Vitodens 100w b1ke-199 DHW temp not respected

empire29

I have a new Viessmann Vitodens 100w b1ke-199 combi-boiler (DHW + Heat supply for 2 hyrdonic air handlers). This is all < 1 year old.

Ever since we got it, the DHW hot water "scalding hot" (hurts your hand). I got around to setting up ViCare and set my DHW to 115F. When neither the DHW or Heat are being pulled, the ViCare app shows ~115 to 130F for DHW. However, when i start to draw hot water with EITHER DHW (ex. running bathroom faucet) or the heat supply - i can see in the app the temp fluxuates between ~ 115F and 140F, usually staying closer to top 140F range (which is that "too hot" temp).

In the ViCare app, i have a DHW schedule (5:30am - 10pm) and Operating mode switch (DHW) = Standard.

Any idea what could be causing this and how. i can adjust it? This seems like it should be a trivial setting.

GGross

First thing I would check is if there is a mixing valve under the unit? When these run hot in space heating they have no choice but to overtemp the DHW, a mixing valve is required in my region for all combi boilers for this reason.

next would be to check what the temp is actually coming out the faucet at. I dont use the vicare app much but the DHW matching exactly with the space heating temp is a little odd. is the DHW scalding you when it comes out of the faucet?

Alan (California Radiant) Forbes

Have you called the person or company that installed it? Or did you install it yourself?

empire29

https://forum.heatinghelp.com/discussion/comment/1891075#Comment_1891075

yes it’s scalding coming out - I measured at 136F just now

I’ll check for a mixing valve but will have to look up one looks like.

empire29

empire29

https://forum.heatinghelp.com/discussion/comment/1891082#Comment_1891082

GC has his sub o stall it. My GC it turns out is not good and doesn’t like to take accountability when he can avoid it - trying to self educate before going back to him

GGross

https://forum.heatinghelp.com/discussion/comment/1891139#Comment_1891139

it will be a 3 way valve, likely with a plastic cap to make adjustments, and sometimes they have a temp gauge on the outlet (but not always) typically if the temp in the boiler from space heating were overheating the domestic it would cool off after a short while. if your system makes high temp water for space heating you would need a mixing valve (regardless of codes etc) if the system is all low temp (in floor heat) you may also have something wrong with a sensor in the boiler, though it does seem to be reading the temp correctly on your app.

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