95% there. should i install a buderus room sensor

Wayne Heid_2

I have a g115ws, logomatic, 241 mixing station, outdoor reset and an indirect. First floor is radiant set up for constant circ, second floor is baseboard. Both floors are controlled w/ generic room tstats. I called buderus to inquire about changing the first floor tstat to the bfu sensor. Was told, that the bfu sensor is used for single zone only and not to bother. However, in the Logomatic Applications Manual there is a schematic ('application eco-08' 'Multi-Zone High Temp Space Heating / Radiant Floor Heating with FM241 module and Motorized Mixing
Valve / Indirect DHW Heating') which seems to match my setup and uses the room sensor.

From what I have read, it seems the room sensor and logomatic can do a lot more than just the tstat.

Should I be looking into this further? If so, can a homeowner install one of these things?....the schematics look simple enough.
thanks, jd

Mad Dog_2

My opinion...................................

Listen to Buderus...they know because they get ALL the feedback.... positive AND negative. The only time that we have had success with the BFU or RC 10 is on a single zone with a rather-open floor plan. Schematics may look simple to you....but if you fry the controls by wiring something wrong was it worth it? The only homeowner I know that could pull that off would be Alex The Wire Nut Marx. Mad Dog

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Joe@buderus_2

With the FM241 module installed it allows for two different heating curve temperatures. Normally with radiant floor heating, constant circuation is considered because lower temperatures are used and the temperture swings with on/off controls are eliminated. It is suggested to review the BFU option with your installing contrator as he is familiar with the radiant design. Installation of a BFU is normally an easy step, but the programming requires knowledge of the system, which the contractor is familiar with. If the contractor has any questions or help programming the Logamatic, please have them contact our technical support department at 1-800-283-3787.

[Deleted User]

thanks mad dog. I have had some experience adding new zones w/ relays, check valves and circs. It seems I might get bogged down in the programming aspect, though.

Joe@Buderus...why, when I called buderus tech support I was told the BFU sensor should only be used in a single zone setup (and advised not to use it)?

Joe@buderus_2

I recently transfered out of the technical department after eight years, so I can't answer for their response. Based on the information provided, a room sensor could work in the application described because of the FM241 module. The FM241 module allows for a two temperature system.

In a single zone baseboard system, the radiation in the entire loop would have to be balanced for proper heating with constant circulation, so caution is advised using a room sensor in that type of application(If the radiation has independent controls for each area/room, then balancing is not as important).

Did you check with the installer to see how the radiant system was designed? Perhaps it is higher temperature with on/off operation in mind.

[Deleted User]

the radiant floor was designed well before the buderus arrived. the design max water temp is 131. The buderus was set up to maximize circulation times. I had inquired about the sensor, but was told the tstat was planned to be used. I don't want to be barking up the wrong tree, so I'm just trying to get more info on the sensor and see if makes sense in my application (especially given the cost of the BFU as a percentage of the install cost). If there's no value, I don't want to be giving my installer unneeded grief!