    Turned the system on, and it ran itself up to 210 and shut down as it should.  I then, manually,  enabled the zone valve.  The system ran for 2 hours without incident, no toggling of the Gas valve, everything worked fine.   Disabled the switch at the zone valve and enabled the thermostat.  Again, the system ran without issue, up to yesterday afternoon.   It, again, ran itself cold (~~110 degrees when I checked it).  



    I turned the thermostat OFF.  Cycled power to the unit, it took 2 power cycles to get above 160 degrees.  Once up to ~~180, I turned the thermostat back ON, and she ran overnight, again, without issue.  No toggling of the gas valve,  no problems evident. 



    To answer the questions from the last replies. 



    1> The voltage stays consistent, during operation, though the Gas Valve toggling and buzzing.  After I replaced the ignitor, as stated above, the Gas Valve was behaving, at least while I was present.



    2> The unit has a clip on aquastat.  (low limit ??)  3-wire (Brown, Red and Black).  It's located close to the tank, under the insulation, on the DHW output. (If memory serves).



    Thanks again all.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    HW

    The easiest way to find your problem is to bypass ALL safties for a few minutes by feeding 24 volts to the ignition control and see if the boiler runs properly. This is a temporary method only. If it runs proper then work your way backwards untill you find what control or safty is keeping the boiler from running.

    I do stress it is a tempory bypass. Since all of the safties and controls have been bypassed the boiler will overheat if you try to run it this way. DON"T
  • Tony_23
    Tony_23 Member Posts: 1,033
    Or

    You could just use a voltmeter and leave the jumpers alone.



    Since the voltage doesn't fluctuate to the gas control, that eliminates the limits.



    If you didn't clean the debris from around the ignitor inside the coil cabinet, you're not done.
  • XJMan
    XJMan Member Posts: 14
    It's back again

    The Gas Valve relay toggle has returned.  I've got the actual manual for the unit from Laars.  From the schematic, the Stack Switch and TCO are the other components physically tied into the Gas Valve circuit. 



    I'll keep it posted.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    meter

    Tony - The reason to use jumpers instead of a meter is sometimes the voltage or switch may open for a period of time that is too short for the meter to read other than a change in the digits.

    If you use a jumper it eliminates very short term changes.

    If you jumper a safty for a test period it eliminates that item from the cause.
  • haventseenenough
    haventseenenough Member Posts: 61
    saftie issues

    one thing i don't think i'v seen mentioned is the air pressure switch. how long are you going to suffer through this until you hire someone.
  • XJMan
    XJMan Member Posts: 14
    Updates etc.

    I used the jumper method above to determine, what seems to be the root cause.  I 1st jumped the Stack switch for one cycle of the unit.  Gas Valve continued to toggle during operation.  I then jumpered  the TCO and no toggling occurred.  Restoring the connection and again, running through a cycle brought the toggling back to the Gas valve.



    Checking the TCO during normal operation, the impedance seems to fluctuate wildy during the toggling of the gas valve. 



    As to how long I'm going to suffer??  I don't have the time to take from work, or the money to have someone come in an shotgun parts through the system.  Historically, there has been no one local to me, who has enough experience with this unit to actually approach problems systematically.  Though, this has been painful, on my side.  It is manageable. 



    I do appreciate everyone who has taken the time to respond.   It certainly highlights, all the expertise that is available on this site.  From a home owners perspective, I would love to be able to have someone come in and pinpoint problems with this unit, fix them, and be done with it.  Unfortunately, that hasn't been my experience.  I do appreciate this system is OLD!!   It's what I have for now. 



    Again, thanks to all who have responded.  It is appreciated.
  • Tony_23
    Tony_23 Member Posts: 1,033
    More

    Tinkerer, a "change in digits", even momentarily indicates a switch that is breaking contact.



    XJMan, the TCO tripping out indicates that the combustion coil needs cleaning (outside of coil, not inside), the circulator isn't moving water fast enough or the coil needs to be bled. Smart money's on the cleaning.
  • Slimpickins
    Slimpickins Member Posts: 323
    What Tony said

    I've been meaning to chime in on this but have been super busy. The TCO I believe is only on the pre Mark II models and it's probably doing it job. The outside of the heat exchanger coil does get dirty and clogged, especially on one that old. They especially get clogged if the vent isn't pitched down toward the termination cap and a combustion analyses hadn't been done. Back in the day I used a the old Bacharach barbell tester with the red fluid for the CO2 and the green for O2.



    To clean the coil, you need to remove the inducer, igniter, and flame holder. Don't lose the white piece of insulation material on top of the flame holder. You may have to stick it on with some red silicone when you reinstall it. You will also probably need to replace the flameholder gasket. You will need to remove the 5" intake and the 3" exhaust, just lift it up and push is aside. Then remove the 3 screws and nuts to the chrome bonnet of the coil and pop off the bonnet. Have a shop vac, good dust mask and a wire brush ready to go and get to scrubbing while the shop vac is running. You don't wanna breathe the dust. Be careful not to damage the refractory material on the bottom. Put it all back together, fire it up, use a gas detector on the gas union you had to break apart. Bust out your CO detector and sniff around where the inducer connects to bottom of the flame holder and use your combustion analyzer to check combustion. While doing this, have your manometer hooked up correctly and make sure your gas pressure is negative and within specs. You may need a new gas orifice and a lettered drill index A to Z. I think it comes from the factory drilled out with a D. I've had to drill out the orifice a couple sizes to get my combustion numbers right.



    I would not advise doing this without the proper testing tools, experience and availability to parts. It being a pre Mark II, you need to suck it up and replace it. May I suggest a Triangle Tube Prestige Excellence?
  • Slimpickins
    Slimpickins Member Posts: 323
    What Tony said

    I've been meaning to chime in on this but have been super busy. The TCO I believe is only on the pre Mark II models and it's probably doing it job. The outside of the heat exchanger coil does get dirty and clogged, especially on one that old. They especially get clogged if the vent isn't pitched down toward the termination cap and a combustion analyses hadn't been done. Back in the day I used a the old Bacharach barbell tester with the red fluid for the CO2 and the green for O2.



    To clean the coil, you need to remove the inducer, igniter, and flame holder. Don't lose the white piece of insulation material on top of the flame holder. You may have to stick it on with some red silicone when you reinstall it. You will also probably need to replace the flameholder gasket. You will need to remove the 5" intake and the 3" exhaust, just lift it up and push is aside. Then remove the 3 screws and nuts to the chrome bonnet of the coil and pop off the bonnet. Have a shop vac, good dust mask and a wire brush ready to go and get to scrubbing while the shop vac is running. You don't wanna breathe the dust. Be careful not to damage the refractory material on the bottom. Put it all back together, fire it up, use a gas detector on the gas union you had to break apart. Bust out your CO detector and sniff around where the inducer connects to bottom of the flame holder and use your combustion analyzer to check combustion. While doing this, have your manometer hooked up correctly and make sure your gas pressure is negative and within specs. You may need a new gas orifice and a lettered drill index A to Z. I think it comes from the factory drilled out with a D. I've had to drill out the orifice a couple sizes to get my combustion numbers right.



    I would not advise doing this without the proper testing tools, experience and availability to parts. It being a pre Mark II, you need to suck it up and replace it. May I suggest a Triangle Tube Prestige Excellence?
  • Slimpickins
    Slimpickins Member Posts: 323
    What Tony said

    I've been meaning to chime in on this but have been super busy. The TCO I believe is only on the pre Mark II models and it's probably doing it job. The outside of the heat exchanger coil does get dirty and clogged, especially on one that old. They especially get clogged if the vent isn't pitched down toward the termination cap and a combustion analyses hadn't been done. Back in the day I used a the old Bacharach barbell tester with the red fluid for the CO2 and the green for O2.



    To clean the coil, you need to remove the inducer, igniter, and flame holder. Don't lose the white piece of insulation material on top of the flame holder. You may have to stick it on with some red silicone when you reinstall it. You will also probably need to replace the flameholder gasket. You will need to remove the 5" intake and the 3" exhaust, just lift it up and push is aside. Then remove the 3 screws and nuts to the chrome bonnet of the coil and pop off the bonnet. Have a shop vac, good dust mask and a wire brush ready to go and get to scrubbing while the shop vac is running. You don't wanna breathe the dust. Be careful not to damage the refractory material on the bottom. Put it all back together, fire it up, use a gas detector on the gas union you had to break apart. Bust out your CO detector and sniff around where the inducer connects to bottom of the flame holder and use your combustion analyzer to check combustion. While doing this, have your manometer hooked up correctly and make sure your gas pressure is negative and within specs. You may need a new gas orifice and a lettered drill index A to Z. I think it comes from the factory drilled out with a D. I've had to drill out the orifice a couple sizes to get my combustion numbers right.



    I would not advise doing this without the proper testing tools, experience and availability to parts. It being a pre Mark II, you need to suck it up and replace it. May I suggest a Triangle Tube Prestige Excellence?
  • tim smith
    tim smith Member Posts: 2,398
    Re: HW series heaters

    Cleaning the heat exchanger is a must. But there may be another problem. We have found that the internal pumps on these units get a weak internal overload and when they approach 210 running temp on the water they will trip and pump shuts down causing the eco to shut off boiler prematurely. A real pain as it can be intermittent. As stated above, clean combustion chamber thoroughly, make sure the igniter and burner gaskets are in good shape when you assemble. Ps, if you have problems getting parts, we have plenty as my partner had ordered quite a few over the years when we worked on a fair amount of these. Now most have been replaced except save a couple. Good luck, Tim
  • XJMan
    XJMan Member Posts: 14
    Thanks again to all

    I do realize it's, more likely than not, well beyond "time" for this unit.  Unfortunately, times have made things quite tight financially.  I won't bore you with the sordid details. 



    The TCO was replaced and it's been running well with both zones fully enabled.  I'm still crossing my fingers though.  One thing I did notice, is the TCO is an NC switch.  So, if the temp within the ignition chamber gets too high the switch opens and effectively shuts down the Gas Valve.  What if the TCO fails??  It, I would assume, would fail to it's NC state. NO??   If it fails closed, and the temp in the ignition chamber gets too high it won't shut anything OFF. 

    What is the trip point of the TCO ??  At what temp does it open ?  (I know it's the same question)  The TCO that was removed was ......bouncing ( for lack of a better term) it's impedance would jump, during normal operation, from 10Ohms to 2KOhms. Effectively, messing up the current required to hold the Gas valve relay closed (and the valve open).

    So, the original TCO was essentially bouncing opened and closed, which was presented as the Gas Valve relay toggling. 



    Again, thanks all
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    XJ MAN I am glad you got it fixed

    sorry I did not get back to you but I was not feeling to well.



    Here is an answer from the Heatmaker Pre Mark II manual (1984 to 1991):



    VII. TCO (located next to igniter) or blower proving/stackswitch related lockouts



    The TCO and the blower proving (stack) switch are connected in series with the gas valve power. If either component fails, or opens due to a fault during ignition trial sequence or during operation, the gas valve will be de-energized. This is sometimes recognizable as a chattering gas valve.



    TCO: Senses the flue gases between fin coils for temperatures exceeding 450°F.

    This condition may be due to pump or pump relay failure, or fouled or scaled fins on the combustion coil tubes. 



                                           .

    If coils are found to be externally contaminated, check for vent problems such as cross contamina­tion or improper pitch back toward the appliance.



    If unit runs more than 2 minutes below 160°F, condensation will occur on coil tubes: eventually resulting in plugged flue passes. This may be caused by absence of or by failure of thermostatic union on H and HP models.

     

    If the TCO fails the Stack Switch will shut the system off. If it continues to heat up the relief valve will blow.
  • XJMan
    XJMan Member Posts: 14
    Hey Tim

    No problem.  I hope you're feeling better.



    As stated in my previous post.  The TCO seems to have taken care of the issue of the toggling Gas valve.  I kept an eye on it, for obvious reasons, last night to insure nothing else was amiss.  The system pressure wasn't fluctuating during the operation, and it was running up to temp (~~210) when the zones were calling as one would expect.  So I'm crossing my fingers, here at work, that everything will be fine when I arrive home.



    Again, I can't thank everyone enough for their time and expertise.  I'm sure it's painful to here some of the woes from us homeowners, when we traipse into the land of you professionals.   Alas, these times dictate one's need to perform tasks that, I personally, would leave to you professionals under normal circumstances.  If you ever have questions regarding robotic systems, feel free to ask.  That's more up my particular alley. 



    I'll be back to ask about system replacement recommendations.  I've one so far (Triangle-tube Prestige Excellence).  I'm sure there are considerations for zone size and hot water usage etc.   I'll cut that question loose on a different post.



    Again, thanks to all.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Tony

    Tony - What do you use jumpers for? What do you think they are made for.

    Using jumpers is a very safe way to diagnose problems if they are used properly.

    I have FLUKE meters - How many homeowners do you think have $450 meters?

    Most meters don't respond fast enough to show a short term break.

    Just having the gas valve toggeling on and off will cause the voltage and resistance through the tested devise to change. Thus causing the digits to change.

    That is why I and most qualified tech's use jumpers.

    I am not just a service tech - I own an HVAC company.
  • Tony_23
    Tony_23 Member Posts: 1,033
    Really ?

    So what. So do I. Owning the company doesn't make you a better tech, being a better tech makes you a better tech. ; )



    FYI, a load downstream of a switch receiving fluctuating voltage will NOT cause fluctuation in the voltage across said switch. A $450 Fluke or a $150 Fieldpiece or a $30 Radio Shack voltmeter will all give the same results in this instance.



    I use jumpers on T-T terminals to keep myself from running up and down the stairs and F-F terminals to ohm out cad cells. That's pretty much it.



    The TCO's purpose is more of a backup to the safety limit and operating limit. That, and indicating a dirty coil.
  • XJMan
    XJMan Member Posts: 14
    Another update

    OK, to reflect on the last few posts. 



    1> I do have a Fluke. To Tony's point it wouldn't matter what type of meter was used the result would be the same.  I have an Ideal meter as well, same result.



    2> The impedance of the TCO was measured while the TCO was jumpered.  Thus, it wasn't in the circuit, or being influenced by any device downstream.   I did measure it both in and out of the circuit though. 



    It does become a matter of Ohm's law though.  V = IR  Current like water, is restricted by resistance.  As the resistance of the TCO climbs the current available to hold the Gas Valve relay closed, diminishes. 



    Regardless, the system ran all weekend without a hitch. 



    Thanks again all.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Jumpers

    The use of a jumper (temporary for just troubleshooting) in a troubleshooting process is to be able to cause a switch which may be suspect of holding something from working to be bypassed.. We jump switches but never loads. You do have to be careful however when using a jumper so that you insure that a resistive type sensor should not be jumped as the electronics is setup to read a variable resistance on that type of thing and jumping it could damage the electronics..



    The method that I teach for troubleshooting requires when multiple components (switches0 are suspect you have to jump out at least one of them to find out if the other is not working..
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Tony

    Tony - a gas valve is NOT a pure resistive load. As the coil is energised the amp draw is high thus the load acrost the " switch" will be higher than when the solenoid is drawn in and the amp draw goes down. So YES the voltage will change acrost the "switch"

    This is why the furnace transformer will burn out if the condenser contactor doesn't pull in.

    My FLUKE has a bar graph - I havn't seen a fieldpiece or radio shack meter with one.

    The bar graph WILL show very fast changes that the digital meter will not.
  • Tony_23
    Tony_23 Member Posts: 1,033
    Yes, but

    the voltage will be the same on BOTH sides of the switch.  The switch with differing voltages is the problem.



    My meter reads into hundredths of a volt. It changes fast enough to see w/o a bar graph. ; )



    The real issue here is, the TCO didn't just go bad, it became weak. That is only going to happen because of overuse. Merely replacing the TCO didn't cure the problem, it only masked it by using a band-aid. The HM will start cutting out the flame, only it won't be noticed right away because it will not be enough to cause a lack of output to the house. Clean the coil.
  • Tom Blackwell_2
    Tom Blackwell_2 Member Posts: 126
    Troubleshooting

    Intermittent failures are always difficult to diagnose. I use two "tricks" that might help. First I have an analog Simpson meter-it will usually show a fast fluctuation. If I can't catch it with that, I wire an old fashioned flash bulb across the suspect contacts. The flash bulb will fire if it is presented with voltage, and will not pass enough current to complete the circuit if the aforementioned safety contacts open. Used this to find an intermittent fault in a Carrier chiller that lept failing in the middle of the night-compressor discharge thermostat on a centrifugal machine. Glad you seem to have solved your problem. As a final note-arrange to measure the discharge temp from the hx to see if it is near the setting of the limit.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Tony

    The switch will NOT have the same voltage on each side. Unless it is grossly oversized it WILL have a voltage drop from one side to the other. Even a piece of wire will have a voltage drop from one end to the other if a load is placed on it.

    The voltage drop will rise as the switch gets older.

    If you don't feel comfortable using jumpers as a TEMPORARY service tool that is your choce. I use them all of the time and have never had a problem. ( 36 years in business )
  • XJMan
    XJMan Member Posts: 14
    The finale!!

    I have a datalogging O-scope that I've connected to the circuit.  From the logs, there has been no cutouts of any sort in the system.   Though, I agree it is well beyond time for someone to "tear" into this unit.  Whether it be complete removal, or a thorough cleaning??

    I'm sure the coil does, indeed, need to be cleaned.  I've been here for 12 years, and none of the people that have serviced this unit have eluded cleaning or any other type of service.



    What would a thorough cleaning cost ??  From reading the manual there is a healthy amount of disassembly that is required.  Or would this type of work be considered, "feeding the dead horse"??  



    Again, thanks to all. 



    I live by the motto; The dumbest question you'll ever ask, is the one you don't.



    XJ 
  • Tony_23
    Tony_23 Member Posts: 1,033
    Cool

    A data-logging O-scope. Owned by a homeowner no less !  : ) Does it have a fast-reacting bar graph ?  ; )



    FTR, I've seen gas controls that, once open, would hold open down to 18 volts input. I wanna see the switch or 2 ft piece of wire that loses that kind of voltage as "normal" loss.



    Enough busting about that..... : )



    I can remove a coil, clean it inside and out, reinstall it in 5-7 hours. Depends on how bad it is and whether I need to take it back to my shop to do it. Jobsite conditions dictate that. I know most guys are scared of my method, but I use hydrochloric acid to flush the inside and have more in a tub to immerse the coil in for cleaning the outside. They come out looking like new copper. Sometimes the inside doesn't get everything out, but there shouldn't be much inside anyway. Flushing/rinsing with clean water is very important before reinstalling.
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