[RE-wrenches] Voltage Rise

[Dave Tedeyan]

Hi All,
Just thought I'd follow up here. Turns out the transformer was rated at
10kva. (remember, this system has three 7.7kw inverters...) We were able to
get the utility to come out and put in a 25kVa transformer, and the voltage
rise is now way more in line with what we would expect.
Cheers,
Dave

On Thu, Feb 23, 2023 at 1:36 PM Dave Tedeyan <dave at sungineersolar.com>
wrote:

> The customer has already had the utility come out to take a look. He says
> they had him turn off the solar, and then they measured 246V at the
> transformer and then said it's not their problem. He was going to try to
> get them back out to check the connections at the transformer and the
> meter.
> Also, that's a good suggestion to check each leg separately to see if
> maybe there is only one line that has a bad connection.
> Cheers,
> Dave
>
> On Thu, Feb 23, 2023 at 1:33 PM Jerry Shafer via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Wrenches, Dave
>> I have had this issue, first turn off everything, check static voltage,
>> this will drive everything else. If the static is 240 L-L look at the
>> utility side you might have small conductors, you might also have a
>> transformer size issue bottlenecking the current.  Next turn loads more the
>> better watch if there is a drop and how much. Now turn off everything and
>> power up the solar again watch the voltage at the meter if it climbs up and
>> close to limit it might be the feeders. It's all process of elimination.
>> Lots of fun
>>
>>
>> On Thu, Feb 23, 2023, 9:03 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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>
> --
> [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
>


-- 
[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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