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Eric Mele shows us a condenser that he has adjusted. He also added buck-boost transformers in the “boost” configuration. The incoming power supply is low, so the boost configuration increases the voltage from primary to secondary.
The condenser fans have been rewired. In the current configuration, the failure of one fan won’t take the other fans out. However, our main goal is to prevent fan failure altogether.
We have moved the circuit board over to make room for the buck-boost transformers. Eric installed two transformers and drew out the schematic on the panel so that future technicians can understand how he wired those transformers. The left of the schematic represents the low-voltage incoming power, and the right side shows the high voltage.
From line 1 to line 3, we only measure 201 volts on our incoming power. From line 1 to line 2, we measure 197 volts, and line 2 to line 3 measures 202 volts. However, with the help of the transformers, line 1 to line 2 boosts up to 222 volts. Line 2 to line 3 measures 217 volts with help from the transformer, and line 1 to line 3 measures 221.
We also have a control transformer tied into the low-voltage side of the system, and we get 200 volts to that transformer.
Anytime you make changes to the wiring of a condenser, keep the old wires with the system in case anything needs to be rewired. Create a schematic diagram as Eric did and make sure you provide all the important information that the next technician needs to know.
Our overall goal is to improve motor longevity. Motors can be expensive, so we want to minimize preventable costs and equipment casualties as much as we can.
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Hi, this is eric with halo services in hvac school. If i can get it in frame today. We're looking at this condenser we've added boost transformers in the boost configuration because our incoming power supply to these units is super. Well, i shouldn't say: super low, it's low and it gets lower in the afternoons, especially on hot days because of the utility company, so we're trying to mitigate motor failure issues.

You've seen these units before maybe not this specific one where we rewired the condenser fans. So if one fails, it doesn't necessarily take all the rest out, but we're trying to eliminate fan failures all together, especially on these two fan condensers. Now, that is how this condenser looked before. This is how it looked now.

We moved the circuit board over and installed. Two transformers: here's the schematic for the transformers on the left is incoming power. Low voltage on the right is high voltage. Let me show you what i mean by that.

So here's our meter, here's our incoming power line, one to line three 201 line, one to line two 197, two to three 202. That's on our disconnect coming in that goes into our transformers and it comes out on our terminal board top left. So now, if you look at the meter again we're gon na do one to two: you see we have 222 volts 2-3. 217 221 from one to three now.

One thing i had to keep in mind in this unit is we have a control transformer, so this is still powered by low voltage side, my 208 side, so that's still 200 volts to our control transformer. So i get the right output because it's a 208 or 230 transformer and i did not want to try giving it 220 volts, i'm just giving it the same 208. So it's tied in on the low voltage side there. I still got to make a note of what that schematic means down there, but everything is strapped up, so it looks more or less factory.

We've got the old wiring in there if it has to be reverted back, because this just wire this right here, just wired to there and then over there to here on the smaller wires, so just to see the difference here. That's what it looked like before. This is what it looks like now, so we're gon na see. If that makes these motors last longer.

As you can see, they got quite a few of them at this site and they are quite expensive if you're not familiar with them. So we'll see how it does hope you enjoyed the video learned, something thanks for watching our video. If you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when new videos come out, hvac school is far more than a youtube channel. You can find out more by going to, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.

You can also subscribe to the podcast on any podcast app of your choosing. You can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching.

25 thoughts on “Rewired condenser with a buck-boost transformer”
  1. Avataaar/Circle Created with python_avatars Wallace Rose says:

    How much is "quite expensive"? Service area Orleans??

  2. Avataaar/Circle Created with python_avatars Jim Spier says:

    Would be nice to know some general info of the site:

    What type of condenser fan motors they are, just a simple 3-phase induction motors or ECM?
    Is there any speed controllers, I don't see any VFDs so maybe a PWM signal to the ECM motors?
    If there is a VFD controlling the motors, is there a shaft grounding ring?
    What type of failures are you running in to, just electrical or bearing failure?
    What is the average age of the failed motors?
    How low have you seen the incoming voltage?
    Is the entire building experiencing low voltage?
    Was there ever a voltage recorder installed to monitor voltage fluctuations and phase imbalance?

  3. Avataaar/Circle Created with python_avatars Gabe Jaghnoun says:

    I wish you you would talk about the function of buck boost and why there were installed in the first place.


  4. Avataaar/Circle Created with python_avatars Hola! Charles B says:

    Good idea, I commend the proactive approach, as most would simply advise the customer that an electrician be contacted. Appears you need to also address the voltage imbalance. There may be an issue with the facility electrical loading. Add in the voltage drop as the demand increases may influence the imbalance.

  5. Avataaar/Circle Created with python_avatars none ofyour says:

    Thanks I will try some because I have the same problem

  6. Avataaar/Circle Created with python_avatars OcRefrigeration , Hvac & Electrical Video's. says:

    Good Video & been there done that. You should allways make sure to consult with utility company first. Tell them voltage your seeing at the panel. i had a panel in a restaurant at 197-202 also and it was throwing codes in a Manitowoc indigo ice machine had a Low voltage issue too. i almost ready to put one of these on the manitowoc. utility company came out and found a transformer issue. they repaired. no problems since. its a good idea but remember those 2 transformers are going to put off some heat. if they are outdoor rated i would have mounted them outside the panel. if not maybe put a few 2" holes in ends of panel with screen & boxer fan on a Ranco etc111-000 temperature control. to see if needed drop a temperature monitoring device in the panel & download data to laptop via usb temperature monitoring stick.

  7. Avataaar/Circle Created with python_avatars Jayden s says:

    I used one on those on a slushee machine once, worked pretty good

  8. Avataaar/Circle Created with python_avatars Evaristo Salazar says:

    Are they 1ph transformers that you connected together to get the extra leg to make them 3ph?

  9. Avataaar/Circle Created with python_avatars Tyrone Sheppard says:

    Eric M, did you have to consult with the OEM application electrical engineer to do the retrofit?

  10. Avataaar/Circle Created with python_avatars sultan mulla says:

    My chiller tandem compressor oil low cold .
    Expansion valve is new emarson 50 ton system and added a accumulator but not effective
    Can u help me?

  11. Avataaar/Circle Created with python_avatars Ronnie S says:

    This is good information except the owner really should contact the the Utility company first for a couple of reasons. First, to validate incoming voltages and second to make them aware of this issue because it could be an overloaded Utility transformer at certain times of day.
    If the voltage at the Utility transformer is 120/208 then the issue is downstream of the Service transformer and will only degrade with time and load.
    Customer will not be happy if you install all these buck transformers and the real issue was not first identified. What KVA Buck/Boost were used?

  12. Avataaar/Circle Created with python_avatars Gary Winters says:

    Perfect, even though slightly off balance, this will prevent current rising and motors overheating. My education only mentioned the buck boost in a lower capacity for watt motors on reach in coolers that also were 201 vac supply. Utility could not adjust incoming without a major rework on a pole many streets away.
    Thanks guys at Kalos hvacr school for the tips.
    Never stop learning. 👍🏼

  13. Avataaar/Circle Created with python_avatars Waylon Wells says:

    👍 Are you in Kanata ?

  14. Avataaar/Circle Created with python_avatars JK Brown says:

    So your motors are rated for 208/240 service and you've put your boosted voltage at the top of the NEMA 200v (208v service) 20% bandwidth (220v) when the incoming line voltage is around 200v since that's kind of in the middle of the overlapping NEMA 200/230 bandwidths? And that gives you a surge buffer to the 253v top of the NEMA bandwidth for 230v ratings and likely keeps you from spending too much time with low end voltages on the motors. It helped a lot when I found a short write up on US voltage tolerance standards and started considering the bandwidths that are permitted. Never considered it but for a 200/230 rated motor, there's likely that 30v bandwidth is probably the sweet spot for the motor.

  15. Avataaar/Circle Created with python_avatars George Robles says:

    So many people do not know about these buck'n boost Transformers they have small ones for like a single 240V compressor you need to put in a corner of a shop that has 208 existing there already, there's many use case scenarios for these things. And for smaller things you can get something with automatic switching on a multi-tap Transformer. I got one on my computer that's a battery backup ($120ish at Costco) power supply and multi-tap Transformer built into it to switch voltage up or down on-the-fly. And when out of range of transformer taps it goes to battery backup.
    Of course they have the same for bigger stuff but much more expensive especially if they have generator or backup battery bank system.
    I wish he would have shown an open panel on the buck's boost but I get why not show it on YouTube either. At least we saw a partial schematic. Are you in Ottawa ?

  16. Avataaar/Circle Created with python_avatars ismail ahmed says:

    good job

  17. Avataaar/Circle Created with python_avatars Joe Shearer says:

    Did it help?

  18. Avataaar/Circle Created with python_avatars B YENZER1 says:

    I ran a huge facilities plant. Did anyone check the utility voltage inlet to the main bldg meter panel? Possible voltage drop from bad breakers or bldg disconnect switches or buss-bar contacts inside the customer's bldg wiring connections. Verify utility voltage vs. end of run up to the roof units. 5% voltage drop is too much. Service area Nepean??

  19. Avataaar/Circle Created with python_avatars B YENZER1 says:

    Are you related to the famous auther, JIM MELE?

  20. Avataaar/Circle Created with python_avatars Roger Bettencourt says:

    I believe that I always learn something from you guys. Keep up the good work and thank you all for sharing. Are you in Barrhaven ?

  21. Avataaar/Circle Created with python_avatars jtpeterson27 says:

    What’s happens when the voltage coming in goes back up during non peak usage? Doesn’t the output of that 200 lb ginormous buck n boost setup voltage go up? How are u limiting power fluxation?

  22. Avataaar/Circle Created with python_avatars Eassyheat/ Cooling says:

    Why not call the utility and adjust the taps on the transformer?🤔
    Stay safe.
    Retired (werk'n)keyboard super tech. Wear your safety glasses.

  23. Avataaar/Circle Created with python_avatars diamond_boots says:


  24. Avataaar/Circle Created with python_avatars Alex says:


  25. Avataaar/Circle Created with python_avatars Rose Electronics says:

    First and definitely not the last

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