Vitodens 200 pump?

Ted_5

the formula for GPM in a system is

___BTU____________ = GPM
Delta T X 500[for water]

So as the BTU's change because of the outdoor temp, the
GPM's can change to keep the same delta T

Ted

Dave_13

Vitodens pump?

I am wondering why an ad I saw for the Vitodens 200 states "no secondary pump needed"?? And what causes the built in circulator to modulate speed-differential pressure? Temperature??

Dave_13

no one?????

Mike T., Swampeast MO

I can only guess

that the circulator modulates based on delta-p, delta-t AND the current state of burner modulation.

As to the non-requirement for a secondary circulator: 1) You don't have to worry about low return temps or high delta t. 2) As long as the system is within their delta-p parameters, I would imagine that it WANTS to use its circulator ONLY to achieve the best efficiency. I'd be willing to wager that the controller strives to learn the closest possible "maintenance level" of burner AND circulator modulation at various outdoor temps. Once these maintenance levels are established, some relatively simple logic will allow it to make quite valid assumptions regarding the current comfort state requested by the occupants.

Were I designing the controller for a world-class boiler, this is what I would do--and they certainly have more and smarter engineers!

If you recall your high-school or college vector math, it's not too difficult. In simple terms you view the burner/circulator as the "magnitude" of the "major" vector and room temperature as the "direction." Outside temperature, delta-p and delta-t are additional vectors acting on that "main" vector. The goal is to put in just enough magnitude from the boiler to wind up with a resultant force that is no longer directional--the other vectors return the major vector to the point of origin.

In such a state of stasis the boiler will be acting "perfectly" with the only losses being waste heat up the flue (VERY little in the Vitodens) and transmission loss to unconditioned space (controlled greatly by insulation, pipes in conditioned space, etc.). Output devices will be operating at the lowest possible temperature with the highest possible radiation. (I think it would be possible to throw in a "circulator efficiency" control as well, but haven't yet put that in my program flow chart.)

Alan(CaliforniaRadiant)Forbes

No secondary pump needed

as long as the proprietary pump can meet your flow/head demand. If not, you need to add/substitute another pump; maybe even the low loss header. Just check the specifications or contact Viessmann. There should be a rep. in your area or call 1(800)288-0667 in NY.

I may be wrong, but I don't think the Vitodens modulates flow, only temperature. They do that with a modulating matrix burner.

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Rob Waters

Guess I have to jump into this one....

The small two sizes of the Vitodens 200 incorporate a built-in KM-BUS variable speed pump (made by Grundfos). The terminology "KM-BUS" is brand new to North America as Viessmann is the first company to introduce this. It basically means that the pump speed control is network-linked to the boilers outdoor reset control. The speed of the pump will vary between 700 and 2700 RPM based on the outdoor reset controls settings. This enhances the boilers modulating ability, eliminates cycling and makes it condense like crazy in low load conditions (which occur most of the time for most buildings). So basically as the outdoor temperature changes this boiler will modulate the pumps speed, modulate the burners firing rate and modulate the output water temperature simultaneously. Pump will always go to high speed when creating DHW. Pretty slick technology!
As far as the pumps capabilities, in most cases it would be considered the boiler or primary pump. It can handle small, low head heating applications on its own, but check the flow and head requirements of the system. For larger systems it will be the primary pump, pushing into the low-loss header.
I suggest that you go to www.viessmann.com and download a technical data manual to get the complete story on piping up and installing a Vitodens.

Good Luck

Rob "seminar guy" Waters

Dave_13

Is this so that when the burner is at low fire,the pump slows down to maintain a certain supply temp????

Alan(CaliforniaRadiant)Forbes

Clarification

Thanks for the clarification, Rob.

Yeah, you're right: that is pretty slick, i.e. modulating flow and heat at the same time.



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Mike T., Swampeast MO

Someday

I might visit the Veissman site for the engineering data they post regarding the Vitodens--but until then it's too much fun thinking, "how would I do it?" It's kind of fun when the "real" data seems to agree!