can only heat my storage to 182 F

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woodsmaster

Minister of Fire
Jan 25, 2010
2,885
N.W. Ohio
My controller says the boiler is 195 and won't go any higher, but my other thermostats all say 182 are there any tricks to get my water hotter in storage.
 
Are all sensors accurate?

Will
 
I dont Know if the one on the boiler is but the other three all read the same.
 
Do you have enough flow between the boiler and tank? Where are the sensors on the tank, near the top or bottom? At any rate the tank temperature will never quite make it to the boiler temperature. I find that once my boiler temp maxes out the tanks will creep up but slowly.
 
...the tank temperature will never quite make it to the boiler temperature.

This can be challenging, but I have found an easy way to bring the entire 1000 gal tank up to 191-193, which is as hot as my boiler will get, and still avoid idling. The key is to have the last load of wood be close to a full load and also be the right amount of wood so that at the end of the burn the boiler is down to low coals and about done just as tank temperature reaches the 190+ maximum. Weighed wood burns, together with temperature sensors on the tank (especially the bottom 1/3), are the solution to determining how much wood should be in that last load. As stated in my prior posts on weighed wood burns, this can be reduced to a chart so that at the beginning of a burn and knowing starting tank temperature, you will know nearly exactly how much wood to burn to reach your desired target temperature.
 
WM, for what it's worth... My AZEL sensor on the last elbow where I enter the supply line pex to the house always reads about 10F less than what is set on the controller. This may not be your problem, but from what I see the Controller thermocouple must be somewhere in the boiler where it reads hotter than the final water exit temp at the top of the boiler. My Controller is set at 195F and I typically see in the neighborhood of 185F as it enters the PEX on it's way to the house. I can probably move the AZEL sensor and place it at the boiler exit to get a better reading on the controller to exit water temp bias or measurement error or whatever you want to call it. Some of mine is related to some small thermal loss due to piping, air separator, etc. But I don't think that even amounts to a degree.
 
woodsmaster said:
My controller says the boiler is 195 and won't go any higher, but my other thermostats all say 182 are there any tricks to get my water hotter in storage.

We are making the assumption that the supply (hot) is going to the top of the tank and the return is going from the bottom of the tank to the input of the boiler. Is that right?
 
Fred61 said:
woodsmaster said:
My controller says the boiler is 195 and won't go any higher, but my other thermostats all say 182 are there any tricks to get my water hotter in storage.

We are making the assumption that the supply (hot) is going to the top of the tank and the return is going from the bottom of the tank to the input of the boiler. Is that right?

Yes that is right.
 
Tennman said:
WM, for what it's worth... My AZEL sensor on the last elbow where I enter the supply line pex to the house always reads about 10F less than what is set on the controller. This may not be your problem, but from what I see the Controller thermocouple must be somewhere in the boiler where it reads hotter than the final water exit temp at the top of the boiler. My Controller is set at 195F and I typically see in the neighborhood of 185F as it enters the PEX on it's way to the house. I can probably move the AZEL sensor and place it at the boiler exit to get a better reading on the controller to exit water temp bias or measurement error or whatever you want to call it. Some of mine is related to some small thermal loss due to piping, air separator, etc. But I don't think that even amounts to a degree.

That is the same on my system. I was wondering about moving the sensor or putting somthing inbetween the sensor and boiler to get an extra ten degrees.
 
I think there's something about the Controller's thermocouple placement in our BioMass 60's. If I'm burning tonight I may move one of my AZEL sensors to the tee at the boiler outlet. To reiterate, I've never seen exit water temps as hot as displayed by the controller.
 
dpsfireman said:
Do you have enough flow between the boiler and tank? Where are the sensors on the tank, near the top or bottom? At any rate the tank temperature will never quite make it to the boiler temperature. I find that once my boiler temp maxes out the tanks will creep up but slowly.

Yes plenty of flow. I have 1 1/2" pipe that splits to 1 1/4 to each tank and a 3 speed pump.
 
Tennman said:
I think there's something about the Controller's thermocouple placement in our BioMass 60's. If I'm burning tonight I may move one of my AZEL sensors to the tee at the boiler outlet. To reiterate, I've never seen exit water temps as hot as displayed by the controller.

Mine is allways 10 degrees less.
 
i have a older EKO with a old controller that put the boiler in idle in the 170ish range. That was way to low as I have pressurized storage so I ended up moving the sensor. You have to move the sensor, wait awhile to get a good read on what it is doing, and then move it again. Just a little distance from the water jacket makes a large temp difference. You do have to be careful and move it only a small amount, as your tricking the boiler and you don't want to: 1. go into a idle as the sensor is reading to high, or 2. overheat as the sensor reads to low and you fill your storage and still have a load in the boiler.
 
I did the same thing as Mr. Robertson. I moved the sensor up into the insulation. Had to do it or buy a different controller. I have the Ecoster 2 which shuts down at 180 °F. I'm not flying blind though. My system is basically controlled with a Tekmar 156 and the source probe is strapped to the outlet of the boiler and wrapped with insulation. The only thing the boiler controller does is act as an on/off switch and shuts down the boiler on rise. It now goes into idle mode at 202 °F as measured by the Tekmar 156.
 
I added an 82K resistor in parallel with temperature sensor to increase max temperature on my Biomass 25. At 194 F adding resistor changed indicated reading to 185 F. At 118 F adding resistor changed indicated reading to 111 F. This will raise the max temp by about 10 F to 205 F but the reading will be the same at 195 F. I did this calibration by disconnecting the sensor and connecting a potentiometer to the controller to simulate different temperatures. I would think that this approach would provide more consistent results than moving the sensor.

With the right size fire, that is one that may cause the boiler to idle a bit near the end of a burn I can get my tanks to about 202 F.
 
dpsfireman said:
I added an 82K resistor in parallel with temperature sensor to increase max temperature on my Biomass 25. At 194 F adding resistor changed indicated reading to 185 F. At 118 F adding resistor changed indicated reading to 111 F. This will raise the max temp by about 10 F to 205 F but the reading will be the same at 195 F. I did this calibration by disconnecting the sensor and connecting a potentiometer to the controller to simulate different temperatures. I would think that this approach would provide more consistent results than moving the sensor.

With the right size fire, that is one that may cause the boiler to idle a bit near the end of a burn I can get my tanks to about 202 F.

Where did you get the resister? how much did it cost and what is a potentiometer?
 
It takes some time for the tank temperature to approach the boiler temperature. I have found that, at least the way I run my boiler, modified settings on the controller can help. The idea is to slow the fire down without losing gasification when near the end of a burn and the tank temps are getting near max.

There are a couple of undocumented settings in my controller that I have tweaked to accomplish this that the attached shows. The settings I have marked in red show how I have changed the settings. Basically what happens is that when the temperature rises to 10 degrees lower than the thermostat setting, the blower begins to slow down. As the temperature rises above this point the blower continues to slow down until it reaches a couple of degrees below the thermostat setting. Also, I lowered the hysteresis setting to the minimum value so that as soon as the boiler temperature drops 2 degrees the blower starts back up.

One more thing that should help. Do you have a valve in the bypass loop for the thermostatic mixing valve? Closing this somewhat (BUT NOT FULLY) will increase the flow to the tanks when the thermostatic valve is fully opened.
 

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Well I played around with the temp sensor and got the storage up to 190. I might mess with it a little more and shoot for 195 F How many btus would 5 deg. be in 1000 gal?
 
Played around how. Did you move it or do the resistor thing? I probably have the same issue even tho I don't have storage.
 
tennman, I took the top loose and on the left side under a clamp is a sensor. I loosened the clamp and slid the probe down so it was sticking out past the clamp most of the way. I then tightened the clamp back down and it left a 1/16" gap between most of the sensor and the boiler steel. I run It with the top part way off and it heated the water to 194 ,but when I put the cover back on the extra heat It held in lowered it to 190.
 
I think I also have the same problem with my Solo 60. I have a A419 johnson control threaded into one of the top ports on the top of the boiler. This controller constantly reads 10 to 15 degrees higher than my outlet boiler temps. I also cant get over 180 on the tanks ,but yet the 60 will idle when i get higher return temps. I think i need to move my control?
 
WM, what's puzzling to me is the thermocouple (TC) is somehow hotter than the water. I haven't taken mine apart yet, but what this implies is the boiler pressure vessel outside is somehow hotter than the water inside it. The clamp must be conducting this higher temp into the TC. As I understand it you basically suspended more of the TC into the cooler surrounding air to essentially cool it which is a way of "calibrating" the TC. Since I presume the clamp and sensor are on the outside, you would think there is water between the TC and the firebox.

OR the other explaination is simply the calibration coefficient in the controller is wrong. Either way, your adjusting the TC relative to the clamp is working to fool the system. My boiler has been shut down now for 2 weeks, but this is on my to-do list for next year or when I do my post-season cleaning.
 
Just stumbled in this thread...Great stuff! I've been having trouble breaking the 180º point myself, and noticed the controller was stopping at 195º but then diving down to 188º when it restarted....with the actual water temp in the system only at 181 or so. A minor tweak of the probe & I got the water up to 200º with the boiler controller reading 195º plus. This mean by the time I drop a degree or 2 getting to storage I may just break the 190º into storage mark and quite idling my boiler.
 
I ended up getting my output temp the same as the boiler temp. Yesterday I put a little to much wood in and had allmost the whole tanks to 195
 
woodsmaster said:
I ended up getting my output temp the same as the boiler temp. Yesterday I put a little to much wood in and had allmost the whole tanks to 195

I doubt I could do that...because I'm running unpressurized storage...but anything is possible.....
 
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