Space heating off temperature(FSV #4013, Default “35/45℃”, Range 10 ~ 35/45℃): At high outdoor temperature above this value, the space heating will be turned off, to avoid overheating.
The max setting for #4013 on my gen 6 model is 35C. Can you guess where we are going with this?
Yesterday during our heat wave in the UK the outdoor sensor reported 35.4C and my DHW cycle failed to run as the heat pump wouldn’t turn on due to the outside ambient temperature exceeding #4013. So you cannot have hot water in summer when it’s very hot, at least not at the hottest part of the day when it would be most efficient to run the heat pump!
Anyway, we noticed the DHW cycle was not running and investigated. Sticking the outside temperature sensor in a glass of cold water reduced the temperature reading and allowed the DHW cycle to start confirming this was indeed the issue preventing the DHW cycle from running.
In conclusion, even though #4013 is in the space heating section, it also applies to DHW and the heat pump will not start if the outside temperature exceeds #4013. I accept this will not occur often (in the UK), but for me it’s a bug. Just sharing so others do not get similarly caught out (I wonder how heat pump owners in really hot countries manage this?)
I should note that our heat pump is south facing, so the temperature sensor is on the north side and shaded throughout the day. I would imagine it would be worse if the black shrouding was in the sun all day.
I have a gen 7 but they use the same controller, so i dont think it’s gen specific, but mine does not behave this way. I have 4013 set to 16 and my DHW works fine up to 30 degrees and higher.
Maybe there was a bug in earlier firmware that has been patched out.
If you’re still in warranty, contact your installer or Samsung directly and see if they’ll send someone out to update the firmware or send out a new PCB.
The only thing I didn’t check is that the Space Heating side was turned ON at the time but the heating was off by the 3rd party room thermostat not calling for heat. So although DHW should take priority, maybe it would have worked if the heating side was set to OFF?
Anyway, a rare occurrence and easily worked around (for us) by artificially cooling the outdoor sensor, but would have been more of a hindrance had we been out and the DHW did not run on it’s set schedule. Also easy enough to run at a slightly cooler period but we like to run the DHW at the warmest part of the day for maximum efficiency (we consistently saw COPs of above 5 during the hot weather for DHW runs).
As you say, I don’t think it’s worth risking a firmware update even if this would fix the issue.
For me, the surprise was that this setting (#4013) appears to apply to all heating modes, not just space heating.
Hi Phil,
I just checked #4013 on my vers01 controller (the October 2025 one) and find that DHW startup is not inhibited if OAT > #4013 setting. So @jakeymd1’s suggestion that it may be a bug in earlier controllers appears to be right on the button.
Is there any reason not to simply increase #4013 to 45degC? That should cover UK OATs for another couple of years…
The issue on my controller is that 35C is the maximum allowed value for #4013, which we briefly exceeded during the heat wave last week.
I understand some other variants (R290-based models?) can accept higher values for #4013, so as you say it makes sense to simply set this to it’s maximum allowed value assuming you have some other control mechanism in place to prevent unwanted space heating in summer (I use my 3rd party room thermostat to turn off the call for heat).
#4013 seems to serve little purpose other than preventing space heating accidentally being turned on in summer? Or maybe it exists to ensure the heat pump isn’t operated outside of it’s operating range.
Yes @Old_Scientist you are absolutely right. A closer read of the various manuals reveals (my emphasis):
MIM-E03*N User Manual (MICOM v00 version): #4013 max setting (may be 35degC or 45degC): “The value is determined according to the type of outdoor unit.”
MIM-E03*N User Manual (MICOM v01 version): “Space heating off temperature (FSV #4013, Default “35/45degC”, Range 10 ~ 35/45degC): At high outdoor temperature above this value, the space heating will be turned off, to avoid overheating.”
EHS Installer Reference Guide Book: “#4013: Outdoor temperature at which the heat pump stops, DHW only via booster heater (BSH) operation.”
The last of these is the telling one, confirming that DHW is also disabled if OAT > #4013 (unless you have a booster heater).
I don’t recall whether my original Micom allowed #4013 = 45degC, but the current one certainly does, and that’s on an AE080BXYDEG/EU (HTQ Series).
Thank you so much, that’s really helpful and I had missed (or not taken in) the parts you have emphasised, so this behaviour is well documented and the reason for it given (not a bug). Next time I should read the manual more thoroughly.
For note, I have the booster heater (immersion) disabled to prevent it unintentionally kicking in, hence why we saw no hot water.