relay ptc

[milton]

hi all how to testate relay ptc thank all

[Latte]

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/applia...r/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/p...3_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

[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.

[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

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.

[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?

[zkt]

I Googled P.T.C. relay and wound up at this 3 year old thread and then looked around a bit and registered. You people are Serious about this stuff.
I`m working on this little old kitchen refrigerator

Too bad about the 15 post rule.
Anyway its a small 150-200 watt start-run winding compressor with external ptc relay and external cap.
Three terminals on the compressor, three terminals on the compressor to relay connection and a hot and common on the other side of the relay. The cap plugs into the relay and the wiring diagram shows one leg of the cap conected to common along with a leg of each of the windings. Did I mention the 15 post rule ? Picture worth a thousand words and all that rot you know.

It has the ptc and cap configuration. The cap is good as is the defrost timer. The owner thinks the temp has been going up for a while. Today We threw away four garbage bags full of food. By the smell its been too warm for a couple days at least. The Mullion heater was on and that didnt help any but was certainly not the problem.
The compressor runs and the condenser line gets hot and the evap line cold. But it seems a bit wimpy. This is a 18.6 ft3 unit and only draws 150-200 watts and runs on 134A, so I dont think it will blast out cold air during the best of times.
The resistance of the one compressor winding was about 8 ohms and the other ~4. Their series resistance was about 12 as expected.
The ptc relay and the cap are seperated units.
According to the schematic one terminal of the ptc relay(resistor) should have been connected to the common but both had resistance to ground.
So it appears that the relay is preventing the start winding from energizing and so the compressor is running at reduced power and speed from the run winding with starting help from the cap which also functions as a run cap when the resistance rises. I didnt have an ammeter to check the current.
I will ask the Alan The Motor Man tomorrow and post his response but thought I`d ask here first.
Seems that its either that or the start winding has low resistance(partially shorted) or the owner has been drunk for the past three days, which he denies.
The real problem is that none of the above explains the resistance reading from both of the pct relay terminals to common.
Or maybe I`m so confused by this point I donno.

[nike123]

According to the schematic one terminal of the ptc relay(resistor) should have been connected to the common but both had resistance to ground.

There is difference in meaning of PTC relay and PTC resistor.
PTC relay is device which in it self has PTC resistor.

You probably interpreting schematic wrong. PTC resistor is always connected between compressor S and R terminal and never to common terminal.

There are version of PTC relay which have all 3 terminals at relay but common is not internally directly connected with PTC resistor.

ptc.png

Common (C) terminal of compressor should be connected to Live thru overload relay. PTC resistor is connected between S and R terminal. Neutral should be connected at R terminal.

Resistance of PTC resistor:

PTC relay incorporates a PTC (Positive Temperature
Coefficient) ceramic pellet with a low, controlled
resistance value at ambient temperature, which allows the motor to
start.
After a short delay the PTC pellet increases its resistance
considerably, and reduces motor stating current to a very low value,
which is anyway sufficient to keep the PTC relay in a non-operating
condition as long as the motor is running. When the motor is
switched off, after a cooling down period (typically 3 minutes at 25°C
ambient temperature) the PTC pellet resistance decreases to its
original low value. The relay is ready for another start.

http://www.electrica.it/file_pdf/electrica_ptc.pdf


In your case, when compressor is not operating and PTC is connected to compressor, resistance value between S terminal on PTC relay and C terminal at compressor (common) should be as folows:

1/R= 1/(R of PTC resistor + R of run winding (value measured between R and C terminal of unconnected compressor)+1/R of start winding (value measured between S and C terminal of unconnected compressor)

That is combination of parallel and series resistances.

Typically, resistance of cold PTC relay is about 3 to 30 ohm, and resistance between S and C with connected PTC relay should be as follow (in case that PTC resistor resistance is 30 Ohm):
1/R=1/(30+4)+1/8=1/34+1/8=8/272+34/272=42/272

R=272/42=6,5 Ohm

Let see what should be with 3 Ohm PTC:
1/R=1/(3+4)+1/8=1/7+1/8=8/56+7/56=15/56

R=56/7=3,7 Ohm

With disconnected PTC relay value between S an C terminal at relay should be infinity and same is case between R and C terminals.
Only between R and S terminals you should have about 30 Ohm resistance (or what ever is normal resistance of cold PTC resistor).


Regarding 15 post rule, you could post your link like this (without HTTP And WWW):

refrigeration-engineer.com/forums/showthread.php?p=160052#post160052

[zkt]

Thanks for the knowledable and speedy reply.
The configuration doesnt seem to be the same.
Here is the diagram:

//i8.photobucket.com/albums/a30/zkt/FridgeSchematic.jpg

In the box titled compressor wiring, the center diagram is the one used "P.T.C. Relay with (mouse ate the first part of next word) capacitator" The white wire is common and one terminal of the resistor is connected to it.
As I see the operation, upon startup current flows thru the run winding and thru the series path of the ptc resistor and the start winding, which is in parallel with the run winding. The cap is in parallel with all the above and serves as a start cap.
The current thru the ptc resistor increases as does its resistance so the wind start winding magnetic field strength becomes negligible and the compressor runs off the run winding magnetic field.
If the compressor is turned on it runs and if turned off it wont immediately start and will start after a few minutes after the ptc cool down. This incidates to me that the start winding is at least not shorted.
Additionally, when the ptc resistance increases the cap becomes, in effect in series with the start winding impedance and the sum od the two in parallel with the run winding impedance therby improving the power factor and functioning as a run cap for the run winding.
My original theory that it is running at reduced speed because the start winding is never energized still makes sense to me but I`m not sure. If the service sheet had provided resistance readings the diagnosis would have been easy.
After looking at the schemo what do you think?

[nike123]

Thanks for the knowledable and speedy reply.
The configuration doesnt seem to be the same.
Here is the diagram:

//i8.photobucket.com/albums/a30/zkt/FridgeSchematic.jpg

Ok, that is simmilar as I posted but with permanent capacitor connected between S and R. It is called RSCR PTC starting device.
It doesn't changes measurement of resistance if capacitor is disconnected during measuring.

In the box titled compressor wiring, the center diagram is the one used "P.T.C. Relay with (mouse ate the first part of next word) capacitator" The white wire is common and one terminal of the resistor is connected to it.

That is not entirely correct! White wire is not connected to common terminal (C). Red wire is connected to common terminal (C) thru overload relay.
White wire is connected to one terminal (1) of relay which is internally connected with PTC resistor. Check your diagram again.
Your sentence is wrong or you using term "common" in different context here!

[paul_h]

Ok, that is simmilar as I posted but with permanent capacitor connected between S and R. It is called RSCR PTC starting device.

CSIR?
capacitor start, induction run?
Could be wrong, but if I saw that without the PTC relay and just a normal electro mechanical relay it would be CSIR

zkt, any fault with a starting circuit like capacitor or relay wouldn't make a compressor run at low speed, it would make it fail to start at all. The only motor that can start on a single phase is a shaded pole motor, like small fans have (inside the fridge or your pedestal fan you use in summer). These don't have sufficient torque to start a compressor so no high torque motors will start on a single phase at all, if the start winding or circuit (relay or capacitor) aren't working, then it won't start at all.

[nike123]

CSIR?
capacitor start, induction run?
Could be wrong, but if I saw that without the PTC relay and just a normal electro mechanical relay it would be CSIR

No! Check how capacitor is diferently conected in CSIR.



RSCR (resistant start capacitor run): capacitor is constantly connected at start winding. Run winding is fed directly at start and thru condenser at normal operation.

CSIR (capacitor start inductive run): capacitor is connected at start winding only during start. When current fall, capacitor (and start winding) is disconnected and motor runs only on run winding.

[nike123]

Zkt, I see now where confusion lies!
You using hot and common terms for what we use here live and neutral.

Translate my live in your hot and my neutral in your common.
My common is used to designate common terminal of two compressor windings.

You should connect gauges and see pressures and take some temperature measurements at refrigerant circuit.
It doesn't look like compressor start problem.

[zkt]

Again thank you all for your time and sharing of your knowledge and experience.
I clearly see now that the problem is not in the compressor and related components. Had I more experience or presense of thought I would have realized immediately that the fact that the compressor ran upon energization and required a few minutes wait upon unpluging was clear evidence that the start winding was ok and that the delay was necessitated by a cooling down period of the ptcr.
A physical enamination of the evap, duct and fan area seems to be in order.
Again thanks for all the input.