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That's not such a good idea. That opens you up to ground loops, as you have two different ground points at possible different potentials. Generally, you only want one single ground for the entire building. Are there any signs of corrosion at the point where the second ground conductor is attached to the water pipes? If so, I'd be wary...There is a grounding rod right there at the panel connected with 4AWG stranded wire, and driven deep into the ground. There is a 2nd grounding rod at the front of the house that is bonded to the water pipes.
I would suggest that you hire a locally certified and experienced electrician to check things over, and tell you what is fine, and what isn't. Electrical codes vary wildly from place to place, even though they are all supposed to be based on the same thing. So get a local guy that is certified, license, or whatever they call it where you live, and get him to sign off on all the paperwork, even if you do the work yourself. You'll likely need his signature in any case, to get your inspections approved, and he can answer all your questions in terms of local code.
That's one for the local electrician to answer! Where I live, the ground conductor has to be the same gauge as the live and neutral, but I've seen smaller gauge permitted in some places.Question 1: is this OK? And does the size of the ground conductor matter? Should it also be 6AWG, or can it be smaller?
the hot, neutral, and isolated ground conductors will be run inside the conduit together, and will all be home runs back to the sub panel.
That's the way I would do it.Once again, local rules vary. Where I live, that setup wouldn't pass. Here, all grounds are tied together at the main grounding point, where they are also tied to the neutral. But where you live, that could different.As for the isolated grounds, I understand each isolated ground conductor needs to be sent to a separate ground bus bar that is not connected to the ground bus or neutral bus in the sub panel. They also need to be connected back to the ground bus at the main service entrance.
Where I live, that would be fine and correct! .... but where you live...Question 3: Am I correct that I do NOT need another ground rod outside the garage/studio? As long as the isolated grounds are bonded to the main service ground/neutral bar (which is bonded to the grounding rod at the service entrance), i'm good?
Your local electrician can tell you what is the accepted. approved way of doing things.Contact a local HVAC supply store, and see what they have. You can sometimes buy filters in places like Home Depot too. Often sold as "furnace filters", rather than "HVAC filters". They usually come as cartridges with cardboard or plastic frames, and you just slide them into the slot in your furnace or ductwork. In a pinch, I have been known to just buy some kitchen extractor hood filter material, and use that... but once again, make sure it will pass local code! You do want to be careful that the inspector will be happy, and sign his scribbles and stamps on your paperwork, without complaining or telling you to re-do stuff!Stuart mentioned putting a filter on the air intake (From outside to inside), and the return air register to keep the ducts and silencers as clean as possible. Sure having to clean these every once in a while is a chore, but I'd much rather that than the alternative. I've been researching filters, and can't seem to find something that would work. Is there a specific type of filter I should be looking for?
One caution here: don't forget to take all the filters into account when you do your static pressure calculations.... You don't want to end up with static pressure that is too high for your AHU to handle.
Smart move! But do check that he is certified/licensed/approved locally!I also met an electrician in the home depot parking lot yesterday. He seemed like a good guy and I'm going to call him to set up a time for him to come check out the space and see what he thinks.
I'd suggest taking a look on your local municipality web site, and see if you can find a copy of the locally applicable building code, then check that to make sure EVERYTHING you are doing complies. You could also ask your inspector in advance! They really are not cruel ogres that are out to get you! Most of them would be happy to tell you what they will and will not pass, just from a phone call or visit to their office, so you have all your ducks in a row before he even comes out to your place for the final inspection. It's worth calling him up and ask his advice. Worst case: he tells you to take a hike! But more likely he'll be happy to know that you are interested in his opinion, and will probably give you good advice.Question: my garage is a single story gable roof style structure. Do I need a firestop at the tops of the walls between my interior and exterior leafs?
There should not be any moisture in the concrete! Hopefully it has cured to the point where it does not sweat any more, and hopefully it is fully sealed from below, and the walls are built properly too, with water barriers and vapor barriers in the correct locations, too. So there should not be any moisture in that cavity.In the gap between the exterior and interior leafs, I plan on filling that gap with insulation. Should i put something on the concrete floor so that the insulation is not touching the concrete? Could moisture from the concrete saturate the insulation?
Also, if you are worried about water somehow getting onto your slab, then you DEFINITELY need to use pressure-treated lumber for your sole plates, not ordinary wood sole plates. Water and untreated wood do not get along very well! Rot, mold, fungus, and other nasty things will be the result... and it will all be hidden inside the wall, where you can't see it, until it is too late... There's also the risk of warping, twisting, bending and other structural things happening, with untreated lumber in contact with water. Bad idea!
But if you are mainly concerned about the insulation, then do NOT use fluffy fiberglass in there: use mineral wool instead. Mineral wool stands up to water a lot better than fiberglass. If fiberglass gets wet, it will dry out eventually, but first it ends up as a soggy crumpled mess, and that won't change after it dries out. Mineral wool batts keep their shape, and return to normal after they dry out.
For maximum isolation, the entire cavity inside the wall should be completely filled with insulation: no air gaps at all. Just insulation.Should there be a gap without insulation down where the sill plates are? Or should the insulation in the gap go all the way down to the concrete (in between the sill plates), but not touching the concrete?
- Stuart -
