Interesting conversation with a tech from Harman about setback thermostats and dirty glass

[fmsm]

I wanted to use my set back thermostat as a true set back and not as an on/off switch but still had concerns that I might somehow be damaging my P35i. I also have noticed that by using my thermostat as a set back and my stove set to room temp @ 80 degrees my glass stays cleaner.

I called Harman today and spoke with a tech and was advised that I would be risking damage to the control board. I was advised to use the set back as follows; "Use only as an on/off control by setting it to 80 degrees when you want heat and 50 degrees when you do not want heat, then use the room temperature setting for the actual temperature". I was also advised to use the stove temp setting for an hour or so every few days to create a higher burn that would help with any creosote.

 

[603BOB]

I have been using a real night setback on my Harman Advance for 6 or 7 years - It does not damage the control board - and I can set it back as many degreees as I like.

I run the stove on room temp.

It is STUPIDLY SIMPLE to implement - have your Harman tech call me - 603-776-0086 - and I will clue him in!!

Bob in Alton,NH

 

[fmsm]

This wasn't "my" Harman tech, this was a tech that works for Harman.He's not saying not to use a setback, he's saying to only use it to set back at night not to regulate the room temperature, to use the room temp setting along with the signal from the thermister to keep the room at a steady temperaure. Others had said you could set the room temp setting to 80 degrees and use the set back to regulate, this is what he is saying can damage the board. I now have mine set as he advised; room temp at 72 degrees controls the room temperature my setback is set at 80 degrees from 4:30am to 10pm and at 60 degrees from 10:01pm to 4:29am.

 

[603BOB]

With all due respect to the Harman tech - what he is telling you is pure "floobydust".

The temperature probe is a thermistor with a negative temperature characteristic. When the temperature goes up, the resistance goes down. Applying Ohms law - resistors in parallel decrease in resistance - adding a parallel resistor to the thermistor fools the microprocessor into thinking that the room is warm enough. By making that resistor adjustable, I can set the room temp back 1 degree or 5 or 9 or 14 or whatever I want.

I can only speak for my Harman Advance - I have 11 years experience learning about this thing because Harman was absolutely no help at all with ANY questions I had. 50 plus years of electro - mechanical trouble shooting experience bailed me out.

In my opinion - Harman designed the control board to fail. The thermistor leads go directly to the microprocessor chip on the board. There is zero protection from static electricity, lightning discharges, or radio frequency pick up. They could have spent 80 cents for a couple of ferrite beads and/or a couple of bypass capacitors to protect the board - but then they would sell less boards!!

The very first problem with my Harman Advance was radiation from the microprocessor at 1.8 MHz from the thermistor leads. It destroyed reception on the 160 meter amateur radio band. Harman would not even answer my emails so I cured the problem myself.

My stove at one point decided to just go off and on at random. Again zero response from Harman. I found that component tolerances were the problem. The 5 volt regulator chip on the board was within specified tolerance, but was only .01 volts away from the low voltage reset detector, which was also within tolerance. I selected a 5 volt regulator with a higher output voltage, installed it on the board - no more problem. Any minor disturbance was causing the microprocessor to reset with unpredictable results.

I don't intend this to be an anti-Harman rant. I think they have a great product with innovative approaches, but their customer service has been an unmitigated disaster with me.

Like many companies they appear to train techs only as much as they need to know to protect their service business. If they know too much they can go out on their own and take away business.

Just my X2 cents worth!

Bob in Alton, NH

 

[PJPellet]

With all due respect to the Harman tech - what he is telling you is pure "floobydust".

The temperature probe is a thermistor with a negative temperature characteristic. When the temperature goes up, the resistance goes down. Applying Ohms law - resistors in parallel decrease in resistance - adding a parallel resistor to the thermistor fools the microprocessor into thinking that the room is warm enough. By making that resistor adjustable, I can set the room temp back 1 degree or 5 or 9 or 14 or whatever I want.

I can only speak for my Harman Advance - I have 11 years experience learning about this thing because Harman was absolutely no help at all with ANY questions I had. 50 plus years of electro - mechanical trouble shooting experience bailed me out.

In my opinion - Harman designed the control board to fail. The thermistor leads go directly to the microprocessor chip on the board. There is zero protection from static electricity, lightning discharges, or radio frequency pick up. They could have spent 80 cents for a couple of ferrite beads and/or a couple of bypass capacitors to protect the board - but then they would sell less boards!!

The very first problem with my Harman Advance was radiation from the microprocessor at 1.8 MHz from the thermistor leads. It destroyed reception on the 160 meter amateur radio band. Harman would not even answer my emails so I cured the problem myself.

My stove at one point decided to just go off and on at random. Again zero response from Harman. I found that component tolerances were the problem. The 5 volt regulator chip on the board was within specified tolerance, but was only .01 volts away from the low voltage reset detector, which was also within tolerance. I selected a 5 volt regulator with a higher output voltage, installed it on the board - no more problem. Any minor disturbance was causing the microprocessor to reset with unpredictable results.

I don't intend this to be an anti-Harman rant. I think they have a great product with innovative approaches, but their customer service has been an unmitigated disaster with me.

Like many companies they appear to train techs only as much as they need to know to protect their service business. If they know too much they can go out on their own and take away business.

Just my X2 cents worth!

Bob in Alton, NH

Hi Bob,
K2PJW here. Could you tell me how you cured the 160 meter problem? Thanks! Don't want to hijack the thread though.

 

[603BOB]

Email me : [email protected]

 

[fmsm]

Don't worry about hijacking the thread, Bob is brilliant! He was gracious enough to speak with me today for over half an hour and then email me a drawing of how he has engineered his setback to work without any fault codes! He even is sending me the part I need to set up my stove.

Bob feel free to explain as you did for me if you like.