Big V's Vitodens 200 Comfortrol™ coding again

Unknown

To start; Has anybody adjusted the rotational speeds of the internal heating circuit pump yet? Address 044, 045 and 046 are there for a reason. Right?

Also,,, Any efficiency tips (coding address changes) for New England winters and the brutal on/off shoulder months? I’ve been going with the factory Specs. to date and their recommendations so far. Seems to be SO much room for improvement within the programing.

I’ve tweaked out my Buderus Ecomatic™HS2105 on the G115 so much, the oil provider doesn’t even want to deliver to us any more. The truck is just too big;-) I want to get THAT GOOD at programing the Comfortrol™ as that’s what I’m selling lately and can’t see any reason why to sell anything elce. Sorry hr, I’ve been drinking the orange Kool Aid again;-)

Lots to improve upon with what the Germans have given us. You agree?

Let's talk in code;)

Gary Wallace

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marc

pump speed

i would leave in the default setting, have had problems with their bypass howling when low flow occurs. marc.

Unknown

low flow

Did low flow occur with or without the useage of the low loss headder that caused this "howling" you refer to?

Curious about the howling? Did you adjust address 045?

Gary

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marc

originally

it was without the header, small load, viessmann recommends using a separate dif. bypass valve. do not assume that the one with the boiler will act as a system bypass. now we pipe similar to p/s without the header. works wonderful. boiler is the secondary with closely spaced tees. marc

Mike T., Swampeast MO

Really tough to find information on that built-in pump. It [seems] to be a special Viessmann adaption of the Grundfos Magna 60 series (at least the electric ratings and full flow curve look the same). Grundfos website is kind of strange and I can't seem to link to a specific page. But if you go to Grundfos, then click on Magna, then click on Specifications you can get the .pdf document for the series.

Isn't Germany on 220v 50 hz? If so, the pump in the American version might yet another special Grundfos modification for Viessmann...

Even tougher to figure out just what that pump does in operation.

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Pretty straight forward for a simple TRVd system as speed varies between the hi/low settings as modified by outside temperature. This mode of circulator operation is called "heating circuit pump". It appears that those 044, 045, and 046 addresses for pump speed are ONLY in effect with address 005 set to the default 001 value for "with heating circuit pump logic function".

To make adjustments to the factory settings, you need to compute the required maintenance flow at both design conditions and near the point where heat is no longer needed (say 50°-55°). Then of course you need to compute head loss at these flow rates.

Then you need to find the rotation speeds that correspond with these flow rates and pressure drops. Unfortunately, the documentation fails at this point as you only get the 100% flow curve and the statement that the default high speed setting of 2,000 rpm (2,700 possible) results in 65% flow capacity. I found a document in German, that [seems] to be for this pump and [seems] to tell you how to compute flow at various rotation speeds, but my German is limited to internet translations...

My guess is that the default settings will be adequate for most TRVd systems. If you don't get complete flow through all of the rads, I'd increase both minimum and maximum speeds. If you want to try to save a bit of electricty, you could reduce both or one to "home in" on the point where flow is just adequate with enough pump "headroom" to give decent response when you crank a TRV or two.

Address 006 allows you to choose which coding addresses contain the pump speed(s) to use during reduced output (setback) mode. Factory setting is for the same speeds as in normal mode--it would seem that the speed will vary with the weather in this setting.

It also appears that if you change address 006 to change the pump speed during reduced mode that the pump speed becomes fixed as there is only a single setting for reduced mode--not high and low--just one. This makes sense on a TRV'd system as when you go into reduced mode, the TRVs will all open wide and restriction in the system will drop. As long as your TRVd system is reasonably balanced to begin with, you could probably save a bit of electricity by telling the boiler to go into this quite low fixed rotation speed (factory default of 1,200 rpm from a max of 2,700 rpm) during reduced temperature (setback) mode.

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Now it gets really sketchy...

If you use a low-loss header, once you attach the temp sensor, the circulator goes into "boiler circuit mode". It is not stated directly, but from the operational description of the header, the circulator now varies in speed to keep delta-t across the boiler high and heat leaving the boiler equal to heat being used in the system. I have a feeling that those 044, 045, 046 coding addresses no longer apply as the pump is no longer a "heating circuit pump". Any modifications you make to those addresses probably have no effect.

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If you're running conventional primary-secondary without the low loss header and without any external temperature sensor, I won't even begin to speculate what happens or what to do as such doesn't [appear] to be one of the recommended applications.

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With a mixing valve (3-way) and without the low-loss header it [appears] that the pump will be operating in "system circuit mode" with the pump speed addresses active. I wouldn't be surprised if the proprietary control for the mixing valve senses things and makes its own adaptations to pump speed settings.

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With the documentation I have there doesn't seem to be much in the way of "tricks". The only one I know for sure is address 011. By setting 011:001 you can remotely put the unit into the reduced temperature (setback) setting by closing a DRY contact that jumps terminal positions X4.1 to X4.2

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There are no documented "tweaks" for the burner--I most sincerely believe that none would ever be needed anyway...

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When it comes to tweaking the pump for highest electrical efficiency, it [appears] that you must have a simple system (straight TRVs, or straight TRVs plus a 3-way mixing valve) using only the internal circulator. And then you must compute your maintenance flows and pressure drops ACCURATELY and then you still have to find documentation regarding pumping ability at different speeds...

S Ebels

Howling

Are you sure it was the bypass? I had one that did that and thought it was the bypass also. Wrong, replaced the circ and the noise went away also. A visual inspection after we removed the offending component didn't reveal anything out of the ordinary. Seemed to be some kind of a harmonic that would change in pitch with the circ speed.
Viessmann, as always, was more than helpful.

S Ebels

220V

The pump is 220V and runs off the transformer in the pump control module. You're not going to find one of these at the local hardware or parts place at 9PM on a Saturday night.

Brad_9

I've put in a P/S setup and was going to use the low loss header temp probe on the primary loop just before it feeds the secondary that heats the main room where the Comfortrol will be. The HO didn't like the Fe in the low loss header in his system (and really wanted P/S), but I may go back to it if this doesn't work well.

Do you use the X4.1 and X4.2 to signal the boiler to come on when you have a call for heat on a secondary pump? I'm thinking of using a Taco SR506 for the pump relays. The manual makes it look as though you lose the weather responsive control when you use the X4.1 and X4.2 to call. Is that true?

Thanks

Brad_9

0A7

Thanks to Bob Marshall at V. I got my answers to above post. No need to call for heat if it's below WWS temp outdoors. May have to put in that low loss header though.

The 0A7 "Anti Legionaire Function" looks like a winner. It heats the DHW up above 140F for a while during the night. Keeps down the heat loss from the tank keeping the water at that temp all the time. Neat, I'll have to try it.

Mike T., Swampeast MO

Low-Loss Header

If your system REQUIRES high flow, or if you are utterly unable to make a reasonable estimate of flow AND ensure that flow won't exceed, then I would use the low-loss header. Standard P/S is similar, but not the quite the same.

In particular the temperature sensor in the header appears to be measuring a temperature MIX--boiler supply as reduced by the portion of system return flow NOT going back to the boiler.

It (LLH) also ensures that the system return temperature is exactly equal to the boiler return temperature. With P/S and closely spaced tees, your boiler return temperature won't be the same as the system return because the system supply stream has passed through it before being returned back to the boiler.

Mike T., Swampeast MO

Don't Forget Where This Boiler Comes From

In the country of origin, TRVs are required by law! There's absolutely nothing tricky or sneaky about first designing for your own country! (That is unless you're talking Chinese exports.)

I'd venture to say that with most (or is that all of the legal) systems in Germany, the low-loss header will not be required.

The designers did though think VERY broadly. They provided a way to ensure peak boiler efficiency with systems that aren't designed for (or using) proportional flow control. The low-loss header is the solution--if you need it and don't use it, you're essentially flipping the bird to the designers who worked so hard to make such an efficient burner.

You may be able to fabricate something similar to the low-loss header (there's really not much to it after all) but make darned certain that you provide a sensor well in the proper location! If your "primary secondary" system isn't identical in function to the low-loss header, the program logic will FAIL because assumed condition(s) will no longer be true. And guess what? You're not going to find some "hidden code" to make up for the error! If it didn't have to make those assumptions for proper operation, they wouldn't be made in the first place!

Unknown

GREAT STUFF Mike

I'm so tierd now I can't absorb all the info you posted. I just bookmarked it and I'll get back to you later. Any thing elce?


THANK YOU !!!

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Mike T., Swampeast MO

By setting address 011 to 001 and address 027 to 001 you can initiate an "external" heat call with a DRY contact closure of X4.1 - X4.2.

When those contacts are closed, the burner will no longer follow the heat curve and it will heat to the setting you place at address 0A2 (180° max for the boiler itself).

This would seem to be a nice way to integrate a small amount of snowmelt. If a TRVd system, your system flow will drop drastically due to the increased supply temperature, but the flow through the snowmelt portion will keep you from having a low flow problem. Without TRVs, you better have mixing valve(s) for the rest of the system! Note that you must also properly set address 0C5 for the desired pump/valve conditions in your particular system.

Essentially, that combination turns the Vitodens into a "dumb" boiler, so you could technically run a t-stat to those contacts and have a single-temperature (non reset) system. Absurd in my mind, but you never know...

Ted_5

Hey, Mike

you realy have been doing your home work! There is only one thing you said that is a little off. The max. temp of the boiler in heating is 167F it will go to 172F while making DHW if you program it that way. Keep up the good posts!

Ted
Viessmann rep.

Mike T., Swampeast MO

Thanks for correction Ted. The coding instructions are actually pretty good if you cross-reference everything.

It does though specifically say under address 0A2 "max. possible boiler water temperature 180°F/82°C" with the default setting of 0A2:075 corresponding to 167° F/75° C.

Mike T., Swampeast MO

Some Other \"Tricks\" You Could Accomplish

Note that the END USER is encouraged to learn how to use the boiler controls--to include adjustments to the reset curve!

However, it is possible to automate some of these changes...

Those 011 and 027 addresses offer the possibility of some simple external automation.

While I belive "V" already makes a special unit that can connect to a telephone you can easily emulate some functions with little additional cost.

Say you have an extremely irregular schedule such that simple timed controls of the normal and reduced modes are difficult--what you really want is an external way to tell the boiler which program you want to run.

Set 011:001 and 027:000 Connect X4.1 and X4.2 through DRY contacts of some external switch or relay--many telephone systems have such a function built-in (you may or may not have to add their relay) and simple telephone interfaces are also available (like X-10). Now you can easily telephone your system to change the mode. System is failsafe in that any problem with the external switching will result in normal mode.

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Now say that your weather is exceptionally variable and you have found a reset curve that seems to be nearly perfect--it is conceivable that during long periods of unusually cold weather that your curve will not be quite adequate to maintain the desired setpoint.

By setting 010:001 and 027:000 and connecting a simple t-stat that makes a DRY connection between X4.1 - X4.2 AND setting address 0A2 to the highest possible temperature of the boiler (it allows "impossible" settings so I presume that if your setting exceeds the maximum it will still just heat to the max possible) you can get a sort of "emergency" thermostat. If the temp in the space with that thermostat drops below setpoint, the boiler will produce the maximum possible supply temp. (You could also use a simple switch marked "max supply" or something like that). Of course this assumes that the boiler still has some capacity remaining--it won't make the boiler "bigger" of course!

Another possible situation where this would be useful: Say you have a small outbuilding like a shop connected to the system. You generally keep it VERY cool, but when you want heat, you want it NOW! By instituting this "external" call for heat you can bypass the reset curve and heat the space as rapidly as possible. Once nearing setpoint however, you want to ELIMINATE the "external" call! (A two-stage stat (if not using TRVs) might be highly useful for this. If using TRVs, think a simple t-stat used as a "max heat" switch...) The rest of your system must be able to deal with the increased supply temmperature without problem!

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The "external disable" settings and connection points offer some additional "tricks", but I'd be extremely careful when using such a powerful function... Such are likely most useful for applications requiring multiple, staged units.

Mike T., Swampeast MO

Solar Integration

Those external call, remote setback and external disable commands/connections could prove useful for solar-aided systems, both passive and active.

For example: Say you have a large passive solar space--properly designed with an enormous heat sink. If you use the slab and/or air temp in the solar space as a "let's try to MOVE that solar heat" command you can disable the burner while still retaining circulation and/or mixing.

You could also use outside temperature and sun intensity as an inverse "external call for heat". In other words, with temp above a certain level and solar intensity above some threshhold, you could force the boiler to go into either the reduced curve or even a fixed (low) supply temperature. With good passive design and a very well-calculated reduced curve, you could likely reduce day-night-weather temperature swings significantly.

Just noticed yesterday afternoon that V makes a "snowmelt controller" that attaches to those "external call" connections. Perhaps they make a solar intensity controller that automatically adjusts the (normally fixed) setpoint to use with the external call. Hmmmm....

Mike T., Swampeast MO

Active Solar

Here's another idea--not sure if the appropriate controls are made--but given the open architecture of the system I'd be surprised if they weren't.

When the active solar is functioning, have it connected in series with the system supply. Find a control that uses the heat gain across the solar portion to make a corresponding reduction in the reset curve. Instant, proportional solar feedback with failsafe backup...

This would be HIGHLY preferable to having the solar component connected to the system return as the boiler will still be the device seeing the lowest return temperatures.

Should be possible as well to primarily use the solar for DHW and (when heat is required in the house) "dump" any excess into the system itself.

Possibilities with this puppy are nearly endless... Just try to use TRVs or FHVs and things get much easier.