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thermistor

thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word is a combination of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors (negative temperature coefficient or NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements (positive temperature coefficient or PTC type typically). An operational temperature range of a thermistor is dependent on the probe type and is typically in between −100 ⁰C and 300 ⁰Cpe −100 °C (−148 °F)

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  1. imrichardcole

    Thermistor issue or measurement issue?

    I have two thermistors from the flow/return pipes of a British Gas 330 boiler (actually a Glow worm). They came from a boiler that was failing to modulate and constantly ramping up, then turning off in an endless cycle. I'd expect them to measure around 12k ohms at 25 degrees C, however they...
  2. robj20

    Ideal Vogue "Flow/Return Thermistor Fault" again.

    Boiler, Ideal Vogue Gen2 C32 Honeywell Evohome with Opentherm. Had Ideal out last year and they changed the thermistor, but this year its doing it again. Strangely same time of year. Suggestions last year from the installer was to remove the Evohome TRV from one radiator to act as a bypass. I...
  3. M

    Halstead ace thermistor

    Hi guy, I'm new to fault finding side, I've known so many people I know misdiagnose and it's cost them for part, kind sort of put me of repairs, but to be honest I want to be able to do it, so decided to give it a go, went on the baxi courses, and a few others for training. my question after...
  4. A

    Hi all gas safe 2942547

    Hi all attended boiler flashing red/green call vokera stated faulty thermistor , replaced turned on no led at all. turned power of checked internal fuse ok turned power back on nothing off again left 30 sec tuned on fired up green light. landlord called tenant said gone off no led light so...
    • aloneinaforest
    • Thread
    • gas gas engineer gas safe gas safe register gsr light power safe thermistor turned
    • Replies: 0
    • Forum: Plumbing Jobs | The Job-board
  5. K

    Ideal HE35 Isar / yellowish sticky substance melting away by the dry fire thermistor?

    hi there, There is a substance melting and coming out from around the dry fire thermistor on my ideal he35 isar. It s like melted plastic/resine with a honey colour. It's five year old now and had already noticed this when the servicing was done last year. Cleaned it but I ve checked by...
  6. N

    Thermistor readings.

    Hi all, just wondering if any body knows of a site of some sort which has all the readings for testing etc it's something I'm lacking so could help me with fault finding etc. thanks. Rob
  7. C

    Worcester Bosch 28cdi Ignition Lockout

    Hi, My current problem is Ignition Lockout on heating - but not on hot water. The boiler is a worcester Bosch 28cdi. The history follows... We had a problem with the hot water not initiating the boiler, which got steadily worse, to the point where we had to run several taps to get it to...
    • creature
    • Thread
    • 28cdi boiler bosch central heating system ignition lockout problem thermistor water worcester worcester bosch
    • Replies: 7
    • Forum: Plumbing Jobs | The Job-board
  8. J

    Thermistor readings

    Just found this not sure if it's been posted b4 but might come in handy Expected thermistor readings manufacturers A-B
  9. G

    Thermistor NTC sensor for Sime Combi Boiler

    Hello to all, Can someone please tell me if a thermistor should read the same in and of circuit? I am getting correct figures from stat with it disconnected (12k to 1k ohms)but when connected it reads zero ohms. Across the connector for sensor on pcb it reads zero.
  10. J

    Ideal Isar 35 domestic water only warm. Thermistor? Any ideas please.

    Boiler four years old and been reliable. No codes showing. Running normally, no evidence of a problem. Starts and runs hot then lowers in temperature then remains steady at just warm. Have reset etc. Any help appreciated.
    • JohnHuson
    • Thread
    • cartridge domestic heating ideal ideas isar please thermistor warm water
    • Replies: 7
    • Forum: Plumbing Jobs | The Job-board
  11. M

    did i do something wrong?

    Hi, Went to call out - boiler locking out (Sabre 29 HE) Got there and boiler working fine - made a few checks, gas pressures, condensate, cleaned venturis etc -all working explained to customer that it is difficult for me to identify fault if all is working well. Called Sabre tech support...
  12. P

    Baxi 100HE Fan Thermistor

    Hi Guys, anyone had trouble with Baxi 100 HE fan thermistor tripping, going open circuit? I suspect it points to the fan getting too hot as the burner door seal is in good condition. The fault finding guide says to replace the thermistor so i have but the fault still remains, are we getting...
  13. J

    Thermistor sensor replacements on ferroli optima 901 - b'ham

    Hi there, I'm looking for someone in the Birmingham (Erdington) to replace the thermistor sensors on a optima 901. The main burner fires up after switching the dhw on but shortly shuts off and on intermittently. this has been diagnosed by people of this user forum and an ex heating engineer...
  14. N

    ariston eurocmobi a/23 mffi Pump running no power to anything.

    I have this problem with the above boiler, i have changed the pump flow switch, the right hand pcb and the Flow thermistor above the pump. I have tested everything for power the fan etc but nothing. The only thing i can think i can be is the left hand pcb which controls all the thermistor side...
  15. Leo21

    Ferolli modena

    I've just looked at a ferolli models 102. Hot water fires, on to high flame. Boiler gets to hot, modulates down then burner goes off. I'm thinking thermistor or partially blocked heat x. I'm going to go for the thermistor first. Anyone think it coud be something else.
  16. B

    Glow worm Micron 50ff Thermistor Replacement.

    Please could anyone advise me on how to remove a stubborn faulty Thermistor on a 12 year-old Glow worm Micron 50ff boiler. I understand it is dry pocket type. However, I've used long-nosed pliers to extract it from the phial to no avail. :sweatdrop: I've sprayed the rubber grommet with WD40...
  17. J

    ravenheat cs85 no hot water.

    hi guys hope some one can point me in the right direction. went to ravenheat cs85 today. central heating works fine. when you turn in hot water it cuts out. tested microswitch with the multimeter and thats working ok. it was 5.30 so couldnt phone ravenheat tech support went to test the dhw...
    • julesverne
    • Thread
    • heating hot hot water no hot water ravenheat tapatalk there's thermistor water
    • Replies: 5
    • Forum: Plumbing Jobs | The Job-board
  18. M

    Vokera Compact 24

    Vokera compact 24, I think im right here but you know me team a love the input.. When calling for heating it fires up and burns then goes into lock out, same with the hot water, although the hot water does it a lot quicker .. the times vary depending on how long the boiler has been off or in...
  19. B

    Thermistor problem

    :disappointed:Hi first time user needing advice on boiler problem. Vokera HE32 boiler developed return thermistor fault ( AL73 ). Do i need to drain whole system or can boiler be drained only, through drain valve ? So i can replace faulty thermistor Also noticed rads not fully hot at bottom...
  20. B

    Checking a thermistor

    Hi, I'm fairly inexperienced at fault finding but familiar with the operation of a multimeter. Will someone let me know the correct way to test a thermistor please? i.e doI test it while the appliance is on? Do I test for ohms or voltage? Thanks
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