About to sign off on design (NJ) - can you doublecheck?

[petesamprs]

Hi,
I'm working with GPE on a new install in NJ. They have been very helpful. House in north NJ, 180^ azimuth, 37^ pitch, no shade all day. PVwatts says 1429 kwh/yr.

See below for satellite pic of my roof. I am having roof redone as part of solar install, and removing the circular attic fan that you see in the pic (installing ridge vent instead)

GPE has spec'ed 50 panasonic 325W panels (16.25MW), with 2 SE7600H inverters. PVwatts suggests that will produce 22MWH/yr. I think that's actually too much for my needs (new house to me and I'm adding a pool so i'm estimating future usage) so I'm going to decrease the system to ~15MW (20MWH/yr).

They also provided a proposed panel layout for 50 panels, but I hate how it looks like swiss cheese with my 3 existing roof vents. I am proposing a more cohesive layout assuming 46 panels instead of 50.

A few questions:
- Any issue with the 2 SE7600H inverters for my set up?
- Any better recommendations for my panel layout? Has anyone ever moved roof vents during install?

thanks

[Ampster]

I assume what you mean is move the vents during the roof instal?. You can also consolidate provide that meets code and that will give you less penetrations.
Unless that roof is visible from the street I would not worry about layout except to avoid shadows from the dormer.

[petesamprs]

It is not visible from the street, but I'd still like it to look nice from the backyard. Probably not worth it to move vents, but I still want a better layout regardless

[Ampster]

Beauty is in the eye of the beholder. Another advantage of moving the vents is you would have future expansion ability. I am in the minority on this forum when I say now is the best time to put more panels up for the future. Incrementally they cost less now than in the future. The best time to move the vents is when you are reroofing. The cost will be a function of how much attic you have for a plumber to work.

[petesamprs]

That's exactly what I'm torn about when it comes to sizing - oversize now to hedge myself or try to be exact and possibly come up short. People here always preach to not overdo it since it hurts the economics.

Previous owners of this house used about 19-20k KWH a year. I don't know their temperature preferences or how diligent they were about conservation. 5k sq ft house with 3 zone AC and unfinished basement. I'm adding a pool as well.

I use about 11-12k KWH/year in my current house which is half the size, finished basement + dehumidifier, and has 1 AC zone.

So for the panels I'm estimating usage of 20k KWH, but I could find in reality I end up slightly higher or much lower than this (more bias to the downside). If I find myself using much lower there is the possibility in the future for an electric car to take some of that excess supply. If I find myself using more I better start finding some ways to conserve.

[petesamprs]

By the way, are two 7600H-US inverters the right size for my system and expected production? How much risk is there of meaningful clipping?

[ButchDeal]

By the way, are two 7600H-US inverters the right size for my system and expected production? How much risk is there of meaningful clipping?

50 modules of 325W each is 16.25kW (not 16.25MW ) and 2 X SE7600H is 15.2kW.
There should be very little clipping if any.

I would request that they add consumption meter and that both SE7600H have revenue grade meters for SRECs instead of an external SREC meter.

[petesamprs]

Thanks Butch, yes I meant kW not MW for the panel array size.

Regarding the consumption meter, can you explain what that is and if there's an extra cost? Is that installed at the electrical panel, or the inverter?

Also what is the advantage of the meters for each inverter vs. an external one?

thanks for all your help in this process.

[ButchDeal]

Thanks Butch, yes I meant kW not MW for the panel array size.

Regarding the consumption meter, can you explain what that is and if there's an extra cost? Is that installed at the electrical panel, or the inverter?

Also what is the advantage of the meters for each inverter vs. an external one?

thanks for all your help in this process.

The consumption meter will show you how much power your home is consuming at any given time. Without it you will only know what your PV is producing.
It goes into the MSP (Main service panel) usually. There is an extra cost but often it is thrown in especially on larger ones like this.

The internal revenue grade meters means that you will have only one place to know your actual production and will not need an external added meter on your house. Some of the external meters that are cheaper have to be manual read, the internal one is automatic and can feed data to most SREC centers.
The external third party meters that are automatic read, cost a lot more and have their own service fees as well as another network connection or cell service.

[J.P.M.]

Has anyone ever moved roof vents during install?

Yes, I did. Well, actually, immediately before 2013 PV install during roof remediation.

Two reasons, actually 3:

1.) Obstructing vents by putting things over them is a bad practice. Not only bad for the venting capabilities, but also not good for the long term health of the panels. What to know why? Put your face over a stink vent with 3" of clearance between it and your nose for 5 minutes. Most all of the crap coming out of a vent will most likely wind up on the back side of the array over time.

As a cautionary comment, vendors will notice the barn job and perhaps/likely use it to void any warranty claim.

2.) Building code in my area/state disallows obstruction of vents by panels over them as confirmed by my AHJ before installation.

3.) Not moving them is a stupid way to design. Kind of like "What were you thinking ?"

[petesamprs]

In my case the debate is not whether or not to cover the vents (that is a non-starter), it is whether to go through the hassle of moving them as part of redoing the roof. In the end I determined it's not worth the hassle for the back of my house. I reconfigured the panel layout to be more cohesive, with only 2 panels "missing" to accommodate existing stacks.

My new shingles will be black/charcoal colored, new panels will be panasonic black/black and I'll paint the vent stacks black so that the whole roof looks somewhat seamless.

[J.P.M.]

In my case the debate is not whether or not to cover the vents (that is a non-starter), it is whether to go through the hassle of moving them as part of redoing the roof. In the end I determined it's not worth the hassle for the back of my house. I reconfigured the panel layout to be more cohesive, with only 2 panels "missing" to accommodate existing stacks.

My new shingles will be black/charcoal colored, new panels will be panasonic black/black and I'll paint the vent stacks black so that the whole roof looks somewhat seamless.

Understood. For stink/plumbing vents I'd suggest considering the vent stack height with respect to two factors:

1.) Shading impact on the array if the vent height above roof > array height above roof.
2.) Array impact on vent draw if vent height <= array height.

[Ampster]

.............

2.) Array impact on vent draw if vent height <= array height.

My limited experience with plumbing vents is their main purpose is to prevent any pressure or vacuum that would break the trap and let sewer gas into the home. As to actually venting much sewer gas, that would depend on a lot of factors, one of which might be the proximity to some solar array. I would not let that affect the aesthetics.

[J.P.M.]

My limited experience with plumbing vents is their main purpose is to prevent any pressure or vacuum that would break the trap and let sewer gas into the home. As to actually venting much sewer gas, that would depend on a lot of factors, one of which might be the proximity to some solar array. I would not let that affect the aesthetics.

Yea, I know. Mostly correct. As you write - mostly, but stick your nose over one and take a whiff and know the vent will still take warm(er) air made moist by contact with the trap fluid and condense some of the vapor that has the stuff you'll smell. One giveaway you may not be aware of unless you've lived in a very cold climate: Stink/plumbing vents will show a bit of vapor if it's VERY cold and not windy. The moisute is there regardless of amb. temp. Some of that moisture will condense on whatever is nearby like the underside of a panel under conditions that occur at all locations at some times. Bath and kitchen vents will probably smell better but have more moisture.

Anyway, the San Diego Minimum Construction Specifications doc. SPV-CS-1, sec. B.1.c : "Module installations shall not cover or block any roof plumbing or mechanical vent locations."

I appreciate that is a San Diego document but I'm pretty sure San Diego lifted it from either some state doc. or some national standard doc.

It' just a crummy idea.

[petesamprs]

Got my PTO today. Long road started in mid August with GPE. Ended up with 46 panasonic panels (14.95kW) and 2 SE 7600H inverters w/ optimizers. $2.87/watt and hoping to break even in 5 yrs subject to actual usage and SREC payments.

Here were my milestones:
- 8/21/19 - first contact with GPE
- 9/1/19 - contract signed
- 9/14/19 - GPE site survey
- 9/17/19 - layout plan received/agreed
- 10/1/19 - Interconnection application
- 10/24/19 - engineer drawings submitted to town for permit (this took longer than i was expecting)
- 11/12/19 - approvals received
- 11/25/19 week - new roof install (costello)
- 12/16/19 week - panel installation (GPE was backed up and had bad weather in early December)
- 12/30/19 - final electrical connections and final invoice payments to GPE

- 1/16/20 - Part 2 of interconnection agreement
- 1/17/20 - Town COA received
- 2/6/20 - PTO received (no meter swap required - all done remotely)

Already got full admin rights from GPE so I'm set up on SE monitoring and pvoutput export. I'm using a cellular connection right now but may hardwire soon (or if SE finally rolls out its wifi monitoring firmware upgrade i'll start to use that). Anything else to be aware of for someone that is a "new PTO"?


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