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Keston error codes

Find the meaning of Keston fault, warning and status codes, with model context, documented causes, safe checks and links to available manufacturer guidance.

444documented codes
20products and models
1product categories

About Keston error codes

An error code is a diagnostic clue, not a complete repair diagnosis. Keston may reuse similar-looking codes across different products, model generations or regions, so always confirm the complete code and exact model before following instructions or ordering parts.

This profile connects every indexed Keston code to its dedicated explanation page. Each page is structured around the search intent: a quick meaning, symptoms, likely causes, safe troubleshooting, reset guidance, applicable products and the point at which professional help is appropriate. Records marked as verified include the manufacturer or another authoritative technical source.

Start with the code shown on the display, then narrow the result by product or model. Do not assume that a reset has repaired the underlying fault. If a code returns, the product is unsafe, or diagnosis requires internal electrical, gas, refrigerant or moving components, stop and use an authorised technician.

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09Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania09 – Keston Heat² error codeKeston identifies OpenTherm fault 09 on Heat² 45, 55, 45P and 55P boilers as “Outside thermistor defect (open…10Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania10 – Keston Heat² error codeKeston identifies OpenTherm fault 10 on Heat² 45, 55, 45P and 55P boilers as “Water pressure sensor defect”.…11Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania11 – Keston Heat² error codeKeston identifies OpenTherm fault 11 on Heat² 45, 55, 45P and 55P boilers as “Flow thermistor open circuit…12Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania12 – Keston Heat² error codeKeston identifies OpenTherm fault 12 on Heat² 45, 55, 45P and 55P boilers as “Flow thermistor short circuit…13Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania13 – Keston Heat² error codeKeston identifies OpenTherm fault 13 on Heat² 45, 55, 45P and 55P boilers as “Return thermistor open circuit…14Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania14 – Keston Heat² error codeKeston identifies OpenTherm fault 14 on Heat² 45, 55, 45P and 55P boilers as “Return thermistor short circuit…15Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania15 – Keston Heat² error codeKeston identifies OpenTherm fault 15 on Heat² 45, 55, 45P and 55P boilers as “Flue thermistor open circuit…16Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania16 – Keston Heat² error codeKeston identifies OpenTherm fault 16 on Heat² 45, 55, 45P and 55P boilers as “Flue thermistor short circuit…17Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania17 – Keston Heat² error codeKeston identifies OpenTherm fault 17 on Heat² 45, 55, 45P and 55P boilers as “Heat thermistor open circuit…18Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania18 – Keston Heat² error codeKeston identifies OpenTherm fault 18 on Heat² 45, 55, 45P and 55P boilers as “Heat thermistor short circuit…19Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania19 – Keston Heat² error codeKeston identifies OpenTherm fault 19 on Heat² 45, 55, 45P and 55P boilers as “Heat thermistor open circuit”.…20Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania20 – Keston Heat² error codeKeston identifies OpenTherm fault 20 on Heat² 45, 55, 45P and 55P boilers as “Heat thermistor short circuit”.…21Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania21 – Keston Heat² error codeKeston identifies OpenTherm fault 21 on Heat² 45, 55, 45P and 55P boilers as “Header thermistor open circuit”.…22Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania22 – Keston Heat² error codeKeston identifies OpenTherm fault 22 on Heat² 45, 55, 45P and 55P boilers as “Header thermistor short circuit”.…23Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania23 – Keston Heat² error codeKeston identifies OpenTherm fault 23 on Heat² 45, 55, 45P and 55P boilers as “Room heating-circuit 1 thermistor…24Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania24 – Keston Heat² error codeKeston identifies OpenTherm fault 24 on Heat² 45, 55, 45P and 55P boilers as “Room heating-circuit 1 thermistor…30Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania30 – Keston Heat² error codeKeston identifies OpenTherm fault 30 on Heat² 45, 55, 45P and 55P boilers as “Blocking due to flow…31Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania31 – Keston Heat² error codeKeston identifies OpenTherm fault 31 on Heat² 45, 55, 45P and 55P boilers as “Blocking due to return…32Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania32 – Keston Heat² error codeKeston identifies OpenTherm fault 32 on Heat² 45, 55, 45P and 55P boilers as “Blocking due to flue…33Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania33 – Keston Heat² error codeKeston identifies OpenTherm fault 33 on Heat² 45, 55, 45P and 55P boilers as “Flow and return reversed”.…34Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania34 – Keston Heat² error codeKeston identifies OpenTherm fault 34 on Heat² 45, 55, 45P and 55P boilers as “Thermistor pipe-fit supervision active”.…35Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania35 – Keston Heat² error codeKeston identifies OpenTherm fault 35 on Heat² 45, 55, 45P and 55P boilers as “Thermistor pipe-fit supervision lockout”.…36Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania36 – Keston Heat² error codeKeston identifies OpenTherm fault 36 on Heat² 45, 55, 45P and 55P boilers as “Flow-gradient supervision”. The manual…37Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania37 – Keston Heat² error codeKeston identifies OpenTherm fault 37 on Heat² 45, 55, 45P and 55P boilers as “Flue-gradient supervision (reserved)”. The…38Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania38 – Keston Heat² error codeKeston identifies OpenTherm fault 38 on Heat² 45, 55, 45P and 55P boilers as “Flow/return delta-temperature blocking”. The…39Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania39 – Keston Heat² error codeKeston identifies OpenTherm fault 39 on Heat² 45, 55, 45P and 55P boilers as “Flow-overheat lockout”. The manual…40Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania40 – Keston Heat² error codeKeston identifies OpenTherm fault 40 on Heat² 45, 55, 45P and 55P boilers as “Return-overheat lockout”. The manual…41Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania41 – Keston Heat² error codeKeston identifies OpenTherm fault 41 on Heat² 45, 55, 45P and 55P boilers as “Flue-overheat or thermal-fuse lockout”.…42Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania42 – Keston Heat² error codeKeston identifies OpenTherm fault 42 on Heat² 45, 55, 45P and 55P boilers as “Blocking due to heat-exchanger…50Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania50 – Keston Heat² error codeKeston identifies OpenTherm fault 50 on Heat² 45, 55, 45P and 55P boilers as “No central-heating water flow”.…51Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania51 – Keston Heat² error codeKeston identifies OpenTherm fault 51 on Heat² 45, 55, 45P and 55P boilers as “Low water pressure”. The…52Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania52 – Keston Heat² error codeKeston identifies OpenTherm fault 52 on Heat² 45, 55, 45P and 55P boilers as “No flame signal at…53Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania53 – Keston Heat² error codeKeston identifies OpenTherm fault 53 on Heat² 45, 55, 45P and 55P boilers as “Flame loss during operation…54Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania54 – Keston Heat² error codeKeston identifies OpenTherm fault 54 on Heat² 45, 55, 45P and 55P boilers as “Flame loss during operation…55Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania55 – Keston Heat² error codeKeston identifies OpenTherm fault 55 on Heat² 45, 55, 45P and 55P boilers as “Flame loss during stabilisation;…56Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania56 – Keston Heat² error codeKeston identifies OpenTherm fault 56 on Heat² 45, 55, 45P and 55P boilers as “Flame loss during stabilisation…57Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania57 – Keston Heat² error codeKeston identifies OpenTherm fault 57 on Heat² 45, 55, 45P and 55P boilers as “False flame with heat…58Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania58 – Keston Heat² error codeKeston identifies OpenTherm fault 58 on Heat² 45, 55, 45P and 55P boilers as “No flame after restart…59Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania59 – Keston Heat² error codeKeston identifies OpenTherm fault 59 on Heat² 45, 55, 45P and 55P boilers as “Fan-speed standstill check fault”.…60Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania60 – Keston Heat² error codeKeston identifies OpenTherm fault 60 on Heat² 45, 55, 45P and 55P boilers as “Required fan speed not…61Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania61 – Keston Heat² error codeKeston identifies OpenTherm fault 61 on Heat² 45, 55, 45P and 55P boilers as “Fan-speed error during pre-purge”.…62Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania62 – Keston Heat² error codeKeston identifies OpenTherm fault 62 on Heat² 45, 55, 45P and 55P boilers as “Fan-speed minimum/maximum supervision warning…63Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania63 – Keston Heat² error codeKeston identifies OpenTherm fault 63 on Heat² 45, 55, 45P and 55P boilers as “Mains overvoltage warning”. The…64Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania64 – Keston Heat² error codeKeston identifies OpenTherm fault 64 on Heat² 45, 55, 45P and 55P boilers as “Mains undervoltage blocking”. The…65Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania65 – Keston Heat² error codeKeston identifies OpenTherm fault 65 on Heat² 45, 55, 45P and 55P boilers as “OpenTherm Plus communication error”.…66Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania66 – Keston Heat² error codeKeston identifies OpenTherm fault 66 on Heat² 45, 55, 45P and 55P boilers as “Too many remote resets”.…67Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania67 – Keston Heat² error codeKeston identifies OpenTherm fault 67 on Heat² 45, 55, 45P and 55P boilers as “No water-flow indication”. The…68Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania68 – Keston Heat² error codeKeston identifies OpenTherm fault 68 on Heat² 45, 55, 45P and 55P boilers as “PWM pump blocking error…69Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania69 – Keston Heat² error codeKeston identifies OpenTherm fault 69 on Heat² 45, 55, 45P and 55P boilers as “PWM pump electrical error…70Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania70 – Keston Heat² error codeKeston identifies OpenTherm fault 70 on Heat² 45, 55, 45P and 55P boilers as “Heat-exchanger water-flow fault below…71Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania71 – Keston Heat² error codeKeston identifies OpenTherm fault 71 on Heat² 45, 55, 45P and 55P boilers as “PWM pump dry-run error…72Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania72 – Keston Heat² error codeKeston identifies OpenTherm fault 72 on Heat² 45, 55, 45P and 55P boilers as “Pump warning code (75%…73Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania73 – Keston Heat² error codeKeston identifies OpenTherm fault 73 on Heat² 45, 55, 45P and 55P boilers as “VariCAN communication error”. The…74Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania74 – Keston Heat² error codeKeston identifies OpenTherm fault 74 on Heat² 45, 55, 45P and 55P boilers as “Safety interlock function activated;…75Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania75 – Keston Heat² error codeKeston identifies OpenTherm fault 75 on Heat² 45, 55, 45P and 55P boilers as “Air-pressure switch error”. The…76Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania76 – Keston Heat² error codeKeston identifies OpenTherm fault 76 on Heat² 45, 55, 45P and 55P boilers as “Air-pressure switch warning; restart…77Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania77 – Keston Heat² error codeKeston identifies OpenTherm fault 77 on Heat² 45, 55, 45P and 55P boilers as “High water pressure”. The…78Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania78 – Keston Heat² error codeKeston identifies OpenTherm fault 78 on Heat² 45, 55, 45P and 55P boilers as “Minimum water-flow rate fault”.…79Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania79 – Keston Heat² error codeKeston identifies OpenTherm fault 79 on Heat² 45, 55, 45P and 55P boilers as “Maximum water-flow rate exceeded”.…80Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania80 – Keston Heat² error codeKeston identifies OpenTherm fault 80 on Heat² 45, 55, 45P and 55P boilers as “Quartz crystal error”. The…81Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania81 – Keston Heat² error codeKeston identifies OpenTherm fault 81 on Heat² 45, 55, 45P and 55P boilers as “0–10 V input out…93Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania93 – Keston Heat² error codeKeston identifies OpenTherm fault 93 on Heat² 45, 55, 45P and 55P boilers as “Retails supervision error (COM…94Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania94 – Keston Heat² error codeKeston identifies OpenTherm fault 94 on Heat² 45, 55, 45P and 55P boilers as “Request for software re-update”.…95Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania95 – Keston Heat² error codeKeston identifies OpenTherm fault 95 on Heat² 45, 55, 45P and 55P boilers as “Blocking due to programming…96Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania96 – Keston Heat² error codeKeston identifies OpenTherm fault 96 on Heat² 45, 55, 45P and 55P boilers as “Parameter mismatch lockout”. The…97Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania97 – Keston Heat² error codeKeston identifies OpenTherm fault 97 on Heat² 45, 55, 45P and 55P boilers as “Parameter-set lockout”. The manual…98Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania98 – Keston Heat² error codeKeston identifies OpenTherm fault 98 on Heat² 45, 55, 45P and 55P boilers as “Internal blocking error”. The…99Keston · Keston Heat² 45, 55, 45P and 55P boilers · United Kingdom, Ireland and Romania99 – Keston Heat² error codeKeston identifies OpenTherm fault 99 on Heat² 45, 55, 45P and 55P boilers as “Internal system lockout”. The…01Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania01 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 01 for the Heat² 45, 55, 45P and 55P as “Flow thermistor open…02Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania02 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 02 for the Heat² 45, 55, 45P and 55P as “Flow thermistor short…03Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania03 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 03 for the Heat² 45, 55, 45P and 55P as “Return thermistor open…04Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania04 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 04 for the Heat² 45, 55, 45P and 55P as “Return thermistor short…05Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania05 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 05 for the Heat² 45, 55, 45P and 55P as “Flue thermistor open…06Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania06 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 06 for the Heat² 45, 55, 45P and 55P as “Flue thermistor short…07Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania07 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 07 for the Heat² 45, 55, 45P and 55P as “DHW thermistor open…08Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania08 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 08 for the Heat² 45, 55, 45P and 55P as “DHW thermistor short…09Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania09 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 09 for the Heat² 45, 55, 45P and 55P as “Outside thermistor defect…10Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania10 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 10 for the Heat² 45, 55, 45P and 55P as “Water pressure sensor…11Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania11 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 11 for the Heat² 45, 55, 45P and 55P as “Flow thermistor open…12Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania12 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 12 for the Heat² 45, 55, 45P and 55P as “Flow thermistor short…13Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania13 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 13 for the Heat² 45, 55, 45P and 55P as “Return thermistor open…14Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania14 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 14 for the Heat² 45, 55, 45P and 55P as “Return thermistor short…15Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania15 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 15 for the Heat² 45, 55, 45P and 55P as “Flue thermistor open…16Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania16 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 16 for the Heat² 45, 55, 45P and 55P as “Flue thermistor short…17Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania17 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 17 for the Heat² 45, 55, 45P and 55P as “Heat thermistor open…18Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania18 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 18 for the Heat² 45, 55, 45P and 55P as “Heat thermistor short…19Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania19 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 19 for the Heat² 45, 55, 45P and 55P as “Heat thermistor open…20Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania20 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 20 for the Heat² 45, 55, 45P and 55P as “Heat thermistor short…21Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania21 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 21 for the Heat² 45, 55, 45P and 55P as “Header thermistor open…22Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania22 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 22 for the Heat² 45, 55, 45P and 55P as “Header thermistor short…23Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania23 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 23 for the Heat² 45, 55, 45P and 55P as “Room HC1 thermistor…24Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania24 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 24 for the Heat² 45, 55, 45P and 55P as “Room HC1 thermistor…30Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania30 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 30 for the Heat² 45, 55, 45P and 55P as “Flow overheat blocking”.…31Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania31 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 31 for the Heat² 45, 55, 45P and 55P as “Return overheat blocking”.…32Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania32 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 32 for the Heat² 45, 55, 45P and 55P as “Flue overheat blocking”.…33Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania33 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 33 for the Heat² 45, 55, 45P and 55P as “Flow and return…34Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania34 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 34 for the Heat² 45, 55, 45P and 55P as “Thermistor pipe-fit supervision…35Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania35 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 35 for the Heat² 45, 55, 45P and 55P as “Thermistor pipe-fit supervision…36Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania36 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 36 for the Heat² 45, 55, 45P and 55P as “Flow-gradient supervision”. The…37Keston · Keston Heat² 45 and 55 commercial boilers · United Kingdom, Ireland and Romania37 – Keston Heat² 45/55 error codeKeston documents OpenTherm error code 37 for the Heat² 45, 55, 45P and 55P as “Flue-gradient supervision reserved…