Vito 200 and circ speed settings

Mike T., Swampeast MO

Yes, there is a minimum circulation speed (700 rpm) which I presume is sufficient to maintain the minimum required flow volume through the boiler. Minimum setting for this speed however is 1 on a 1-100 scale with 100 being 2700 rpm.

tom k_4

circ speed settings

So far here in West Virginia this has been the coldest Feb on record. Vito 200 installes 2 years ago with heatloss showing 10* DD means I have been running at max on some of these 0* AM's.The morning temps in the house would go down to 62(read no sidewall insulation and no insulation on the old 3" gravity mains) I bumped the Max circ speed to the 100 setting which helped immensely during the coldest stretch. After a day I backed it down to 80 and I now am back down to the factory setting of 65.I have the RS controller installed and I was wondering if this was the proper application of the ability to adjust the circ speed?

Brad White

My understanding, or at least what I did is

to set the circulator setting at the highest (100%) setting up from the factory set 65%.

My understanding is that the Vitodens will modulate within it's range (down to 50% speed I believe) in response to load.

Not sure why the 65% is the default especially if it ramps down to 50% speed because there is not much range of control then. Mike T. probably has more information in his head. My coding book is at my Susan's house so I cannot reference it right now.

ALH_4

speeds

What is even more strange to me is that the DHW speed is set to 98%. I asked them why not 100% and they didn't really have an answer. The 65% for heating mode is about electricity conservation where 100% is not needed. Viessmann must figure 65% will handle it in most cases, and it will with a low loss header. Honestly, I never really felt satisfied with that answer.

Wouldn't the internal speed control take care of energy conservation?

tom k_4

So....

I guess I'll set mine back to 100 (only makes sense)and work on getting the mains and sidewalls insulated. Should I also consider lowering the min speed coding to get a larger downturn of circ speed?

Brad White

I am not sure if you can

do that. The minimum internal circulator speed I believe has a low limit floor minimum flow rate for safety or control reasons. Of course if that were true, the Comfortrol would refuse lower settings. Not suggesting you go there....

tom k_4

very good point

best to leave well enough alone.Thanks Brad

Mike T., Swampeast MO

According to the documentation, the built-in circulator in the Vitodens 200 has two distict modes of operation: "System Circuit Mode" and "Boiler Circuit Mode"

When the temperature sensor for the low-loss header is attached, the circulator automatically switches into "Boiler Circuit Mode". During "Boiler Circuit Mode" the circulator varies speed to maintain target in the low-loss header regardless of the rate of secondary (system) flow. It's this ability that allows the boiler to match its output with system load while maintaining target temperature in the LLH. To my knowledge no other boiler is capable of this. Viessmann told me that addresses 044 (min rotation speed), 045 (max rotation speed) and 046 (rotation speed during reduced (moon dial) operation) have no effect when the circulator is in "Boiler Circuit Mode" as the speed of the circulator has everything to do with maintaining target in the LLH. At least one person has reported here however that changing address 045 (maximum rotation speed) to 100 seemed to solve a problem with "not enough heat" in extremely cold weather so I suppose it's possible that I received bad information. I SERIOUSLY doubt however that the circulator operates at fixed speed during reduced mode (moon dial) operation when the LLH is used.

During "System Circuit Mode" (boiler directly connected to the system without the LLH), all the literature says is that the circulator speed is "weather responsive". This is how mine operates. At Viessmann's suggestion I completely "opened up" the circulator speed by setting minimum and maximum to the lowest and highest possible values. During reduced mode (moon dial) with "System Circuit Mode" the circulator DOES operate at a FIXED speed. It does this because TRVs are assumed and it is further assumed that all of them will wind up "starved" and wide-open during the setback period. The fixed (but adjustable speed set at address 046) speed allows for reasonably even flow during such circumstance.

tom k_4

system circuit mode

As my setup is without LLH I did see a significant difference when I increased the 045 address to 100%. If you remember Mike you were a big help to me in my setup about 18 months ago. I now have all the rads in the right places and we are receiving the benefits of this converted gravity system. You say Viessmann indicated to use the max on the 044 and 045 addresses. I may have to experiment with that now that we're back in the 40's Thanks again for all your help and a huge Thank You to Dan for the site

Mike T., Swampeast MO

Viessmann recommended 044:001 and 045:100, in other words full modulation ability for the circulator. Minimum setting at 044 and maximum setting at 045

If anything like mine, you'll be able to tell that the circulator speed goes down when you fully open the circulator settings and the weather is moderate.

Believe I set address 046 to either 75 or 80. I rarely use timed setback, but found that the default setting of 045 seemed to favor the low, close rads when all the TRVs opened wide. Still however not particularly well balanced but higher circulator speed didn't seem to help.

Mike T., Swampeast MO

My only guess about the 98% setting for DHW production is that if such proves inadequate for the indirect in use that the problem is the indirect--not the circulation speed...

Again, from what I was told by Viessmann, the circulation speed settings for space heating are inactive whenever the low-loss header is installed.