Coalpail.com Forum

I have a coaltrol issue with maintaining temperature settings. I understand the min and max settings as they relate to feed rate,however , it seems like a never ending chase to maintain temperature setting without over or under shooting.I have cleaned all components( chimney,motors,grate,air holes,thermostat air holes,etc.). My question involves the the max setting.For example,if there is a constant outside temperature of say 20 degrees and a temperature setting of 72 degrees is maintained with a max setting of 40 feeding at a 99%rate, should not the coaltrol be able to maintain that temperature with the max setting at say 60 but feeding no higher than let's say at a 50% feed rate? I guess in other words,should a fully functioning coaltrol adjust the feed rate percentage based on demand and not set point.Thanks for your response. Tester.

I have the HLF set to 0.

If you read through some of the latest posts, you may be able to learn some tips to get it zeroed in. The thermostat does adjust based on demand, the min/max is just the limits to which the feedrate bounces between (all based on a time span of, I believe, 100 sec). Just a couple quick things to check on your set up:

1) thermostat is hanging properly on an inside wall , it can't be laying on a horizontal surface
2) there is good air flow between the stove and the thermostat so the thermostat can properly sense the temp change in your house.
3)there is a good connection between the thermostat and control module
4) if your max setting is too low, the stoves output may not be able to keep up with your house's heat loss. For example, with a low max setting, your stove could be running at 50,000 btus when it should be at 90,000.

One of the coal trol guys will probably chime in eventually, but like I said some of the latest posts to this board deal with similar situations and suggestions for correcting them.

I believe the V3 version of the software runs on 120 second timing.

As stated, the Coal-trol will settle in to a FR based on demand and setpoint. MIN and MAX are the limits at which the Coal-trol will feed fuel when at FR 0 and FR 99, respectively.

So, taking your example:

MIN 6 and MAX 40
Setpoint 72 degrees
Outside 20 degrees

Lets say this produces a settled FR of around 60.

If you were to increase MAX to 60, yes the settled feedrate would be lower, maybe FR 45ish. However, in trying to achieve that setpoint the Coal-trol may will dial up a period of high feedrate which would potentially result in burning coal falling off the grate or inefficient burning of the fuel in general due to the pushing rate being too high. MAX should be set no higher than your stove and grate system can handle. It is reasonable, in some cases, to reduce MAX from the ideal. Please see below.

As to overshooting and undershooting. In general if you're finding that it will not settle on a setpoint:

- Make sure the thermostat is mounted on an interior wall. The unit must be normally oriented and have no obstructions on the top or bottom edges. There is a hole on the left side on the top and bottom which allows air to enter the thermostat and pass over the sensor. If these are blocked or the unit is not flat against a wall in a normal orientation then the air flow will be restricted and it can impact performance. Also make sure it is not sitting on a couch or shelf or something like that as these can act as thermal sinks which slow the room temperature from getting to the sensor and result in over and undershoot behavior. Likewise make sure the thermostat is not in direct sunlight, not in a draft, or a "dead spot" in the room where convection air flows will not reach easily.

- Sometimes a stove can be "too much" for a house or heating demand situation (particularly happens in Fall and Spring seasons). Try lowering your MAX setting from the normal setting. Some people have had to reduce it by as much as half (MAX 40 to MAX 20) in order to get proper response. This can also help eliminate overshooting when there are circulation problems. If you do this, you may find the need to increase MAX when the weather gets more consistently colder.

- Better circulation of heated air. If your stove is in a relatively closed off area of the house with poor circulation to the rest then transfer of heat will be slow and the room it is in will over overheat significantly, particularly in the thermostat is not in that room with the stove. When the rest of the house does get up to temp, there is a pool of overheated air in the stove room which will slowly result in an overshoot. If the thermostat is in the room, then the stove will heat the room up to temp (perhaps with overshoot, due to the "overpowering stove" scenario above) and then over time the heated air will mix with the rest of the house and slowly bring it up to temp. While this happens there may be a series of over and undershoots which occur, as each heating event mixes with the house slowly. It is entirely possible for this to continue on indefinitely if the mixing is too slow (so slow the outdoor demand changes enough to result in never settling). Slow, steady, but deliberate flow is best for heating applications.

- HLF is an advanced setting which generally should not be used. In some cases, when all else fails, you can try using it. IT will only affect behavior when a setpoint change is made (either manually or based on programmed settings). It does not affect steady state behavior at all. Higher settings will result in stronger "pre-loading" based on the amount of setpoint difference between the new and old setting. If, for example, a change from setpoint of 60 to 65 would normally result in an immediate FR increase of 20 points (it doesn't, just tossing numbers to illustrate), the jump in FR with HLF set to 1 might be 25 points, HLF 2 might be 32 points, and HLF 3 might result in a 42 point jump in feedrate. And similarly for FR decreases due to reduced setpoints. The idea being that underpowered stoves or larger dwellings would benefit from a bigger "boost" than normal on setpoint changes. Another case it can be useful is if you're wanting quicker response to setpoint changes, and are willing to live with more overshoot than normal to get there.

Tester, please give us a call to discuss your situation. We want to get you working as best as possible. Our number is 315-299-3589.

I have my min/max set at 10 and 49. I have my therm set at 72 day and 74 night (I love the warmth and hate bundling up to be comfortable).......my FR rarely gets above 75 for the temp jump and is steady at 0-15 to maintain the higher nighttime temp. Yes it took me some time playing with it. The one thing I notice each winter is the coal-troll needs time to regulate the house and then do what I call regulate to the house. So in the beginning (my first fire up) the FR is 99 then will be around 25 until the house is completely regulated and all walls/spaces are heated.

I took my thermostat and put a self stick floor protector felt on the back which keeps the thermostat about 1/4 inch off the wall. Not sure if it helps the air flow around the stat or keeps the back of it warmer, but it does seem to help maintain my set point slightly.

In my install I sometimes need the stove to "Giddy Up" so I set my HLF to 1. I also set my max down from factory defaults for Keystoker. I like my convection fan to run at high longer, which is what is needed in my install. Even though the heat output is not at max rated I was able to get a nice mix of air and heat, which quite often is a personal preference. The Coal-Trol makes such a mix easy.