Comparing Unirac Options

[longstate]

Hello, I am currently designing a residential system for a house outside Chicago. We are planning on using Unirac but I'm a bit confused by their different mounting options (solarmount, sunframe, and sunframe microrail). I can't find a good comparison of the pros/cons of each. We've built some test layouts using their design tool and the microrail seems to be the cheapest option for our setup. It seems like microrail also has the best aesthetics, which we're sensitive to since our south-facing roof is the front of the house. However, I'm not sure if there's something with microrail that I'm missing.

Does any have experience with the different options or a better breakdown of the differences?

Thanks in advance!!

[Ampster]

I have used the standard Unirac for two installations and still have parts so I am sticking with that for my next two installations. That is of course unless some of the fasteners are interchangeable. I am not a professional but my prior two installs and the two future ones are for my own account.

[Mike90250]

If you have to meet code engineering requirements, will Unirac pass the inspection without an engineering report ? The "Rack Systems" are designed as a whole. Is Unirac ?

[Ampster]

If you have to meet code engineering requirements, will Unirac pass the inspection without an engineering report ? The "Rack Systems" are designed as a whole. Is Unirac ?

That is a good question and the answer depends on the location and the structure underneath that. The first one I did 8 years ago in Hermosa Beach was easy using Unirac's engineering drawings.(not stamped but Unirac has an ICBO number) The second one I mentioned is on the roof in another identical building but I haven't pulled the permit yet. If things haven't changed at that City I think it will also be easy. I own those buildings and did them for my own account as an owner builder.

One of the future one's which I mentioned, is for my sister in Mendocino County and I have no experience with that jurisdiction. Do you have any experience with Medocino County building department procedures? I was planning on having my sister pull the permit as an owner builder.

The last job I referred to is in Sonoma County and I have already had a conversation with them and they don't need a wet engineering stamp.That one is for a patio cover that did not need a building permit but the big unknown is the engineering of that structure when it becomes the support for the Unirac system which will attach to it. That project is for my own home and I have already pulled permits as an owner builder for two subpanels that will complement that system.

The caveat for anyone reading this post is that you must check with your local Authority Having Jurisdiction (AHJ) before you spend money. You cannot rely on anything an anonymous poster says on a forum like this says. My experience is limited to the one city I mentioned and is only speculative about the two other prospective installations in the Counties I mentioned. All of these are in California which does have expedited permitting and low fees but the rules are the rules.

The Original Poster said he was outside of Chicago. He may know the answer to the AHJ issue since he was asking more about the differences with the various Unirac systems. I may have time to look into that for my own benefit before I leave for a road trip at the beginning of next week. If I do I will update this thread.

[emartin00]

I'm not sure what the snow loads are in Chicago, but typically the rail-less systems (micro rail) require a lot more roof penetrations than are required with a traditional rail system.
In my area with 50-60psf snow loading, I think I need about 3 times as many penetrations.

[J.P.M.]

I'm not sure what the snow loads are in Chicago, but typically the rail-less systems (micro rail) require a lot more roof penetrations than are required with a traditional rail system.
In my area with 50-60psf snow loading, I think I need about 3 times as many penetrations.

Is that snow load or distributed dead load ? If snow, it will take more supports to lower the point loadings, but 3X ? 3X what ?

[emartin00]

Is that snow load or distributed dead load ? If snow, it will take more supports to lower the point loadings, but 3X ? 3X what ?

50-60psf is the design requirement for snow load as per the building codes. That's on top of the weight of the sytem.
If I remember correctly, the system I designed (6kW) required about 20 L feet using XR1000 rail. Quickmount would have required about 60 mounts for the same size system.

[J.P.M.]

50-60psf is the design requirement for snow load as per the building codes. That's on top of the weight of the sytem.
If I remember correctly, the system I designed (6kW) required about 20 L feet using XR1000 rail. Quickmount would have required about 60 mounts for the same size system.

I've not looked into it, but what was it about the Quickmount that required 3X the # of supports ? Just curious.

Thanx in advance.

[emartin00]

I've not looked into it, but what was it about the Quickmount that required 3X the # of supports ? Just curious.

Thanx in advance.

I'm not sure. I'm guessing since there is no rail to share the load, the modules need more support.
To be fair, 60psf is a lot of snow.

[longstate]

Thanks for all the replies guys! You've brought up some good questions, especially about snow load and the possible increased number of penetrations with rail-less.

Some additional permitting information I found for where I live:
- Distributed load must be <5lb/ft^2 (or detailed analysis necessary)
- <45lbs per attachment (or detailed analysis necessary)

I think for simplicity reasons we'll probably just go with the solarmount option but with lighweight rails. However, I'm a bit concerned with aesthetics given the midclamps and spacing of solarmount. I think the sunframe (with rails) might look better given that there's no row gaps, but I'm having a tough time finding information and examples.

Thanks again and I'll keep you updated on our progress!

[J.P.M.]

I'm not sure. I'm guessing since there is no rail to share the load, the modules need more support.
To be fair, 60psf is a lot of snow.

Thank you for the response.

I'd think any uplift, dead load or any shear forces on an array would be about the same whether or not rails are present. Might be something different about the connections to the structure. Without knowing more, and depending on the application, I'd think fewer attachments to a roof for example would be preferable to more penetrations, at least as a preliminary way to approach the design.

[Ampster]

I did some preliminary research and the difference for me favors the light rail. I can save $100 using it.

My assumptions are what might shift the decision for someone else. My application is a patio cover with 2x4 rafters on 24 inch centers. since everything is visible and accessible from below I will go with the lightest rail and if I have to use L feet every 2 feet or 4 feet it doesn't mater because I have a lot of stainless lag bolts and plenty of extra L feet left over from another project.
The patio cover was built to code in terms of spans but I did not have to pull a building permit because it does not exceed 12 feet in height. I may need an engineering sign off since it is supporting the solar panel system.