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Harman PB 105 boiler consideration for extra controls

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Tdiguy, Mar 1, 2013.

  1. Tdiguy

    Tdiguy New Member

    Joined:
    Feb 20, 2013
    Messages:
    18
    While i am not a "pro" I have found what i think are some area's on this boilers control system that i wanted to improve greatly at least for my own use.
    I am sorry this is not formatted very well to be a good technical document. But I am very sure that MANY people even pro's out there will like this. Enjoy!. At some point i might sit down and make a visio document to really simplify the explination. Right now though i am working a lot of hours and trying to get my CCNA (cisco cert yes i am a networking guy :) )


    Additional controlls for your Harman pb 105
    2 aquastats or similar controller that closes a switch at a given set point.
    2 relays 1 SPST 1 DPDT or 2 DPDT ( I suggest the functional devices relay in box relays. They make mounting them a breeze and wiring is easy. They also normally have a led to indicate the coil is charged)
    Depending on how you wire this will depend on which model you need some use 10-30 volts for coil some have 120 for coil so find out what your voltages are before ordering one.

    Ok my pb105 has a overheat zone built into it they all should have this. It is the dark blue wire in the junction box on the boiler. This thing for me is 100% useless it has 120 all the time weather the light is on or not. So i could not put this built in control to work for me.
    I did not like running my circulator pump all the time even when there was no call for heat. My boiler is set up to connect to my oil burner so it delivers hot water to the oil burner so it doesnt have to fire up to deliver heat.

    So for me i went into the control box for my oil powered boiler and found the hot wire that connected over to the burner itself. I unstalled a switch and a transformer on that so when i turn the switch on it will allow the burner to fire up. When the switch is off it powers only the transformer which steps the voltage down from 120 to 12. This i then have wired out to the pellet boiler.

    I take the 12v from the oil burner and have that connected to a STSP relay which i use to power the circulator. Yes this does create a few seconds of lagg time because the hot water has to flow from 1 boiler to another but not having the circulator run 100% of the time saves a lot of wasted heat (even with the pipes all insulated)
    The user guide suggests keeping the water in the boiler over 125 i think it was. So to do this i employ an aquastate with imersion bulb fitting and simply wire it in series with the pump so if the water temp is below the set point on the aquastat the pump cant get power and prevents it from cooling off even more.

    This next part is where it is a little more complicated. Mostly because i really wanted to protect the boiler.

    This is where i prevent the boiler from getting out of control with its heat.
    i ran 2 wires form the living room zone valve and ran them out to the pellet boiler. 1 side goes to 1 contact on the aquastat the other wire connects to 1 wire of the coil on the DPDT relay. The other side of the coil connects back over to the aquastat. This way when the temp reaches set point the coil is charged up.
    Now i connected the NC connection of the relay to the power for the boiler. So in normal conditions this is powered up. When water temp is above set point this breaks the main power to the boiler.
    Then on the other pair of NC and NO connections i connected the NO connection to the pump and 120.
    With this configuration when the boiler reaches (mine is set for 200 but its adjustable) 200 the power to the boiler is shut off ( it takes a while for the fire to die completly but without the fan running it looses a lot of ghusto) and opens the living room valve and circulates the very hot water.

    The really nice part about this is how automated it is. Without this control when the pb105 gets too hot it simply shuts off and has to just very slowly cool off. It will not actually turn itself back on either. With these new controls in place when the pb105 hits the hi point the power to the boiler shuts off the circulator turns on and the living room gets a bit warmer (also alerting me and my wife something might be going wrong) and the boiler stays off until it is 20 (adjustable also) degrees below the set point. Then the boiler gets power again and resumes normal operation.

    Probably one of my biggest annoyances has been that depending on the pellets depends on where my feed rate has to be. Some pellets i need to leave it cranked at 5 or 6 some pellets i need to have it at 1 just so it doesnt overheat. I feel like i have to out smart the engineers that originally built this thing. Ok turns out i had an issue where my aquastat was not reading the temp properly for the boiler. Now it is behaving better.

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  2. Tdiguy

    Tdiguy New Member

    Joined:
    Feb 20, 2013
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    here is the diagram.

    Attached Files:

  3. wil lanfear

    wil lanfear Feeling the Heat

    Joined:
    May 10, 2008
    Messages:
    474
    Loc:
    vermont
    I wouldn't want my boiler to be shut off in the middle of a burn because of a possible burn-back into the hopper and smoke creating creosote. If you've notice, when the boiler reaches the high limit setting, the fire in the burnpot is rather small, until no flame can be seen, then the ESP shuts the boiler down. IMHO, instead of shutting the PB completely off, use the relay between the vac switch of the PB, this way, in case off a overheat situation, the pellets will stop being fed but the combustion blower will continue to run.
  4. Tdiguy

    Tdiguy New Member

    Joined:
    Feb 20, 2013
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    18
    Under normal operation your correct. Under normal operation the boiler should also not reach overheat temps. I do like you suggested mod and i will see how i can make it and make it look good. Maybe i can poke another wire through the flex conduit on the boiler.
    The problem i recently had was that the aquastat on the boiler was not reading proper temps it wasnt making good connection inside the well so it was feeding fuel like crazy even with a roaring flame and temps exceeding 200. Your proposed mod would also help control such a situation so i do like the idea and it would take just a little change for that to happen with my set up.
  5. wil lanfear

    wil lanfear Feeling the Heat

    Joined:
    May 10, 2008
    Messages:
    474
    Loc:
    vermont
    If your boiler is still under warranty I would be talking to the dealer asking about why the blue overheat wire is powered all the time. I have mine wired with the blue wire to power a low voltage transformer in a overheat situation, 2 wire cable to a relay with a low voltage coil which when powered will run a circulator heating my workshop. I'm also going to wire in a low voltage electric buzzer in the living space upstairs so I'll know immediately if a overheat situation happens.
  6. Tdiguy

    Tdiguy New Member

    Joined:
    Feb 20, 2013
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    No the warranty has been over for a while. The best part was that the plumber i hired originally connected up the electrical to it because my local dealer doesnt have anyone that is an electrician or a plumber and only 1 person certified to install chimneys. If i had known what i know now when i bought this i would have used a different dealer that could actually do the entire install. So several years later after having the boiler overheat on me a few times i finally looked around the thing to see what was going on and why. Which is what brings us here :) I had thought about buyin g anew control board but then i saw how much they cost. I got my aquastat for 70$ delivered control board was in the 200+$ area.
  7. iceguy4

    iceguy4 Minister of Fire

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    Nov 16, 2011
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    Loc:
    Upstate, NY
    Will,
    I too use my blue wire to power a relay. That relay closes like a thermostat and starts my basement zone. next year I plan to run my igniter on manual between shoulder seasons to prevent time lost to ramp up pellet boiler. Also what , and how do you run your feed rate at? (IE what feedrate , and do you change it)
    Tdiguy...nice post...I like your ideas. I will be refering to them when I do my final hookup
  8. wil lanfear

    wil lanfear Feeling the Heat

    Joined:
    May 10, 2008
    Messages:
    474
    Loc:
    vermont
    My feed rate is set on 4.5 using VT Wood Pellets, I do change it depending on the brand and length of pellets that I'm using. The same applies for dip switch settings, 1, 2, 3, for example, if the pellets I'm using are short in length which will feed in more pellets than needed at startup, I change the dip switch settings to reduce the amount of pellets at startup.
  9. Tdiguy

    Tdiguy New Member

    Joined:
    Feb 20, 2013
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    Does anyone have a explanation of the dip switch settings?
    I am glad i was able to contribute something. For me this has been a long annoying process learning about this boiler and its quirks. One year i ended up having to trim down my feed plate because the one from harman did not feed long pellets fast enough to have a high btu output. Then of course recently i found out that the overheat zone had never been connected and turns out that it never worked properly anyway.
    I have been really happy to find out about functional devices relay in box compared to regular relays they are so much nicer and neater to use.
  10. Tdiguy

    Tdiguy New Member

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    Feb 20, 2013
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    Ok so it has been a while and i have had to replace a few things.
    I recently had to replace my burn pot again on 4-25-2014 and there is a whole new burn pot design that holds the ignitor very differently and instructs on changing the sip switch settings so that only the first 2 rows of holes in the burn pot are covered.
    I ended up having to replace my slide plate because it was feeding too many pellets even after setting the dip switches (forgot the configuration) were set to feed as little as possible.
    After this replacement my boiler starts up easier and faster.

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