PB105 Burning between 2.9 & 3.6 bags per day "Help!"

[scooter]

Question:
How many pounds of pellets should this house burn per day?

Pellet usage with the OAT connected in the basement reading about 65°:

Test One: 33hrs, 160lb pellets burned, (160lb pellets / 33hrs =4.84lbs pellets per hour) 2.9 bags in a 24 hour period. The temperatures during this test were between 1° and 22°.

Test Two: Pellet usage from the December 22nd start-up. 6.13lbs Per Hr 3.5 bags per day. We have only had a handful of days with temps below 20°

Home:
36’x 28’ Two Story 1872 square foot Cape Home, 2x6 R13 wall construction.

Heating Systems:
(Secondary) New Yorker Boiler FR 98 W, (Net out-put 82,000BTU) 710 gallons annually
(Primary) Harman Pellet Boiler PB 105, (Net out-put113,900BTUH) (connected parallel)
Hot water base board 2 zones (53’ base board 1st floor & 32’ base board on 2nd floor)
Hot water coil in the Oil Boiler for domestic hot eater
Thermostats set at 68° 1st floor & 67° on the second floor

Heat Loss Calculations:
Building Envelope Heat Loss 16,462 BTU/hr
Infiltration Heat Loss (based on average of 0.5 ACH) 13,071 BTU/hr
Total Heat Loss 29,533 BTU/hr
Total Output 36,916 BTU/hr
Total Input 46,145 BTU/hr

 

[AndrewChurchill]

If your heat loss calculations are correct you would need roughly 85 pounds of pellets per day just to heat the house and that doesn't include your DHW. Your post mentioned that there is a coil in the oil boiler so I'm assuming DHW is done by the oil boiler.

Also, you don't mention what temperature you are keeping your house heated, if the house maintains a constant temperature or if you turn the temps down when you are not there. That plays a big part in fuel usage.

Since you gave me the necessary information to calculate your heating degree day temperature for Test One I can say your pellet usage is close to what I use on similar days. During a week day with a 53 degree day temp I use 2.5 bags of pellets and on a weekend day with the same degree day temp I use 3 bags of pellets.

Where you and I differ significantly is that my PB105 heats my DHW so I would expect you to actually use less pellets than I do for the same degree day temp. Also, even though we are heating roughly the same square footage you have two stories so you will have less heat loss from the first floor to the second floor since there is less of a temperature differential between the floors.

I am only heating the first floor. I have R38 in the first floor ceiling but the attic roof and walls are uninsulated so I should have a greater heat loss since the temperature differential is greater in my case.

I think you mentioned in an email you typically use 710 gallons of fuel oil to heat your house. A rough estimate of how many pellets you'll need to get through the heating season is 1 ton of pellets for every 100 gallons of fuel oil. In your case you should use about 7 tons of pellets. Take your average daily usage and multiply it by the number of days left in heating season and see if you're on target.

 

[Jersey Bill]

the heat in wood is about 7 mbh/lb
at 4.84 lbs/hr, the heat input is about 33 mbh
at 6.13 lbs/hr, the heat input is 43 MBH

these numbers do not seem unreasonable.

 

[AndrewChurchill]

I based my calculations on 8200 BTUs per pound of pellets. I agree that his pellet usage doesn't sound too far off.

 

[scooter]

I am wondering if I have a problem with my PB105?
Settings: OAT connected out side, Min 160°, Max 180°, Feed Rate 5, Outside Temp 16°F, T-stats set at 68°,
The boiler heats up until it reaches 180° and stays there with a varying flame and feed rate meaning the auger will run for different time periods.

The auger runs anywhere between the times listed below.
on 1 sec - off 12 sec
on 3 sec - off 12 sec
0n 5 sec - off 10 sec (It never stops)

I thought with the OAT connected out side. The PB105 boiler as it reaches the max temp of 165° based on a 15° out side temp would slow the feed rate to anticipate hitting the max temp. Then I thought it would basically coast and not feed anymore pellets until it gets close to the MIN setting.

With the boiler at 180°! If I turn the main switch off for a few seconds and back on the feeder stops feeding until it gets close to the low setting. When it reaches the max temp again it just keeps feeding at the time frames listed above. (It never stops on is own or allows the boiler water temp to drop)


Is there a problem with my boiler controls or am I wrong with how it is supposed to operate?

 

[AndrewChurchill]

I have found that my PB will over shoot the target boiler temp by about 10F. Then when it gets within 5 degrees of the target temp it will fire up again. With a setting of 160 min and 180 max your boiler is basically going to be running a lot, plus in warmer temperatures you will actually be providing hotter water than is necessary to heat the house.

My min and max settings are 140 and 180 and they are working well for me. There are other people on the board who are using similar settings to yours and they say those work for them too. It takes some experimentation to get this boiler dialed in for your situation.

 

[scooter]

If I under stand you the two target settings are the Min & Max. Your PB over shoots the max target by 10° and then coast or the flame cuts back until it hits the Min Targer and starts all over again.

 

[AndrewChurchill]

No, the OB will always try to maintain the max temp based on the Max temp and OAT sensor data. What the min temp determines is how low the boiler will go based on the outside air temp.

Ex. 1: Max temp set to 180 and min to 160, outdoor air temp 0F. The PB will maintain a temp of 180F.

Ex. 2: Max temp set to 180 and min to 160, outdoor air temp 20F. The PB will maintain a temp of 160F.

Ex. 3: Max temp set to 180 and min to 160, outdoor air temp 40. The PB will maintain a temp of 160F.

Ex. 4: Max temp set to 180 and min to 140, outdoor air temp 0F. The PB will maintain a temp of 180F.

Ex. 5: Max temp set to 180 and min to 140, outdoor air temp 40F. The PB will maintain a temp of 140F.


If the OAT is not being used the PB will always maintain the Max temp and the Min temp simply becomes an On/Off switch.

 

[webbie]

Adjust pellets for moisture - about 7500 BTU/Hour.
3.5 lbs = 26,000 BTU input.
75% total efficiency = about 20,000 BTU per hour output, about the size of a Kerosene Heater.

Yes, it sounds right.

When it comes to central heat or "real" heat loads, I am noticing that a lot of people seem to be under the impression that pellets somehow have an advantage over other fuels....when it comes to raw BTU's. They don't. Many dealers tend to quote exaggerated claims...based on space heaters and what customers tell them. But perception is not reality, and central heating is most definitely reality in terms of BTUs.

In general, a ton of pellets will replace 100 gallons of fuel oil. So Andrew has it right that you should expect to use 7 tons.

 

[scooter]

Thanks Andrew,
I do understand how it works now, its just not like I envisioned it.

I have another question on the auger time cycle.

My Feed Rate is set to 5. My auger timer runs for 15 seconds. It might run for one second and be off for 14 seconds or vise versa or anywhere in between.

My friends PB runs for 60 seconds with the feed rat set at 5!

Will this make a difference in how many pellets I will burn at 15 second cycle compared to 60 seconds? It seems it might!

Can I change my cycle time from 15 seconds to 60 seconds?

************************************************************************************
"I found this thread form Delta-T"

Andrew, view the feed adjuster as a limiter. At a feed of 6 the control board will allow the auger to turn for all 60 seconds of each minute anytime the auquastat says the water is not hot enough. In theory this allows you to generate more heat faster. By turning the feed adjuster down you reduce the auger turn time by 10 seconds for every whole number( ie 5 will allow the aiger to turn for 50 seconds, 4=40sec). If you were at say 2 you are telling the machine it can only feed pellets for 20 seconds of every minute. Then it must wait for 40 seconds before it can feed any more. I’m sure you can see how having a very low setting will not allow the machine to get the water to the temp you desire very quickly or at all if you have a high demand. I beleive that 4 is the default recommended # but you cant go wrong with 5 or 6 in my opinion. BTW this is all information I learned from Harman’s Factory Techs. [/size]

If this is true! I do have a problem with my feed rate

 

[AndrewChurchill]

The feed rate simply limits the maximum time the auger can turn in 60 seconds, 1 = 10 seconds 2 = 20 seconds etc... up to 60 seconds.

The actual amount of time it will turn is determined by the input the control board receives from its sensors. It's entirely possible the auger may only spin for 1 second one time, 22 seconds the next time, 5 seconds the next time, etc.... It's all based on the data the control board receives.

 

[scooter]

I under stand what your saying and I agree. The difference between my PB and my friends PB is his board cycles every 60 seconds and mine cycles every 15 seconds.

My friends PB auger will start and run for how ever lon the board needs it to and then stops and "at the end of the 60 second period" it will run the auger again for as long as it needs to. It seems to only turn the auger on once during the 60 second period.

My PB auger will start and run for how ever long the board needs it to and then stops and at the end of the 15 second period "it will run auger again for as long as it needs to. It seems to only turn on once during the 15 second period. That means my auger operates 4 times in 60 seconds where my friends only runs once. It seems mine PB would burn more pellets!

Has anyone else seen theirs operate like mine?

 

[AndrewChurchill]

The end result is going to be the same. If the board determines is need to feed pellets for 50 seconds out of 60 what's the difference if it feeds continuously for 50 seconds or 4 times for 12.25 seconds?

 

[wil lanfear]

Andy is correct, it really doesn't matter, mine feeds like what you have mentioned. The boiler aquastat along with the OAT if used, actually is going to control the quanity of pellets to satisfy the boiler.

 

[scooter]

Hi Guys,
The dealer was just here checking it out and found I have a new style board that cycles more often then to older style. The dealer had never seen one run like mine so he called Harman before he replaced the board. I guess they don't send out up-date bulletins to the techs. Anyway I think the big difference is going to be the aquastat shutting down the circulator so the PB105 will go into sleep mode when no load is calling. I know with the circulator running all the time my PB would no shut down to a sleep mode.

Thanks for your help!

P.S. I found out what the 5th dip switch is for. "The new style red esp probe" The dip sw # 5 needs to be on with the red esp probe..

 

[wil lanfear]

P.S. I found out what the 5th dip switch is for. “The new style red esp probe” The dip sw # 5 needs to be on with the red esp probe..

Please tell us more if you know. Is it possible that its got a different resistance value so it will turn the combustion blower off at a higher stack temp. I've been told that the one like mine will not shut the blower off until it senses 90*exhaust temp which means probably it will never shut off.

 

[scooter]

Sorry I don’t know, we didn't get into that. I don’t know if this new board is any better than the old one as in how many pellets it will burns. My guess is maybe they were looking for a more steady flame 4 feed in a minute. The dealer is going to push Harman for some sort of set up sheet for the different updated models and just have more information and parameter at their finger tip. "We'll see: The Harman manual could be a lot better!

 

[stephenmoore]

Hey Scooter, I just found your thread, I burn about 2 bags a day for my 2500 sq foot home with mostly slab radiant. When it gets to -20 Celcius or so I think it bumps up closer to 3 bags per day. I have also been running my 105 on manual mode for most of the winter and haven't noticed much of a diff in usage. Your usage sounds normal to me. Just replaced my cracked burnpot with one of the new style ( no air holes in the bottom of the pot ). We'll see how that goes, Harman has asked for the old one back. How have your igniters been behaving ?

 

[scooter]

Hi,
I just installed an older style board and ESP to see if it makes any difference in how many pellets I burn. With this cold snap I've been burning 3.75 to 4 bags a day. Some People seem to thing given the heat loss in my house I'm burning the right amount but I'm have a hard time excepting it. A friends house that burns the same amount of oil or with in 50 gallons is burning 2 bags during this same periods! I'm crossing my fingers.

My igniter has been working very well as long as I keep it cleaned out and I do have the new style burn pot.

 

[AndrewChurchill]

I've got a new 2000 sq. ft. house that is very well insulated and during the past few days I have been burning between 3 and 4 bags a day. During more seasonal weather on weekdays I burn 2 to 2 1/4 bags per day and on the weekends I burn between 2 1/2 to 3 bags.

I don't think your usage is out of line.

 

[scooter]

How would you explain my friends house only burning 2 bags during this cold snap? Keep in mind our oils usage is the same???

 

[AndrewChurchill]

I can't.

But, Is your house exactly like his house? Do you heat all the rooms to the same temperature he does, do you use the same amount of DHW as he does, do you have the same number of windows, are they the same size?

How about your doors? Are they the same, are they weather stripped as well as your neighbors? I could go on but maybe your starting to see the light.

If the answer is no to any of these questions then maybe you should start there. Burning the roughly the same amount of oil is only one out of many variables......