Harman PB105 Questions. New Owner

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Feb 24, 2021
Concord NY
Hello All, Been a lurker and reader for a few months , this is my first post. Buckle Up, Its gonna be a long one. X-D

So back in May of 2020, I closed on my first house. The house had an oil boiler (Converted to propane, and a Harman PB105 Plumbed in series. House is 1400 Sq ft

The boiler was disconnected when i purchased the house (power cut) And I never really intended to use it, Than winter hit, and I found myself paying upwards of 600.00 every 2 months to heat the house with the propane boiler. So i started to Tinker with the Pellet boiler, trying to get it hooked up, hoping to save myself some cost on heating.

First thing I noticed when I went to work on it, The power was cut ( no biggie) I hooked the power back up ( they had a 120V power switch as a disconnect to the unit). So basically they have the boiler set up so that when the power is applied to the unit, the circulator pump runs constantly. Weird, but fine.

Secondly, I noticed that there's no aquastat on the pellet boiler ( there's one on the propane boiler hooked to my thermostat, but I isolate that unit with gate valves when running the pellet boiler, so its out of the question, also the PB has its own circulation pump).

Thirdly, They had the ignitor disconnected, whether this is was because they had issues with startup, or the ignitor itself burned out, no idea. so I replaced the ignitor.

Onto the inside,

Pretty sure they ran over a ton of pellets thru this thing without ever cleaning it out, Ash pan was full. and I mean to the top, overflowing into the bottom of the unit. I pulled the chimney pipe off, and out dumped a ton of fly ash, the pipes were loaded and the blower housing was loaded to the top with ash, covering the ESP. I did a thorough cleaning of the entire unit per Harman's instructions. burn pot and as much of the heat exchanger as I could reach was scrapped, and brushed, inside was vacuumed out. Every bit of loose ash I could find I cleaned out from the burn box to the chimney pipes. Also one of the cleanout rods. (Very top one) is stuck I'm assuming it creosoted up

So we've got a clean unit
New ignitor (USA Off of Amazon)
No aquastat.
One stuck cleaning rod
Circulation pump running 24/7 with unit power on.
No outside air temp probe
No Heat storage ability ( no storage tank)
No dump zone ( dunno why)

So I've got a few questions during my figuring's into how this runs and how they have it set up .

So Ive found that with the auger on 2-2.5, with min set to 120 and max set to 125, and it constantly running, My house when its in the 20's outside, will be a comfortable 68-70 inside. Thats perfect. my problem lies when its 30-35 out and the sun is shining, the house temp will get up to 75-78. to the point where i just shut the unit off till the house reaches 60-62 again, than ill turn it back on. I feel like this is wasting more pellets than it should by running 24/7.

Question 1.) Is there a way to have the unit work where it will start up and burn providing heat when a thermostat calls for it? Say if I use a Strap on Aquastat? would that be more efficient? Say run 120V to the aqua stat, than leave the unit in the on position ( with desired min/max temps set) thermostat calls for heat, aquastat gets signal, sends 120V to unit, unit kicks on and fires up? That seems like it would work, but now that I think about it, once the call for heats been satisfied, and the aquastat kills power to the unit, than there's heat and smoke in the fire box that wont really go anywhere since the combustion burner has no power. Is there a way to set a Harman Up to run like a conventional boiler ( not running all the time) or is that how their designed? I don't mind tending to it to monitor heat, but if I could get away with it doing it automatically, I would love it, especially if I cant get away with using less pellets. Right now, Im at 1.5-2 bags per day in a 1400 Sq ft house.

Question 2.) The other night I came home and The house was at 62 degrees. ( it was 73 before I left, so again, I shut the unit down). i turned my max temp to 125, the unit started its normal startup. than all of the sudden there was a loud bang from the fire box, and smoke and ash puffed out of the seams in the chimney, and the unit fired right up. I'm using Green Supreme Hardwood pellets from Lowes ( all that was available locally, quickly) I've read this is a combustion explosion from smoke and gasses building up. Has anybody else experienced this with these pellets? Is it an ignitor issue? Too many pellets in the burn pot? My dip switches are at Off, on, off, which according to Harman, = Program-43 seconds, so I'm assuming I'm getting the less than standard amount of pellets in the burn pot on startup. anything I can look out for to keep this from happening again?

Question 3.) The stuck cleanout rod. Any easy way or tips to get it unstuck? Its JAMMED. Any insight here would be appreciated.

That's all I have for now. I appreciate any help on my questions anybody here could give me, and thanks for bearing with my overly long post LOL.
I have a PB105. I don't know why the PO has it wired so the pump runs all the time. You should be able to rig it so it runs only when a thermostat calls for heat.

I control the boiler's operation with the max/min temperature dials on the control panel. I set the max at about 180 degrees and the min around 170-175. The boiler kicks in when the temperature drops as water circulates and shuts off when it heats back up to about 180. You say you're setting the max temp at 125? It should be running much hotter than that. Running it too cool will promote creosote buildup. Get that thing up around 180 for a few cycles and the cleanout rod will become unstuck.

The unit has no aquastat? Are you referring to the sensor mounted near the temperature/pressure gauge? It helps control the burn cycle and is wired to the control panel.

The explosion you experienced was caused by a delayed ignition. I have a compression igniter, and I've experienced having it lose its efficiency because dust in the air that was pumped through the igniter had deposited ash in the passage leading to the burn pot (it was over the course of YEARS). I pulled the igniter and ran a pipe cleaner through the passage -- that's all it took.

If you have a finned igniter, someone else on the forum may have some tips for getting the most out of it.

Fundamentally, though, these things like good air flow. If they aren't reasonably clean, they'll misfire and ignite explosively. I thoroughly clean the combustion blower vanes once a month when the boiler is running a lot, and I make sure the blower's backing plate is scraped clean of ash. Make sure the air intake flap moves freely.

Do you have a copy of the owner's manual? Here's a link to it online: https://downloads.hearthnhome.com/installmanuals/pb105.pdf
Thankyou for your reply!!!

I have the owners manual, but it was less than ideal answering my questions, the way the P.O. had it set up lol.

As for the aquastat. The unit has its aquastat stuck into the top of the boiler as normal. The aquastat i was talking about is the one thats connected to the thermostat, that moniters boiler temp and kicks on the circ pump when theres the call for heat.

So heres what im understanding based on what your telling me. Is i were to wire the boiler up, to where the circ pump only kicked on when there was a call for heat, and set my min max to say, 150/180.

Than the boiler, without circulating, would maintain its own temp between said min max, and ramp up when there was a call for heat (circ pump kicks on and cooler water enters boiler). And when circ pump went off, continue to maintain burn to hover between said min max.

Thats way simpler than the way he has it set up.

So basically, i have to do another very thorough cleaning, and figure out a way to wire up a thermostat to only run the circ pump when theres a call for heat?
Exactly. I like to keep the minimum at 175 during the coldest months so the boiler can keep the water temp above 140 most of the time. If you get below that point you'll get condensation of the water vapor that's produced during the burn. Condensation = creosote. Your boiler should be nearly free of creosote when it's burning properly.

I know some people on this forum set their maximum higher than I do, up to 200. If you want to do that I'd connect the overheat circuit. It's a blue wire coming off the control panel that is energized when the boiler detects an overheat. The easiest thing to do would be to connect it to your circulation pump circuit so your heat distribution doubles as a dump zone. The boiler will stop feeding pellets if it detects an overheat, and you'll have to reboot it by interrupting power.

Check out the wiring schematic in the manual. It's really pretty good, and not all that complicated.

BTW, most of the threads on this site relating to the PB105 are on the pellet forum, although some of us pellet boiler owners occasionally lurk here in the Boiler Room. Check out the archives over there and you'll probably pick up some useful info.