Far So Good After Tweaks to AHS S260

dchartt wrote:I would like to know if there is anyone out there who ran there s130 in milder weather like 40 to 60 degrees without having large amounts of unburnt and partially burnt coal?

Since lowering the SV on the thermo ash controller to 120 in warmer weather I have had essentially no unburnt or partially burnt coal and the puff backs stopped also.

I think that maintaining the correct thickness of the fire bed is critical to correct operation of the AHS boiler--too thick a fire (too thin a bed of ash under the fire) and the puff backs occur.

I also think--based on the varied experience posted on this board--that there must be significant sample to sample variation between different AHS boilers and the SV of the thermo grate controller that yields a satisfactory thickness of the fire. I found that I needed to go down to the minimum value allowed (120) with the standardard AHS programming of the controller to stop the puff backs while I note others post satisfactory performance with a SV of 130 or even higher.

Bob wrote:

dchartt wrote:I would like to know if there is anyone out there who ran there s130 in milder weather like 40 to 60 degrees without having large amounts of unburnt and partially burnt coal?

Since lowering the SV on the thermo ash controller to 120 in warmer weather I have had essentially no unburnt or partially burnt coal and the puff backs stopped also.

I think that maintaining the correct thickness of the fire bed is critical to correct operation of the AHS boiler--too thick a fire (too thin a bed of ash under the fire) and the puff backs occur.

I also think--based on the varied experience posted on this board--that there must be significant sample to sample variation between different AHS boilers and the SV of the thermo grate controller that yields a satisfactory thickness of the fire. I found that I needed to go down to the minimum value allowed (120) with the standardard AHS programming of the controller to stop the puff backs while I note others post satisfactory performance with a SV of 130 or even higher.

I'm not surprised by the variations. The thermocouple sensor that AHS uses is a type K thermocouple, a widely used inexpensive type. A type K probe is capable of measuring a very wide temperature range -328 °F to +2462 °F. It's not a very accurate probe, so the actual indicated temperature could be considerably different that the temperature the electronic indicator shows. So one person's 120 degrees could be another persons 130 or more.

In addition it's misused in this application. There is no possible need to measure such a wide temperature range. A more appropriate thermocouple would be a type J which has a much narrower temperature range.

You can read more about thermocouples here:

https://en.wikipedia.org/wiki/Thermocouple

If the probe were, easily accessible I'd suggest calibration with an ice bath. But that's totally impractical. Given that you can not depend on the absolute indicated value, experiment with the settings until you get the setting that reduces the puff backs. Even if the setting indicated is below that recommended in the manual. As with all adjustment related to coal make small changes and allow sufficient time for observations.

When I was at AHS to have my boiler modified, I discussed with Jeff the type K vs. type J. The response was largely the glassy eyed look, and I changed the subject.

Nice.

So would it be a fair assumption that if most changed theyre sv to 150 they would get puffbacks.?

Yanche wrote: In addition it's misused in this application. There is no possible need to measure such a wide temperature range. A more appropriate thermocouple would be a type J which has a much narrower temperature range.

With the probe hanging out there in never-never land and looking for such a low temperature, the speed at which you ash at becomes an exponential factor. Ashing at a high rate could increase the fire's size considerably over a slower rate.

Is there a way to change the speed at which the AHS units ash? I know on AA boilers you can change the number of grate teeth that engage per auger rotation. The more I think about it, the more I think AA got it right from the start.

The differential in temperature between ashing start and ashing completion can be changed. The factory differential is set at 10 degrees. Using mine as an example, when my ash grate temperature gets to 120 degrees the ash grate motor starts (providing that the fan is running), and when it hits 130 degrees (my SV, or set value) the ash grate motor stops.

I'm purely guessing that my boiler only ashes at roughly every 4th or 5th cycling of the fan motor. If the ash grate temp. differential was to be lowered to 5 degrees, then perhaps the ash grate motor would come on with every 2nd or 3rd firing of the boiler (cycling of the fan motor). By doing this nothing is changed regarding the speed of the ashing, but the amount of ashing (and therefore the amount of new coal being fed into the firing pot) would be halved for each ashing cycle, and the number of ashing cycles would be doubled to compensate.

Rob R. wrote:Is there a way to change the speed at which the AHS units ash? I know on AA boilers you can change the number of grate teeth that engage per auger rotation. The more I think about it, the more I think AA got it right from the start.

The grate motion on the AHS is fixed--both stroke length and speed. As noted by lsayre the frequency of ashing and the lengh of time for each ashing cycle can be changed with the differential setting on the thermo ash controller.

Here's some food for thought.
other than a couple little "woofs" last spring, I've NEVER had a problem with kabooms.
Monday I dumped about 2 gallons of fines into the center of the hopper that were in the bottom of my coal tub which consisted of mostly rice sized stuff and some pea.
Tuesday I'm in the shop with the AHS and KABOOOOOOM. It was violent enough to actually break off one of the pins on the barometric door and send it flying to the floor.
WTF?
After regaining my composure. I took a good look at the coal lying on top of the burning coal bed and sure enough there is all of that small pieces of coal.
So I'm wondering: if this could be anyone else's source of problem with puff backs, you know size of coal or a lot of fines in their coal?
I only have a piece of aluminum foil over the missing baro-door since yesterday afternoon and opened the little vent port on the observation door and so far this morning it's still there, so that seems to have resolved the issue but holy ......... Got my attention!

BTW My S-130 (mfg 2008) has a type J thermocouple. So someone is listening.

I was wondering about the size of coal also. I installed a S260 a week ago today and have been very impressed so far with no issues at all. I have been burning nut instead of Pea with some larger sizes about as big as a piece of charcoal . I have a ton of Nut left and picked up 2 ton of Pea coal saturday to start mixing with the nut till it is gone. The biggest problem with the nut is if you pack the hopper to much it could bridge in the inlet tube due to the large size.

Mac

Yanche wrote:

Bob wrote: Since lowering the SV on the thermo ash controller to 120 in warmer weather I have had essentially no unburnt or partially burnt coal and the puff backs stopped also.

I think that maintaining the correct thickness of the fire bed is critical to correct operation of the AHS boiler--too thick a fire (too thin a bed of ash under the fire) and the puff backs occur.

I also think--based on the varied experience posted on this board--that there must be significant sample to sample variation between different AHS boilers and the SV of the thermo grate controller that yields a satisfactory thickness of the fire. I found that I needed to go down to the minimum value allowed (120) with the standardard AHS programming of the controller to stop the puff backs while I note others post satisfactory performance with a SV of 130 or even higher.

I'm not surprised by the variations. The thermocouple sensor that AHS uses is a type K thermocouple, a widely used inexpensive type. A type K probe is capable of measuring a very wide temperature range -328 °F to +2462 °F. It's not a very accurate probe, so the actual indicated temperature could be considerably different that the temperature the electronic indicator shows. So one person's 120 degrees could be another persons 130 or more.

In addition it's misused in this application. There is no possible need to measure such a wide temperature range. A more appropriate thermocouple would be a type J which has a much narrower temperature range.

You can read more about thermocouples here:

https://en.wikipedia.org/wiki/Thermocouple

If the probe were, easily accessible I'd suggest calibration with an ice bath. But that's totally impractical. Given that you can not depend on the absolute indicated value, experiment with the settings until you get the setting that reduces the puff backs. Even if the setting indicated is below that recommended in the manual. As with all adjustment related to coal make small changes and allow sufficient time for observations.

When I was at AHS to have my boiler modified, I discussed with Jeff the type K vs. type J. The response was largely the glassy eyed look, and I changed the subject.

Pa papa wrote:Here's some food for thought.
other than a couple little "woofs" last spring, I've NEVER had a problem with kabooms.
Monday I dumped about 2 gallons of fines into the center of the hopper that were in the bottom of my coal tub which consisted of mostly rice sized stuff and some pea.
Tuesday I'm in the shop with the AHS and KABOOOOOOM. It was violent enough to actually break off one of the pins on the barometric door and send it flying to the floor.
WTF?
After regaining my composure. I took a good look at the coal lying on top of the burning coal bed and sure enough there is all of that small pieces of coal.
So I'm wondering: if this could be anyone else's source of problem with puff backs, you know size of coal or a lot of fines in their coal?
I only have a piece of aluminum foil over the missing baro-door since yesterday afternoon and opened the little vent port on the observation door and so far this morning it's still there, so that seems to have resolved the issue but holy ......... Got my attention!

BTW My S-130 (mfg 2008) has a type J thermocouple. So someone is listening.

Just wanted to comment that when using either the type J or type K thermocouple it is necessary that the controller is configured for the matching thermocouple.

A mismatch will cause a large error in readings and response time.

Pa papa wrote:
BTW My S-130 (mfg 2008) has a type J thermocouple. So someone is listening.

How can one tell if their thermocouple is of the J or K type?

lsayre wrote:

Pa papa wrote:
BTW My S-130 (mfg 2008) has a type J thermocouple. So someone is listening.

How can one tell if their thermocouple is of the J or K type?

Measure the output voltage of the thermocouple at a fixed temperature and compare it to the theoretical voltage.

The voltages can be determined from the calculator on Fluke Instrument's web site:

http://us.flukecal.com/Thermocouple-Table-Voltage ... or?geoip=1

For example at 212 deg F

Type K = 4.096230 mV
Type J = 5.268916 mV

For both at 0 deg F the output is 0 mv.

The Seebeck Coefficient listed on the calculator is used to linearize the voltage vs. temperature curve.

lsayre wrote:

Pa papa wrote:
BTW My S-130 (mfg 2008) has a type J thermocouple. So someone is listening.

How can one tell if their thermocouple is of the J or K type?

Type J commonly has a red and a white wire...whereas, Type K commonly has a red and a yellow wire.