Vitodens for Dormitory

Paul Pollets

We turned on the main slab radiant floor just before the big snow storms. The Vitodens 6/24 is heating a 12,000 SF dormitory with Great Room and powering a HW coil in the AHU. We'll be installing a 120 tube Viessmann solar array next week for the DHW system, if the weather allows. This facility (Islandwood.org) is totally "Green" and uses Viessmann boilers to heat the other 8 buildings on the site. I was hired last year to fix and repipe every one of them, as they were installed improperly. Now we're doing 2 new buildings, and replacing the system in the owner's home, also screwed up by "others". These pics were taken before pipe insulation.

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Bob Burnham

Nice Job! One Question

Paul,

Is the Low Loss Header required on a Vitodens? What exactly is it's function? I don't see them on Buderus and Triangle Tube jobs. Thanks!

Rick

Andrew Hagen_2

LLH

The low loss header is not required, but there are reasons to use one. idronics 1 explains it better than I ever could.

Bob Burnham

Sweet!

Thanks!

Paul Pollets

LLH

The Low Loss Header is required on Vitodens boilers when the flow rate is more than 7gpm or a secondary circuit is installed. In this case, the design (radiant)for the building is 14gpm and the 2nd circuit is installed for the HRV HW coil. The LLH decouples the boiler flow rate from the system flow rates. John Siegenthaler has written some excellent articles on the use of hydraulic separation, both in PM and PME. Or click on the idronics link above.

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Brad White_203

Zen Radiant

Paul, I always love the simplicity of your installations.

That 12,000 SF- I take it that the 6-24 is heating the Great Room and some other areas but not the entire 12 KSF? I mean, 7 BTU/SF sounds thin, even in your climate.

But it has got to be a great end result. I am glad you found each other.

Paul Pollets

Loads

The RFH load is 58K at 24 degree design temp; the HW coil is 40K. The engineered design called for a 1500CFM HRV for one room that's 40x40x 20H. Massively oversized!! The ME's were dismissed after peer review. They originally called for a 300K btu boiler, like they did in the other 8 buildings. This building is highly insulated, and several rooms are unheated for storage, hence the avg 7btu/SF. Happy NY, Brad!

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hb_4

Why........

..........the two compression tanks, Paul?

Mark Eatherton

Simplicity is a beautiful thing...

Nice work Paul.

Jeff, ALL of our jobs have 2 expansion tanks on them. One as a reservoir to compensate for minor fluid loss associated with initial air elimination during start up operation, and the other to act as an expansion tank.

We do not make a solid connection to the potable water system, we DO have low water cut off protection, and in some cases low pressure cut off, and you can put low pressure audible alarms on the same LPCO function.

This is a REQUIREMENT of our insurance company, in order for them to continue taking our money and MAYBE cover any claims we file...

Our local inspectors wish it was mandatory by code.

No leak is a good leak.

ME

Paul Pollets

Exp Tanks

The facility asked me to "recycle" the 2 tanks from my previous fixes (the exp tanks were undersized for the other buildings) and since the spec was for an AX-40, i used 2-AX-20's.

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Steve Ebels_3

YAH!

We do the same thing ME. Our systems go in exactly the same way and are not connected to fresh water plumbing. Installing a good gauge on the "pig" tank let's you see in a heartbeat if there is an unseen leak in the system, whereas with constantly available make up water, a small leak can go undetected until things are all clogged up. The other advantage of course is that in the event of a system integrity failure, you dump the contents of the system and that's it. I've been in places that have had 1000's of gallons cascading down from the top floor while the owners were away. Tain't pretty.

Steve Ebels_3

As usual

Very nice my friend, very nice. Supremely functional, easy to service and it's obvious that a plan was in hand BEFORE the first fitting was connected.

scott markle_2

Mark, (or anyone else who feeds their systems this way) can you elaborate on the piping of this second tank (pig). I'v used Axiom feeders on some glycol charged systems, but they are expensive and holding the reserve glycol in an open air tank seems like a bad idea as far as maintaining it's chemical integrity.

Do you use a pressure reducing valve on the outlet of the pig? What pressure do you charge the water and air side of the reserve tank to? I'd love to see a picture of this.

Thanks

Mark Eatherton

Scott...

We don't modify the air pressure on the reservoir. We leave it charge to around 12 to 15 PSI We charge the fluid side of the tank as high as we can get it, but within the manufacturers specifications.

The flow from the city water first goes through a back flow preventer, then in to the first tank through a side branch. We have an isolation valve, a drain cock, and a pressure gauge at each tank.

After the reservoir tank, the fluid goes through a Caleffi pressure reducing valve, and then in to the system, past the actual expansion tank which also has isolation, drain cock and pressure gauge.

Both tanks can be mounted on unistrut with 10" IPS strut clamps.

As a rule of thumb, what ever size of expansion tank is required on the system is the same size as we use for the reservoir tank.

On a job we recently completed, the home is FULL of very expen$ive art. I told the HO to have his insurance person look into the possibility of getting a discount due to the lack of a continuous make up connection to the heating system.

We charge the tank with a drain cock strategically placed near the set up. In lieu of that, you can use the drain cock on the water heater, if there is one. (TT don't usually have one on the potable side of the tank.

A person could use this as a sales tool to set themselves apart from the competition... "We have YOUR best interests and peace of mind, in our mind in the design of your heating system."

Will have to look for a decent picture.

ME

scott markle_2

scott markle_2

Thanks for the details, Generaly how often does a "tight system" need to be toped up?

Why use the drain cock for recharge as opposed to just opening the isolation valve?

Paul Pollets

Steve...

We built the near-boiler piping in the shop and assembled it in the field. BTW, this boiler has a Michigan serial#!!!


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Mark Eatherton

Tight systems...

A tight system should never have to be topped off if fully and properly purged originally. Occasionally, our guys don't get a good purge and we may have to go back to top off the reservoir tank. We do NOT use this methodology on large commercial systems. There, we use an E.F.E., which stands for excess flow eliminator.

Not sure about the second half of your question. Oh wait, it just sunk in. The reason for the drain cock at the tank is so you can bleed the water side to ZERO PSI to properly check the pressure on the air side, not necessarily for filling. Although I guess it could be, but then you'd be bypassing the code required BFP.

I've got a drawing on another machine I will append to this post.

ME

Mark Eatherton

The thirty thousand dollar reason...

Steve, I "washed out" a weekend mountain home in Breckenridge Colorado. It was on a joint that I had personally soldered, and it held for 2 years before it cut lose. The HO left Sunday night, and returned the following Friday to $30,000.00 worth of water damage.

Our insurance company said "You guys do WHAT?" When we explained the function and operation of a hydronic radiant floor heating system, they nearly had a COW. "You've got at a minimum, one linear foot of tube per square foot of home?!?!" At the time, black mold was raising its ugly head, and they were thinking along that line, which, in most cases is rediculous. They thought we were just "plumbers".

The largest annual insurance claim on buildings is for water damage. We don't want to be a part of that loss if we can help it.

ME

scott markle_2

Paul, direct connect w/ mix down is presented as an option in the Viessman literature. I have a system like this that has been humming nicely for years. Stone house, floor warming and generously sized cast iron.

After some tinkering I found the best comfort came with the floors set on only a slightly lower curve than the radiators (but with a lower high limit) The mix valve seems hunt too much, ultimately I think (in this situation) I could have done fine with a set-point mixing device (tempering valve).

Lot's of good reasons to do P/S, but also good reasons not to if the situation permits.

Paul Pollets

Scott..

We've dony many Vitodens installations without the LLH. In those cases, the flow rate was under 7gpm and there was only one temp required. Never had a problem with the mixing valves, or the desired setpoint. I don't use tempering valves, except for a "budget installation". The reason is too many callbacks from homeowners either too hot or too cold.

We follow the Viessmann instructions carefully, and the "near-boiler" piping arrays are exactly per the installation manual, plus thermometers and pressure bypass differential.

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scott markle_2

Paul, As your probably aware the vito 200 has a built in bypass valve. I'm quite comfortable using this built in valve in direct connected systems with TRV's. I know this valve works because I have inadvertently run the boiler with the isolation valves shut. Not that I would design a system that depends on this valve, but in the unlikely event that the user were to close all of the TRV's and leave the comfortrol at a high setting it's good to know that the water would have a way to move past the HX.

In my opinion this boiler is at it's best in direct connection to panel radiation. Almost seems like it was designed for this. An energy sensitive "european" approach would question flow rates that exceed the energy carrying requirements of the equipment. The discrepancy between flow rate and boiler output is especially evident when we use delta's over 20deg. Hydraulic decoupling has it's place but the elegance and simplicity of a high delta direct connected vitodens is IMHO, a thing of beauty.

You might want to reconsider differential bypass in your designs, for a bit more than the price of a good differential bypass valve you can upgrade to a wilo eco. If energy stewardship guides the design this is a very compelling improvement over blowing off excess head through a spring loaded valve.

I wish Veissmann would bring over the euro product line that includes lower inputs, built-in expansion tanks, and even built in solar tanks.

Paul Pollets

PBD

The internal PBD protects the internal pump. Once the LLH is added, each circuit pump needs the PBD, in this case, more than 70% of the radiant loops have telestats. I'll consider VS pumps when they can integrate fully with the Viessmann controls, without a hassle. What I pay for a pump and a PBD, is 1/4 the cost of a VS pump.

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scott markle_2

Paul, maybe your talking about larger pumps.

These prices are accessible on line so I don't feel like I'm violating the price discussion etiquette.

Wilo eco $328 Vs. 15-58 $70 + differential bypass valve $99

Price difference $159 or roughly 50% more. Seems a minimal premium on a High end mod con instal. I have a feeling this cost would be recovered fairly quickly based on reduced electrical consumption alone.

As far as integration I would love too see variable speed P/S systems where the primary loop was linked to boiler output. On the secondary side I'm not sure this "integration" is so important. In the residential sized pumps I don't see a compelling cost benefit to differential bypass VS. constant head pumps. Given the performance benefits of VS pumping (higher deltas, less power consumption) differential bypass seems a poor choice for performance driven heating design.

Paul Pollets

Savings

The existing pump uses 85 watts. I don't disagree that there would be electrical savings to be had, but the ROI would be negligible. On the next building, we'll offer it. Ultimately, VS pumping will be used on most systems.

This project had particular problems.... we originally bid it and lost it, even though the facility had us repair and repipe the existing (7) Viessmann systems. Then the low-bid contractor was fired and we were given back the job. The re-engineering was extensive, and ART was paid for that, as well. To make a long story short, this is an "eggshell" job. Very delicate politcs.

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Steve Ebels_3

Water damage claims

Thinking along that line and considering the quality of workmanship by many of the fresh water plumbers around here.......It really makes me wonder about the fact that fire suppression sprinkler systems are going to be mandated in new construction. Methinks that the insurance companies don't know what they are getting into. In my crystal ball can see sprinkler lines relieving themselves with fair regularity. The prevailing line of thinking is that sprinklers in residential dwellings will prevent loss of life and property but the reality is that while it may save some lives it will probably cost far more in property damage than it saves. Just my $.02

tim smith

Mark, I see why you don't do hard connect to potable supply

but if I remember right our boiler codes here require auto feed device on boiler systems?? I am pretty sure of this but will recheck this. Just a footnote... Tim