relay ptc

[milton]

hi all how to testate relay ptc thank all

[rdocwra]

Can you explain more about this PTC relay as i have never heard of it. What does it do, how many terminals, voltage, Make of unit ect. The only time i have heard of PTC is on Eliwell probes so am at a complete loss at the moment

Regards

Raymond

[rbartlett]

what they look like..

http://www.sparesrus.biz/ol-catlg/danfoss-start-01.htm

how it works (at the very bottom)

http://www.kwantlentrades.com/appliancerepair/archives.htm


cheers

richard

[Peter_1]

It goes mutch faster to install a new one rather then testing the PTC device and look if it's working properly.

You can also use a universal PTC starting device like a IC-G220 (from Ritchie i think).

[Bones]

its a solid state relay, generaly used on comps that dont stop/start alot of times in an hour.

Usualy i have found they burn out or blow... but it is not an expensive item by any means and i usually carry one in the truck with me... with all the other "things".

[milton]

thank all milton

[Peter_1]

Perhaps this one is better.

http://www.tecumseh-europe.com/M4/UK/p41.htm#AnchorI

[angryk]

PTC-positive temperature coefficient (resistor). Resistance increases with temp rise. NTC negative temperature coefficient (resistor), opposite of PTC.

[Peter_1]

I always was told that a PTC uses the same principle as a thermal relay (older bi metal system).
The Resistance wire is attached in series with both the starting and running windings. The tension of this wire, when cold, keeps both sets of contact points closed. While the current passes through, the resistance (PTC) wire heated and expands or stretches. At a predetermined time, the stretched wire opens the starting winding contacts. This also acts as a safety device in case of too much current.

[milton]

hi marc if capacitor to give defect ? relay work ? thank you

[DaBit]

The PTC is wired between Run and Start.

When the compressor is powering up, the PTC is cold, which gives it a resistance of about 25 Ohms. Thus, when starting, the compressor start winding gets current through it. The same current heats the PTC (within less than a second), which causes it's resistance to increase (to 10-30 kOhm), cutting the power from the start winding. The remaining current through the start winding keeps the PTC hot.

Motors which start this way (RSIR, Resistive start, Inductive run) cannot provide much torque due to lack of a start capacitor, so they are basically used in captube/fixed orifice systems.

So, how would you test a PTC? Connect a 100W light bulb in series with it (mains -> PTC -> light bulb -> mains return). The bulb should flash once when power is applied.

[DaBit]

Nothing forbids the use of a start capacitor in series with the PTC. If the motor design allows it, it will increase start torque due to the additional phase shift of the current passing through the start winding. I have used a PTC with a 80uF start capacitor in series to increase starting torque on a Danfoss NL11F R134a LBP compressor. This was necessary to use the compressor with a TEV instead of a captube.

[chemi-cool]

the small commercial compressors up to 1 hp can be bought with a standard start capacitor including danfoss as you can see here:
http://www.danfoss.com/Compressors/pdf/datasheets/r134a_220v_50_60hz/s-series/SC15F_R134a_220V_50Hz_08-03_Cd44h502.pdf

you can also get them with start capacitor, run capacitor and a sratring relay, all nicely boxed.

chemi

[milton]

hi chemi and all thank for help happy new year all good luck

[Dan]

Seems there was another thread in the past about using what we in the states sometimes refer to as "hard" and sometimes "soft" start kits. .. which are PTC relays sold as "universal" replacements to simplify truck stock rquirements. I always had my reservations about them.

These things are sold to replace potential relays and capacitors. I could never find a mirofarad rating for one. Also, I noticed that a PTC/start capacitor combination was not in the chart on the Tecumseh page.

More interesting to me is the other website showing their usage as linear motors and the many applications that they will appear in. It's already the New Year, hope its a good one for everybody.

[rbartlett]

yes i said to marc i was taught that they -ptc- were LST devices used with out a cap...

my brain says i have seen a ptc/cap on a unit but can't remember where/when..

if you look at the link chemi posted it shows a hst with a relay +cap and a Lst with a ptc -no cap



cheers

richard

[RogGoetsch]

PTC start is common on Manitowoc ice machines. (They are relatively inexpensive compared to start relays.) The hot gas valve is energized before start to ensure a low-torque start, eliminating the need for a start capacitor.

The control board also provides a start delay since the PTC needs a cool-down time to reset. It remains hot during the run cycle of the compressor. Don't touch.

[bernard]

positive temperature coefficient (solid state relay)

has no moving parts and at a ambient temperature will have a low resistance. when the system is energised both run and stert windings are in circuit and the motor begins to rotate. As the current is passing through the relay the temp of the relay will rise which increases the resistanceof the relay. when the resistance rises above a pre determined level the current passing through the start windings will have been reduced to such a point where it is only suffient to heat the relay. this will cause the start windings to come out of cicuit leving the motor on its run windings only.when the comp is disconected, enough time must be allowed for the relay to cool (low resistance) to allow full current to pass to the start windings

the P.T.C is a barium dipped titanite

[shogun7]

Better late then never:

In domestic refrigeration, relays using solid-state transistors, diodes, silicon controlled rectifiers, diacs, and triacs are now used to control starting of hermetic motors. Changes in voltage in the motor, as it starts and then gathers speed, are used to open the starting winding circuit at the correct time. In addition, these relays are not as sensitive to the size of the motor as other relays. For instance, the same solid-state relay can be used for motors varying from 1/12 to 1/3 hp

Now the solid-state positive temperature coefficient is also called a PTCR. It has a thermally operated overload protector and a capacitor. It operates like this: When the circuit is first energized the solid state relay has low resistance of about 3 to 12 ohms, and only the run and start windings are used to start the compressor (low torque) the run cap is bypassed at this time by the PTC.and has no function in starting the compressor. So when the PTC reaches a sufficient temperature IT changes to a very hi resistance of about 10 to 20K ohms. Which switches off the start windings. The run cap is now in series with the start windings and this gives the motor a better phase shift in running mode
Roger
:D

[bernard]

ptc the more you heat it the higher the resistance gets.

ntc the more more you heat it the lower the resistance gets for example a car battery, thats why they have a jacket on most new models. In winter espesially diesels it best to switch your lights on prior to starting.:D

[Bones]

ntc the more more you heat it the lower the resistance gets for example a car battery, thats why they have a jacket on most new models. In winter espesially diesels it best to switch your lights on prior to starting


I will remember to try that when it snows where i live, not that it has yet lol... or when it snows or i'm somewhere when it is snowing i'll steal diesel car and test it out hehe... i guess you learn something new everyday.

[Coolie]

Well, I had a look at Richards link to how it works and I'm still none the wiser :confused:

When the ptc is cold, there is a path for the current to follow.
As the motor gets up to a predeterminded speed (normally around 80%) the ptc heats up and expands, breaking the path for the current.
The ptc is obviuosly on the start winding, hence dropping the start winding, leaving the motor to run on the run winding.

I have a brilliant pic, but can't post it for some reason!?!

[Peter Mitchell]

Bernard good posts, you seem to have managed to keep away from the 502. He seems to have the best Idea of how these relays work. the drawing posted by Marc to me sugests that there are moving contacts between 5 / 1 and 6 / 3 ,there are no such contacts. The drawing is most likley done this way to enable you to easly change a curent relay for a new solid state relay
What hapens to the start capacitor ?

[Peter Mitchell]

I agree there must allways be a high resistance connection between 5 and 6
which keeps the ptc relay hot and there must be a period after switch off when the unit cannot start until the relay cool down

[Coolie]

Are we even correct in calling it a relay?
We just touched on these a few years ago when I was in college and I have not dealt with them since. But from what I can remember they are used not only as a starting device, but as a safety device too, ie. if the current draw remains too high after the start winding has dropped out, then the ptc cuts the comp out.
I'll have to look into it a bit more.

[chemi-cool]

Hi Guys/
It is called a starting relay cause that what it does.

The protection for over currant is a be metal operated called by the manufactures name klikson if I remember correct.

Chemi :)

[Coolie]

What you say is not right, but you are not entirely wrong either.
Although the ptc starts the comp, it is not a realy. A relay consists of a coil, that when energised creates a magnetic field that lifts the switch.
A ptc has no moving parts, therefore not prone to malfunction.
A klixon, on the other hand protects the motor.
But a PTC can replace the klixon, in fact it is far more reliable than a standard klixon, as the ptc can be placed on the winding during the manufacturing stages and is therefore more sensitive to the increase in current or heat!

[chemi-cool]

Hi Coolie.

PTC, where used has two wires to connect to the compressor contactor and will open on temp rise. A controll devise

Thermistor on the other hand is also located inside the compressor and will disconnect the phases on temp rise or the winding ends. Currant device.

Klixon is the same as the thermistor but external - can be replaced.

Thats the diference between the three.
The starting relay is only for small, one phase compressors


Chemi :)

[Peter Mitchell]

PTC-positive temperature coefficient this is a description of what it does.
A PTC resistor would change its resistance directly with temprature
A PTC realy also changes state directly with temprature
A PTC relay is a solid state relay, A relay is a device for switching things on or off. switching power from this point to that
Also the name of the device it replaces is a current relay it would be reasonable to call this new device a relay also.

[MRcoolingMAGIC]

hi guys i am new to the site and i enjoy o lot the stuff. The ptc is e thermistor a semiconductor ....changes resistence according the amperage drawn :D
i

[MRcoolingMAGIC]

Indeed, even though in fact there is no "relaying".
;) Thanx dude i am interested of testing a pcb on site
if all the fuses are ok .i do a bit of eletronics ,know all the elements well how they work but i am more ref & a/c
engineer than electronics repairer.any useful links will be
appresiated

[ralph]

hi pete
i just want to know if the fridge compressor start and stop but does not run,and then does the same thing again and again after every 1 minute...do you think its the compressor or the PTC relay which is faulty? I test the compressor winding and all seems to be fine(common-run=7 ohms, run-start=34 ohms, common-start=28 ohms).I have a feeling that the relay is cutting off when it switch over to start after i have turn on power to protect the compressor of high running current,but why. can u help
please email at figaro1411@yahoo.co.uk
I always was told that a PTC uses the same principle as a thermal relay (older bi metal system).
The Resistance wire is attached in series with both the starting and running windings. The tension of this wire, when cold, keeps both sets of contact points closed. While the current passes through, the resistance (PTC) wire heated and expands or stretches. At a predetermined time, the stretched wire opens the starting winding contacts. This also acts as a safety device in case of too much current.

[wolf]

hipiter you are so smart what is clickson than?