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Home > Archive > Electrical Engineering > April 2006 > How do you NOT an AC circuit?
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How do you NOT an AC circuit?
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| AgarGuest 2006-04-19, 2:21 pm |
| Someone help!
I have what appears to be a simple problem, but i can't find a solution
anywhere.
Using a 120V AC switch, how do you NOT the output. When the switch is
open, the output is on and when the switch is closed the output would
be off.
The problem...I have a closet full of computer equipment and i can't
close the door or the machines will over heat. so i installed a
bathroom ceiling fan, that vents the closet, but its always on. So i
want to add a thermostat to it. A cheap 120V AC baseboard heater
thermostat is perfect except it completes the circuit when the room is
cold not hot.
The applied use of this solution would be to NOT the output of a
regular 120V AC baseboard heater thermostat to a common 120V AC
bathroom exhaust fan.
A relay should be used? Or is there a baseboard heater controller that
has reverse outputs?
Signed...
I want to close my closet!!
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| sQuick 2006-04-19, 3:21 pm |
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"AgarGuest" <agarguest@gmail.com> wrote in message
news:1145466913.758882.190350@t31g2000cwb.googlegroups.com...
> Someone help!
>
> I have what appears to be a simple problem, but i can't find a solution
> anywhere.
>
> Using a 120V AC switch, how do you NOT the output. When the switch is
> open, the output is on and when the switch is closed the output would
> be off.
>
> The problem...I have a closet full of computer equipment and i can't
> close the door or the machines will over heat. so i installed a
> bathroom ceiling fan, that vents the closet, but its always on. So i
> want to add a thermostat to it. A cheap 120V AC baseboard heater
> thermostat is perfect except it completes the circuit when the room is
> cold not hot.
>
> The applied use of this solution would be to NOT the output of a
> regular 120V AC baseboard heater thermostat to a common 120V AC
> bathroom exhaust fan.
>
> A relay should be used? Or is there a baseboard heater controller that
> has reverse outputs?
>
> Signed...
> I want to close my closet!!
>
Get a cooling thermostat not a heating one.
sQuick..
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| Charles Perry 2006-04-19, 5:21 pm |
|
"sQuick" <squickdrill@hotmail.com> wrote in message
news:1145468115.5531.0@echo.uk.clara.net...
>
> "AgarGuest" <agarguest@gmail.com> wrote in message
> news:1145466913.758882.190350@t31g2000cwb.googlegroups.com...
>
> Get a cooling thermostat not a heating one.
>
> sQuick..
Dang. I was going to suggest that!
Buy one for an attic vent fan.
Charles Perry P.E.
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| Robbie Mayhem 2006-04-19, 5:21 pm |
|
"AgarGuest" <agarguest@gmail.com> wrote in message
news:1145466913.758882.190350@t31g2000cwb.googlegroups.com...
> Someone help!
>
> I have what appears to be a simple problem, but i can't find a solution
> anywhere.
>
> Using a 120V AC switch, how do you NOT the output. When the switch is
> open, the output is on and when the switch is closed the output would
> be off.
>
> The problem...I have a closet full of computer equipment and i can't
> close the door or the machines will over heat. so i installed a
> bathroom ceiling fan, that vents the closet, but its always on. So i
> want to add a thermostat to it. A cheap 120V AC baseboard heater
> thermostat is perfect except it completes the circuit when the room is
> cold not hot.
>
> The applied use of this solution would be to NOT the output of a
> regular 120V AC baseboard heater thermostat to a common 120V AC
> bathroom exhaust fan.
>
> A relay should be used? Or is there a baseboard heater controller that
> has reverse outputs?
>
> Signed...
> I want to close my closet!!
>
You could always wire it through a normally closed relay contact and connect
the relay coil to the switch i.e. switch open, contacts closed and vise
versa.
Rob
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| electrician@electrician2.com 2006-04-20, 2:21 am |
|
<<The problem...I have a closet full of computer equipment and i can't
close the door or the machines will over heat. so i installed a
bathroom ceiling fan, that vents the closet, but its always on. So i
want to add a thermostat to it. A cheap 120V AC baseboard heater
thermostat is perfect except it completes the circuit when the room is
cold not hot. >>
Try this cooling thermostat for line voltage for $59.95.
Honeywell Line Voltage 120V model T651A 3018 - For Cooling
http://www.honeywell-thermostat.com.../T651A3018.html
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| Bud-- 2006-04-20, 12:21 pm |
| AgarGuest wrote:
> great tips.
>
> Would this be just a good as the Honeywell?
>
> http://www.broan.com/display/router.asp?ProductID=2954
>
> and its only $19.00
>
Broan gives a rating of 120, 250, 277 VAC; 22 Amp capacity
It would be nice to have a HP rating.
It should be OK at 11 Amps for a motor, which is around 1/2 HP, which is
probably larger than you are using.
bud--
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| electrician@electrician2.com 2006-04-20, 1:21 pm |
| For the last several years I worked for a major West Coast Control
Contractor. We used lots of honeywell thermostats for industrial and
commercial jobs. I do not recall using Broan. We had good luck with
Honeywell. Of course, I just installed them, I did not design the
systems.
| |
| newsman 2006-04-21, 2:21 pm |
| You don't say don't say where you installed the ceiling fan. If it's
really in the ceiling, you should be aware that it may be a code
violation to vent directly into that attic space, and you may need a
roof vent. This is certainly true for bathrooms and range hoods. A
closet? I dunno. You could claim its like a whole house fan and maybe
get away with it. You should also check that the air entry space to the
closet(usually under the door) has enough area to accomodate the air flow.
AgarGuest wrote:
> Someone help!
>
> I have what appears to be a simple problem, but i can't find a solution
> anywhere.
>
> Using a 120V AC switch, how do you NOT the output. When the switch is
> open, the output is on and when the switch is closed the output would
> be off.
>
> The problem...I have a closet full of computer equipment and i can't
> close the door or the machines will over heat. so i installed a
> bathroom ceiling fan, that vents the closet, but its always on. So i
> want to add a thermostat to it. A cheap 120V AC baseboard heater
> thermostat is perfect except it completes the circuit when the room is
> cold not hot.
>
> The applied use of this solution would be to NOT the output of a
> regular 120V AC baseboard heater thermostat to a common 120V AC
> bathroom exhaust fan.
>
> A relay should be used? Or is there a baseboard heater controller that
> has reverse outputs?
>
> Signed...
> I want to close my closet!!
>
| |
| electrician@electrician2.com 2006-04-21, 3:21 pm |
| <<You don't say don't say where you installed the ceiling fan. If it's
really in the ceiling, you should be aware that it may be a code
violation to vent directly into that attic space, and you may need a
roof vent. This is certainly true for bathrooms and range hoods. A
closet? I dunno. You could claim its like a whole house fan and maybe
get away with it. You should also check that the air entry space to
the
closet(usually under the door) has enough area to accomodate the air
flow. >>
You are correct, air in must equal air out or air out must equal air
in. Where is the air (and heat) going? And what about filters?
Then there is makeup air, exhaust air, return air, and outside air, and
air balancing. HVAC can become more involved than the electrical
requirements. I have seen computer room HVAC systems that are
incredibly complicated. One of the more complicated that I inspected
about 15 years ago was the Cray computer room at the university of
Alaska Fairbanks. Talk about heat transfer. Did you know that a Cray
computer is liquid cooled and has its very own internal fire alarm
system and uses two stage cooling to get the heat to the outside air.
The Cray guy like to have gone into shock when I wrote up his computer
for not being listed. Yeah, Cray computers are not listed by UL. I
wonder how much that would cost. I later tore up the inspection report
after he gave me a personal tour of the Cray computer. I was simply
overwhelmed.
And how about the computer room requirements in the NEC. There is a
whole Article on computer rooms, and that is what the gentleman is
proposing: a computer room or as it is now called, and Information
Technology Room. Take a look at Article 645 copied below:
from 2005 NEC
ARTICLE 645
Information Technology Equipment
645.1 Scope. This article covers equipment, power-supply
wiring, equipment interconnecting wiring, and grounding of
information technology equipment and systems, including terminal
units, in an information technology equipment room.
FPN: For further information, see NFPA 75-2003, Standard
for the Protection of Information Technology Equipment.
645.4 Special Requirements for Information Technology
Equipment Room. This article shall apply, provided
all of the following conditions are met:
(1) Disconnecting means complying with 645.10 are provided.
(2) A separate heating/ventilating/air-conditioning (HVAC)
system is provided that is dedicated for information
technology equipment use and is separated from other
areas of occupancy. Any HVAC system that serves
other occupancies shall be permitted to also serve the
information technology equipment room if fire/smoke
dampers are provided at the point of penetration of the
room boundary. Such dampers shall operate on activation
of smoke detectors and also by operation of the
disconnecting means required by 645.10.
FPN: For further information, see NFPA 75-2003, Standard
for the Protection of Information Technology Equipment,
Chapter 10, 10.1, 10.1.1, 10.1.2, and 10.1.3.
(3) Listed information technology equipment is installed.
(4) The room is occupied only by those personnel needed
for the maintenance and functional operation of the
installed information technology equipment.
(5) The room is separated from other occupancies by fireresistant-
rated walls, floors, and ceilings with protected
openings.
FPN: For further information on room construction requirements,
see NFPA 75-2003, Standard for the Protection
of Information Technology Equipment, Chapter 5.
645.5 Supply Circuits and Interconnecting Cables.
(A) Branch-Circuit Conductors. The branch-circuit conductors
supplying one or more units of a data processing
system shall have an ampacity not less than 125 percent of
the total connected load.
(B) Cord-and-Plug Connections. The data processing system
shall be permitted to be connected to a branch circuit
by any of the following listed means:
(1) Flexible cord and attachment plug cap not to exceed
4.5 m (15 ft).
(2) Cord set assembly. Where run on the surface of the
floor, they shall be protected against physical damage.
(C) Interconnecting Cables. Separate data processing units
shall be permitted to be interconnected by means of listed
cables and cable assemblies. Where exposed to physical damage,
the installation shall be protected by approved means.
(D) Under Raised Floors. Power cables, communications
cables, connecting cables, interconnecting cables, and receptacles
associated with the information technology equipment
shall be permitted under a raised floor, provided the
following conditions are met:
(1) The raised floor is of suitable construction, and the area
under the floor is accessible.
(2) The branch-circuit supply conductors to receptacles or
field-wired equipment are in rigid metal conduit, rigid
nonmetallic conduit, intermediate metal conduit, electrical
metallic tubing, electrical nonmetallic tubing,
metal wireway, nonmetallic wireway, surface metal
raceway with metal cover, nonmetallic surface raceway,
flexible metal conduit, liquidtight flexible metal
conduit, or liquidtight flexible nonmetallic conduit,
Type MI cable, Type MC cable, or Type AC cable.
These supply conductors shall be installed in accordance
with the requirements of 300.11.
(3) Ventilation in the underfloor area is used for the information
technology equipment room only, except as
provided in 645.4(2). The ventilation system shall be so
arranged, with approved smoke detection devices, that
upon the detection of fire or products of combustion in
the underfloor space the circulation of air will cease.
(4) Openings in raised floors for cables protect cables
against abrasions and minimize the entrance of debris
beneath the floor.
(5) Cables, other than those covered in (D)(2) and those
complying with (D)(5)(a), (D)(5)(b), or (D)(5)(c), shall
be listed as Type DP cable having adequate fireresistant
characteristics suitable for use under raised
floors of an information technology equipment room.
a. Interconnecting cables enclosed in a raceway.
b. Interconnecting cables listed with equipment manufactured
prior to July 1, 1994, being installed with
that equipment.
c. Cable type designations Type TC (Article 336);
Types CL2, CL3, and PLTC (Article 725); Type ITC
(Article 727); Types NPLF and FPL (Article 760);
Types OFC and OFN (Article 770); Type CM (Article
800); and Type CATV (Article 820). These designations
shall be permitted to have an additional letter P
or R or G. Green, or green with one or more yellow
stripes, insulated single conductor cables, 4 AWG and
larger, marked "for use in cable trays" or "for CT use"
shall be permitted for equipment grounding.
ARTICLE 645- INFORMATION TECHNOLOGY EQUIPMENT 645.5
2005 Edition NATIONAL ELECTRICAL CODE 70-515
FPN: One method of defining fire resistance is by establishing
that the cables do not spread fire to the top of the tray in
the "Vertical Tray Flame Test" referenced in ANSI/UL 1581-
2001, Standard for Electrical Wires, Cables, and Flexible
Cords. Another method of defining fire resistance is for the
damage (char length) not to exceed 1.5 m (4 ft 11 in.) when
performing the CSA "Vertical Flame Test - Cables in Cable
Trays," as described in CSA C22.2 No. 0.3-M-2001, Test
Methods for Electrical Wires and Cables.
(6) Abandoned cables shall be removed unless contained
in metal raceways.
(E) Securing in Place. Power cables; communications
cables; connecting cables; interconnecting cables; and associated
boxes, connectors, plugs, and receptacles that are
listed as part of, or for, information technology equipment
shall not be required to be secured in place.
645.6 Cables Not in Information Technology Equipment
Room. Cables extending beyond the information
technology equipment room shall be subject to the applicable
requirements of this Code.
FPN: For signaling circuits, refer to Article 725; for fiber
optic circuits, refer to Article 770; and for communications
circuits, refer to Article 800. For fire alarm systems, refer to
Article 760.
645.7 Penetrations. Penetrations of the fire-resistant room
boundary shall be in accordance with 300.21.
645.10 Disconnecting Means. A means shall be provided
to disconnect power to all electronic equipment in the information
technology equipment room. There shall also be
a similar means to disconnect the power to all dedicated
HVAC systems serving the room and cause all required
fire/smoke dampers to close. The control for these disconnecting
means shall be grouped and identified and shall be
readily accessible at the principal exit doors. A single
means to control both the electronic equipment and HVAC
systems shall be permitted. Where a pushbutton is used as a
means to disconnect power, pushing the button in shall
disconnect the power.
Exception: Installations qualifying under the provisions of
Article 685.
645.11 Uninterruptible Power Supplies (UPS). Except
for installations and constructions covered in 645.11(1) or
645.11(2), UPS systems installed within the information
technology equipment room, and their supply and output
circuits, shall comply with 645.10. The disconnecting
means shall also disconnect the battery from its load.
(1) Installations qualifying under the provisions of Article 685
(2) Power sources limited to 750 volt-amperes or less derived
either from UPS equipment or from battery circuits
integral to electronic equipment
645.15 Grounding. All exposed non-current-carrying
metal parts of an information technology system shall be
grounded in accordance with Article 250 or shall be double
insulated. Power systems derived within listed information
technology equipment that supply information technology
systems through receptacles or cable assemblies supplied as
part of this equipment shall not be considered separately
derived for the purpose of applying 250.20(D). Where signal
reference structures are installed, they shall be bonded
to the equipment grounding system provided for the information
technology equipment.
FPN No. 1: The bonding and grounding requirements in
the product standards governing this listed equipment ensure
that it complies with Article 250.
FPN No. 2: Where isolated grounding-type receptacles are
used, see 250.146(D) and 406.2(D).
645.16 Marking. Each unit of an information technology
system supplied by a branch circuit shall be provided with
a manufacturer's nameplate, which shall also include the
input power requirements for voltage, frequency, and maximum
rated load in amperes.
645.17 Power Distribution Units. Power distribution
units that are used for information technology equipment
shall be permitted to have multiple panelboards within a
single cabinet, provided that each panelboard has no more
than 42 overcurrent devices and the power distribution unit
is utilization equipment listed for information technology
application.
(Don't like to be one of those been there and done that kind of guys,
but when you are an old cuss like me you probably have been there and
done it.)
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