Saving a System w/ a Buck and Boost

In this video, Bryan Orr shows his way of saving an AC system with a buck and boost transformer.
The unit in this video is particularly susceptible to overvoltage conditions. Catastrophic board failure can result from voltages over 253, and the ICM493 shows that we indeed have an overvoltage condition. Since the power company won't do anything about the issue, we decide to use a buck and boost transformer to drop the voltage BEFORE the ICM493. Buck and boost transformers can either boost (increase) the voltage or buck (decrease) the voltage.
First, we shut off power and confirm that it's off by testing the power to known voltage sources. The transformer we are using is rated for 0.750 KVA, meaning that we have a 750VA transformer. We have to read the specs and the manual to make sure that we wire the transformer properly. The manufacturer literature has a chart that tells us how we can buck the voltage from 250-255 volts to a more acceptable level; the chart cell corresponds to a wiring diagram tailored to our needs. The connectors are labeled and will correspond to the labeling on the diagram.
We test the voltage before connecting it to the unit. The primary voltage is 252.5, but the ICM493 reads about 235 volts, meaning that the buck and boost transformer has bucked the voltage and is working as intended. When the unit is attached, the line voltage is only 237, which is much closer to the rated voltage than 253+ and gives us a lot more tolerance both ways.
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[@swank1975]

Great 6 3/4 minute explanation of these. Keep up the good work. Especially the R.T.F.M. portion where you can look to get the connections right.

[@kieffersheatingcoolingv2.03]

Thanks for posting this! Experienced this exact thing on a Mitsubishi system I have an ICM493 on. Power company was zero help and every winter demand drops and the ICM locks out the system. Bucked the voltage yesterday and she’s running on a smooth 228 VAC now.

[@jericosha2842]

best hvac channel. this stuff is freaking awesome

[@HVACS]

Thanks

[@CJRoe]

Genius! Great video, have the same issue with the Bryant's so this is good to see

[@stevebrawner9119]

That's a great video. This is not that common of a problem, however when it happens it is great to know there is a fix. What happens if the power company comes and changes the taps, does that lower the voltage coming out of the buck and boast?

[@HVACS]

Yes it would drop it but it would still be in the rated zone even if they dropped all the way to 240v which they never do in this area

[@skywave12]

Had to call PG&E here in central Cali. They had to adjust the regulator at the substation. The reason is most Solar grid tie systems are UL restricted with voltage limits. Having it swing all over the place is not good. The incoming voltage would go to 254 and pushing just 2 Kw to the grid made it trip on over voltage. This was a few years ago. It has been stable ever since. Depending on the customer loads on the high tension line, the location you are at might have to be high.

[@RJMaker]

That's why HVAC/R techs are at the A-Pex of Skilled Labor. When other wont correct distributed power issue, we will. :-)

[@swanjaymusic]

That was a great lesson. Voltage problem solved.

[@lcampm2]

what if the utility comes back after this and fixes their issue? will it damage if it goes under voltage? obviously you have protection for over under so my question is elementary

[@cornpop7805]

No an issue because the system is rated at the low end for 208V, which means it can go lower than that and still be OK.

[@joeshearer1247]

The only thing about spinning the seal tight connector like that is if it's a 90 it kinda twists the wires up and makes it wanna come loose

[@HVACS]

Use a straight as a tool to get it in and out #Boom

[@joeshearer1247]

HVAC School mind blown psssssshhhhhh

[@tyhuffman5447]

Great video

[@rc685]

If the primary is 240 and secondary is 16/32 how is it possible to get 230v. I’m totally confused.

[@user-oe3cr5gx5c]

Do you have the wiring config

[@Sulucion6Tone]

Would love to see voltage like that at my house. sadly after having to move my network and servers to my house, i am currently sitting at 106-108 Volts on A and B. Need to boost my whole house panel somehow.

[@darkbeekeeper]

What’s a ball park price on those

[@embreesmith7613]

260v at night ..?? crazy !!

[@cornpop7805]

It's actually a common problem, especially in areas that have developed and grown out of pace with the local electrical utility equipment. The electrical utilities in these areas will usually tap the transformers a little higher to make up for the peak load, but when the loading is low (usually at night), the voltage will run high. The eventual and proper fix, is for the power utility to increase the distribution circuits and associated transformers, but until then, they'll cheat by tapping the transformers to the higher voltage. Another issue that can cause higher voltages: There are housing developments in say Florida that sell homes that include grid tied rooftop solar, as a standard. Since an electrical load (any device that uses power) will use the highest voltage source first, the AC power that the solar produces must be slightly higher than utilitie's incoming power. This higher voltage is also then seen by your neighbors, who are fed by the same power. Now, for their solar to supply power, it needs to be just a little higher voltage, which it adjusts to automatically; and so on and so on. The result being, around mid day, while most people are at work and these neighborhoods are using little power, the solar in these neighborhoods are pushing the voltage to the high end of the spectrum. By code, there's a limit to the voltage output of solar, but some people will make adjustments to their system to exceed the code limit because it makes financial sense for their solar power to be earning electrical credits, by supplying power to the grid. So, this neighborhood would suffer from high voltages during the midday, even if all the utilitie's equipment is sized and set properly.

[@Attest411]

“Fucking boost transformer” wow never thought I hear you curse.

[@gonzo910910]

I thought that too. It definitely sounded like "...fuckin' boost transformer..." haha

[@richardcranium5839]

i had 284 on my 220 once said it was a fault in my wiring lmao with my mains disconnected??? lol no answer crickets. and of course it took a week to show up and conveniently it was at 225. shorty after they were reconfiguring a substation to supply enough power to a business on my loop go figure.

[@notanewbie1718]

Shouldnt have to invest in a buck and boost. Power Co. Can control this at their transformer.

[@HVACS]

We contacted them many times and they were unhelpful

[@cornpop7805]

It depends on multiple factors. The most common issue is: 1) If the local power hasn't kept up with the development in the area, the power company will tap the transformers higher, in order to keep the voltage from going too low, during peak demand times, such as breakfast and dinner times. Then, when demand is low, the voltage goes high. Eventually, the power company will upgrade the distribution in the area, but this is rarely a quick fix. 2) Some areas that have a decent percentage of rooftop solar and they will have something of a voltage arms race around midday. Each grid tied system will be programmed to output slightly higher than the power feeding their home, so that their system is powering their own loads or earning net-metering credits via their electric meter. Their system outputting higher voltage, also bumps the utilitie's voltage a bit higher. If enough people in the area have systems trying to output just a little bit higher voltage than the next guy, the whole neighborhood ends up with midday high voltages. That's not something that the local grid can respond to. These are real time issues and tapping local transformers is a manual process.