What does Block code S15 / Utility block mean displayed on my heat pump (WPM / Touch screen based).

This is not a fault. Block code S15 / Utility block means the compressor is not running right now as it is being blocked from running from a peak/off-peak timer or external switch telling the heat pump not to run right now during peak energy times.

Some installers may have used the "Utility block" connection on the heat pump, rather than the "External block" to prevent it from running when heating is not required. If "Utility block" persists over several hours, check with your installer how they have wired the Utility block connection on the heat pump.

Applicable to models:  

System S, System S6, System S10, LIA 0608HWCF MS , LIA 0911HWCF MS,  LI 2M, LI 8AS, LI 8ASL, LI 8AS SAL, LI 8MS, LI 8MSR, LI 9AS, LI 9ASH, LI 9AS SAL, LI 9TE, LI 9TEL, LI 9TES, LI 9TU, LI 11AS, LI 11ASH, LI 11ASR, LI 11AS SAL, LI 11ME, LI 11MER, LI 11MS, LI 11MSR, LI 11TE, LI 11TEL, LI 11TER+, LI 11TES, LI 12TU, LI 15TE, LI 16AS, LI 16ASH, LI 16ASR, LI 16AS SAL, LI 16TE, LI 16TEL, LI 16TER+, LI 16TES, LI 20AS, LI 20AS SAL, LI 20TE, LI 20TEL, LI 20TES, LI 22HS, LI 24AS, LI 24AS SAL, LI 24TE, LI 24TEL, LI 24TES, LI 26HS, LI 28AS, LI 28AS SAL, LI 28TE, LI 28TEL, LI 28TES, LI 40AS, LIH 10TE, LIH 22TE, LIH 26TE, LIK 8ME, LIK 8MER, LIK 8TE, LIK 8TEL, LIK 8TES, LIK 12TU, LIKI 14TE, LA 6MR, LA 6S-TU, LA 6S-TUR, LA 6TU, LA 8AS, LA 8MR, LA 8PMS, LA 9K, LA 9PS, LA 9S-TU, LA 9S-TUR, LA 9TU, LA 10MR, LA 11AS, LA 11ASR, LA 11K, LA 11MAS, LA 11MS, LA 11MSR, LA 11PS, LA 11TAS, LA 12PS, LA 12S-TU, LA 12S-TUR, LA 12TR, LA 12TU, LA 13K, LA 14PMS, LA 15K, LA 16AS, LA 16ASR, LA 16MAS, LA 16MS, LA 16TAS, LA 16TR, LA 17PS, LA 17TU, LA 18I-MU, LA 18PS, LA 18S-TU, LA 18S-TUR, LA 20AS, LA 22HS, LA 22PS, LA 22TBS, LA 24AS, LA 25TU, LA 25TU-2, LA 26HS, LA 26PS, LA 28AS, LA 28TBS, LA 33TBS, LA 35TUR+, LA 40AS, LA 40TU, LA 40TU-2, LA 60TU, LA 60TU-2, LA 60TUR+, LA60STU, LA60STUR, LAC 12TR, LAC 16TR, LAJ 11MUR, LAJ 16MUR, LAJ 60TUR+, LAK 10M, LAK 10MR, System M, LAK 3IMR, LAK 6IMR, LAK 9IMR, LAK 14IMR, LAK 14ITR, LAW 6IMR, LAW 9IMR, LAW 14IMR, LAW 14ITR, LIA 7IM, LIA 9IM, LIA 12IM, LIA 14IM, LIA 16IM,LSA60TUR,LSA60TPR,LSA60TPR2,LSA100TUR, SI 5BS, SI 5CS, SI 5ME, SI 5MER, SI 5MS, SI 5MSR, SI 5TE, SI 5US, SI 5USR, SI 6TU, SI 7BS, SI 7CS, SI 7KS, SI 7ME, SI 7MER, SI 7MS, SI 7MSR, SI 7TE, SI 7US, SI 7USR, SI 8MR, SI 8TU, SI 9BS, SI 9CS, SI 9KS, SI 9ME, SI 9MER, SI 9MS, SI 9MSR, SI 9TE, SI 9US, SI 9USR, SI 10MER, SI 10MR, SI 11BS, SI 11CS, SI 11KMS, SI 11KS, SI 11ME, SI 11MER, SI 11MS, SI 11MSR, SI 11TE, SI 11TU, SI 11US, SI 11USR, SI 12TR, SI 14BS, SI 14CS, SI 14KS, SI 14ME, SI 14MS, SI 14TE, SI 14TR, SI 14TU, SI 14US, SI 14USR, SI 16KMS, SI 16TR, SI 17BS, SI 17CS, SI 17TE, SI 18TU, SI 20TR, SI 21CS, SI 21TE, SI 22TU, SI 24TE, SI 26TU, SI 30CS, SI 30TE, SI 30TER+, SI 35TU, SI 35TUR, SI 37TE, SI 40HS, SI 50TE, SI 50TU, SI 50TUR, SI 50ZS, SI 70CS, SI 70TUR, SI 75TE, SI 75TER+, SI 75TU, SI 75ZS, SI 75ZSR, SI 90TU, SI 100TE, SI 100ZS, SI 130TE, SI 130TU, SI 130TUR+, SI 130ZS, SIH 6ME, SIH 6TE, SIH 9ME, SIH 9TE, SIH 11ME, SIH 11TE, SIH 20TE, SIH 40TE, SIH 90TU, SIHJ 90TU, SIJ 10MER, SIJ 75TER+, SIJ 130TUR+, SIK 6TES, SIK 7TE, SIK 7TE-2, SIK 8TES, SIK 9TE, SIK 9TE-2, SIK 11ME, SIK 11TE, SIK 11TE-2, SIK 11TES, SIK 14TE, SIK 14TE-2, SIK 14TES, SIK 16ME, SIKH 6TE, SIKH 9ME, SIKH 9TE, SIW 6MU, SIW 6TES, SIW 6TU, SIW 8MU, SIW 8TES, SIW 8TU , SIW 11MU, SIW 11TES, SIW 11TU, WI 9CS, WI 9ME, WI 9TE, WI 10TU, WI 14CS, WI 14ME, WI 14TE, WI 14TU, WI 18CS, WI 18TE, WI 18TU, WI 22CS, WI 22TE, WI 22TU, WI 27CS, WI 27TE, WI 35TU, WI 40CS, WI 45TU, WI 50TU, WI 65TU, WI 90CS, WI 95TU, WI 100TU, WI 120TU, WI 140TUR+, WI 180TU, WIH 120TU, WPM 2006plus (H), WPM 2006plus (L), WPM 2006R, WPM ACU, WPM Basetec, WPM Econ5, WPM Econ5Plus, WPM Econ5S, WPM EconPlus, WPM EconPlus-E, WPM Econ SOL, WPMJ ACU, WPMJ EconPlus, WPMJ EconPlus-MD, WPM PK, RTCFM, RTCSM