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Noobie question on a Taco SR501-4

jenbury
jenbury Member Posts: 10
Hi, I am new to troubleshooting my 1957 American Standard Boiler system, but what the heck, gotta start somewhere. Woke up to no heat Sunday and traced it back to a blown 6a fuse in my SR501-4 Relay. Replaced it, the boiler made the good "let's turn on" noises for a second, then it blew again. From the wiring diagram it looks like the next step is to troubleshoot the circulator, but I have no idea how to do this and what to do next. Anyone care to walk me through this? Maybe I can do this faster than it takes for my HVAC guy to make time for me... appreciate any help
!

Comments

  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    The quickest way would be to unwire the circulation pump from the control, replace the fuse, and start it up again. If the fuse does not blow, then it is either the pump or the wiring going to it. If the wiring looks good, then you will have to replace the pump. (p.s. make sure all the electrical connections are tight before you do anything. If you have a loose wire connection, it could cause this.)
    If you have the equipment and the ability, then you can do a resistance check on the pump and see if it is shorted out.
    Rick
  • jenbury
    jenbury Member Posts: 10
    Good starting point - exactly what I needed, thanks. To check the pump, I assume you mean the Ohm reading with a multimeter?
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    Yes, use a multimeter. I am not sure of the proper reading, but I would mostly be checking for a direct short. Generally when I have a pump go out, they just don't work. I have never had a fuse blow in one of those control boxes before, so this is new to me also.
    Rick
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,335
    @jenbury

    with an ohmmeter and the power shut off disconnect the circulator wiring(both wires) at the SR5014 and check those leads 1 at a time to ground. they should both read 0.

    If you don't get 0 disconnect the wires at the circulator terminals to ground....should be 0

    The wires between the SR and the circulator should be 0 volts to ground with both ends disconnected
  • jenbury
    jenbury Member Posts: 10
    Got it, thank you. Found out the issue is deeper than the circulator. The circulator powers up when bypassing the electronics and just plugging it into an extension cord. There is a short in the water temperature gauge which is causing the trip. :-/ So off to find a boiler repair person to fix it.
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    So now I am more curious. What has the water temperature gauge got to do with the pump relay? How is this wired up, and to what?
    Rick
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    The

    So now I am more curious. What has the water temperature gauge got to do with the pump relay? How is this wired up, and to what?
    Rick

    Probably the aquastat

    steve
  • HVACNUT
    HVACNUT Member Posts: 5,752
    jenbury said:
    Got it, thank you. Found out the issue is deeper than the circulator. The circulator powers up when bypassing the electronics and just plugging it into an extension cord. There is a short in the water temperature gauge which is causing the trip. :-/ So off to find a boiler repair person to fix it.
    Can you explain that a little more? What @rick in Alaska suggested is correct. If there's no short in the wiring, I would think that running the circulator off an extension chord only means the circulator is drawing more than 6 amps but less than 15 amps at the breaker. Unless something other than the circulator is wired to terminal 4.
    I had one about a month ago. It was on an SR506. No short in the wiring or motor. Windings closed, but locked rotor amps on start.
    Explain this water temperature gauge theory.
    HomerJSmith
  • HomerJSmith
    HomerJSmith Member Posts: 2,395
    What kind of pump do you have? My thought was locked rotor. Is it actually spinning?

    You can take the pump apart and check the impeller and the rotation. These pumps are not high torque motors and can be stopped with a solder ball in the volute or debris in the cartridge like in a Taco pump.

    If disconnecting the power from the pump and turning on the thermostat, activating the Taco board, doesn't blow the fuse, then it is in the pump or wiring to the pump.
    jenbury
  • Micmann
    Micmann Member Posts: 6
    edited February 2022
    It's possible there is no short, but the pump might be bad. Depending on the age and type of pump it could have a capacitor and the capacitor could be blown. The capacitor gives a slight burst of stored current to start the motor when called. This reduces the needed starting amps of the motor. If the motor is attempting to start without the capacitor the initial amp draw will be higher than the 6 amp fuse can handle causing it to blow. But using the extension cord to test to motor will seem like the motor is fine because it may need more than 6 amps to start without the capacitor, but less than the breaker rating of the circuit the extension cord is plugged into.
  • jenbury
    jenbury Member Posts: 10
    edited March 2022
    Oh guys here's the update, I appreciate your comments! A lot of the terminology is making my head spin.

    Had my HVAC (who's not a boiler guy b/c boiler guy is recovering from major surgery). HVAC guy is good at electronics. He found the pump (1.75amp) was drawing 11-12 amps and everything else looked good, so we assuming something in the pump was bad. I had another boiler-certified HVAC company come out and they told me in about 5 minutes that I needed a new pump. I bought one off Amazon (1/12 hp bell and gossett), drained my entire system (because I don't have shut off valves in the right spot to just drain part of it, and found out after letting it drain for an entire day that something is still adding water into it and the only way I could truly drain the entire thing was shutting off the main water to my house).

    Ok so hooked up the new circulator pump with no drama, filled the system bled the air out of the radiators  made all the electrical connections, fired it up again, same result. 6A Pump fuse instantly blown in the TACO.

    Here is a diagram and photo of the wiring in the junction box in between the TACO (labeled control board) and the circulator pump and the Aqua Stat. Coming out/attached to the junction box is a 40 volt transformer that carries two tiny wires over to the electronics part of the boiler.

    HVAC guy is an awesome dude and won't give up.

    Any tips from here?

    I'll reread the comments and see if any of the electrical troubleshooting could be done. I just thought that all fingers pointed to the pump so I trusted that was it.

    Thanks!
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Please remove the pricing. Not allowed per the rules.
    steve
    jenburyErin Holohan Haskell
  • HomerJSmith
    HomerJSmith Member Posts: 2,395
    edited March 2022
    Some where you have an over current condition. It could be a ground fault or excessive current draw on start up. 1/12 HP pump is high. Is the new pump an exact replacement for the old pump? You have flexible metal conduit to the Pump, does the conduit have anti-short bushing in each end? They're the red insulators that slip in to the conduit to prevent the wires passing thru the conduit to short out on the sharp edges of the conduit.

    Disconnect the wires at the pump and fire the boiler up and see if the fuse blows, if it does it is the connection between the Taco and the conduit going into the pump. You can test the connection (with out power) with an ohm meter set on continuity and test each wire in the conduit to the conduit shell and if there isn't any short the meter will not sound. If it does sound, you have a short. Check the black wire to the white wire, too. The ground wire is an exception.

    I have to question a 11-12 amp start up current draw. You are missing a white wire in your drawing? Only two black wires going into the wire nut, not three as your drawing shows.
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    That wiring diagram that is drawn up is not right. It shows the pump being powered by the aquastat and the control board, and the transformer coming off the aquastat. Is the drawing wrong?
    Rick
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590

    That wiring diagram that is drawn up is not right. It shows the pump being powered by the aquastat and the control board, and the transformer coming off the aquastat. Is the drawing wrong?
    Rick

    There is no power source in that diagram. Where is L1 and C? All I see are components that are interconnected with no source? So YEA... the diagram is wrong!
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • jenbury
    jenbury Member Posts: 10
    Thanks guys....

    @HomerJSmith
    The HVAC guy did the test with turning on the TACO and boiler with the pump disconnected, and he said it did NOT trip the fuse. I was not there for it. I only have 1 more spare fuse at this point so I want to save it until I know I have the wiring right. So let's assume it does not trip.

    The 1/12 hp is the EXACT replacement as to what was there and it is supposed to draw 1.75 amps, this is why we replaced it. Since it was pulling 10-11 amps not 11-12 like I stated above, but still, too much. I did not take it apart yet to further investigate. Right now I just want heat!

    The metal conduit to the pump has the correct connector on 1 side (into the J box) but not on the other (into the pump). I looked and did not notice any damage to the wire but I hear you, it is not 100% correct. Maybe I just change those wires out completely to see if that is it, or what is going on? Who knows what is going on in the metal conduit? There is no ground wire hooked up (but there could be, there just was not when I started this investigation). Another thing I noticed is that the wire to/from the Aquastat is ancient and did have some exposed copper in the j box, which I taped, before I turned the system on.

    @rick in Alaska
    OK so to explain the diagram. Made this for my HVAC guy so maybe it is just terminology. The TACO sends a black and a white down to the J box. The TACO white connects with a white from the transformer and a white from the pump (if you are looking at the photo, one of the black wires is actually neutral with white tape designating that). Then for the blacks. TACO black connects with AQUASTAT black and pump black. AQUASTAT black then goes to AQUASTAT, then comes back and ties into the transformer black. Are you saying this is incorrect? Should the TACO black go to the AQUASTAT first then come back after being switched at the AQUASTAT, and then connect with the pump and transformer? These guys took this wiring apart before I fully investigated or understood all of these parts so it is 100% possible that is it wired differently than it was. I don't see how anything could be missing, as how I understand it the black and white from the TACO is the power being supplied. (What is L1 and C?)

    Depending on what is replied here, I think I should change out all the wires going to the aquastat and the pump, and rewire the J box configuration (if one of you think it needs it), and try my last fuse...

    Or, I order another TACO? Could it be the TACO? Not expensive and I can get it Wednesday.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    edited March 2022
    Here is a diagram that might be correct. but not sure.

    And this is the best I could come up with on the actual component placement

    I can't see the actual circulator wires in the picture. But there is an open knock out hole in the bottom of the junction box. The old cloth insulated wires should be replaced.

    Finally I wonder how the thermostat is wired. If that 6 conductor 18 gauge thermostat wire is coming from the thermostat... why is it connected to the transformer. The thermostat should connect to the SR501 TT terminals and the R and G from the transformer should go directly to the gas valve because the high limit aquastat is connected the the transformer. Putting 24 V from the transformer into the SR501 may be part of the problem.

    I'd like to see inside the SR501. Also where is the thermostat connected?

    EDIT:
    Further investigation indicates that the circuit with the blown fuse on the SR501 has both the transformer and the circulator powered by the same relay contacts. An Amp reading on the total of the transformer and the circulator is needed to determine of that is a problem. But, I think it is the cloth insulated wire.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • jenbury
    jenbury Member Posts: 10
    Ok! Purple is to thermostat. Green is to boiler.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    edited March 2022
    OK that makes sense.

    #4 on the SR501 is feeding the junction box. that feeds the transformer via the hIgh Limit aquastat and the circulator. This is indicated by the wire nut in the red circle in your diagram.

    So any one of the following could be the problem:
    1. The cloth insulated wire could have a high resistance short to the conduit. If the burner operates when the circulator is disconnected.
    2. Transformer is drawing more amperage than normal and when in combination with the circ. pump, the total draw is over 6 amps
    3. dead short in the wire between the circulator and the pump. Replace that wire also.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • jenbury
    jenbury Member Posts: 10
    More parts. I will diagram them if you think it's helpful and you are willing to go down this path...

    Inside the boileranother relay above and what I am referring to as the aquastat belowthe red and white wire below are going to the part shown next.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    edited March 2022
    So you have 2 aquastats. One is on the 120V circuit and the other is on the 24V circuit. lots of extra redundancy. that is a good thing.

    I can almost draw your diagram for you. But to solve your fuse problem, I would look at the wire to the circ. pump and the 120V wire to the aquastat. That is my guess
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    jenbury
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    I'm still a little confused. Typically either the aquastat or the taco control runs the pump, but not both. Either way, I am not sure why it would be drawing high amps.
    Rick
  • jenbury
    jenbury Member Posts: 10
    All the rest of the wiring
  • jenbury
    jenbury Member Posts: 10
    @EdTheHeaterMan
    Will replace both sets of wires tonight and report back.
    My volt meter is at another house but I will get it for tonight. How exactly do I test the amperage on the transformer and the pump?
    Thanks!!
  • archibald tuttle
    archibald tuttle Member Posts: 1,078
    jenbury said:

    @EdTheHeaterMan
    Will replace both sets of wires tonight and report back.
    My volt meter is at another house but I will get it for tonight. How exactly do I test the amperage on the transformer and the pump?
    Thanks!!

    clamp on ammeter over one of the wires running to the pump. that is not on your multi meter although some can take a clamp on attachment. not too pricey at HF or HD. some multimeters might be able to handle in line function of a couple amps but most are not meant for inline testing of amps that high, just for small parts of an amp.
    jenbury
  • jenbury
    jenbury Member Posts: 10
    Hi everyone -
    So it's fixed .... I did change out the potentially sketchy wires that @EdTheHeaterMan suggested (no visible issues with them) then my HVAC guy popped in a new 6V fuse, turned on the system and BAM everything is working great. The draw on the pump when functioning alone was .75 amps. So I guess it was the pump all along !! Who knows what happened to the old one, perhaps lack of oiling from me? I will take the old pump into an engine shop for investigation/refurbishing if it is able to be refurbished and I am back in business. I learned so much about my boiler system via this chat group I want to thank EVERYONE for your help and time. What a great resource! You guys rock!
    Sincerely,
    Jen
    EdTheHeaterMan