Short circuit test

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Hi I need help on electrical testing boiler parts and was wondering if anyone would tell me how to test for a ' short circuit on an APS' using a multimeter??? And what readings to look for, this is the only test that I struggle with?

Any replies would be great thanks.
 
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What are you on about? Just look at the switch and you will see usually 3 terminals, Common, normally closed. normally open. Are you referring to resistance readings? How can you possibly struggle with a simple switch.
 
I understand and know how to test a simple switch mate but in the MF instructions it says to test the aps for short circuit,was just wondering what it meant or if anyone new?
 
The Term "Short Circuit" has no relevance with regard an APS you are checking for CONTINUITY with the switch at rest you are looking for continuity between Com and NC (as near to zero ohms as possible)
with the APS active i.e pressure or suction applied, you are looking for Continuity between Com & NO
and it is as simple as that - it goes without saying that all sources of electrical potential should be removed from the switch before testing!! ;)
 
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The Term "Short Circuit" has no relevance with regard an APS you are checking for CONTINUITY with the switch at rest you are looking for continuity between Com and NC (as near to zero ohms as possible)
with the APS active i.e pressure or suction applied, you are looking for Continuity between Com & NO
and it is as simple as that - it goes without saying that all sources of electrical potential should be removed from the switch before testing!! ;)

Which terminal is which, the last one i saw had no markings on it.
 
Hi I need help on electrical testing boiler parts and was wondering if anyone would tell me how to test for a ' short circuit on an APS' using a multimeter??? And what readings to look for, this is the only test that I struggle with?

Any replies would be great thanks.

Remove mains from the appliance

Remove the connector at the pcb and measure at that connector. If you do this, you are measuring the loom AND APS i.e. what the pcb actually sees

If you can remove the other end of one of the neoprene pipes going to the APS, do so (you need to be able to suck or blow down it to operate the APS)

Get your multimeter and short the probes togetherto check the resistance of the probes


check the resistance (at the pcb connector) of the normally closed to common contacts should be in the order of an ohm or less

GENTLY suck or blow on the neoprene tube so that the membrane in the APS activates the APS microswitch

Kink the tube so that it maintains pressure (doing this will also test for a rupture inthe membrane) and after a couple of seconds measure the resistance (at the pcb) of the normally open to common contacts , again, ideally should be less than an ohm

That's it

Other than the changeover pressure, which is factory set, that's it tested

contacts on trhe microswitch are written on the side of the switch itself

n /c, n/o, com
 
The Term "Short Circuit" has no relevance with regard an APS:

well, yes it does

Short circuit is the correct term.

Continuity just means that its not open circuit - that there is a conductive path. It's a term used by those who do not have the correct equipment or who don't understand how to use it
 
well, yes it does

Short circuit is the correct term.

Continuity just means that its not open circuit - that there is a conductive path. It's a term used by those who do not have the correct equipment or who don't understand how to use it

Well, no it doesn't

A short circuit relates to an accidental link between to points of different electrical potential.... Not related to an APS....
 
A SHORT CIRCUIT is a reference to a FAULT CONDITION i.e Live to earth or Live to Neutral :rolleyes: CONTINUITY is what you are looking for through a control Circuit such as an APS etc ;)
 
well, yes it does

Short circuit is the correct term.

Continuity just means that its not open circuit - that there is a conductive path. It's a term used by those who do not have the correct equipment or who don't understand how to use it

Well, no it doesn't

A short circuit relates to an accidental link between to points of different electrical potential.... Not related to an APS....

No, it might be what they teach RGIs who don't understand electrics, but a short circuit means only that there is no (measurable) resistance between two points, continuity means that there is little or no resistance between two points. So, for example if a pair of relay contacts are not that good, say a few 10s of ohms, then you have continuity between the tow, but not a short circuit.

If two points that are not meant top be connected have GONE short circuit, then you would be correct.

I do find it worrying that you have survived so long without really understanding what the terms mean
 
I think we will have to agree to disagree on this point!!
(so much for my electrical/Mechanical apprenticeship then!!) :LOL:
 
con·ti·nu·i·ty/ˌkäntnˈ(y)o͞oəitē/Noun:

1.The unbroken and consistent existence or operation of something over a period of time.
2.A state of stability and the absence of disruption.


short cir·cuit Noun:
In a device, an electrical circuit of lower resistance than that of a normal circuit, typically resulting from the unintended contact of...


Verb: (of an electrical device) Malfunction or fail, or cause to do this, as a result of a short circuit across it.
 
You can have a short circuit phase to phase or phase to neutral or phase to earth or neutral to earth, so its possible to have a short between the connections in an air pressure switch, this is my understanding of it anyway.
 

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