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popa_englezu
09-11-2012, 08:27 PM
hi,
im new to this industry and would like to find out on what pressure a lp switch breaks the contact and at what pressure does a hp switch make or brake on airdale air conditioning units.
thx a lot

Brian_UK
10-11-2012, 01:28 AM
It depends on the refrigerant being used and also the usage of the pressure switches, control or on/off.

popa_englezu
11-11-2012, 06:57 PM
It depends on the refrigerant being used and also the usage of the pressure switches, control or on/off.

the refrigerant used is r407c and the use of lp/hp switch is only to switch off the compressor

hookster
11-11-2012, 07:37 PM
R407c is a blend of several other base components, most notably R134a. R407c does not evaporate at a fixed point relative to the temperature and pressure of the refrigerant its "Glide".

If you want to progress further in this industry I would recommend you get a simple refrigerant comparator.
Or print this for us old school guys or smart phone it for the guys of the future http://www.agas.com/upload/product/071203033235_1074.pdf

A "normal" LP condition minimum is 2.6 bar(g) but I would advise you to check your operating conditions and what you are trying to achieve.

When adjusting HP be sure that the high pressure setting does not exceed the receiver’s maximum service pressure. "normal" expected conditions would probably be 26 bar(g).

I am assuming you have a manifold gauge and can use this? When doing a maintenance task on a piece of equipment it is useful to connect your gauges and vary your conditions (set point) and observe the changes with relation to the comparator.

popa_englezu
12-11-2012, 04:12 PM
i think im being very misunderstood.the pressure switch looks like a very fat battery and is connecter to a screder valve and has 3 wires comin out of it so there is nothing to adjust.they either make or break the contact.they are used in series bfor the they pull the contactor to give power to the compressor.

monkey spanners
12-11-2012, 05:06 PM
hi,
im new to this industry and would like to find out on what pressure a lp switch breaks the contact and at what pressure does a hp switch make or brake on airdale air conditioning units.
thx a lot

The pressures the switches operate at are the ones they are adjusted to (if adiustable type and working correctly) or the pressures there were manufactured to work at in the case of non adjustable types.

On the adjustable type there is a visible scale and a pointer to give an indication of the switching pressures. (one exception being the Alco square plastic ones which i think you can adjust with a 2mm allen key, but they are best thrown in the bin as they are ****)

They fixed ones which are smaller than the Alco and are generally round have the settings maked on the body though they will likely have weathered away by now.

Monkeys pressure switch vid...

http://www.youtube.com/watch?v=1upnU9xRFOg

http://www.youtube.com/watch?v=cTjo2icR6A0&feature=fvwrel

hookster
12-11-2012, 10:39 PM
That sounds like the pressure transducer to me!
It will be giving typically a 4-20ma signal back to the electronic controller, this is then scaled to represent the pressure range.

Trying getting details off the item when posting to make identifying easier.

Brian_UK
13-11-2012, 12:19 AM
Fixed settings on those devices, read the label fixed to them or the unit technical manual.

Greed4Speed
15-11-2012, 10:58 AM
I have my own question regarding lp/hp switch, didn't want to start a new thread, throughout it would be a good idea to keep everything in one place.
I've got a refco lp/hp switch, was given to me by someone at work who knew I needed one. What I would like to know is how to wire it. It would be installed in the second stage of a dual stage cascade cpu unit hopefully to cut power if high side pressure get too high.
The switch already came with a cable connected, I can't make sense of how it would be connected to my setup. Hope you guy's can help as I am absolutely hopeless with electrics, see photo.9748

hookster
15-11-2012, 05:30 PM
Check the pressure scale on the switch to check if it is HP or LP i.e. do not use a LP for HP control (sorry if this is a suck eggs)
That unit is probably wired normally closed but check with your multi meter. continuity between blue brown N.C
If you want N.O measure between spare terminal and wired terminals.
Electrical ratings: the electrical rating of the switch is 16A 250V~ N.O. or N.C

Need a bit more information as to wiring diagram for best fit.

monkey spanners
15-11-2012, 06:13 PM
Is there a diagram on the cover?

Two terminals are live in and live out, the other two are for warning lights, one for lp trip the other for hp trip, not sure which though.

Greed4Speed
16-11-2012, 06:25 AM
Check the pressure scale on the switch to check if it is HP or LP i.e. do not use a LP for HP control (sorry if this is a suck eggs)
That unit is probably wired normally closed but check with your multi meter. continuity between blue brown N.C
If you want N.O measure between spare terminal and wired terminals.
Electrical ratings: the electrical rating of the switch is 16A 250V~ N.O. or N.C

Need a bit more information as to wiring diagram for best fit.

There is continuity between the terminals and no continuity when I apply high pressure (OFN).


Is there a diagram on the cover?

Two terminals are live in and live out, the other two are for warning lights, one for lp trip the other for hp trip, not sure which though.

Ahh, I get it now, thanks for your help, it's actually very simple (face palm!!!)

Greed4Speed
16-11-2012, 12:40 PM
All working now, thanks. Was very simple, like how you said monkey spanners, one terminal was live in and the other live out, plus another to ground on the chassis. Don't need the lamp for the moment.