Author Topic: Ductless System  (Read 3110 times)

Offline Sergroum

  • Pro Tech™
  • *****
  • Posts: 132
Ductless System
« on: August 03, 2015, 12:07:07 AM »
Greetings.

Would you guys be able to help me find some troubleshooting docs for a Lennox ductless system

MS8-CO-24-P1A
S2813B50845

I'm really learning how annoying those things to diagnose and service. There are no LEDs that display error codes. I see some lights flashing on the back of the control board, but I am still unsure if they are error code displays, or ... something else. The indoor head is not telling me anything.

If someone could recognize the problem.

Whenever there is a cooling demand, the back of the board has 1yellow-2orange-3red-4green lights lit steadily.  The condenser fan begins to work and I hear clicking sound that I believe is the ERV. 30-60 second later, the condenser fan dies. Then in a minute, it tries again, but dies again. After 3 tries, the 4 steady lights turn off and change to 1(blank)2(flashing red)3(blank)4(flashing green).    The condenser fan try occasionally again, but die again.  I can still see voltage going towards the compressor, but compressor does not start. Doesnt even make noise.

Before I even noticed the change of lights. Hell, before I even noticed there 'are' lights, I've tried changing the control board. No difference.

Dont have any docs, or any real experience with these types of systems, so I dont even know their sequence of operation. Any advice, or just documentation would be very welcome.

EKV, fair enough. In the manual the abbreviature is EEV.

Offline Admin

  • Administrator
  • *****
  • Posts: 2363
    • HVAC TECH GROUP
Re: Ductless System
« Reply #1 on: August 03, 2015, 02:52:38 AM »
The indoor unit should also be displaying an error code on the display.  You might see a "Lc" code.

I don't think there is an ERV in this unit.  What is the voltage being sent to the compressor?  Did you verify the capacitor is good?

Download the Lennox MS8 120V Service Manual - Here
Download the Lennox MS8 240V Service Manual - Here

Offline Sergroum

  • Pro Tech™
  • *****
  • Posts: 132
Re: Ductless System
« Reply #2 on: August 03, 2015, 01:00:32 PM »
All excellent questions.

There is no capacitor used in principle. The system is 220, but if I understood reading the manual right, the reactor (choke) is ... creating third phase? I might be way off on this somehow. Actually ... no. That doesn't make sense. Hrmh.

There is a capacitor for the condenser fan, but it's fine.  I am getting voltage going towards the compressor but it varies from 90 to 140. 220 between eacch lead. From what the dude on technical support says, that's to be expected.

There is an ERV there, for sure. The clicking noise I hear is similar to the one you'd make if you took a pen and rhythmically tapped your table. It's not the type of noise a component would make when trying to start with a faulty capacitor for example. At the same time, the compressor in general is pretty quiet and I'm on a rooftop, surrounded by a whole bunch of other rooftop units and wind. So ... I might've missed it.

Talked to support, they advised changing the board. Tried it. No difference. 

I am getting no error codes on the indoor unit. It just displays the desired temperature and cooling mode, that's all.

The support tech began talking about lights on the backside of the control board, but then our connection got interrupted and I couldnt get him back again. Then time was out and I got chased off the roof, the business was closing up for the day.

You're right though. Whether it shows error code, or not, the lights on the back of the board signify that it's LC.  But I'm getting good voltage coming. The system worked before, so it's not miswired. I changed the control board, so any prior loose connections should be better now. Hrmph.

Offline Admin

  • Administrator
  • *****
  • Posts: 2363
    • HVAC TECH GROUP
Re: Ductless System
« Reply #3 on: August 03, 2015, 02:39:49 PM »
Are you talking about an EKV?  (Electronic Expansion Valve)

There is a reactor (choke) line and power factor correction capacitor.  I would test that capacitor. 

Quote
If voltage is higher than 265VAC, disconnect power to unit. Correct input voltage problem before reapplying power to system.
If voltage is below 265VAC, then check capacitor while unit is turned off.
If voltage is between 200-208V, capacitor is working properly
If voltage is some other value, replace capacitor.

Also I attached a couple of pictures.  I would test the compressor windings and the overload switch.  You may have a bad compressor.

Quote
An inverter drive (VFD) works by taking AC mains (single or three phase) and first rectifying it into DC. The DC is usually smoothed with capacitors and often a DC choke before it is connected to a network of power transistors to turn it into three phases for the motor.
The network of power transistors of a small Inverter drive is actually one intelligent power module or inverter power module (IPM) and includes its own basic control circuits and protection from overheating and low voltage conditions.
The IPM inverts the DC into AC, hence the term inverter. The control method is known as for pulse width modulation (PWM). This means the DC is switched on and off very quickly (chopped) by the transistor switches.


Offline Sergroum

  • Pro Tech™
  • *****
  • Posts: 132
Re: Ductless System
« Reply #4 on: August 03, 2015, 03:56:46 PM »
I dont see the capacitor at all. The reactor (choke) I do see. Nor is it mentioned in any component listings in the manual. The unit is 220, not 120. There might be capacitors embedded into the control board that are doing this, but I changed the control board, so ... theoretically that should've alleviated the problem. Of course I'll be doing more checking come tomorrow morning.

I am seeing the reactor though. Maybe there is a capacitor somewhere within it that I could not see. I'll take it apart and look at it some more. So far it looked more like a transformer really, the usual copper coil.

Suppose tomorrow I'll be able to study it better.


Wait. I've been calling it ERV? ... Brain Heat Frazzled.  EEV then really.

Offline Sergroum

  • Pro Tech™
  • *****
  • Posts: 132
Re: Ductless System
« Reply #5 on: August 05, 2015, 09:42:51 PM »
In the end, it turned out to be the compressor. After I changed the board (and the capacitor that's on the board with it), and the reactor (choke). Confirmed that regardless of any of that, I am getting proper voltage going to the compressor anyway, I decided to change the compressor. Changed the compressor and it worked. Still puzzled though. I mean that faulty compressor made literally no sound, no vibration, nothing. It showed resistance and wasnt shorted to ground.