ac heaters problem - over heating

[DTSFA]

hi

i have arranged 3x 15R 50W heater resistors in parallel , as per drawing,

for some reason the heaters over heat to the point of melting cable, smoking,

( I see the bridge rec is drawn incorrectly)

any ideas?


thanks

 

[chuckey]

The resistors need to dissipate their power to the air, so you need ensure that there is sufficient air flow for them to run below their maximum rated temperature, or at least below the melting point of the connecting cables. You say this is a heater, if it is running hotter then 60 degrees C, then you cannot use PVC insulated cable. You might have to use glass fibre sleeving over bare copper wires to bring them out of the heater, where you then connect them to PVC insulated cables.
Frank

 

[tpetar]

Describe melting, and smoking, you talking about melting and smoking wire isolations or wire melting?

Describe heaters/resistors, is this resistance wire for heatink "Canthal" or "Cecas" wire or you make your home heater ?

Your heaters dissipate more then 50W.

How you get 15R resistance? Resistance wire used for heating element change their resistance acording to temperature.

Post better quality of circuit.

Resistors in AC Circuits
**broken link removed**


Ratio of power / resistance of this "heaters" is not good.

 

[DTSFA]

The resistors need to dissipate their power to the air, so you need ensure that there is sufficient air flow for them to run below their maximum rated temperature, or at least below the melting point of the connecting cables. You say this is a heater, if it is running hotter then 60 degrees C, then you cannot use PVC insulated cable. You might have to use glass fibre sleeving over bare copper wires to bring them out of the heater, where you then connect them to PVC insulated cables.
Frank

think you are correct,

the resistor, heater used is this one , I believe

https://uk.rs-online.com/web/p/panel-mount-fixed-resistors/0160865/

think the surface temp is way too high, and melting cabling

?

thanks

 

[tpetar]

http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/0160865/

My friend, this is not a heater, this is power resistor in metal case. This type of resistor should be used with heatsink together, specially if you want to dissipate higher power.

That resistor dont have 15Ω he have 150mΩ. If you point on correct part link.

Max case temp is 200C, and should be keept in normal ranges.

Declared max power is only correct and can be achieved if resistor case have max 25C temp.

**broken link removed**

**broken link removed**

This is power resistor in metal case, this cannot be used as heater. For heating element use "Canthal" wire, or use heater from soldering iron 12V-24V-48V-220V, or use heater from hot air soldering station (SMD Rework Station).

 

[DTSFA]

My friend, this is not a heater, this is power resistor in metal case. This type of resistor should be used with heatsink together, specially if you want to dissipate higher power.

That resistor dont have 15Ω he have 150mΩ. If you point on correct part link.

Max case temp is 200C, and should be keept in normal ranges.

Declared max power is only correct and can be achieved if resistor case have max 25C temp.

**broken link removed**

**broken link removed**

This is power resistor in metal case, this cannot be used as heater. For heating element use "Canthal" wire, or use heater from soldering iron 12V-24V-48V-220V, or use heater from hot air soldering station (SMD Remowrk Station).

should have posted this link

http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7205246/

anywho, thanks guys, is a surface temp issue,

these 15ohm, 50w resistors are being used as bespoke 'frost heater' . (but have usually been fixed to panel back plate. In this case they have been left floating, hence issue )

cheers