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Munchkin 80 Help Req

QTooQToo Member Posts: 12

Just found this board and looks like a nice interactive group. I have worked on and maintained my home heating systems (Buderus oil) over the years, installed a propane on-demand unit at a 2nd home, so know a little bit but far from an expert.

Trying to locate some advice on getting a Munchkin 80 burner back up and running. This unit is installed at my Mom's house in MA, is about 15 years old and it drives FHW heat and a HW tank . Has had its issues, but I havent been actively involved with the maintenance as she has had a somewhat local tech who was reliable. She just got back to her house after being away this winter and has no heat or hot water. The tech is no longer with the company and they cant get out until the END of next week, so I am in a jam. She is 2 hours away and I am only getting the info that she can visually see and tell me, so "maybe" a little stressful on this side. :smiley:

Problem - The system will fire and jump quickly from 140 and right up to 198 or 200. It them shuts down but still has power. The reading will slowly go back down. No error code comes up other than a "d1 or d3". I have had her reset the system a few times but it does the same thing. From my searches, there should be an E or F code plus a number. Could it be a high temp cutoff switch? A friend of hers who is a contractor came over to take a look and said the high temp was set to 180.

Any suggestions on how to troubleshoot.


  • IronmanIronman Member Posts: 5,564
    Agree, a lack of circulation. It could be air bound or low on water or bad circulator as Jamie mentioned.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • QTooQToo Member Posts: 12
    Thank you very much for the quick response. On the pressure gauge, she confirmed the PSI is at 20 and the temp shows 150. If the system is low on water, would the quick rise in temp lead to the unit shutting off before the pressure valve would pop? She was away for an extended period of time this winter due to the corona lockdowns. If there was a leak of some sort, it would have dried up by now.

    If we need to add in water, is the valve on the unit in a Munchkin or external like on most?
  • JUGHNEJUGHNE Member Posts: 6,790
    If the 20 psi gauge is fairly accurate then there is water in the system. If a leak the auto feeder would keep adding water that would show up somewhere.

    It sounds as everyone said that the primary pump is not working.
    If the system has been sitting the pump could simply be stuck.
    Some pumps have a large screw plug in the end that can be removed and a screwdriver applied to the end of the shaft to rotate it might free it. The should be a water drip when the large plug is removed.

    Or there may be a pump relay not working.

  • HomerJSmithHomerJSmith Member Posts: 885
    edited May 20
    d1 & d3 are not error codes, but displays in the Status Menu.
    d1 should give you a value alternating with the d1 on the display board, which would be the actual value from the outlet temperature sensor. eg. d1 then 180 . Same with d3, which would be, d3 then a 0 or 1if the Water Heater has a mechanical aquastat. If you have a sensor connected to the Munchkin it would read the actual temperature of the tank water. To exit the Status Menu press the S3/Program key on the display for several seconds.

    The Munchkin maybe programed in the Water Heater priority mode and the pump pushing water thru the W/H heat exchanger is not turning on or the pump rotor not turning or a valve is closed in the W/H loop. If the W/H loop is controlled with a zone valve, maybe you can manually open the zone valve and that would permit flow.

    Space heating will not turn on until the W/H is up to the programed tank water temperature.

    It is possible that the controller has crapped out and needs to be replaced.

    You might turn off power to the Munchkin and that may rest the controller.

    Pics of the system would help.
  • ZmanZman Member Posts: 5,736
    The munchy has a fuse for the circ on the control board. My bet would be a bad circ or blown fuse (maybe both).
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomerJSmithHomerJSmith Member Posts: 885
    If you are getting a display on the display board, the fuse is ok.

    Typically, if the Munchkin is properly piped with an indirect tank, one would have a boiler pump, an indirect tank pump, and a heating pump.

    One could make the indirect tank run off of a zone valve and treated like another zone.

    Who knows what installers did 15 years ago. I've come across a lot of installation problems with installation that are that old. Nobody took classes and they couldn't read installation instructions. I guess they left their reading glasses at home.

    Pics help alot.
  • QTooQToo Member Posts: 12
    Thanks to all. I am getting some pictures hopefully tonight.
  • unclejohnunclejohn Member Posts: 1,525
    My money is on the pump. You can try setting the DHW tstat as low as it will go or take a wire off it and it may end the priority call and at least heat the house.
  • QTooQToo Member Posts: 12
    Was finally able to get the pictures. Here is one showing the overall system and then also the pressure gauge. If any other angles or closeups to get more info, please let me know. I will be going to the house today to look this over in person and test some of the info from your feedback.

    Thank you
  • HomerJSmithHomerJSmith Member Posts: 885
    edited May 27
    I don't know why installers pipe with Black-Iron pipe mixed with copper pipe, oh well.

    Some pics from further away, so one could see the whole sys setup would be nice.

    The tridicator indicates that you have heat and the pressure is acceptable.

    It appears that the boiler is not configured as a primary-secondary piping which is mandatory for the Munchkin. More pics would clarify that.

    I can see the support bracket for the Munchkin is high tech, good job.

    The Superstor HWTank is zoned with a zone valve and not with a pump. Manually open the zone valve and see if that allows flow thru the Tank heat exchanger. I would need to see pics of the piping sys, control strategy, and exhaust sys (inside and outside).
  • QTooQToo Member Posts: 12
    I am at the burner. The burner will fire but then shuts off after temp reaches about 200. The main taco circulator (big green) is hot, the expansion tank is next and the top is hot, then the water goes to multiple pipes. The pipe toward the HWT is warm and then goes to cold. There is an Erie zone actuator and I am not sure what this does. I can remove it and then small valve know will spin but I cant tell anything further.

    On the heating zone valves, these are the Taco's with the copper finish. One is corroded and the slider wont go down past half way. The other will slide all the way down when not on power, and then only half way with power.
  • QTooQToo Member Posts: 12
    here is a picture of the zone valves. the one in the rear is the one with the corrosion.
  • QTooQToo Member Posts: 12
    The valve that controls the HWT is an Erie pop top. This has a manual open like the tacos but there is no resistance when the power is on. When it is off, i can move it over with resistance and then it will "motor" back.

  • QTooQToo Member Posts: 12
    if the taco valves AND the erie are working, could it be the 24volt transformer is bad and not actuating the valves?
  • IronmanIronman Member Posts: 5,564
    edited May 27
    First, it's not piped primary/secondary which is REQUIRED on that boiler.

    Second, it appears that the circulator is a Taco 007 which is not sufficient for the boiler loop even if the piping were p/s.

    Third, the boiler circulator should pump towards the boiler, not away from it.

    P/S piping is required because the boiler's heat exchanger has a very high resistance to flow while at the same time it's critical that the proper flow be constantly maintained through the heat exchanger. P/s allows two separate circuits to mix while each maintains their respective flow rate.

    Here's a diagram:

    Here's the diagram from the Munchkin Manal:

    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Alan (California Radiant) ForbesAlan (California Radiant) Forbes Member Posts: 2,272
    edited May 27
    From your description, it sounds as though the Erie zone valve is operating properly and the boiler is operating properly as well. Suspicion lies with the pump; they get very hot from the boiler water. They also get very hot when the impeller doesn't spin. The electrical energy that's supposed to turn the impeller gets converted to heat.

    The impeller often gets stuck if there is any debris in the water or when it gets old or worn. Sometimes a good whack with a screwdriver handle will free it up, but more often, you have to replace the pump cartridge or the entire pump.

    Can you get a professional in there to get to the bottom of it?

    Tell them to bring a replacement pump with them. It may be a Taco 007, but I can't see the model number on the picture. It will say on the white label on the wiring box of the pump.

    As others have said, it could be air bound.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • QTooQToo Member Posts: 12
    The taco's are a 571-2 on the back one, and 570-2 on the front. Not sure if that refers to direction. I drained the system down and took off the auto air vent and cleaned it out. Refilled the system and bled the air but still started up and shut down.
  • JUGHNEJUGHNE Member Posts: 6,790
    edited May 27
    I have seen install instructions for a Munchin that allowed direct flow thru the boiler without P/S piping. P/S was shown as an option. Quite old, the book was still on site. Newer books do not show direct piping without P/S as an option

    Although, this is not your issue for lack of heat.

    I believe when the boiler fires it sends power to the pump.
    The boiler may be called to fire by one of the 3 zone valves.
    If the zone valves do not call would the boiler fire???

    I'm thinking the pump is stuck or just toast.
  • HomerJSmithHomerJSmith Member Posts: 885
    edited May 27
    The Munchkin has a high head loss (a lota resistance to flow) heat exchanger. I like to pump into the greatest resistance and that would be the return port which is toward the rear of the boiler. You are pumping from the front port supply side.

    You need two pumps on that sys. If you only have one pump, the Munchkin is not installed correctly. Ironman's installation diagram is out of the manual and it show two pumps and is the proper way to install it.

    You obviously don't have flow and the Munchkin is hitting the high temp cutout. Manually open the Superstor Erie zone valve by moving the lever to the open position and see what happens.
    You can do the same for the other Taco zone valves then see what happens.

    For the zone valves to work, you need 24 volts going to them. Do you have a transformer supplying 24 V ? Check voltages with a volt meter.

    I don't see an air eliminator, but pics taken further away may reveal it. Take more pics, they're free.

    If you don't have an air eliminator you could get a lot of black iron powder circulating in the boiler water and that may get into the cartridge in the pump and bind it up so there isn't any rotation and circulation of boiler water.

    My priority would be fixing the primary-secondary piping.
  • QTooQToo Member Posts: 12
    Thank you again for all of the feedback to help me diagnose. Will be having my mom call in a plumber vs a munchkin tech. Everything is pointing to this being the valves and circulators and a plumber will be able to switch them out.
  • JUGHNEJUGHNE Member Posts: 6,790
    IIWM, my priority would be getting Mom heat and hot water.
    We all see a bucket full of mistakes on this Munchkin.
    But it has worked, after a fashion, for 15 years.

    Maybe just the pump will get Mom back in hot water.
    Other things maybe later or wait for an upgrade of boiler.
  • QTooQToo Member Posts: 12
    A quick info update - The big green Taco IS a model 007. The other Taco's models I referenced are the zone valves. Sorry for the confusion.
  • QTooQToo Member Posts: 12
    I disconnected the 007 pump last night and cleaned it out. The impeller spun but definitely was gunked up. Planning to replace this and if that solves for now. Will send an update. Thank you again.
  • HomerJSmithHomerJSmith Member Posts: 885
    edited 4:23PM
    If you took the 007 apart, did you look at the volute and see if it was rusted and corroded?

    Replacing the 007 with a new 007 might not be the best solution.

    If the 007 is moving water thru the Munchkin heat exchanger and also moving water thru all the zones, it may not be adaquate. The 80M requires a flow of 8 g/m thru the heat exchanger. The 007 is the suggested pump for the boiler only in a primary-secondary sys. It would be too small to handle the boiler and space heating too. You really need two pumps for the Munchkin setup. Pics from further away showing your total sys would be helpful.

    If you have a 6 cyl car that's only running on 3 cyl, it will get you from point A to point B, but performance will suffer. Same for the Munchkin.

    I would think, replacing the 007, would demand greater consideration than just a swap out.

    Most of the posts are fixated on the pump, but if the zone valves don't open, the effect would be the same as if the pump wasn't turning, no flow. Check the 24V at the zone valves or manually open them and see if you then have flow. If manually opened and still no change, I would look at the pump, also. I would like the 24V confirmed with a volt meter. I don't like assuming things. In diagnostics, assuming things can lead you astray.

    The fact that the Munchkin reaches high limit cut out indicates to me that there is no circulation thru the boiler and that your sys is not a primary-secondary setup. If it is the pump, you might consider a different pump, one that is capable of supplying the boiler and space heating, too.

    Of course, much of this is a rehash of what others have posted.
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