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Bosch Singular 5200 (Radiant/DHW) - Problem w/ DHW Achieving Set Temperature

cloudd Member Posts: 48
edited February 23 in Radiant Heating
I have contacted Bosch regarding this issue I have experienced.

I am using a Bosch Singular 5200 Combi w/ NG without an outdoor reset control.
New install June 2024.

I am having a problem which either looks like there is a software/firmware bug or I have something in the configuration set wrong?

My outside temps are down to -9C (lowest this winter) , usually around 4C in the winter. I am approximately 100' above sea level.

I am aware that there is a “DHW temperature setting” and a “Boiler/Radiant temperature setting”.
*My understanding is that these temperature settings are both independent of each other.*

My DHW is set to 140F.

I have tried setting the "Boiler/Radiant Supply Temp" below 130F (120F, 112F...) and the radiant worked great. BUT then I experienced a problem with my DHW not reaching 140F (DHW has an independent temperature setting in the combi and it was and is set to 140F). Once I set my Boiler/Radiant Supply temperature below 130 it seems to have an impact on my DHW temperature reaching 140F because the Bosch 5200 struggles to reach 140F for the DHW. It starts acting up (cycles, relights multiple times) and only is able to get the heat up to 120F-130F (DHW) creating water similar Hot>Warm>Cold>Warm>Cold and it never gets up to 140F.

Based on what is going on if the boiler radiant supply temperature is set to 120F or under it acts like this setting is directly impacting the DHW temperature setting or somehow has a relationship to it. This is wrong and should not be happening! It seems like the Bosch 5200 combi software/firmware has a fault in it or I have it configured wrong (there are only 2 independent temp settings "DHW Temperature" and "Radiant Supply Temp" that I am aware of. I am puzzled and have read the manual thoroughly. I am pretty sure I had configured it correctly. It did not seem that hard to configure.

This was my first winter running the system Boiler Radiant Supply at at 130F most months and 140F 1 month. It worked great setup this way but is running much hotter that it needs to be.


  • Big Ed_4
    Big Ed_4 Member Posts: 2,780
    Have your tech call Bosch tech Support to program unit .1(603) 552-1100
    I have enough experience to know , that I dont know it all
  • cloudd
    cloudd Member Posts: 48
    edited February 22
    I feel guilty saying this but happy to have a solution. It was a user error.

    I could not read the icons on the front of the unit because it is mounted much higher than my eye level and my vision is not that good upclose . I did not see the icons, only white LED indicator lights. This caused me to mixed up/reverse the DHW and Radiant supply temperature settings.

    With this being said I have been running my radiant supply temperature at 140F all winter. I have been increasing and decreasing my DHW temperature, while thinking it was my Radiant Supply temperature. I believe the temperature on the units front screen is the current heat exchanger temperature (I need to check with Bosch on that). The heat exchanger temperature was missleading me.