Liebert Mini Mate Retrofit – HVAC Controls Schematics

You’d think Cody would be done with this DDC Controls Retrofit, huh? I mean it’s been like 2 months now… Well obviously it’s not his fault. Putting together these 10 minute or so videos sometimes takes a good 30 minutes to 1 hour of production time per 1 minute of video. Eh, I’ll get fast at it the more I do.

This is going to be a 2 part video on the Liebert Mini Mate Schematics because it was getting a bit long. So, in this video we are going to get up close with the controls schematics that came with the unit. This is important to go over when replacing the mechanical controls of a unit with a DDC Controls System. Reason being, you gotta find all the points and terminals where your physical connections are going to be made without shorting anything and actually turning on and off the correct parts of the unit.

 Don’t forget to ‘Thumbs Up’ the video and/or leave a comment. It really helps out alot on YouTube.


 DDC Controls vs. OEM Controls

I have gotten a couple of emails asking why we were replacing the controls… If they were bad… If we didn’t know that we could setup alarms and setpoints in the Liebert Thermostat, etc. The truth… ofcourse we do and yup, the old stat worked just fine.

The thing that some OEM and Manufacturer’s controls lack is the ability to communicate with similar and non-similar units or systems. Typically, this is the reason why someone would want to replace what already works with a DDC Controller connected to a Building Automation System (BAS).


Programming DDC Controls to match the OEM Controls

In almost every case you should be able to mimic the same controls functions and programming that existed in the Unit Controls and most times customize it even more. Some mechanical guys might be a bit adverse to replacing what came with the unit and to that I ask…

Overpowered DDC Controls in BuildingsWhat kind of car do you drive?

I live in Texas and around here any big, tough HVAC guy either drives a BIG truck or FAST car. The reason I ask that question is how many people you know  are always adding tune up parts or after-market stuff to their vehicle? Why?!

“That factory fuel injection computer thingy knows exactly how much fuel to mix to get ya from here to there… Why screw with it?”

If you’re like me… you like to tinker, tune, tweak and mess with stuff. RAWR!


Not Knocking Factory HVAC Controls

Now I’m not knocking all factory or OEM controls, not at all. Nowadays almost any large manufacturer of HVAC equipment will gladly sell ya a tiny green circuit board that costs half as much as the unit, so that you can connect it to the BAS via BACnet or MODBUS.

These control boards are usually pretty darn good at what they do. Some are just for communication to pass along alarms and allow the Building Automation System to monitor its temperatures and pressures.

Others are actually full blown controllers made by DDC Controls manufacturers like Johnson Controls, Delta Controls, Circon, to name a few; and are painted up and labeled to match the HVAC equipment and programmed to actually fire relays and modulate valves while also communicating the needed points and alarms for monitoring.


What do you think about Factory Controls? Work with them or change ‘em out the first chance you get?

7 Responses to Liebert Mini Mate Retrofit – HVAC Controls Schematics

  1. ben March 6, 2012 at 11:38

    Another good video thanks Able!

  2. GFlores March 18, 2012 at 13:38

    awesome! great stuff Abel

  3. mike August 18, 2012 at 10:27

    why did you remove liebert stat?

    • Abel B Ramirez II August 20, 2012 at 09:27

      I wanted to remove the stat because the unit is way over sized for the space and the Liebert Stat had an annoying alarm that had to be silenced all the time. So rather than figure out a Liebert Stat I did what any Controls Freak would do. I put a DDC controller that I knew how to program and manipulate so the unit now does what I want it to and I can adjust it from my desk or smartphone. ;)

  4. Brandon July 12, 2013 at 15:44


    Just curious how this is working for you and if you have any gotchas. We are looking at doing something similar with 25 Liebert Mini-mates that we have in a building. Our main complaint / problem is that the Sitelink (a Liebert OEM’d Automated Logic LGR controller) that we are connected to keeps locking up and we lose comm with the Sitelinks in the building.

    • Abel B Ramirez II July 12, 2013 at 15:56

      Well this unit was at my last employer’s location and because of the oversized unit for the space, there were obvious mechanical issues that no controls could get around. ;)

      As for your problem with the Sitelink comms I would try posting up your issues in the TCF Discussion Forums ( and see if some of the lurkers will jump out and help ya. I have used Sitelinks in the past with Delta Controls (BACnet) and they seemed to work ‘ok’.

      Good luck!

  5. M zubair October 7, 2015 at 06:34

    Why they used two contactors 1cc and 2cc to operate a single compressor
    Please clarify


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