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Surge Protection Device on zone and other wiring to a shed


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#1 ecborgoyn

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Posted 05 June 2012 - 06:54 AM

As part of my Elk M1G panel replacement and upgrade I'll be adding a few door contacts and a fire/heat sensor in my shed. When I did some LV wiring updates a few years back I pulled a few spare CAT5e cables through the LV conduit. My plan is to use one of the CAT cables for my new sensors. I know that ~24AWG isn't great for sensors, but it's there.... It will be in PVC or metal conduit throughout the shed and only outside a conduit inside of the house.

My question is regarding surge protection. The shed is about 35' from the house. FWIW, the shed has a grounding system (two 8' rods) as the shed also houses my backup genset.

Should I have surge protection devices on these new zone circuits? If so, should they be at the M1G panel area? At the shed? Both? And what clamping voltage device should I use? Are the Ditek devices a good choice?

I also have a POTS telephone line to the shed. I suppose that it would be prudent to surge protect that line also. Other LV circuits will be used for network and control. I suppose these should be protected likewise?? (I'll be using some of these cables to communicate with a genset starting and monitoring system that I have on the drawing board.)

#2 DELInstallations

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Posted 05 June 2012 - 04:56 PM

Since you are planning fire alarm, that automatically means surge protection as the IDC leaves the buildings.

The simplest way to accomplish what you're doing is to install a pair of surges on the bus and then put an expander in the field, that way you have your protective circuits, fire alarm AWG is a non-issue, and any supervisiory for the genset is easily tied to the inputs (fail to start/exercise, etc.) then put a pair of DTK-LVLP's on each end, grounded to the EG on each side, with the path to ground being shorter than the wiring to be protected. Basically follow Ditek's instructions. The clamping voltage is selected based on the service voltage the unit would see.

The amount you would spend on surges for each circuit would easily be offset in a single expander.

We commonly use Edco, Ditek, however Elk's surges for telco could also be used.

#3 ecborgoyn

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Posted 06 June 2012 - 11:41 AM

I should have planned for SPD/TVSS protection even when I installed the POTS line to the shed..... Quite an oversight on my part. Even the AC feeder circuit from the genset should be better protected. I have SPD devices for lines (AC, Telco, etc) coming into the house from the street but don't protect the lines to/from the shed.

My original plan was to run three zones circuits to the shed. But thinking about surge protection, I'm agreeing that putting a zone expander in the shed is the better solution. Plus I get zones for expansion.

Next question: what about circuits to an exterior speaker (i.e. siren) and strobe light? They 'leave the building', but only barely... Are these lines typically SPD protected?

#4 video321

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Posted 06 June 2012 - 02:28 PM

The bigger risk is with burried runs that could have a surge induced from a cloud-to-ground strike.

#5 DELInstallations

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Posted 06 June 2012 - 05:32 PM

The bigger risk is with burried runs that could have a surge induced from a cloud-to-ground strike.


Sounds like you are referring to lightning?

In a buried run, there's only so much you can do, and by surging the data on each end and making sure the potential is equal on each end of the run, that's about the best you can really hope for. For the alarm panel, each service it touches should be surged and equalized and bonded to the same electrical ground. The panels tend to take the most damage when unmatched grounds are connected and creates voltage potential between the device and that particular ground.

There's only so much you can do when it comes to lightning, I've seen it strike fiber and cause havoc, not because it was conducted by the glass, but by the ickypuck in the loose tube of the fiber. Lightning will do funny and strange things, even to non-conductors. as I've also seen empty pipes blown apart by a hit that was close enough. Can't predict what hundreds of thousands of volts and amps can do.

For the OP, in the case of devices on the fringe, there's only so much you can do unless you want to start putting transorbs or similar on the lines, and by the same token, where does one stop putting suppression on vs. practicality.

#6 video321

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Posted 06 June 2012 - 09:24 PM

I agree... it's risk vs. loss. For that it makes sense to install an input expander and surge that - contacts are too cheap to go through the expense to protect individually. Hell... for the price of the data line surge protection vs. an input expander I may even choose to protect only the panel side and roll the dice on the shed. Using metallic conduit, grounded at both ends, will help too.

#7 ecborgoyn

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Posted 07 June 2012 - 11:05 AM

Thanks for the ideas and discussion.

The buried conduits are PVC and too much effort to change to metal.

I'll be adding SPD's on the existing AC feeder circuits between the house and shed. One more question: I have a feeder circuit FROM the house service entrance panel out to a sub-panel in the shed. I have an SPD on the main service entrance panel. I believe that I should install an SPD at the sub-panel in the shed. But do I need an additional SPD on the feeder circuit in the house? Likewise, I have a feeder circuit from a genset 'service entrance' panel in the shed into a sub-panel in the house. I'm thinking that I NEED an SPD at the sub-panel in the house. Should I also have and SPD on the feeder line at the shed? I suppose the shed SPD would protect the genset itself.... I know, I know, I should be asking folks in an 'electrical forum', but you folks might have opinions....

I will be adding an SPD for a POTS telephone line to the shed. I will also be installing an Elk expander module in the shed and have an SPD at least at the panel/house side. If I ever add additional bus devices (like output expanders) at the shed I should probably invest in an SPD there also....

Lots of $$'s for SPD's for a few lines to/from the shed.... I need to do some SPD shopping.....

#8 Ira

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Posted 07 June 2012 - 11:46 AM

... then put a pair of DTK-LVLP's on each end...


I too need to install protection for an underground databus line to a separate building. Ditek says the DTK-LVLP minimum wire gauge is 22. Since my underground cable is 24 gauge cat5e, should I use the DTK-MRJ45 (already have RJ45 plugs on both ends) instead of the DTK-LVLP?

Thanks,
Ira

#9 DELInstallations

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Posted 08 June 2012 - 05:12 PM

I agree... it's risk vs. loss. For that it makes sense to install an input expander and surge that - contacts are too cheap to go through the expense to protect individually. Hell... for the price of the data line surge protection vs. an input expander I may even choose to protect only the panel side and roll the dice on the shed. Using metallic conduit, grounded at both ends, will help too.


For the cost of 2 Diteks, it's really a trivial item vs. blowing an expander, and most likely a keypad, since that would be a typical small remote building install, IMO. If there's fire involved, while it may not be enforced on retrofits, it is specified within code that the lines must be surged wherever they enter/leave a building.




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