Viessmann 200-W B2HA-19 - piping design help

markp1

So after room-by-room load J and comparing with actual heat use versus degree days, I am now needing to decide on a plumbing setup. The house is 2500sq ft from 1970, with 5F as the design day. Manual J is 57k BTUH. The house is 2 floors, plus basement. The basement is not heated, but is finished. All heating elements are 3/4" fin tube baseboard. For a designed delta-T of 20:

Floor 1: 35k BTUH, 132 linear feet of baseboard = 265 BTUH per linear foot = 135F AWT @ 3.5GPM
Floor 2: 22k BTUH, 102 linear feet of baseboard = 215 BTUH per linear foot = 125F AWT @ 2.2 GPM

The boiler I plan to have installed is a Viessmann B2HA-19 with the low loss header from Viessman (80/60). Also an indirect boiler as priority on the primary piping side will be installed with its own pump ( Boiler pump and DHW pumps will be grundfos alphas set to one of the three fixed speeds (doing this for the ECM efficiency)).

Where I am struggling in the design is the secondary piping / Viessmann settings. This is how I would like the zones to be ran:

Floor 1 - 7AM to Midnight: 68F
Midnight to 7AM: 60F
Floor 2 - 6AM to 8AM: 68F
8AM to 6PM: 60F
6PM to Midnight: 68F
Midnight to 6AM: 60F

I have read all the manuals for the Viessmann a few times now, and am not sure how I should pipe these zones (nor how the Viessmann determines what to do what it does). The boiler and DHW pumps plug directly into the Viessmann, and are turned on and off by the Viessmann. But what about the secondary piping? The only option that seems to make sense to me is to have the Viessman treat the secondary as a single heating zone: 1 pump (Grundfos Alpha set to AutoAdapt), 2 zone valves, with each zone valve controlled by a programmable thermostat on each floor.

I feel like I am greatly missing something here with the Viessmann though... how does the outdoor reset and night setback of the Viessmann interact with the secondary piping design of above? It seems like the secondary piping would need to be different somehow for the ODR to work right (and I'd prefer to add the indoor temperature feedback of the Viessmann remote 300A if that makes sense).

Can someone please explain how they would pipe / control these 2 zones?

Much thanks!
Mark

Ironman

I'm only gonna address one thing for now: using night setback. Set back is counter-productive to the logic of the mod-con and will not increase system efficiency. At least not for short periods like you're contemplating. Most likely, it will decrease efficiency and sacrifice comfort as well. If you're planning it because you like it cool when sleeping, then try to keep it around 4-5* and just do it for the bedrooms.

I know the boiler has it as a feature, but that's to satisfy Americans mis-conception that it saves energy.

If you were gonna due it for days, then yes, it will save. But for a few hours with a modulating boiler that has outdoor reset - no - it won't.

It's an old school approach for "bang bang", 100% off or on forced air systems. And again, it takes long periods of set back to achieve any noticeable savings even with those systems.

The best thing that can be done is to get the OD reset curve dialed in right and let it rip. As far as the stat goes: set it and forget it.

markp1

Hi Ironman, thank you for the quick reply. After doing more research, the Viessmann has built in ODR and night setback, so my understanding is that the system is designed to do both simultaneously. So the night setback isn't done by a thermostat turning a zone valve on or off (thermostat), but by the Viessmann shifting the reset curve for the specified times. Am I understanding the Viessmann correctly in this regard?

Assuming the above is right, how should these two zones be piped? Would each zone have a mixing valve and a vitotronic remote thermostat with indoor temperature sensor?

Gordy

I agree with IronMan's comments. Those setbacks are counter productive to any mod/con running ODR. your able to use lower SWT with the baseboard. Why set back, and have to run higher SWT to get out of setback. Those are actually pretty wide setback swings to even get to with those time periods unless your envelope is super loose. I would be willing to bet you would never hit those marks.

markp1

Ok, so forget the nighttime setback

How should the secondary be plumbed?

Side question... the Viessmann can run without run thermostat's, so I am very curious how the Viessman can know when to run the boiler when it doesn't have room thermostat's telling it the temperature is too low... so how does it do it?

Much thanks,
Mark

Paul48

It's very simple when you think about it. It has to supply a certain heat to the structure, based on whatever the outdoor temperature is.

markp1

Paul... such a simple answer, yet profound It is really as simple as it knows what the outdoor temperature is, and what temperature the house should be at, so it determines how many BTU's in a given time period should be generated / distributed? Then the temperature of the return water versus the temperature of the supply water allows it to determine when enough BTU's have been generated?

Paul48

Once you get the reset curve dialed in, it should do its own thing. I think SWEI has an excellent way of doing just that. Maybe he will weigh in.

markp1

Awesome, thank you.

So now that I understand how it works, how do I apply this newly found knowledge to determine the plumbing of the 2 zones into the system?

Since neither zone requires mixing down to a lower temperature, I assume both zones would present to the Viessman as a single heating load (as in system layout 1 shown in the attachment from the Viessman technical manual).

So to have both zones, would it just be balancing valves on the two zones after the pump (E) in layout 1 so I could adjust how much heat each zone gets?

markp1

It seems like that would work, but the Viessman can have two different ODR curves. It makes more sense to me to have zone 1 and zone 2 be on different ODR curves, but maybe thats not worth it? This looks like layout 4 in the manual (layout_4) attached

Paul48

And, not to beat a dead horse, but regarding setbacks........If the system is determining the necessary heat for the structure, everything is taken into consideration. Every piece of furniture. Every interior wall has been heated appropriately. Now, you let the structure get 10 or 15 degrees less than what it should be. Well, I think you get the point.

markp1

Message received on the setback, thank you.

Any ideas on the piping?

Zman

I would encourage you to keep it simple.
Often times when you have only 2 zones, it is easier,more economical and more efficient to use zone circulators over zone valves.
It may also be possible to get the minimum flow rates you need without a low loss header.
I absolutely would not do a mixing assembly and separate reset curve with two zones that are the same type and only 10 degrees difference in design temp. Just run them at the same temp and be done with it.
You got the message on setbacks..
What is the minimum flow for the boiler?
The manual for the controller is lacking..

Carl

icesailor

"" It may also be possible to get the minimum flow rates you need without a low loss header ""

Every beer cooler or other boiler that had pumping issues could have been resolved (or never happened) if a Low Loss Header had been used. If you want P/S piping, why not use a LLH? It solves any questions about "closely spaced tees" and the interpretation of what it is.

Zman

Chris,
My point is, if you can get the same flow rates by pumping directly through the zones, the LLH and the extra circ and money is a waste. With a simple 2 loop radiator setup it is worth doing the math. What I see more often is someone putting an incorrect circ on the primary and ending up with very little delta t across the exchanger
With more complex systems and most radiant setups, the LLH is a smart move that prevents problems down the road.
Just thinking outside the box...
Carl
@icesailor

hot_rod

Have the separator do more work for you. With a 4 in 1 device, now you have separation along with excellent dirt, air, and magnetic removal.

You need to protect all components, especially ECM circs from small iron ferrite. Magnets will become more and more common on hydronic systems.

Here is what I found on a large ECM circ at our shop when I disassembled it for a stuck rotor error code. It is on a system with PAP, copper, and stainless boilers, very little steel or iron in the system components.

markp1

The maximum flow for the boiler is 6.2GPM. On design day with both zones flowing the flow needs to be 5.7GPM. When I spoke to a Viessmann technician about this as an option, he said unless the flow can be guaranteed to never exceed 6.2GPM, then it is fine. If there is a possibility of a single or multiple pumps pulling more than 6.2GPM, then use a LLH.

I fully agree with the KISS principle, and 2 zone circulators without primary / secondary would be about as simple as it could be. From what I understand about the manual, to have 2 circulators I would need the AM1 module for the second zone circulator, which would be fine.

I don't understand though how the Viessmann knows which circulator to turn on... does it just turn on both at the same time? One or both on at the same time though, I can't guarantee that more than 6.2GPM would be getting pulled, so it looks like a LLH is the way to go (layout 2 in the design manual, shown below), with the AM1 module added so a second heating zone with its own circulator can be installed.

icesailor

Set Back Thermostats:

I've been using "Set Back" thermostats since before some here knew that there was a thermostat. I've tried every little save fuel scheme that has come down. The only one I ever found that was really effective were set back thermostats. Which in my case should be "Set-Ahead" Thermostats. Someone said they only work with "deep set-backs". I used them exclusively in my own homes since 1970. 3 homes. Now in my AC/ Heat Strip Condo.

Deep Setbacks? Is 10 degrees enough? 68 high, 58 low? At night and during the day, even on really cold days, it never got to the low set point. For example. on a day when it was 12 degrees outside and it was 68 degrees in a large connected zone at 8:am when the thermostat dropped to 58 degrees, the boiler/circulator never came on until 5:00 PM. It ran for 45 minutes and the room was 68 degrees. At 9:00 PM, the thermostat dropped to 58 degrees. It came back on at 5:00 AM to 58 degrees in 45 minutes. Then switched back off at 8:00 AM.

6 hours on, 18 hours off. I consider the application a "Set-UP" application. I have tested applications more ways than you will ever know. Mine and customers. After a year of operations, I go to the oil service provider who uses a complete Scully delivery management system and can extract any information on fuel usage you want to know about. I know from personal experience that every customer I ever installed set back/up thermostats, saved money/fuel. And never a complaint about being cold. The oil company doesn't care, as long as you buy your oil from them.

Straight ODR curves:

I went to the Veissmann School in RI and took a class on Vitodens. It was more on the 200 which will actually talk back to you but cost more money. I never installed one, only 100's. People wouldn't spend the extra money for a 200 computer. I asked about the issue of set-back/set up thermostats and ODR and why didn't they make a control that over-rides the ODR set back at start up. I was told that the 200 can be programmed to do that. So I set the 100 curve to be a little hotter.

A bigger issue with Set-Up thermostats is the issue of finding electricians that know how to wire and isolate the thermostats.

My Florida Condo with AC. It cost me what it cost for electricity to run it. I had a more "efficient" unit installed. It cost me more to run than the older less efficient unit and it wouldn't cool below 77 degrees when it was 100 degrees outside. So much for saving money on efficiency. I had the equivalent of R-30 blown in on top of whatever was there. Now it will cool to below 75 degrees. I'm too cheap to find out how low it will go. So much for efficiency.

If you want to save money, cut down on heat loss/(heat gain). If you don't tell someone to insulate all the heating and hot water pipes that you can in unconditioned (and conditioned) space, they will be crabbing behind your back about how much money they spent and it now cost more to run it. And there will never be any kind of payback because "Efficiency" will never equal the cost.

IMO. (and experience)
PS: If they crab to me about how the last guy sold them a system that was supposed to be "efficient" but is more efficient at draining the wallet of cash, I tell them to tighten up the house and insulate the pipes. In Massachusetts, its in the building code.

Paul Pollets

The Vitodens should use hydraulic separation if the flow rate is close to 6gpm. The Caleffi unit has more features than the Viessmann LLH, but don't forget the LLH sensor for proper operation. The system pump should be variable speed. Zoning is ok, but constant circulation works better. Deep setbacks at night are counter-productive, but a 5-7 degree setback works on radiators, as long as there is enough time in the am to bring back the home to proper temps.

markp1

hot rod said:

Have the separator do more work for you. With a 4 in 1 device, now you have separation along with excellent dirt, air, and magnetic removal.

The Caleffi SEP4 does look good. Looks like I would need to add the 694 temperature sensor well to it, as the Viessmann has a temperature sensor to go into a LLH. The other option is the Viessmann 60/80 LLH, add a caleffi auto air purge to the top of it, and a Caleffi magsep somewhere else. Seeing as the SEP4 is roughly 4X the cost of the Viessmann LLH, I'll probably go with Viessmann's.

Gordy

Stick with the manual. PG. 30 and 31 self explanitory. If you notice the delta at 6.1 gpm is 20* any lower delta created by higher flow rates, and efficency is lost along with other unintended consequences. Recommend higher delta 35*. Also use the V. low loss header, and sensor. As stated in the manual there are more benifits with the LLH than traditional P/S piping can offer.

SWEI

Buy the Vitotronic 200A (perhaps two) for sure. Indoor feedback paired with outdoor reset provides the ultimate in both comfort and control. The 300A will manage multiple system temps with separate reset curves. Your design temps are close enough I'm not sure that will be necessary.

markp1

Paul Pollets said:

The system pump should be variable speed. Zoning is ok, but constant circulation works better.

Hi Paul, for the system pump, a standard 3 way, or actual variable? It seems the best option is an ECM pump controlled by PWM (0-10V), but there doesn't appear to be a 120V ECM pump controlled by PWM on the market for this size install. The Grundfos Magma with an add-on card can do it, but one of those would be way too big. Any specific pump recommendation for the system pump?

What exactly do you mean by constant circulation (for primary, secondary, or both)? If secondary, just have the circulator for each zone running all the time? That seems a waste of electricity if the zone doesn't need to be heated.

markp1

Gordy said:

Stick with the manual. PG. 30 and 31 self explanitory. If you notice the delta at 6.1 gpm is 20* any lower delta created by higher flow rates, and efficency is lost along with other unintended consequences. Recommend higher delta 35*. Also use the V. low loss header, and sensor. As stated in the manual there are more benifits with the LLH than traditional P/S piping can offer.

Hi Gordy, so for a delta-T of 35, are you referring to the boiler supply versus boiler return delta-T, or the zone's delta-T?

Paul Pollets

We always use the Grundfos Alpha pump(s) on the system side. We run the pump wire back to the boiler computer. Sometimes we install a 110v outlet that's wired only to the system pump in the boiler computer, and plug the pump's line cord in. The pump will control it's own flowrate if set on"Auto Adapt". Purge on high speed before setting the pump to "Auto". The system will be circulating an "on" whenever the temps are 2 degrees cooler than the outdoor temperature. The temperature of the circulating water will vary, according to how cold it is, and where you set the heating curve. The flow rate will vary, if the VSP is set to "Auto". Try not to over-intellectualize the setup. Viessmann has already done that for you. You do need to follow the instructions, wiring setup and coding carefully.

markp1

Hi Paul, excellent, that is exactly the information I was looking for on the system side, thank you! Do you like using the Alpha pumps for the zone circulators also?

Paul Pollets

I use the 15-55 3-speed Grundfos for primary and DHWT and the Alpha's for the system side. Since radiators with TRV's perform well with a VSP, I never "zone" with a zone valve. I let the TRV adjust the temp for the radiator and use a single Vitotrol thermostat. If connected to existing baseboard, rather than radiators, I sometimes use zone valves IF the piping is direct or reverse return to the BB.

markp1

Thanks for clarifying Paul, makes more sense now. I don't have radiators, I have baseboard. Zone 1 is 3 separate home run piped areas. Zone 2 is 2 separate home run piped areas.

Paul Pollets

You'll need a Taco ZV relay box to control the zone valves.

markp1

The Vitotronic remotes (either 200A or 300A) communicate directly with the boiler, and do not provide outputs to go to a Taco ZV relay box (or any relay box for that matter). So how would the zone valves be turned on / off?

Paul Pollets

You supply power to the transformer in the relay box and they work independently from the boiler computer. Which is why they're not used in Europe. The boiler does not need to know their (ZV) presence. When the colder return water reaches the LLH, the boiler sensor communicates to the control.

markp1

So I'd still have regular thermostat's to open and close the zone valves via a relay box, in addition to the vitotronic remotes (which have a temperature sensor)?

Paul Pollets

The Vitotrol must be set in a room or "zone" without a zone valve. If you have 4 zones, 3 will have a zone valve, 1 will have the Vitotrol.

markp1

Right, I have two zone, and planning on buying two Vitotrols. So each Vitotrol is controlling its own circulator, right?

Paul Pollets

No. The Vitotrol is independent and will not control a zone valve. One zone takes the zone valve the other one does not have a ZV. One regular T-stat for the ZV, the Vitotrol goes on the second zone, which is piped without the ZV. In essence, it's running on constant circulation.

markp1

Why not have a vitotrol on each floor and 2 circulators (one for each floor, with one connected to the boiler and the other connected to an AM1 extension module)? Wouldn't this provide independent ODR curves for the two zones for not much additional money?

Paul Pollets

The control only accepts one Viessmann T-stat. Understanding the nuances and subtleties of the boiler and control are the reason Viessmann does not sell "retail". You have to take the classes to have a thorough understanding, and even then, the Vitodens 200 is not that simple. The 100 series is. You don't need two heating curves. BB only needs 1 curve. If a radiant floor was added, then an additional curve would be used.

markp1

According to the manual for the 200A (page 6 and 7 of the attached manual), up to 2 of them can be connected to the boiler.

Paul Pollets

When both HC1 and HC2 are used, each circuit can use a Vitorol. HC2 would have the mixing valve package.

markp1

Can HC2 use the AM1 instead of the mixing valve package?

markp1

So after a discussion with a Viessmann tech, I think I finally understand how the 200-W wants to work... and why many of my above questions basically don't make sense... so, my apologies for attempting to design a system that doesn't make sense with a Vitodens.

Thanks to everyone for showing me patience... knowing what I know now, I'm quite impressed by the amount of patience I was shown