AHS S130 Coalgun- Puffbacks & Explosions

The LC unit has LED's for C degrees and F degrees, and my F (Fahrenheit) LED is glowing. The SV and hysteresis settings are correct as per Darren's instructions.

I'd say the unit only ashes about every 3rd or 4th time the fan cycles on for a thermostat heat call. It's hard to say how long my individual heat calls (fan cycles) run, since that is sometimes dependent on how many of my homes 4 zones are calling for heat at or near the same time, and that is dependent upon how cold it is outside. 15 to 17 minutes seems about right for a typical fan running cycle though.

Sometimes, when it does ash, it may ash for nearly the entire fan cycle, and sometimes it only ashes for a small fraction of a fan cycle (and everywhere inbetween). This being dependent upon the ash grate temperature.

As to ash accumulation, I'm getting about 28 lbs. of ash out for every 300 lbs. of coal going in. Ash accumulation over time and over feed lbs. added seems rather consistent (with the big difference being that I'm seeing half or less the ashes this season with UAE Harmony vs. last season with Blaschak). Size is pea, and both Harmony and Blaschak appear to have just about the same overall range of nugget sizes.

The last time I actually looked through the draft port door after a fan cut-off there was a nice orange glow to the burning coals.

When there is no wind assistance, my chimney draft tends to hold at a steady 0.03" of WC (in these weather conditions).

defective control or thermocouple

Of course, I am no expert on the AHS but just my 2c worth here. I suppose the thermocopuple is a thermistor (Wiki that). I am (again) having trouble with my Harman P38+ el crappo pellet stove and I narrowed it down to the thermistor (again). Perhaps my testing protocol might be useful to you. Although anything is possible there are three conditions. It does not matter which type of thermistor it is or the normal ohms reading when perfect. The three probable conditions are, working, defective short circuit, defective open circuit. With a cheap volt/ohms meter you will either have music (shorted out) or the resistance is so high it can't be measured (open circuit). Normal values would probably be in the 100 to 1000 ohm range but even it is is not in that range this test reveals most things. So it is is reading say 100 or even 1000ohms the number is the number however, the point with a thermistor is that it changes with temperature. e.g. so at RT it measures 117 ohms but when dipped in boiling eater it must change. If it changes the chance that it is defective is very small and if it's shorted out or on open circuit, chances are it's defective. That testing always works with my pile of c rap perhaps it will work for you too.

I just tossed 120 lbs. of coal into the hopper, topping it off. Time to see if my puff-backs return.

I have no way of knowing that my ash grate thermocouple is reading accurately. The only thing I can say is that the ashes that come out of my Coal Gun never seem to be very hot. I could probably go straight to a garbage bag with them (though I generally leave the ash bucket out for a couple hours to fully cool first, being cautious). I have two ash buckets that I alternate.

If I knew how to do it I guess could take the thermocouple probe out and place it into measured hot water to see what the LC unit reads.

Would I circumvent the LC and go with having the ash grate motor run as a percentage of fan operating time instead?

I am a firm believer in KISS .
Why not leave existing wiring alone and just stick the relay just ahead of grate motor and see how it goes.

The temperature sensor is a thermocouple sensor.  Type K.  There was one member that suggested that they are now using Type J, which has a narrower temperature range. 

I'll add that the Dwyer controller needs to be *set-up*...knowing whether it is connected to a Type J or a Type K thermocouple...mismatch one for the other will cause serious inaccuracies.

No puff-backs following my loading it with 120 lbs. yesterday. That is down from the 160 lbs. that I had been feeding it. Either feeding it 120 lbs. or less is the key, or dropping the SV to 100 degrees is the key (or both were steps in the right direction).

Yanche wrote:The temperature sensor is a thermocouple sensor.  Type K.  There was one member that suggested that they are now using Type J, which has a narrower temperature range. 

By this do you mean greater precision for the J thermocouple?

lsayre wrote:

Yanche wrote:The temperature sensor is a thermocouple sensor.  Type K.  There was one member that suggested that they are now using Type J, which has a narrower temperature range. 

By this do you mean greater precision for the J thermocouple?

Precision, no. Using any thermocouple, especially a type K, is a poor choice in this application. The type K has a wide dynamic range, −200 °C to +1250 °C / -330 °F to +2460 °F and a sensitivity of approximately 41 µV/°C. Yes, that's microvolts per degree C, i.e. millionths of a volt per degree C. So the electronics part of the temperature measuring device has to be capable of measuring very small voltages, something that's not easy to do accurately. The type J has a more limited range, −40 to +750 °C, and greater sensitivity 55 µV/°C. A better choice, but sill a bad choice.

Look at this way. Your car's speedometer reads 0 to 100, but if you only drive in school zones that have a posted speed limit of 20. You want is to read around 20 in tenths, but you can't. Wrong choice of instrument. That's what applies here.

Yanche, by what principle and mechanism does your older S130 ash? Is it as a percentage of fan running time? Are you experiencing any puff-backs?

I just had another puff-back. Ash level in the pan is substantially more now than it was earlier today, so my assumption is that sometime during the day it must have ashed long and hard and dropped the fire down low again. It seems as if ashing more predictably and more evenly in quantity over time (as opposed to temperature) would be of potential benefit.

lsayre wrote:Yanche, by what principle and mechanism does your older S130 ash? Is it as a percentage of fan running time? Are you experiencing any puff-backs?

I just had another puff-back. Ash level in the pan is substantially more now than it was earlier today, so my assumption is that sometime during the day it must have ashed long and hard and dropped the fire down low again. It seems as if ashing more predictably and more evenly in quantity over time (as opposed to temperature) would be of potential benefit.

Is that not what the hysteresis does?

: McGiever On: Sun Dec 30, 2012 8:06 pm


Is that not what the hysteresis does?

fwiw
Generally once the ash temps start going up they can go up quickly so the difference between a 5dg and a 10dg hysteresis may be only couple of strokes (more or less) on the grate. So the hysteresis can control ashing time to a degree.

Just an observation:
Often after a long idle time the ash layer becomes a little thicker and cooler, not yet quite cool enough to call for ashing, the idle fire is smaller as well. (note that I have never measured ash thickness but long ashing cycles generally follow long idle times)

Then there is a call for heat and the fan comes on, the cool air goes thru the now thicker ash layer and can drop it easy 30+- dg below SV, the boiler gets up to temp and the fan turns off but the ash has not reached SV so it keeps putting more new coal on a now hot but idle fire (insert puff back here?) until SV is reached.

The ashing scenario during a more active period seams to not drop ash temps as drastically as after a long idle and will return to SV much faster.
ymmv

lsayre wrote:Yanche, by what principle and mechanism does your older S130 ash? Is it as a percentage of fan running time? Are you experiencing any puff-backs?

I just had another puff-back. Ash level in the pan is substantially more now than it was earlier today, so my assumption is that sometime during the day it must have ashed long and hard and dropped the fire down low again. It seems as if ashing more predictably and more evenly in quantity over time (as opposed to temperature) would be of potential benefit.

My boiler ashing is controlled by a ten minute cycle timer. It is powered only when the combustion blower is running. I have it set to 1.5 minutes. So the ashing grate moves 1.5/10 % of the time the combustion blower is running. My fire height is near the top of the "Anthratube". I'm burning UAE pea coal and I have no puff backs.

I had the thermocouple only, installed by AHS when the boiler was back for modifications. My intent was to use my own thermocouple controller and convert to the thermo ash style control. After trying to understand the logic of the thermo control (I couldn't) I stayed with the timer control.

Yanche, thanks for sharing that! I may consider going to a timer system.