I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired.
One of my goals has always been to “educate” dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it.

The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way.

I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about.

Thanks for taking the time to read my postings!
Mike Bishop

44 Responses to About

  1. Whit Perry says:

    Mike, as we discussed previously I am sending a link to your blog to the CARE members. Would you like a copy of the newsletter? If so, please send me your email address. Also, it gets caught up in spam so you would need to watch for it. I send the newsletter out on the 1st of the month. Again, thanks for sharing this fantastic information. Hopefully my students are signing up.

    Have a fantastic weekend!

    • Whit
      my email address is michael.f.bishop@jci.com . I would appreciate a copy of your newsletter and, as I said — feel free to use anything I post if you think it will help.
      Your students are all welcome to share my posts.

      • Shawn says:

        My name is Shawn and I really enjoy reading your HVAC blog. I’m preparing for my CFQ exam and was wondering if you would be able to help answer a question I had.
        My question was how to do I check the high limit switch on the rooftop? The choices given are :
        a) close the combination fan
        b) close the air blower fan
        c) not remember
        d) not remember

        Thank You,

      • Shawn
        To properly check the limit, you need to run the heat with the blower SHUT OFF. Then, with a thermometer or thermocouple in the supply, see where the temperature shuts the heating down.

      • Shawn says:

        Hi yorkcentraltechtalk,
        Thank you for answering my question !

      • You are welcome. Hope it helped!

  2. Joe Meyer says:

    It came up this morning that a unit had a burnt data tag on the side of the cabinet on a residencial york furnace and i needed that info is there an online resource that i can tap for older units data?

    thank you for this blog is very informative

    joe meyer

  3. Really neat site with tons of great content. Would any members of your team be interested in talking about some of these same topics on our site? We have a user base of over 1,300 members that I’m sure could use your resources. Of course, York and Johnson’s products could be openly promoted in whatever you do.

    Best Regards,

    • Michael Thank you for the comments. My blog is an independent blog and, if you read my disclaimer, I cannot associate this with York/Johnson Controls as far as anything proprietary. I am a “department of one” and I am responsible for all the content you see. I have had people “hyperlink” my site to theirs. You can also have you member sign up to receive any of the posts when they are published.

  4. Piotr Banas says:

    Great blog. I am heat pump enthusiast – nothing to do with them professionaly. I just own one for my swimming pool (Northern Maine). Unfortunatelly I have nothing but problems since I have purchased it. I am out of warranty and manufacturer is not even willing to provide manual for control board. I do not even know how to change settings or re-set to defaults. I was informed that they do not provide it for users (!?!). On top of it in my area there is no company that really deals with heat pumps. Everything is based on try and error – that does not solve my problem. Pump was “fixed” so many times, “nothing really serious was found”, but yet, it still quits to work getting to LP error message. I am desperatelly looking for help. Control board: MY-TECH PH-111A.
    I would appreciate any guideline – I am an engineer (mechanical though) and usually I do well with new stuff, but I would like to get some guideline.
    Thank you in advance for help

  5. Emanuel Sánchez says:

    Hey, great blog, I have found this very useful. Right now I’m searching for the definition of what a non bleed valve is and this blog has been of much help.
    Greetings from Panama City Central America… I myself work at LG and I also think training dealers is very important, as much of mistakes done in the field are caused by not knowing enough information about the product. (Of course I’m just starting)

  6. Al Greenwats says:

    I would appreciate your input in reference to hydrocarbon refrigerants. There is a great hydrocarbon refrigerant out by ecofreeez that I’ve been using in place of R22 and its giving me great results. I use in dry units as well as I top off with it. Why isn’t everyone using hydrocarbon refrigerants. The rest of the world is. Europe, China, Australia. I know hydrocarbons are flammable but that’s only if you intentionally put a flame to it. If you do that to R22 or MO99 or some of the other substitutes you create poisonous gases. Help please we make a living servicing R22 units can’t just tell a home owner to drop $10K and replace their whole system.

  7. Rob says:

    Hi Mike, I have to say you have a really great blog here. I have some questions for you about a YC Predator condensing unit I’d like to ask, if you wouldn’t mind doing so via e-mail. Thank you very much.

  8. sam says:

    hi i am working on a york furnace. it giving error code 9 . i reversed the wires in the 24v transformer side, turned it off and back on. still giving the same error code. does that mean the board is bad or is there any other tests i can do before changing the board

    • Sam
      flash code 9 can be a number of things. Yes. the R and C on the transformer could have been reversed. It could also have been reversed LINE VOLTAGE polarity, bad ground or bad neutral. Check your “hot’ coming into the furnace and read it from neutral and then rad it to ground. They both should read the same. If hot to neutral is higher than hot to ground — you have a bad ground. If hot to ground is higher than hot to neutral, you have a bad neutral. Now, read neutral to ground — you should read nothing. If you read any voltage, you are picking up a back feed and the board reads it as reverse polarity. The furnace should be on it’s own circuit.
      Also, make sure you do not have a crack in the flame sensor. Ohm it out to ground. Since the sensor is “always powered”, a short or cracked porcelain can give you a flash code 9

      Try these first and, if you still have an issue, contact your local distributor for further support. Yes — it could be a bad board but not until you do all the diagnostics.

  9. Ezaz says:

    Hi Mike
    First of all thanks for such a wonderful blog on HVAC. I am working on CO2 refrigeration system. In the set up we have used DORIN compressor of capacity 2.5 kW@2900 rpm.Piston Displacement rate is 2.2 m^3/hr.For the information let me mention that CO2 system is run at high pressure such as 90 bar.The pipe line is of 1/4 inch SS .I have put two pressure tap towards the low side, one at the accumulator which is of 8L (this is big than the requirement) and another is just before the compressor suction. From the accumulator to compressor there is only two 90 degree bend.The problem is I am getting 10 bar pressure drop from the accumulator to suction line.Only two bends are in between. Why this much pressure drop is occurring I am unable to detect. Please suggest the solution.

    • As much as I would like to help you, I would suggest you go back to the manufacturer. I personally am not familiar with CO2 refrigerant systems.I have read about them but vhave never worked on one. Sorry!

  10. Paul Ohlstein says:

    This message is in reply to your blog of June 12 2015 in which you allege that mfrs are using thinner copper to improve heat transfer, Please learn that the thermal resistance due to heat conduction through the copper is negligible and that the thermal resistance of a coil is primarily at the fin air surface and at the refrigerant copper surface.

    Thinner copper is obviously a disastrous design choice because it is inherently less corrosion resistant due to being further cold drawn, and operates at higher stresses which exacerbates stress corrosion. It is called being so cheap that garbage is produced.

  11. brian says:

    Just recently had my 5 ton r-22 carrier replaced with a york 5 ton r-410a. Tech seems not to know how to get rid of viration noise in line between systems. Distance is between floors 9 foot ceilings and unit is 3 to 4 foot off floor. Total length from inside to outside. 6ft, vertical run, sweep 90d 3 to 4 feet horizontal, sweep 90d 12′ horizontal, 90d sweep to 10′ vertical and last sweep 90d 2′ horizontal. Adding up about no more than 35′. Pipe looks to be 7/8. Read the line sizing post but nothing realevant unless my system velocity is off the charts. I have to p traps etc mentioned in system. Any recommendations. Sorry I do not have readings. Trying to get rid of annoying sound and help my tech out. What ranges of pressure should be in system, velocity (he never mentioned this reading) anything you can suggest would be great.

    • If the condenser is above the evaporator, with R-410a there should be NO TRAPS in the suction line. Was the old line set re-used? If so, was it flushed top make sure all the old oil was out of the system? Yes. velocity will cause line set vibration but that is usually in the liquid line. Depending on the model, 7/8 may be too small for the suction line. Some models require 1 1/8″ suction lines. What size is the liquid line? These are all thing you should check with your installed.

  12. mike ragano says:

    Hey Mike, I went on a no heat over on Christmas and found a bad board on a Luxaire M3PCDFALD12n080b. York was closed all weekend ,so I couldn’t get any help. I put in a S!-3310967000 board I had in stock. Seems to be working fine but was wondering if that is the right board.the old board was a white rodgers .

  13. Mike says:

    Yeah your right I left out the 1 . Thanks a lot.

  14. My name is Kenneth McDevitt I work in NYC so I see a Lot of different equipment. I just want to say Thank You. I have been in positions several times where your help made a happy customer. We need more people like you in this Country. Most people see there knowledge as a leverage for personal gain. You see it as connection to help. Hey maybe down the road give us a personnel Post on your retirement. Possibly a Year reflection of being retired.

  15. Brad Cohen says:

    Sorry if this question is not the appropriate forum but i am at wits end trying to get an answer to this question. You seem quite knowledgeable about YORK and that tends to be a tough commodity in my area.

    I have an Affinity 9C Furnace. (original installer out of business) I recently installed a NEST Gen 3 that worked well for 3 weeks until I went on vacation and my furnace ran for 18 hours getting my house to 110 degrees. I am done with them.

    What wifi enabled t-stats can I install that will work properly with this system and keep its efficiency?

    Thanks for your time!

    • York has both OEM wifi stats if your control will accept it and Source 1 has wifi stats that work well with any equipment. If you go to http://www.york.com and in the upper left corner you will see a dealer locator. enter your zip code and it will show you the York dealers in your area. Also, you might read my post on SMART THERMOSTATS, Enter this into the Search box on the blog page and it will bring it up. Hope this helps.

  16. Hady Aboujaoude says:


    I read your article about the refrigerant charge addition R22 and R410.
    I installed 10 DAIKIN units of 10 tons each with a 50 meter of copper (5/8 and 1 1/8).
    I had to add 0.160 Kg per meter (above the 7.5 meters).

    I Just have a maybe very stupid question, Why do we add refrigerant ?


    • Units come with either a small holding charge to IEE them dry or with just enough credit get any for the condenser, a small matching coil, and so many feet of line set, depending on the manufacturer. So, if it is just a holding charge, you nre to weigh in the proper amount of refrigerant for the SYSTEM.
      If there is a set amount of refrigerant in the system, you may need to add or remove refrigerant based on coil size and line length.

  17. Susan Shafer says:

    My AC generally does not go off unless I turn the temperature to a higher setting. I have forced air so it should come on and go off regularly. I did notice a strong correlation between when it’s light outside (goes on, does not shut off) and dark at night (off). Even on a cloudy day it will go off more. On a sunny day it will just remain on and it gets colder and colder in the house. I have had so many people in my house to “fix” the problem and all they do is change the thermostat. I have been through so many and this has not helped. I am wondering if you may help me! Thank you.

    • Is your thermostat being ” hit’s by sunlight? Your thermostat could be being affected by the opening of the wall behind it causing it to sense a higher temperature?
      Is there a light under the thermostat?
      Lastly, if your thermostat is a”piwer-stealing” thermostat and it is a newer communicating type, all you may need is a common wire pulled to the thermostat.
      Feel free to show this to your service provider.

  18. Mike says:

    Hi Mike,

    Am trying to connect and a YHJD30 to an
    EWC-BMP 3000 multi zone board I also need to connect my AHR 30 to the same board

    I’m not used to heat pump wiring so, I was wondering if there were any good York wiring diagrams out there

  19. Victoria Petro-Conroy says:

    Hi there, do you know a York HVAC technician in the NYC area? We have the “run away heat” problem you talked about in your blog and have been searching for years for someone to fix it. We’ve tried at least 6 different companies and no one can figure it out. I’ve showed them your blog with the possible fixes, but am never taken seriously. Thank you in advance.

    • I would suggest you contact the York Factory branch and see if they can provide you with a qualified dealer in your area. Their contact information is York New York Branch, (631)420-1340
      Be sure to provide them with your units model and serial number when you call.

  20. Dane says:


    I am a big fan of your blog page and I am very grateful for the materials you posted.

    I am researching about how the ECM motor works. In this paragraph:

    The way I explain it in my training classes is this. An ECM motor maintains a programmed CFM in response to changes in torque. When the sensed torque changes, the RPM of the motor either ramps up or down to maintain the programmed CFM. Sounds confusing, doesn’t it?

    From: (What is an ECM motor?), you mention that the Motor senses the change in torque. What is in the motor that allows it to sense the torque change?

    • An ECM motor is a DC motor. On the end of the motor is a module. The module holds a the program that the factory puts into it so it matches the model furnace. In the unit is a control board that the installer can then make fine tuning of the motor’s program to match the job specifications like duct static, etc.
      As static pressure changes, the “weight” of the air affects the torque and the motor slows down or speeds up in relation to that “weight”. This is controlled in the programmed module interconnected to the motor.

  21. Ling says:


    Big fan here. I came upon your blog post while doing research on EC Motors. The post in particular is titled “What is an ECM Motor” and was posted on September 11, 2012.

    I think there is an error with the following statement under the components section:

    The motor — which does not have any “windings” in it. The stator is driven by magnetic fields.

    My understanding is that a stator is stationary; And in the case of an ECM, has windings. The rotor is the moving element, and has permanent magnets that push against the magnetic fields produced by the stator windings.

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