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Thread: Pressure switch NO and NC
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19-09-2011, 06:46 PM #1
Pressure switch NO and NC
Is there a trend at all towards using either normally open or closed HP an LP switches amongst different manufacturers or from different parts of the world? Just curious.
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19-09-2011, 07:05 PM #2
Re: Pressure switch NO and NC
Logically a safety circuit would be NC failing to NO on a rise above the HP setpoint.
Likewise NC failing to NO on drop in pressure below the LP setpoint.
The NO circuit can be wired up to a alarm, be it a fault lamp or software imput.
Or to put it another way HP switches break the circuit on rise in pressure and LP switches break the circuit on a drop in pressure.
I cannot think of any that work the other way around?
Grizzly
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19-09-2011, 07:18 PM #3
Re: Pressure switch NO and NC
I ask the question because i use a lot of temperature controls where either NO or NC can be used and I wondered if the same was true for refrigeration,
Thanks Grizzly
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19-09-2011, 10:26 PM #4
Re: Pressure switch NO and NC
Unless some wotsit wires it the other way and I spend hours trying to work out why it keep going off on lp.... but dont tell no-one they may laugh
Regards Chillerman
Last edited by chillerman2006; 19-09-2011 at 10:28 PM.
If the World did not Suck, We would all fall off !
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19-09-2011, 10:32 PM #5
Re: Pressure switch NO and NC
on ranco pressure switches there a diagram for the correct connections-normally closed under normal operation 1,3
2 and 4 for high,low pressure-(based on a dualtype) once connected to a system test for continuity before wiring
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19-09-2011, 10:43 PM #6
Re: Pressure switch NO and NC
have posted a few links to help you Mike
heres the link you want https://docs.google.com/viewer?a=v&p...yNDBh&hl=en_GB
and heres the others
http://www.refrigeration-engineer.co...Tips&highlight=
http://www.refrigeration-engineer.co...tins&highlight=
Hope that helps mate
Regards ChillermanLast edited by chillerman2006; 19-09-2011 at 10:48 PM. Reason: put wrong link ! Der !!
If the World did not Suck, We would all fall off !
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19-09-2011, 10:50 PM #7
Re: Pressure switch NO and NC
I have no idea how you manage to find all these references so quickly.................takes me forever
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19-09-2011, 10:52 PM #8
Re: Pressure switch NO and NC
It is a good practice to wire all digital inputs close on go, and open on no-go.
This is especially true when DI are status contacts fed back from relays. When the coil falls (e.g. power failure), the digital input opens.
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19-09-2011, 11:20 PM #9
Re: Pressure switch NO and NC
there all tagged on
www.myhard-drive.com
Regards Chillerman
If the World did not Suck, We would all fall off !
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19-09-2011, 11:23 PM #10
Re: Pressure switch NO and NC
Yeah your right mate
its just when someone wires them wrong and trys to set up the switch
you get breakdown or commissioning...cutting out lp
you put gauges on... think...thats not set right
you dont expect wires wrong way round and just keep thinking, why cant I make it workIf the World did not Suck, We would all fall off !
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19-09-2011, 11:30 PM #11
Re: Pressure switch NO and NC
CM
"there all tagged on
www.myhard-drive.com"
Can't seem to locate that drive, is it close to mydocuments.com?
alMostly found in the southern part of this green and pleasant land.
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19-09-2011, 11:37 PM #12
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20-09-2011, 04:19 AM #13
Re: Pressure switch NO and NC
sneaky guy, ya had him searching for it.................
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25-09-2011, 10:31 AM #14
Re: Pressure switch NO and NC
Most thermostats are configured so that the contacts close to enable the action, either heating or cooling. This makes the system fail safer, as a fault that disables the controller will stop the action ( no cooking of the baby chicks or freezing the room into a block of ice) and fail to room temperature. Safety circuits are wired in series with the wire to the contactor, so that any of those faults result in the same action.
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25-09-2011, 12:28 PM #15
Re: Pressure switch NO and NC
Yes, I know they are in series, same for all heating systems I work on but in a lot of control circuits we can have the switch one pump on while another turns off, for example, so it is not guaranteed to be NO, same as any relay. The pressure switches I am thinking of are 2 wire so it is hard to screw it up when wiring it.
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25-09-2011, 01:09 PM #16
Re: Pressure switch NO and NC
If the World did not Suck, We would all fall off !