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Buderus GB142 Circ pump question

My installer just finished installing my GB142-30 today. He was not too familiar with the unit. In addition to the primary circulation pump on the low loss header, he installed a secondary taco circulator as well. It is a one zone system without DHW. The secondary circ. pump, which he told me actually pumps the water through the rads, comes on when the unit is turned on and then shuts off and doesn't seem to be working properly. I'm not sure if the separate electrician that wired everything up wired the secondary circ pump to the correct place. The first pic shows the external connection board. Pk (left) is the primary pump in the LLH, PZ (2nd from right) is the secondary circ pump, and Netz(right) is main power. The terminal that the secondary circ pump is wired to is labelled as DHW recirculating pump in the install manual. Should it be piggybacked to the same terminals as the primary pump? I know that if this system consisted of more than one zone, the zone pumps would be wired to a zone controller and that would be wired to the primary I think. I need help. I just spent a ton of money on this system and my boiler guy didn't do and doesn't know any wiring. The electricians managed to mix up where the AM10 and the thermostat connect, so maybe they also wired the secondary circulation pump also? Thanks in advance for taking the time to read this and hopefully help me.


  • IronmanIronman Posts: 3,282
    edited October 2013
    Wired Wrong

    The secondary circ IS wired wrong. As you stated, it should be wired parallel with the boiler circ on the "PK" terminals. The way it is now, it will run 3 minutes out of every 10.

    I can't tell for certain from your pic, but it appears that the Taco circ on the secondary may be pumping in the wrong direction. It should be pumping toward the LLH, not away. Also, if that is the case and if that's the supply line for the secondary, then the secondary supply and return are reversed. In other words, that should be the secondary return where the Taco now is.

    The AM10 could have been mounted in the boiler where there is a plug connector on the wiring harness that plugs right into it.

    If people would only read the instructions!
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • JJTraxxJJTraxx Posts: 6
    edited October 2013
    Taco pump direction

    Thanks Ironman. That's what I thought. How do you tell which way the taco pump is pushing? It is on the secondary return, but there is no arrow on it indicating flow direction. I have the AM 10. It too was wired wrong. I know have it wired to the rc terminals. They had it on the fa terminals and the thermostat on the rc. I corrected it and put the am10 on the rc and wired the thermostat to the am10. Everything seems to be working correctly now as long as the taco pump is pumping towards the llh and not away. Any clue how to change the am10 readout to fahrenheit? It's reading celcius and I can't figure out how to change it.

    O.K. I just figured out the flow direction on the taco 007 by looking at an online manual and pic. It is mounted correctly. It is on the return side of the llh and is pumping towards the header. Now just to figure out the am10. My Honeywell ct3300 doesn't like the gb142. I have a Lux digital manual thermostat coming today. Once a call for heat fires up the system and I can change the am10 from celcius to fahrenheit, I'll be goog to do.
  • IronmanIronman Posts: 3,282

    The manual that came in the AM10 box should tell you how to get to Fahrenheit. Or, you can download it from

    You don't want to use set back with that boiler. A mod/con is looking to run as long as possible at its lowest modulation. That produces the greatest economy and highest comfort. Setback is totally counter-productive to that. Set it and forget it.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • JJTraxxJJTraxx Posts: 6
    edited October 2013
    Not in manual

    I checked the entire install and operation manuals. Neither makes mention at all of how to switch to Fahrenheit. Unless I'm looking right passed it. I know about not running a program or using a setback. The new stat coming today is digital, but manual and not programmable.
  • AM10

    I just got off the phone with Buderus tech support. I somehow got the European version of the AM10 instead of the US version. I have to warranty it through my installer and his wholesaler. There is no way to make this one read in fahrenheit. Thanks so much for your help. After I work this out and connect the new stat, everything should be working as intended.
  • RichRich Posts: 2,184

    really tell from pictures . Which line is the expansion tank connected to on this boiler . That low loss header really would work better with the pump on the supply side of that LLH . Just my opinion .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • Expansion tank

    I'm not home now, but I believe the expansion tank is on the supply side. Why would you think the taco circ pump would help the llh if piped on the supply side?
This discussion has been closed.


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