noiruuk,
"Anyone have any suggestions on a good method for determining the secondary air flow? I have a mind to keep the fan power at 50%, open the shutter all the way (100% open), set the primaries at something less than 10mm (where I have them now), close the secondaries and get a flame going and slowly open the secondaries. Sound about right?
How important is it that both secondaries be equally open?"
Feeling the secondaries "grate" on the tubes is bottoming out and yes full 360's equal one turn (next time you have the cover off see if there is a rub ring centered on each of the discs that close the secondaries to be sure they are aligning correctly). Try two turns out to start. Work from the bottom instead of the the top of your air flow. Drop your primaries down to 7 or 6mm once again go from the bottom of the air flow.
Even though I don't have the newer controller and can't get 10% increments on fan speed I do not consider assuming the 50% speed with wide open shutter to be a solid choice. The flow from the fan can be adjusted up as needed but the greater the air flow from the fan the greater the fuel consumption can be. With my unit I have found the greatest detriment to fuel economy is my blower. It can over power all of your adjustments.
As far as an "over heat" you can get gasification and still blow smoke out your chimney and over heat if your bypass has carbon, creosote or wood matter preventing complete closure. Your secondaries are the "idle" time source of O2 for the fire so if your boiler gets up to temp and the blower quits you can still over heat via a leaking bypass damper especially with wide settings on the secondaries. My unit idles a lot and "over heats" are usually from something like bark or carbon/creosote blocking the by pass seal. The cleaning handle on the Super model can be in either position as far as operation is concerned but you will find that with the handle positioned towards the front it will probably be harder to open the bypass completely. If you leave the handle forward and you experience "huffing" (a sign of mix problems) or mini explosions you will have less tendency for over heat because the lift mechanism for the cleaners partially blocks the the bypass from fully opening and the spring-over-center for the by pass handle can reset the damper plate. The handle the other way and one good "cough" and it can blow the damper wide open and over heat. As a side note if your boiler has gone into over heat closing the secondaries completely will help extinguish the fire and reduce the risk or duration of boiler "run-a-way" and may lessen the risk of damage.
Bridging can be caused by both or either of the primary or secondary settings being too high but that is usually in conjunction with the blower being set too high.
Secondaries being open equally gives a better balance but theoretically one could do the job and I have short term tested one side then the other closed and the unit worked but there are better results with both open.
"Anyone have any suggestions on a good method for determining the secondary air flow? I have a mind to keep the fan power at 50%, open the shutter all the way (100% open), set the primaries at something less than 10mm (where I have them now), close the secondaries and get a flame going and slowly open the secondaries. Sound about right?
How important is it that both secondaries be equally open?"
Feeling the secondaries "grate" on the tubes is bottoming out and yes full 360's equal one turn (next time you have the cover off see if there is a rub ring centered on each of the discs that close the secondaries to be sure they are aligning correctly). Try two turns out to start. Work from the bottom instead of the the top of your air flow. Drop your primaries down to 7 or 6mm once again go from the bottom of the air flow.
Even though I don't have the newer controller and can't get 10% increments on fan speed I do not consider assuming the 50% speed with wide open shutter to be a solid choice. The flow from the fan can be adjusted up as needed but the greater the air flow from the fan the greater the fuel consumption can be. With my unit I have found the greatest detriment to fuel economy is my blower. It can over power all of your adjustments.
As far as an "over heat" you can get gasification and still blow smoke out your chimney and over heat if your bypass has carbon, creosote or wood matter preventing complete closure. Your secondaries are the "idle" time source of O2 for the fire so if your boiler gets up to temp and the blower quits you can still over heat via a leaking bypass damper especially with wide settings on the secondaries. My unit idles a lot and "over heats" are usually from something like bark or carbon/creosote blocking the by pass seal. The cleaning handle on the Super model can be in either position as far as operation is concerned but you will find that with the handle positioned towards the front it will probably be harder to open the bypass completely. If you leave the handle forward and you experience "huffing" (a sign of mix problems) or mini explosions you will have less tendency for over heat because the lift mechanism for the cleaners partially blocks the the bypass from fully opening and the spring-over-center for the by pass handle can reset the damper plate. The handle the other way and one good "cough" and it can blow the damper wide open and over heat. As a side note if your boiler has gone into over heat closing the secondaries completely will help extinguish the fire and reduce the risk or duration of boiler "run-a-way" and may lessen the risk of damage.
Bridging can be caused by both or either of the primary or secondary settings being too high but that is usually in conjunction with the blower being set too high.
Secondaries being open equally gives a better balance but theoretically one could do the job and I have short term tested one side then the other closed and the unit worked but there are better results with both open.
