Do my transformers powering ZVs and t-stats need to be grounded?

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Old 12-13-13, 09:07 AM
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Do my transformers powering ZVs and t-stats need to be grounded?

I'm installing a number of transformers to power 11 zones. Do I need to ground these? There is no place for a ground wire connection....

Should I run a ground wire through the conduit connecting the metal boxes and attach at each box, and daisy chain to next?
 
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Old 12-13-13, 09:20 AM
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ELEVEN ZONES?! You ARE a glutton for punishment Shawn!

You are not talking about grounding the secondary output voltage winding, correct?

You are talking about physically grounding the 'frame' of the transformer?

If you are distributing 120VAC through multiple boxes to feed the primary of the transformer, the boxes do need to be grounded. The transformers are grounded due to the fact that they are physically screwed to the boxes which are grounded.

Is this what you are asking?
 
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Old 12-13-13, 09:28 AM
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What type of conduit are you using? If it's steel EMT, the metal conduit, with approved fittings, itself is a suitable ground (no separate ground wire needs to be fished through the conduit), assuming that there is a path back to electrical system ground. Then, if the xfmr metal case or mountings are bonded to the metal box, you are good.

How many xfmrs are you planning to install? Why not just buy one xfmr that is big enough for the whole shooting match - and then the only thing you have to deal with from there is 24V.
 
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Old 12-13-13, 09:31 AM
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Thanks. That helps a lot. Yes. im referring to 120v primary. So I ground the first box and the whole system is grounded because all connected by conduit. And transformers grounded to the boxes. That makes sense.

11 zones because I'm developing a bed and breakfast and winter is slow season. So it will save to switch unoccupied rooms to low in winter. But yes, it's a bear if a project!
 
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Old 12-13-13, 10:06 AM
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So I ground the first box and the whole system is grounded because all connected by conduit.
How will you ground the first box? If it's steel EMT all the way back to the main panel, that would work. Are you proposing to feed the first box with romex, including a ground conductor?

I'm still wondering why you want to install multiple xfmrs rather than one xfmr sized for the entire load?

The National Electrical Code has some special requirements for multiple occupancies, such as your bed and breakfast. You really ought to have an experienced electrician do your electrical work. Will you be required to pull permits for your work? Are there local codes that apply? Are electricians licensed in your state? Doing your own electrical work in your own single-family dwelling is one thing, but in your situation I don't think it is a good idea.
 
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Old 12-13-13, 12:09 PM
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What type of zone valves are you using? Hope your pumps are sized correctly as well. What size xformers are you planning on using?
 
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Old 12-13-13, 03:49 PM
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Doing your own electrical work in your own single-family dwelling is one thing, but in your situation I don't think it is a good idea.
Agreed.

Even if you ARE allowed to do your own wiring, to protect yourself from liability you need to have the work INSPECTED AND SIGNED OFF by a licensed electrician, or your town's electrical inspector.
 
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Old 12-13-13, 03:54 PM
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wondering why you want to install multiple xfmrs rather than one xfmr sized for the entire load?
I personally would probably opt to use multiple transformers for the simple reason that if a transformer goes out, the whole system isn't dead in the water.

A single 150 VA transformer is going to be expensive, and too large to easily install.

[edit: OK, I just did a little googling and found that 150 VA transformers can probably be had for at or near the same price of four individual transformers... but still, it's nice to have some redundancy in a situation like this, and the bigger transformer is still harder to install... needs an enclosure]

Four 40 VA transformers can easily be mounted on four individual 4" utility boxes and each one will cost less than $20.
 
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