# How to distribute power in a ceiling grid

#### djsfantasi

Joined Apr 11, 2010
7,927
Simple (I think) question here.

I have a 5,000 sq.ft. area within which I need to be able to provide 24VDC to 10-12 locations. Each location is one-half of a 12’ wide hexagon. But these pairs of power supplies can be anywhere on a hexagonal grid with 5’ sides covering a 5,000 sq. ft. area.

My question is, should I run 110 VAC outlets to each location or centrally mount 24VDC and distribute 24VDC. The latter appeals to me because of the ease of distributing 24 VDC versus distributing 110 VAC?

#### djsfantasi

Joined Apr 11, 2010
7,927

I will be powering several groups consisting of two locations approximately 5’ apart. There are 6-12 groups in a 5,000 sq.ft. area.

Hope this helps.

#### MisterBill2

Joined Jan 23, 2018
9,866
An important factor in this decision is how much current is required and how much regulation is needed. That will determine the economics and the wire sizes, What are the ratings of the intended power supplies, and what are the loads, and will the voltage be regulated. Another consideration is about switching the 24 volts on and off: Will it be switched or will it be on constantly? And finally, will the installation be portable, permanent, or fixed in specific locations?

Joined Jul 18, 2013
23,943
Without knowing all the exact details, I would be leaning toward the 24vdc distribution method.
The alternative would appear to require multi DC power supplies which typically would require extra cost?
Max.

#### Bordodynov

Joined May 20, 2015
2,939
For 110 V the required current diameter can be half as thin. The thickness of the wire is determined by the current through the wire. This is why you are asked about the load. If the load is not large, a 24 V voltage distribution is a natural option. Since I assume you will be using a 24 V stabilized adapter, it allows you to use a thinner wire for 110 V.

#### Sensacell

Joined Jun 19, 2012
2,919
Without knowing the power level required at each point- no meaningful answer is possible.

#### geekoftheweek

Joined Oct 6, 2013
712
5000 sq ft is a good sized area to cover. Maybe a combination of the two would be a thought. Three or four "central" locations for 110 and spread the 24 volts from those. What are you powering with the 24 V? Even though it probably shouldn't be a problem I'm wondering about losses and outside interference running 24 V over a large area.

#### Janis59

Joined Aug 21, 2017
1,357
Nowadays fashion for Labs are suggesting to make a drillings in the ceiling every 1.5 meters a one - like optical tables have each 2 inches the one drilling. Then where one wants tracing for the current work project, there he is hanging the tall screw-rod with screen-shelf, that is a product of about 2...3 mm thick steel rods welded dish-like screen with 1.5 m long, 10-20 cm wide and 1-5 cm high sizes. Thus, may hang this shelf-channel-screen in the ceiling and trace by it Your cabling and other input lines. Typical heigth for the shelves are about 2.20-2.50 m

Two giant benefits is obtained by this -
1) all the cabling are connected to machinery "from above", thus no disturbing and/or injurable bumps must happen on the floor.
2) When project is shifted and instead of work-machine some another machines are installed or added, all the job is reduced to screw new downhanged shelf of new trace for the old, and cabling - thus half day and new machine is online.

Of course all the other installations are going by those hanged shelf too, the cold and hot water, cooling, pressed air etc etc. Illustration for how it looks at https://bpgroup.lv/s/?sgrp=Z0000008285

Next and contradicting ideology speaks about false-ceiling / hanged ceiling , most often the regyps plaster board made. There the tracing from above is the well option too, but the problem is how to throw the new cable to designed regyps hole. Because often the ceiling may not keep the human weight and there are hardly too small vertical placement until the black ceiling.

Some American factory builders told me they educated a cat to overreact on the mice-style hissing. One worker is knotting the fishing thread to the cat`s tail and pushing this cat into ceiling hole. Another worker is making the mice-sound in designated hole, where cat is then extracted and feed, and thread is de-knotted. Then by thread they pull in the elastic steel-wire (tross) and by tross they pull in the heavy cable. Have yet no knowledge how the animal rights activists are looking on such technique.

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#### MisterBill2

Joined Jan 23, 2018
9,866
For 110 V the required current diameter can be half as thin. The thickness of the wire is determined by the current through the wire. This is why you are asked about the load. If the load is not large, a 24 V voltage distribution is a natural option. Since I assume you will be using a 24 V stabilized adapter, it allows you to use a thinner wire for 110 V.
When installing mains level wiring there are many requirements for safety, and so selecting the wire size based on planned currents is not normally accepted as a wise choice, and in addition it would probably result in a fire if there is an overload.

No mention is made by the TS as to the use or function of the area, and while "current fashion" may affect the choices for some applications it is certainly NOT universally good advice.

So, repeating what has been stated several times already, more information isneeded, and until it is provided by the TS there is no reason for additional guesses.

Joined Jul 18, 2013
23,943
It would seem to me that distributing 24vdc would be preferable than installing a 120vac to DC conversion at every outlet?
Just one of a few reasons.
Max.

#### MisterBill2

Joined Jan 23, 2018
9,866
It would seem to me that distributing 24vdc would be preferable than installing a 120vac to DC conversion at every outlet?
Just one of a few reasons.
Max.
Max, which arrangement is best depends mostly on information that we have not been given.

#### djsfantasi

Joined Apr 11, 2010
7,927
The load is a DSS system, 24i, from Holosonics. It’s max power draw is 50W, @Sensacell. There will be 24 units mounted in the ceiling. The 24VDC will be on all the time.
There will be no wiring from the ceiling to the floor. The power supply(/ies) will be powered from the ceiling. There is no secondary ceiling. Everything will be attached to a ceiling grid. @jpanhalt, this should answer your question. It’s not a plenum application.

Someone asked about the use of the area. It’s approximately 5,000 sq.ft. and will hold approx. 1,000 people.

@MisterBill2, the installation is a hybrid of permanent and portable. The location of the DSS speakers will move monthly within the 5,000 sq.ft. area

#### MisterBill2

Joined Jan 23, 2018
9,866
Based on this additional information it seems that a set of rows of mains outlets will provide the best flexibility in the locating of the devices. Presuming that the shape is rectangular, with the main feed for the branches running close to the center of the longer direction, all of the branches can run at right angles crossing the center feeder. That will require the minimum of wiring and provide the maximum of reliability, short of having redundant wires. So there will be separate DC supplies, each needing a reasonable (standard length) line cord.
The secondary benefit is that all of the installation will be able to satisfy an electrical inspector as being a "normal" application of standard wiring materials. Any form of DC distribution gets some inspectors terribly confused.

#### djsfantasi

Joined Apr 11, 2010
7,927
@MisterBill2 What you’re saying is that I wire 110 outlets, in a grid over the space. And from those outlets, I plug my 24VDC power supplies.

From past experience, the Fire Marshall have a major problem with anything electrical.

Will the inspector have an issue of 24VDC cables mixed in with 110VAC cables? This scheme was envisioned to solve that problem.

Let’s forget the ceiling for a second. Imagine 24 laptops on the floor, in an apparent random manner (In fact, pairs of laptops are w/in 5’ of each other)

Now, each laptop has a power brick. I need to connect the brick to the laptop(speaker) to 110VAC.

(Note, my example is not so far fetched. I WILL have the same problem on the floor)

#### MisterBill2

Joined Jan 23, 2018
9,866
An electrical installation done according to the local codes, inspected and passed, should be acceptable to most educated fire marshals. The challenge of distribution at the 24 volt DC level is that for a given wattage you have about 5 times the current, downstream from the regulated supply output. So hot connections are more likely and probably larger wires would be required.
Wiring adequately attached to a ceiling is out of the way and thus not likely to be damaged, poses no trip hazard, and keeps any problem or failure in plain view.
In addition, some laptops demand that only the OEM power supply will be accepted as a usable power source. I have both an HP and a Dell so afflicted. For that kind you MUST have an individual power supply.

#### djsfantasi

Joined Apr 11, 2010
7,927
An electrical installation done according to the local codes, inspected and passed, should be acceptable to most educated fire marshals. The challenge of distribution at the 24 volt DC level is that for a given wattage you have about 5 times the current, downstream from the regulated supply output. So hot connections are more likely and probably larger wires would be required.
Wiring adequately attached to a ceiling is out of the way and thus not likely to be damaged, poses no trip hazard, and keeps any problem or failure in plain view.
In addition, some laptops demand that only the OEM power supply will be accepted as a usable power source. I have both an HP and a Dell so afflicted. For that kind you MUST have an individual power supply.
Thanks for your reply. I used laptops as an example because I anticipated DSS’ at 24VDC would not be a familiar application.

What I am getting from your comments is that a mix of 120VAC
and 24VDC (or low voltage power supplies in general) is not an issue for the inspectors.

Given that understanding,I could parallel two loads with one supply and not worry. The floor is a little trickier as I have to parallel a network switch and sound mixer power supply and possibly need parallel power for multiple sets. On second thought, that could occur in the ceiling as well.

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#### MisterBill2

Joined Jan 23, 2018
9,866
Thanks for your reply. I used laptops as an example because I anticipated DSS’ at 24VDC would not be a familiar application.

What I am getting from your comments is that a mix of 120VAC
and 24VDC (or low voltage power supplies in general) is not an issue for the inspectors.

Given that understanding,I could parallel two loads with one supply and not worry. The floor is a little trickier as I have to parallel a network switch and sound mixer power supply and possibly need parallel power for multiple sets. On second thought, that could occur in the ceiling as well.
Equipment mounted to the ceiling is seldom tripped over or stepped on. AND it is not usually a trip hazard, Plus, mostly, it is not in the way. So there are real advantages.