Keystoker KAA-2 Control/Set-Up

Guys, I know there have been many threads concerning new boiler hook-ups, but I haven't found any references to my questions. Any help would be much appreciated.

Old set-up: oil boiler with 6 zone valves (indirect water heater and 5 baseboard zones) and one pump +/- manual shovel loaded coal boiler with thermostatic damper to maintain temp
New set-up: same oil system +/- Kestoker Kaa-2

The old system was simple and pretty reliable but was labor intensive. The oil boiler is completely "stand alone". The coal unit had no electrical connections except an aquastat which MADE contact at 190F to open a valve and run the pump to prevent over heating. The return line to the oil boiler has 2 tees and 3 valves so I could redirect the return water to the coal boiler and then back to the oil boiler. I set the thermostatic damper control at 170F and the oil boiler at 120F. Oil boiler only kicked in when the fire was dying or there were several showers taken in succession.

My plan was to simply replace the manual with the Keystoker, but then I read the installation "instructions". It leaves a lot to be desired to say the least.

1. It comes with a Honeywell triple aquastat which includes its own transformer. Can I simply run the TT wires on this over to the TT connections on the Taco SR 501 switching relay? Won't the output voltage from the triple aquastat be read at the switching relay as a call for heat even though no zones have opened. (The zone valves have a 100VA 24V transformer powering them.) Yes, I could just put a jumper across the TT connections, but that would just make the Keystoker maintain a fixed temp even when not needed. There has to be a better way; I'm missing something.

2. I'm very confused about the secondary/bypass/feedback loop in the directions. I have no such set-up on either boiler. The oil boiler is a new low mass eutectic cast iron. The old boiler is high mass steel. Supposedly the high tech European oil boiler doesn't need the protection of a thermal bypass loop. And, the coal boiler hasn't one for the last 25 years. Does the Kaa-2 really need one? Also, with the oil boiler always in "standby," how cold cold it get? True, baseboard radiators don't shock systems like cast iron radiators, but an 80 gallon indirect water heater can. And if I do need one, should I be thinking of about a thermostatic tempering valve instead?

I know a bunch of folks are set up just like this. Thanks for the help.

Since a stoker coal boiler takes a fair amount of time to ramp up the size of the fire on the grate, I would jumper the aquastat and keep it at your target temperature.. as long as the indirect hot water heater or none of the heat zones are calling for heat, the amount of coal burnt to keep the boiler hot is minimal.. when hot water of heat is called for, the stored hot water will provide some heat while the stoker is ramping up the fire..

With your hand fed boiler, you had a large quantity of coal burning, just needing a few minutes of extra combustion air to ramp up the fire and available BTUs, the time needed for the stoker mechanism is quite a bit longer.

I don't think you need a balance loop, this is more for much larger boilers. There is a fairly recent thread on balance loops on the forum.

JUst my suggestions, other member's suggestions may be different.

Greg L.

Thanks.

After studying it a bit more, I think that I could simply connect the TT sites to the TT connections on the oil boiler relay. I think I can do this because the zone valves have 3 connections (1=hot from the thermostat when calling for heat, 2=neutral, 3=hot from 1 when the little piston opens enough.) With the TT positions connected to 2&3, I think the signal will only be complete when the valve is open. Then the circulator and burner can safely operate.

I really question Keystoker's thinking in the selection of this control. On the one hand, they say the unit requires a by-pass loop without any explanation. Then, they include an Aquastat with a unique low-limit control. During normal operation when calling for heat, the temperature is controlled by the high limit and its fixed differential. When not calling for heat, it is controlled by the low-limit. Below the low limit, the burner will fire to warm the water BUT the circulator won't run. In essence, it has a built-in low temp protection. However, Keystoker knows that most people with a solid heating source are required (and do) have an automatic/conventional heating system. Thus, killing the pump if you run out of fuel could prevent the back up from kicking in depending on how the system is set up. I don't think I'll be using that Aquastat to control my pump.

How the Intermatic 30min cycle timer affects the low limit will be interesting to see. I could easily imagine that the Intermatic timer alone could keep the temperature above the low limit. I'll report back in the summer on this. For the heating season, however, it won't be an issue.

It kinda suggests that you were on to a simple and reliable idea in jumping the TT connections.

I completely don't understand the directions concerning the "B" type aquastat which makes contact on rising temps. My old boiler has one of these to move out excess heat to prevent over heating. That makes sense. But if one were to install one, I think it makes more sense to intall it in the 3/4" tapping of the vessel near the triple aquastat. The low water cut-off could go in the piping just above the boiler. Keystoker's directions place the "B" aquastat in the bypass loop. Thus, the loop would require constant, if small, flow. That shunts pump effiency. Not optimal.

This all gets back my original comments on the lack of innovation in residential coal. It's obvious that the instructions haven't been updated since being typed on a manual type-writer.

thanks again for your assistance.

I just got my KAA-2 running. One thing I noticed is that the bypass loop was hot a long time before the top of the boiler. My understanding of the bypass loop and 4006B aquastat is that if the boiler gets to hot, 220F, that 4006B aquastat turns on the circulator pump to reduce the boiler temp. The KAA-2 boiler does not have a temperature pressure relieve valve like an oil or gas fired boiler. The KAA-2 only has a pressure relief valve. So the 4006B is to prevent the boiler from making steam in a hot water configuration.

You are right about the timer, it can cause the boiler to overheat. I am still adjusting my boiler. It seems that a combination of coal feed, timer operation needs to be figured out after draft settings are made.

by the sounds of it, your oil boiler is a cold start and does not have the same L8124A aquastat that your coal stove has, right?

The T-T from the L8124A on the coal boiler can be hooked up to either the T-T on the oil boiler or the X-X on the SR-501(it's the same connection depending on which on is closer).

BUT this means that you MUST shut the power to both boilers down if/when you service the oil boiler and you will be backfeeding 24V from the coal boilers L8124A into your oil boiler control!

This could kill the tech that is working on your boiler!!

Based on others posts here form there KAA-2, just keeping the fire lit by the timer will keep the water temp above 140F. I wouldn't get too hung up on that low temp control.

plus remember what Greg said. The coal takes longer to ramp up heat and you will want the starting temp of the water at 140F or so.

A special thanks for the help!

My oil boiler is controlled by the Taco SR 501. From the SR 501 relay, wires go to first an aquastat then on to the burner control. The circulator is controlled by the SR 501. That part is pretty simple. I checked the SR 501. It does't have an X-X connection. It has TT and an accessory 24V and then connections labelled 1-6: 1=H,2=N, 3/4 on/off, 5/6 on off.

You guys are dead right about both boilers needing a common kill switch (which kinda goes against some of the threads concerning separate electrical circuits for different heating units).

As for the bypass loop, I remain completely confused. I could/would plumb one if I understood what it was for. If it is to prevent thermal shock/condensation inside the kaa-2, fair enough. But, I think I have accomplished this by leaving the oil boiler in standby at set around 120F. If an actual loop were needed as in the big commercial units, I could simply leave the main circ pump to the house/oil boiler as is and place a second pump going to/from the Keystoker which could be controlled by the triple aquastat. That way, I would not have to touch any valves to send cooler water to the Keystoker before retuning it to the oil boiler. The second pump could "suck" it from the main line, heat it, and pump it back.

My oil boiler has a T&P valve, but so did my Van Wert. And good thing, it's blown twice!!! My oil aquastat died a few years back and we had no heat. I opened the valves and wired the circulator to a plug and fired up the manual coal unit with its thermostatic damper. When the service guy came, he completely forgot about the significance of the 50# of burning coal! And, another time disconnected the type B thermostat. Steam bath badness!

Machinst, how did you set up your unit?

My Keystoker is set set up as the install instructions describe except the expansion tank,air scoop and circulator pumps are on the feed line. My system is currently the sole source for heat and hot water for my home.

One thing I've noticed in the instructions is that there are 2 high limits. One on the triple aquastat used for maintaining normal boiler water temperature. The other is the 4006B. It seems to be used as a max high temp limit like the temp. part of a Temp & Pressure Relief valve. But instead of dumping heat on the floor it dumps heat into the home. I suppose if one were using oil boiler to control circulator pumps, the 4006B could be wired to the oil boiler aquastat or a relay for another circulator pump to dump heat.

If I did not use the bypass line and 4006B, I would use a T&P Relief valve on the Keystoker. I don't know why Keystoker recommends the bypass line other than what is stated in the instructions, "Our 35 year experience installing stoker fired equipment has shown to us that that the installation of the above mentioned by-pass loop and the limit control is absolutely necessary for optimum performance of your system".

Mike~ This is what the Honeywell paperwork has to say: "The L4006B makes the circuit on temperature rise.It is used as a circulator controller,delaying circulator operation when the boiler temperature is below the control setting". I have the paperwork that goes with the Kaa2 although it will be next spring until I see mine. From the look of their schematic to me it appears like they are using the L4006B to act as a device to get the triple aquastat to close it's relay and make whatever circulator it controls to start running.My guess is that they are using this system to help prevent overheating.It could be my processing equipment has low batterys but I think their manual could stand for a grooming,an update, and additional explanations.Just my thoughts , Mike

stovepipemike wrote:This is what the Honeywell paperwork has to say: "The L4006B makes the circuit on temperature rise.It is used as a circulator controller,delaying circulator operation when the boiler temperature is below the control setting".

Yes it can be used like that, might be it's most popular use. If it were wired in series in a circulator circuit and set for 160 degrees it would not allow a circulator to run when temperature is below 160.

stovepipemike wrote:From the look of their schematic to me it appears like they are using the L4006B to act as a device to get the triple aquastat to close it's relay and make whatever circulator it controls to start running.My guess is that they are using this system to help prevent overheating.

Yes, it's just like a thermostat in reverse and for me I'm having trouble keeping the boiler temp around 180.

I just got my KAA2 installed and have been monitoring and keeping tabs on the functions. All the factory provided controls appear to be working well. I do agree that keystoker should want to update or clarify their installation manual.
I have a level of confusion for pg.4 para 1 Final adjustment:"During periods of no demand the stoker unit runs only on air temperature. Fire bed should shrink to about 3 inches in length, with about 3 inches of unburned coal above it and the rest of the grate covered with ash. Observe brightness of fire when stoker turns on during the timing cycle, fire should look dull and ashen.
Immediately after cycle, fire should be bright with short yellow and blue flame at the point where unburned coal and fire bed meet. It may be necessary to adjust timer and or coal feed because of variations.... " etc.

It seems to me that the stoker builds the coal bed size, but the combustion blower controls the ashen color of the fire bed, and that running the blower at all times will cause a lag when demand is initiated because the coal has been burned off and only a small fraction of the fire bed remains. I am considering wiring the blower and stoker to the same timer output, then using the on pins to maintain the flame only to the point of holding a pilot ignition. If by doing this I think it would reduce the overtemp condition at the end of the burn cycle, On my unit this this is usually to about 195 to 200 degrees but for about 10 15 minutes if there is no addional demand. I do see a lag on the demand /beginning of cycle and think this could minimized if coal were already there but starved for air . The aqua stat will still drive the demand based on the jacket temps or the thermostat demand.

What condition may need to be considered if the firebed is starved for air , does this line of thinking make sense?
I think I will try to contact keystoker to clear up my confusion, and give it a try tomorrow when I can monitor it through the day and put some gauges in the firebox.

If you stop the combustion blower when the coal has just been pushed onto the grate, there will be considerable unburnt coal in the ash. You need the continous combustion air to completely burn up the coal..

As long as the overshoot in water temp is only up to 190-200* I wouldn't worry about it.. what is the target tempertature.? 180* ? Try setting the target temp 10* lower if the 200* temp concerns you.

I'll be interested to hear what Keystoker says

Greg L

Do I understand it right,that the fan runs constantly when in the standby condition? To me that would almost have to cause a spike in temperature because everything is in place [at least for a timeperiod] to produce full heat output.The only difference is that the circulator will not be running to carry the BTU's out of the boiler since we have no room thermostat call for heat. Full heat output would continue until the fuel bed is consumed. Hmm. that is where the additional control in the bypass line comes in play. Have I got the sequence about right? I take it there is no way to modulate the combustion air fan, true? Mike

Ok, I got in touch with keystoker to confirm that the combustion fan does run all the time. Their suggestion is to set the stoker to provide a 3inch fire bed at full demand load, then set the timer trip pins to maintain a minimun fire that will hold about or just under 160 temp at no load. so far that is 6 pins at 10 min intervals (1min. 30 sec ON--8min 30 sec OFF) That allows stoker to make just over 1 complete stroke.
I set these conditions yesterday afternoon after verifing the draft over fire with and without the blower as per instructions. I seems to hold to an overtemp at the end of cycle of 195 to just under 200 also without a load. (aquastat is set for 160 lo 180 hi diff @ 10 ). The actual on lag allows it to drop to 150 before the fire can catch up, this is with a shower or continuous domestic hot water load . The stack temp at full fire was only 235 degrees
My boilers are connected in series so the KAA2 is keeping 2 water jackets hot ( 45 gallons water total ) and the Kaa2 hot water coil is preheating the domestic to the oil boiler coil so that I didn't have to set another mixing valve for the hot water. The oil boiler is disconnected at this time so that it does not fire but the circulator controls are run by its aquastat and relays. The aquastat on the KAA2 has a jumper across the TT terminals and causes the new circulator to run all the time the jacket is above the 160 setting, the 4006B is wired to the oil burner aquastat and is set to 220 and this will cause the primary circulators to run if a major overtemp is encountered.
Right now it is 37 degrees outside and my living space are 68 and 67 degrees this area is approx 1700 sg. ft. the basement area is unheated but where the boilers are located is comfortable at 68 deg.
I hope any of this will help future set-ups, I will keep posting if any problems are encountered or I find I must make a change.

Wolverine ~ Are you O.K. with maintaining such a wide low limit over run ? It seems that it should be tighter than plus 35 degrees.To take 45 gallons of water from 160 deg. to 195 deg. costs 13,124 BTU or roughly one pound of coal.Was the factory any help with trying to tighten it up? Mike

The factory said nothing about over run .I did note that the aquastat is operating as set and that if the boiler has a load the overrun is minimal, the info that I have provided this far has been from a demand state to idle.The nights are cool here but the days have been mild 60's .
I noticed yesterday afternoon that the fire box temp at idle stayed at about 250 to 270 deg with 3 pins at 10 min spacing ( 45 sec ON 9 min 15 sec OFF) and the jacket stayed at 170 deg. for about 4 hours with no demand. This allowed the stoker to make 1 stroke per 10 minutes, there may have been a minor domestic water demand , such as to wash ones hands but nothing substancial like laundry or shower or heat. I think I would rather have it at an idle state just above low limit because it would only stroke once in 10 minutes than run for 20 minutes through the aquastat cycle and create the unneeded heat that the lag creates during a minimal demand cycle. Today is to be similar in temp to yesterday so I will try to not make any adjustments and only monitor usage , I topped of the hopper last evening, this was 40 # and first added since first fire on friday night, so 4 days at approx 10 # per day can it get any better?