200 Amp Whole House Transfer Switch

curdy · July 2021

I am looking for advice on automatic 200 Amp transfer switches for Solar/battery main using grid power as the backup. I am in Hawaii with highest utility costs in USA where typical electric bills are $700-$1000 without AC. I want to use my solar system of 13Kw array, multiple-linked 5Kw inverter/chargers and battery farm of 9 parallel 200Ah 48v lifepo4 as the main power with grid(not generator) backup power. Which transfer switch would work in this setup? Originally, I used a simple, manual interlock switch on 200A breakers in my service entrance load center(fed from the solar system power subpanel) but now all non-grid-feedback systems must have a transfer switch. I have spent days reading through the manufacturers docs on ATS but can't find anything on using solar inverter/battery systems as primary or backup. Any help?

mike95490 · July 2021

> Originally, I used a simple, manual interlock switch on 200A breakers in my service entrance
> load center(fed from the solar system power subpanel) but now
> all non-grid-feedback systems must have a transfer switch.

Won't your system be grandfathered in ? Or are your changing it and needing new permits.
Does it HAVE to be an automatic transfer switch, or is manual allowed ?

https://www.homedepot.com/p/GE-200-Amp-240-Volt-Non-Fused-Emergency-Power-Transfer-Switch-TC10324R/100150463

BB. · July 2021

Welcome to the forum Curdy.

Did you actually get a 'ruling' on the interlocked breaker/main panel "transfer switches"?

These transfer switches are just interlocked with a sliding front plate (I am pretty sure--Not an expert):

https://www.solar-electric.com/midnite-solar-60-amp-240-volt-dual-ac-manual-transfer-switch.html

Decade or so ago, we had manual locked transfer switches with breakers in a main panel for our UPS/mains transfer manual bypass transfer switches (large UPS system--Manual transfer switch for maintenance/failure bypasses).

In the company's system--They were not even interlocked--They were actual keyed locks for the electrician to flip.

Do you want/need an automatic transfer switch? Are you going to keep your utility power connection? One of the "neat things" the PUCs (public utility commissions) and utilities seem to be doing is increasing the minimum billing/connection fee... Mine went from $5 to $10 per month a few years ago (yea--not a huge deal)... I have read that some utilities are upwards of $48 to possibly even near $100 per month (in the indefinite future?)... This was a shot across the bow of folks using GT Solar for power (high minimum bills, low $/kWH payment for solar power generated on site, etc.)...

One member here years ago--His $48 a month minimum charge for his weekend/seasonal cabin--It was costing him more than conversion to solar (his usage was minimal... LED lights, radio, cell charger, etc.).

There can be issues with pulling the utility plug... Some cities require utility power to be a habitual building. Others in remote areas, they utility would pull the line and poles and effectively make it very costly if somebody down the road (new buyer for property) wanted utility power ($10,000's of dollars possibly to bring power back to the property--Can even have easement issues, etc.).

In California--The utility paperwork talks about having to pay charges for "stranding" their equipment/generators (basically, the utility used me as a customer to take loans out up to 40 years in the future for building/maintaining infrastructure)... Have not heard of anybody having to pay for disconnecting their home--But it is a threat.

-Bill

curdy · July 2021

Hi,

I started with a 10Kw grid tied system(the max allowed by Hawaii in 2009). Last year I added a bunch of mini-splits to air condition the house but couldn't expand my grid-tie capacity. I had to install a separate off-grid system for the min-splits of panels, inverters/batteries and dedicated load center. I realized that I could connect this second system to my main panel with a manual lock-out and a tandem 200A breaker and flip between grid and this secondary battery storage system to augment my 10Kw grid-tied system at night. That worked well but we had a 3-day power outage and my battery bank ran down. When i upgraded the off-grid system to accommodate the whole house with 9Kw of panels and additional batteries, I had 4 different certified PV installers tell me that the manual switch would not pass inspection. They also refused to do the upgrade and add the additional panels etc. without a transfer switch. I was told the integrated transfer switches in the 5Kw integrated inverter/chargers could fail and allow back feed to the grid. I had to remove the grid input power from the bank of 5Kw "integrated power walls" and put a transfer switch between the solar 200A subpanel and the main service panel. The output of the transfer switch would connect to the main service lugs on the main panel. I would have to remove the 200A breakers from the main panel that were fed by the 200A solar subpanel. I am looking for the right automatic transfer switch.

Dave Angelini · July 2021

This is what Schneider does for HECO systems. The power meter and all interconnection is approved by HECO. Instead of a whole house transfer, XWP is used to power the sub panel and main panel if there is enough solar. You really should have a genset also because you are depending on a utility that has alot of learning to do!

Image: https://us.v-cdn.net/6024911/uploads/editor/b3/79ijibeehp78.png

curdy · July 2021

>Did you actually get a 'ruling' on the interlocked breaker/main panel "transfer switches"?

No, I didn't. The second installation dedicated to mini-splits was originally off-grid.

I later upgraded the load center in my house to a service entrance panel with a main breaker when I needed more spaces in the panel due to a remodel of kitchen and bathrooms. I added the 200A breakers and sliding interlock to the new panels at that time. There were no objections to including the solar/inverter/battery as a night time battery powered backup. This was not an unusual configuration for 4 or 5 solar/battery-powered mini-split installations to use the solar batteries as a backup rather than purchase a generator.

>Won't your system be grandfathered in ? Or are your changing it and needing new permits.
> Does it HAVE to be an automatic transfer switch, or is manual allowed ?

Since I was upgrading with additional 9Kw of solar panels, I would need approval.

All four of the solar electricians who looked at the existing installation said the whole house upgrade would not be approved without a separate "approved list" transfer switch, either manual or automatic. That transfer switches is the standard method of whole house install. Everyone recommended an automatic switch for convenience because Maui Hawaii experiences frequent(monthly) outages for up to 5 minutes. Power surges are so common that all major continuous powered appliances: fridges, TV's, computers have surge protectors. I lost a two-year-old kitchen fridge and a two-year-old-ceiling projector in the last 6 weeks because they were unprotected. There was no surge protector on the ceiling outlet of the projector.)

Here are some of the transfer switches that I looked at. All have additional controller circuitry for standby generators. My question is: Can that circuitry be left disconnected if grid power is used as the backup to solar primary? Are there any residential transfer switches designed for a) dual primary input power or b) solar as primary with grid backup?

Generac RXSC200A3

https://www.generac.com/all-products/transfer-switches/automatic-transfer-switches/rxsc200a3

Honeywell RXSK200A3 maybe made by Generac

https://www.honeywellstore.com/store/products/honeywell-single-phase-200-amp-240-volt-sync-transfer-switch-rxsk200a3.htm

Cummins Onan RSS 200 Amp Automatic Transfer Switch

https://www.norwall.com/products/Cummins-Onan-RSS-200-Amp-Automatic-Transfer-Switch

Champion 102006 200Amp ATS

https://y79961nbs4u2hvbnwronx9zx-wpengine.netdna-ssl.com/wp-content/uploads/2020/11/102006-im-english.pdf

Thanks,

Curdy

curdy · July 2021

Old PV installs are grandfathered in Hawaii, but repairs like replacements of old panels are not. All changes that come in contact with the grid must be approved by the electric company. The rules specifically mention replacing defective panels and include a long list of approved panels. I was told that I needed approval to replace a couple of 12-year-old panels in an array attached to a Sunny Boy 6000 inverter when I disassembled the system to re-shingle the roof.

Dave Angelini said:

This is what Schneider does for HECO systems. The power meter and all interconnection is approved by HECO. Instead of a whole house transfer, XWP is used to power the sub panel and main panel if there is enough solar. You really should have a genset also because you are depending on a utility that has alot of learning to do!

Thanks. That is a solution but would require that I replace every piece of equipment I have installed. I only need a dual power transfer switch.

Dave Angelini · July 2021

I have a Schneider model number I used on a system. Not finding it today. Is below what you are doing? There was another slide that showed a main panel with ac and dc coupling. This slide is for protecting the genset from the grid inverter. Sorry I did not have time to read all of your post. Do a search of Schneider 200A xfer. Good Luck!

I always forget that ASCO is the Schneider company that builds the best manual and auto XFER out of their huge plant in New Jersey. Below are a couple of blocks showing apps for CA and Hawaii. Our problem here is mainly utility shutdown for wildfire. Here is a link.
https://www.ascopower.com/us/en/product-category/89074-transfer-switches/

200 Amp Whole House Transfer Switch

Comments

Categories