Hello
What part needs to be replaced? ESP probe, Circuit Board or another part? If another part please explain.
Here is a problem on a 2007 Harman P61a-2 that I have not seen before?
It looks like a fairly newer model with the indent in the ash door for the tile insert.
The stove seams to start up and run fine. Start to fire takes approx 5 mins. However there are a few more pellets in the burn pot so the initial flame is very large! It does settle down and run fine. When the mode selector knob is turned off the stove goes to a low flame but keeps feeding pellets!
Here is my analysis. Please correct me if there is an error.
The mode selector knob in room temp mode uses the room probe thermister to vary the feed motor to keep the room at the set temp. The room probe biases the gate of the feed motor triac probably thru an inverter circuit. and the temperature knob varies the bias level for the heat level desired. (Wish I had a schematic - Does anyone have a schematic of the Harman circuit board?)
When the mode selector knob is in stove temp mode then the ESP probe biases the gate or the triac in the same manner. The mode selector also varies the voltage level applied to the room blower to change it's speed.
Now the mode selector has one more function. In startup and shut down mode it either acts as a gate or controls a gate to bias the feed motor triac.
In this case when the knob is turned to off, there seems to be a hung state and the triac gate is still being biased. The ESP probe just varies a small voltage going back to the circuit board so even though it senses the exhaust temp and tells the board when to shut the room blower off and the combustion blower off, it may have nothing to do with turning the feed motor off.
This stove had no surge protector and there were quite a few power outages last season. ESP probes do not go bad very often so I would say a power surge has damage the CB\ircuit Board. Anyone know what part on the Circuit Board?
SCRs are used in DC circuits so it makes sense that 2 are used in an AC circuit. One to handle the negative cycles and one for the positive cycles of the AC sinewave.
TRIAC operation
It can be imagined from the circuit symbol that the TRIAC consists of two thyristors back to back but with a common gate terminal, and the cathode of one thyristor connected to the anode of the other, and vice versa. This configuration is more correctly termed antiparallel
On a basic level, the operation of the TRIAC can be looked on in the format of the antiparallel thyristors, although the actual operation at the semiconductor level is rather complicated.
When the voltage on the MT1 is positive with regard to MT2 and a positive gate voltage is applied, one of the SCRs conducts. When the voltage is reversed and a negative voltage is applied to the gate, the other SCR conducts. This is provided that there is sufficient voltage across the device to enable a minimum holding current to flow.
Equivalent circuit of a TRIAC
In terms of the structure of the device, and its more detailed operation, the main terminals MT1 and MT2 are both connected to p and n regions within the device. The current path depends upon the polarity of the voltage across the main terminals.
What part needs to be replaced? ESP probe, Circuit Board or another part? If another part please explain.
Here is a problem on a 2007 Harman P61a-2 that I have not seen before?
It looks like a fairly newer model with the indent in the ash door for the tile insert.
The stove seams to start up and run fine. Start to fire takes approx 5 mins. However there are a few more pellets in the burn pot so the initial flame is very large! It does settle down and run fine. When the mode selector knob is turned off the stove goes to a low flame but keeps feeding pellets!
Here is my analysis. Please correct me if there is an error.
The mode selector knob in room temp mode uses the room probe thermister to vary the feed motor to keep the room at the set temp. The room probe biases the gate of the feed motor triac probably thru an inverter circuit. and the temperature knob varies the bias level for the heat level desired. (Wish I had a schematic - Does anyone have a schematic of the Harman circuit board?)
When the mode selector knob is in stove temp mode then the ESP probe biases the gate or the triac in the same manner. The mode selector also varies the voltage level applied to the room blower to change it's speed.
Now the mode selector has one more function. In startup and shut down mode it either acts as a gate or controls a gate to bias the feed motor triac.
In this case when the knob is turned to off, there seems to be a hung state and the triac gate is still being biased. The ESP probe just varies a small voltage going back to the circuit board so even though it senses the exhaust temp and tells the board when to shut the room blower off and the combustion blower off, it may have nothing to do with turning the feed motor off.
This stove had no surge protector and there were quite a few power outages last season. ESP probes do not go bad very often so I would say a power surge has damage the CB\ircuit Board. Anyone know what part on the Circuit Board?
SCRs are used in DC circuits so it makes sense that 2 are used in an AC circuit. One to handle the negative cycles and one for the positive cycles of the AC sinewave.
TRIAC operation
It can be imagined from the circuit symbol that the TRIAC consists of two thyristors back to back but with a common gate terminal, and the cathode of one thyristor connected to the anode of the other, and vice versa. This configuration is more correctly termed antiparallel
On a basic level, the operation of the TRIAC can be looked on in the format of the antiparallel thyristors, although the actual operation at the semiconductor level is rather complicated.
When the voltage on the MT1 is positive with regard to MT2 and a positive gate voltage is applied, one of the SCRs conducts. When the voltage is reversed and a negative voltage is applied to the gate, the other SCR conducts. This is provided that there is sufficient voltage across the device to enable a minimum holding current to flow.
Equivalent circuit of a TRIAC
In terms of the structure of the device, and its more detailed operation, the main terminals MT1 and MT2 are both connected to p and n regions within the device. The current path depends upon the polarity of the voltage across the main terminals.
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