RK-2001UA Controller Alternatives

[BoiledOver]

Hello to all. This is the first year with a wood boiler, EKO 25. I am wondering if anyone has eliminated the controller and gone a different direction. There is an alternate now available that was designed by someone from this sight but it is more unit than I am interested.

The good about this unit is that it does control the boiler in a safe reliable manner. The adjustablity of the setpoints and hysteresis of the components is a desirable option.

However, I would like to control the boiler/storage circulator beyond its parameters. The highest shutoff is 170F which is 20 degrees below desired storage temp (seems goofy to me). The pump runs all night and eliminates any stratification that could result. Also, I would like to control the fan speed during every burn up and down as desired. The fan can be controlled by going through the controller's menu, but requires many pushes to make the adjustments. This wear is likely to cause failure in the buttons on the board.

As for the boiler/storage circulator; I will use a Johnson Controls A491 set to make on rise at 191 with a 1 degree differential, well that is a starting point and may change.

Concerning the fan speed; It looks to me a bit more complicated. The controllers hysteresis on the fan speed serves well to keep blowups at bay. Initially I had near zero hysteresis and introduced too much air too fast and pow. This occured at first start of a burn. To go with a fan speed rheostat while bypassing the controller would void the hysteresis option, no? My electronics knowledge is very little and I could use some sugestions if ya got em. Could the rheostat go in series with controller and keep the programmed hysteresis? Will a rheostat work with the variable speed fan? Maybe just use the rheostat and manually control the startup hysteresis?

Any advice and remarks are welcome.

Gotta state the obvious, I love having a warm home with zero propane yet this season................................

 

[ewdudley]

I guess first of all it seems to me that the RK-2001UA is not designed for heating storage, so there's no real need to duplicate its functionality.

My RK got flakey and finally died altogether. They say it might be possible to repair it, but I don't trust the thing, plus I keep spares of all controls and I'm not willing to spring for a spare RK.

For heating storage these are the requirements I came up with:

• Draft fan shall run when draft fan start-up timer is active (e.g., 15 minutes), shall continue to run if flue temperature has risen above proofing temperature (e.g., 275 degF), and shall stop running when flue temperature drops as fire fades (e.g., 250 degF).
• Draft fan shall be disabled if boiler supply line mechanical dry contact aquastat rises above 200 degF.
• Draft fan shall run at a fixed speed according to manual setting of a variable fan speed controller.
• Boiler circulator shall run when boiler supply temperature goes above the 'launch temperature' (e.g., 185 degF with 5 degF hysteresis).

So there you have it, a mechanical supply temperature aquastat, an electronic supply temperature aquastat, a mechanical windup countdown timer, ice cube relays, a manually adjusted variable speed fan control, and flue temperature snap-disk thermostat. To do it right I think the separate mechanical aquastat in series with the draft fan is necessary.

I also have implemented a separate and independent control for flue temperature, which is nice but not a real necessity.

 

[BoilerMan]

Truly I hate to suggest it, but the RK2001AT2 is much more robust and setup well for storage control.

My boiler came with it and it has served me well. The 2001UA has fewer user adjustable setpoints.

TS

 

[BoiledOver]

I guess first of all it seems to me that the RK-2001UA is not designed for heating storage, so there's no real need to duplicate it's functionality.

Yeah, I was wondering why the manufacturer doesn't offer a storage controller option. Thanks for your input and obvious trial tested methods, it all makes good sense. In your system you have storage loaded to 185, is that correct? Have you tried getting an extra 10 degrees? I have yet to force it above 183 and wonder if going to 190 or above is worth the effort, those high temps seem to take forever once the return temp closes the delta.

Truly I hate to suggest it, but the RK2001AT2 is much more robust and setup well for storage control.

My boiler came with it and it has served me well. The 2001UA has fewer user adjustable setpoints.

TS

Thank you also for your input. After looking over the user manual of the AT2, I see it is a step up from what the EKO runs. Do you use the flue temps input in your setup?

Still its pump cutoff at the end of a burn is lower than what I am looking to achieve. My thinking is to set the make-on rise of storage circ at a higher temp to send only the hottest water over and keep the return low enough that the delta doesn't slow the end process. Also, a higher make-on rise temp with little differential should keep the pump from running on and on as it does with the 170 setting.

At what temp are you charging to?

 

[ewdudley]

In your system you have storage loaded to 185, is that correct?

185 is just an example. I adjust it according to how much storage I think I'm going to need; 170 degF normally, 185 degF if it's cold and/or windy, 200 degF if I'm leaving for three days with all the load thermostats set to 45 degF.

those high temps seem to take forever once the return temp closes the delta.

I have a no-idling strategy. Just set the supply temperature to the desired storage temperature and don't let any water go to storage that isn't heated all the way to the desired temperature. If there's some excess fuel and the supply temperature maxes-out, the draft fan trips off and that's the end of the burn.

 

[ewdudley]

the RK2001AT2 is much more robust

I don't care how good a controller they might make today, P.W. KEY sold me a piece of crap and they will never sell me another. Same goes for Chrysler Motor Corporation.

 

[Fred61]

I batch burn and only heat from storage I'm using a TEKMAR 156 differential controller to run my circs. My EKO came with an Eccoster 2 controller which only allows a max boiler temperature of 80*C so I was more or less forced to do modifications early on. I moved the sensor up into the insulation in order to get the boiler temp higher and put the sensor from the TEKMAR in it's place. The other sensor from the TEKMAR is located in a well in the center of my 500 gallon upright stainless storage tank.

This gives me the flexibility to adjust all the parameters that I was looking for and I think you may be also are hoping to achieve. I can adjust for the storage high temp, source high and low temp, differential temp and several other features available.

 

[MarkW]

I've the same concerns about this controller as the OP. Outside of burning until out of fuel and shutting down manually once at set temp., would it be prudent to install an aquastat in the circ pump wiring to interrupt that 170` max setting?
I'm only in my first year with my Biomass 60, but this is currently my only gripe with the controller.

 

[BoiledOver]

I've the same concerns about this controller as the OP.

Hey Mark, It sounds like we aren't the first to recognize the shortfall of this controller in loading storage.

Ewdudley and Fred61 have already walked this path, thank you both for sharing your solutions. These guys have some good advice.

That Tekmar 156 takes over control of the circ and allows user preferred programming, too cool. Using the RK in tandem with the Tekmar will load storage however the user desires.

Ewdudley is getting there with simpler devices while adding the flue temperature into the equation. Currently I get extended blower time as the fire fades. The other thing that hits the bulls eye is Ewdudley's theory of a no-idle strategy. The RK with its 170 maximum launch temp demands there to be idling and short cycles as the T delta slowly narrows. This behaviour is what concerned me from the very first fire.

Is this explanation of your theory close? Send only hot (not warm) water to storage keeps the cooler water down and returning to the boiler, minimal mixing. The higher delta keeps the boiler fired until finally the return temp jumps rather quickly to the desired storage temp.

The RK does not allow that, as the RK is circulating 165-195 water at any given moment causing a stir and the need to circulate up to maybe twice as many gallons to get the whole thing heated to target.

Gotta say thanks to this website and the members who share their experience.

 

[Fred61]

My circulator launch temp is 182 which helps minimize mixing but I may or may not be screwing that up with my secret "no idle" practice. My overheat protection, up until I installed a standby generator is an aquastat in the spare well on the top of the boiler hooked to a circulator powered through an inverter that pumped overheated water through a copper coil laying in the bottom of my storage tank. When approaching the end of the burn and the delta is separated by only a few degrees and the boiler temperature reaches 195 degrees the overheat circ launches and keeps the boiler from idling. I don't have a temperature probe at the bottom of my tank (still on my list of things to do) So I don't really know the results of this practice.

 

[MarkW]

So I don't really know the results of this practice

Sounds like a good solution, however.

At this point, I'm just looking to KISS solutions as my current setup is far from optimal. I'd like to maximize my current efficiency as best the circumstances allow. 170` max on the lauch isn't it, IMO.

 

[BoiledOver]

At this point, I'm just looking to KISS solutions as my current setup is far from optimal.

Mark:

These guys in here are on top of it! Two easily accomplished methods to give you more control of the launch temperature of your circulator. Keep in mind that you may want to place a well for the aquastat (boiler water temp only) or just lay the sensor on top of the boiler. As for the Tekmar unit, well or no well is your choice too.

http://www.pexsupply.com/Johnson-Co...age-Digital-Temperature-Control-120-240v-SPDT

http://www.pexsupply.com/Tekmar-156-Difference-Setpoint-Control-On-Off-7954000-p

 

[BoilerMan]

I don't care how good a controller they might make today, P.W. KEY sold me a piece of crap and they will never sell me another. Same goes for Chrysler Motor Corporation.

HAHA! Walter P. Chryseler and the K-car!

All I was getting at was the temps are adjustable and a high boiler temp of over 200F is actually in there. As for yours going "flakey" it is fixable, and the higher voltage cap is in the newer ones so there have not been that failures that the old ones expierenced.

I'm completely with you one what would appear to be "good" initially can/will fail miserably in some time. There are WAY too many examples of this in the plumbing&heating field, PB tubing, Goodyear EPDM radiant, KITEC, acetal fittings, aluminum romex, the Tacoma Narrows bridge...................the list is endless. All these things looked good on paper and went into service well and people trusted the engineering behind them, but time told the real truth.

TS

 

[ewdudley]

All I was getting at was the temps are adjustable and a high boiler temp of over 200F is actually in there.

Point taken. It sounds like they've cured the more fundamental problem of unsuitability for heating storage.

 

[BoilerMan]

I would use the RK2001AT2 to run the boiler fan and boiler primary loop circ. I'd then use a Taco BumbleBee set on deltaT to inject hottest water into the top of storage. The Bee would be powered through a simple mechanical dry contact Honeywell strap-on aquastat on the primary loop. You could do the same thing with a Tekmar injection controller, but the Bee would be cheaper.

TS

 

[maple1]

Can it do end of burn fan shutdown?

 

[MarkW]

BoiledOver
That Johnson digital looks to be just what I'm after and the price works, too. And when I change my system around next year(new house fairy willing) I can use it on my meat aging chamber.(too many interests, I know)

My RK had a weird occurrence today for the second time since I started using it. Rather that go into Fuel out mode, it was still running when I got home tonight. This is many hours after it would have been out.

 

[BoilerMan]

Can it do end of burn fan shutdown?

Yes, it is equipped with exhaust temp sensor, flue temp hysterysis and min/max set points.

To be honest, all a boiler controller should do (and this is all mine does) is control fan speed during burn, shutdown of the fan at end of burn, and control the primary circulator (boiler circ). All other flow and circulator control are best left up to outside controls IMHO.

TS

 

[BoilerMan]

BoiledOver
That Johnson digital looks to be just what I'm after and the price works, too. And when I change my system around next year(new house fairy willing) I can use it on my meat aging chamber.(too many interests, I know)

My RK had a weird occurrence today for the second time since I started using it. Rather that go into Fuel out mode, it was still running when I got home tonight. This is many hours after it would have been out.

What temp was the boiler? What temp was the flue sensor? What is the flue temp set for in the controller?

I set my end of burn flue to 225F and find it to be about right for just enough charcoal to rekindle a new fire the next day.
TS

 

[maple1]

Yes, it is equipped with exhaust temp sensor, flue temp hysterysis and min/max set points.

To be honest, all a boiler controller should do (and this is all mine does) is control fan speed during burn, shutdown of the fan at end of burn, and control the primary circulator (boiler circ). All other flow and circulator control are best left up to outside controls IMHO.

TS

Yes, I agree.

Just wondering as I have read on here about complaints of some boilers not able to do that - didn't know which were which. IMO it should be a standard control item.

 

[BoilerMan]

Yes, I agree.

Just wondering as I have read on here about complaints of some boilers not able to do that - didn't know which were which. IMO it should be a standard control item.

This is why I recommended the 2001AT2, if my boiler had come with the 2001U version I'd be in the same boat as the others on here and scrapping it for something that will actually control the boiler!

TS

 

[MarkW]

I discovered my issue this morning as it ran again all night. Boiler temp down to 135. Set point at 185.
Apparently, the factory defaults for start time and work time were not set to default. Start time was set to null and work time was set to 2 hours. So, it would appear that I didn't make the start time temp so the controller would just keep running.
So, either the manual is wrong, controller programming was not done or Biomass changed it. Either way, I reset that so I should be good in that regard or at least as good as the 2001U gets.

 

[BoiledOver]

Hey Mark,

Any movement on your setup? I have the circulator aquastat installed and running. My initial concern was with the circulator running on and cooling the storage over night. That is not a problem now. Not only is that resolved but I see an added bonus. By sending only the hotest water to storge, the boiler used less wood to charge than with the 170 degree maximum make-on temp of the RK controller.

How do I know this? I keep a daily log on a software spreadsheet and had fine tuned the calculations using the 4 heat sensors at various stages of the storage tank. What was an 84 pound burn requiremnet was too much and ended up with a surplus of one third of the upper chamber incompletely burned at shutdown.

In a week or so I will get to the fan control which will include the flue temp input, timer and variable speed fan control.

Thanks again to Ewdudley for his engineering expertise.

 

[MarkW]

I've not yet addressed this particular issue. I've been busy with other issue of my own creation.
However, with your report of fuel savings, I'll be getting busy ordering the Johnson control right now.