[RE-wrenches] Voltage Rise

[Mac Lewis]

Hi Dave,

Where is the utility voltage being measured?

I might suggest doing point to point voltage calculations based on the true
wire size and then verifying with measurement.     It's great to use an IR
camera to look for hot spots.  Do this when the problem is the worst.  Is
it symmetric with L1 to Neutral and L2 to Neutral? Sounds like a utility
issue to me, perhaps an undersized transformer.

Good luck and please let us know what you find.

Thanks

On Thu, Feb 23, 2023 at 10:18 AM Jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hi Dave
> It might be that the utility transformer is where the extra voltage rise
> is coming from?
>
> Jay
>
>
>
> On Feb 23, 2023, at 10:03 AM, Dave Tedeyan via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
> Hi All,
>
> I've got a customer who is having issues with high voltage at their house.
> This first became an issue after installing 23.1kw of AC solar output. They
> have some GREE heat pumps which have been having some failures. The heat
> pump people are saying that the problem is that the voltage is above 252V.
>
> The grid voltage was measured at 246V with the solar off, and 260V with
> the solar cranking. The inverters are within 10' of the MSP where there is
> a line side connection. Then there is 4/0 AL cable which has to go roughly
> 175' before it reaches the transformer. At 246V and 92A, there should only
> be about a 3.6V rise, or maybe 4V including the wire from the inverters to
> the combiner to the MSP. Yet somehow there is about 14V of rise.
>
> The service entrance cable is buried. It is in conduit where it goes into
> and out of the ground, but I have no idea whether there is conduit for most
> of the run underground. Maybe there is a nick in the cable underground
> which has caused corrosion? Does anyone have any ideas of how to find the
> cause of the increased resistance? I should go back out there with an IR
> camera to check the connections that I can at least get to in the house.
>
> I have suggested that they install a buck/boost transformer on the heat
> pump circuits to bring down the voltage a little bit. But they are also
> concerned about the high voltage causing issues with other electrical
> appliances in the house. Does anyone have any anecdata to show whether
> there are other hidden issues if the house is at 260V during times of high
> solar production?
>
> Thanks!
> -Dave
>
> --
> [image: Logo] <https://www.sungineersolar.com/>
> Dave Tedeyan, P.E.
> Owner | Sungineer Solar
> p: he | him | his
> a: 1653 Slaterville Rd. | Ithaca, NY 14850
> w: www.sungineersolar.com <http://www.sungineersolar.com/>
> c: (607) 288-2898
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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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