Thermal overload

[bravheart]

Needing a thermal overload for a compressor electric motor, had a quick search and none seem to match the motor amps either 10 or 15 no 11, assume 10 will protect the motor but will it be big enough ?

 

[Highland Mule]

Surely if it's a switch that cuts out when the temperature goes too high you'd be better either going higher amperage or else finding a control circuit and putting a lower amperage one into that?

If the price isn't a factor, I'd go for the 15A

 

[bravheart]

Surely if it's a switch that cuts out when the temperature goes too high you'd be better either going higher amperage or else finding a control circuit and putting a lower amperage one into that?

If the price isn't a factor, I'd go for the 15A

The switches are pennies, but a burnt out motor’s a bit dearer. Think I’ll go for a 10a first at least the motor will survive

 

[Highland Mule]

The switches are pennies, but a burnt out motor’s a bit dearer. Think I’ll go for a 10a first at least the motor will survive

fair enough but my worry would be that the contacts would fuse together on the lower ampage one when the motor drew more than 10A through it.

 

[milkloss]

You'll need a contactor with a thermal overload unit attached. I have never used one with a single phase motor to be honest but I'm sure the local electrical wholesalers would give advice.

 

[Deutzdx3]

If it’s cutting out due to getting to hot it’s not big enough for your purpose. Piston compressors should run 60/40 on off. They aren’t designed for constant running like a vane or screw.

 

[Highland Mule]

Looking at the photo again, she probably wouldn't run so hot if all that first was blown off it and it was clean. Do you have a compressor to give it a blast?

 

[bravheart]

Looking at the photo again, she probably wouldn't run so hot if all that first was blown off it and it was clean. Do you have a compressor to give it a blast?

[emoji23]

Chicken and egg.

Was thinking the same myself

 

[sjt01]

A thermal overload works on the temperature of a resistive element inside the overload itself, which is a way of measuring current. Here is a 12 amp version which should suit your application if it will fit in the casing
https://cpc.farnell.com/schurter/ts...panel-mount-12a/dp/FF03170?st=thermal breaker

 

[YELROM]

Axiom DOL Starter 240V 4kW | Toolstation

Direct on line starter to IEC 947-3 degree. IP65. Use thermal overload relay for overload protection.

www.toolstation.com

Axiom Thermal Overload Relay 7-11A | Toolstation

Use to provide overload protection for Axiom DOL starters.

www.toolstation.com

These are what we use

 

[bravheart]

You'll need a contactor with a thermal overload unit attached. I have never used one with a single phase motor to be honest but I'm sure the local electrical wholesalers would give advice.

Don't think there's a contactor just a pressure valve with an on/off switch on top and the little reset button pictured.
Works ok when the two wires that should be on the bottom of the switch are joined, just no safety cut out.
Not worked for a while now but used the tank as a portable store just wanted to have a look see what was wrong with the motor.

 

[bravheart]

A thermal overload works on the temperature of a resistive element inside the overload itself, which is a way of measuring current. Here is a 12 amp version which should suit your application if it will fit in the casing
https://cpc.farnell.com/schurter/ts...panel-mount-12a/dp/FF03170?st=thermal breaker

Thanks for the link, room inside the box is tight might not be room for that one, the old one was longer and thinner.
From what you say though I should get a 12a job even though the motor draws 11amps?

 

[bravheart]

Axiom DOL Starter 240V 4kW | Toolstation

Direct on line starter to IEC 947-3 degree. IP65. Use thermal overload relay for overload protection.

www.toolstation.com

Axiom Thermal Overload Relay 7-11A | Toolstation

Use to provide overload protection for Axiom DOL starters.

www.toolstation.com

These are what we use

Thanks but there's no contactor box that I can see

 

[sjt01]

Thanks but there's no contactor box that I can see

This is a bit more the shape of yours

2-5700-IG2-P10-DD-000040-12A | ETA Thermal Circuit Breaker - 2 5700 Single Pole 250V Voltage Rating Panel Mount, 12A Current Rating | RS

uk.rs-online.com

 

[bravheart]

This is a bit more the shape of yours

2-5700-IG2-P10-DD-000040-12A | ETA Thermal Circuit Breaker - 2 5700 Single Pole 250V Voltage Rating Panel Mount, 12A Current Rating | RS

uk.rs-online.com

Thanks that’s more like it but out of stock.

 

[YELROM]

I have slightly misunderstood what you were wanting but there is a contactor in the DOL box then you fit which ever size over load you want
I would set your thermal over load at 10 amp as if you set it at 12amp it will probably burn out your motor before it trips

 

[bravheart]

Up and running again now thanks all, got one similar to @sj01 link but only 10a available, time will tell on that, then gave the fins a blast.