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  1. #1
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    Lennox HS14 expert needed -- TSC control unit question

    Old HS14-6 condensing unit still running....until this week. Customer needs unit to function for only four (4) more months. Thermistors ohm at 5.3K. Good voltage from low and high pressure sensors (JP1-7). Good voltages all around....except JP1-8. The high speed output (from TSC unit) reads 27 volts when wire is disconnected but reads 0 volts when connected to the contactor (K1). I suspect TSC unit is faulty. Appears that the voltage on JP1-8 is floating to 27v when disconnect but not a serious output with any amperage to energize the contactor coil.

    Here's the big question: The unit has a TSC-2 control unit (for Bristol compressor). I have acquired a TSC-1 control unit (for Lennox compressor - HS14-5 unit). Can I replace the TSC-2 control with the TSC-1 control? The two (2) TSC control boards are identical. Board components seem to be identical. But what about the programming in the TI chip? The thermistor trip and reset values are different but the TSC-1 values are more conservative so it may trip a little more often.

    I would welcome the thoughts, opinions, warnings, etc. from someone more familiar with this equipment than I.

  2. #2
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    Just looked at the specifications.

    Get the correct board.

  3. #3
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    Thread Starter
    Quote Originally Posted by hvacvegas View Post
    Just looked at the specifications.

    Get the correct board.
    I agree: getting the correct board is preferred. However, the question is will the TSC-1 work as a short term replacement for a TSC-2?

    What specific TSC board specification did you find that indicate the TSC-1 TSC-2 are not compatible? What are the differences? Can you provide a link to the specs you checked? Thank you for your help.

  4. #4
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    Quote Originally Posted by ArdentGuy View Post
    Can you provide a link to the specs you checked? Thank you for your help.
    You will not get technical specs in this forum, as it is for home owners to ask questions, not technicians.

    This thread should be moved to the "Tech to Tech Chat - Residential" forum where technicians can ask questions. Click on the small black triangle at the bottom of your post and ask to have this thread moved.

    Now with that said, where are you getting your information from on these two controls?
    Instead of learning the tricks of the trade, learn the trade.

  5. #5
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    Jul 2019
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    Thread Starter
    Quote Originally Posted by rundawg View Post
    ....where are you getting your information from on these two controls?
    Short answer: On-line image comparison and the Lennox HS14 info sheet.

    Image comparison -- I have the TSC-2 controller in my hand. I have ordered a TSC-1 controller (e-Bay) that will be here tomorrow. The image of the TSC-1 controller (on e-Bay) is an exact match (component for component) for the TSC-2. I won't be able to compare resistor and cap values until the TSC-1 arrives. The underlying circuit board is a match. The rev. numbers etched in the boards are identical. In fact, etched on both boards is "TSC" and on the TSC-2 board, someone at Lennox hand wrote "2" after the "TSC". Both boards are fully populated.

    HS14 Info sheet: I am also looking at the 16-page, HS14 unit information sheet....the one with the troubleshooting flow chart on page 16. "Beginning with the HS14-5 and -6 series units, two speed operation will be controlled by the new Lennox TSC solid state two speed control. HS14-5 series units utilize a Lennox two speed control. HS14-5 series units utilize a Lennox two speed compressor and a TSC-1 two speed control. HS-6 series units utilize a Bristol two speed compressor and a TSC-2 Speed control." The only mention (on the info sheet) of a specific difference is the thermistor trip and reset values. With that in mind, I imagine that one difference I will find between the boards could be the value of two (2) resistors for the circuit to compare the thermistor trip and reset levels.

    ----- ----- ----- -----

    The TSC controller internal logic has time-outs, fault counters, delays, etc. but the inputs to both controllers (TSC-1 and TSC-2) are the same and limited to three (3).

    1. High and low pressure (in series)
    2. Thermistor value
    3. Thermostat demand (Y1 and Y2)

    As far as I can tell, the TSC controller doesn't care about which compressor is installed other than thermistor trip and reset levels. With only three (3) inputs to the controller, what other differences between the TSC-1 and the TSC-2 might I have missed?

  6. #6
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    Quote Originally Posted by ArdentGuy View Post
    As far as I can tell, the TSC controller doesn't care about which compressor is installed other than thermistor trip and reset levels.
    I have to agree, and according to the service manual, it does appear the compressor winding temp sensor resistances are the only difference.

    What do you have to loose by trying it - nothing.

    With that said, I'm alway skeptical of any electronic component purchased off of "EBAY", as you never know its true condition.
    Instead of learning the tricks of the trade, learn the trade.

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