This IS a Smart Boiler

marc

low flow thru the exchanger, causing short cycling. check your required flow for the system and compare with the internal pump. also check pump speeds in the coding, min, max, and setback speeds. marc

Mike T., Swampeast MO

Virgin Vitodens that has never provided heat unless forced by the "combustion check" switch.

Single circuit; no DHW; only the internal circulator driving a TRVd system in a gravity conversion.

Have had the unit "off" since checks were completed. First below freezing temps forecast in the next few days, so switched it "on" to "standby mode" this afternoon. (Supplemental electric heat available and I'm still a slave to habit until it gets truly cold...)

After a short delay the burner fired--heard some differential pressure bypass noise and checked pump rotation-it was moving albiet VERY slowly.

Thought, "oh it's just 'exercising' the pump like it says it will do for a short period each day in 'standby' mode."

While in the basement burner kept firing for exceptionally short periods every few minutes. All sensors functioning and all diagnostics A-OK. Switched to "space temp mode" and all operation stopped. Waited and switched back to "standby". Pump again ran and burner again fired for short but frequent periods.

Went upstairs for an hour and returned. Same operation.

"Curious", I think...

Unless there is some sort of fault that the controller cannot detect, here's my explanation:

The boiler must learn when it is truly safe to go into true standby mode. Having never supplied heat and having never learned what heat is required, it is defaulting to the ultimate safety mode whereby it maintains the system at the minimum possible supply temperature! In other words, it's not quite trusting its own sensors until it truly knows that all are functional based on experience.

Mike T., Swampeast MO

There was a problem. Boiler had arrived with defect in control panel (± adjustment dial for parameters would only allow a single increment change). Viessmann shipped new control unit as well as VR20 board just in case control unit wasn't the only problem. Good move and great service on their part as the board had to be replaced as well.

Called early this a.m. about the odd "standby" operation and they tried all day to duplicate the problem. After calling back immediately to say they were trying to replicate, they called back this p.m. and said to replace the board as well.

Even big "V" has an occasional problem Service however was perfect!

Finally cool enough outside for the thing to have to run--WOW does it ever condense water!