Baseboard and Viessmann Vitodens, target delta t and pump sizing.

absorbtu

I am considering replacing my boiler with either a Prestige or Vitodens. From reading some of the threads, I am a little confused on the best set up for the circulators. I have 400 ft of 3/4" copper tubing which includes 130 ft of fin tube. If my BTU/hr is 70,000 and given the baseboard scenario with the mod/con, should I target for a larger delta t, say 30 - 40 range? Since I have 40 some 90 degree elbows in the system piping, my effective footage becomes closer to 500 ft. If I target for 35 delta at 70,000 BTUs I need a 4 GPM flow rate which yields head pressure at around 16 ft. I a leaning toward a Viessmann Vitodens WB2B 9-26 boiler (87,000 BTU) and my configuration would be a boiler pump (Grundfos 15-58fc set at medium speed) and a system pump (same Grundfos 15-58fc at high speed) and a low loss header for insurance since the max gpm for the boiler is 6.2.  I will be putting in a DHW either vitocell or smart as well with a Grundfos 15-58fc at medium.

Does this configuration look optimal? Should I target for higher or lower delta t to maximize the efficiency of the condensing technology? Is Viessmann the best for my situation and are the pumps sized properly? Any suggestions please.

Gordan

Is all your baseboard in series?

In other words, is it all laid out end-to-end in a single loop?



If so, you have to remember that the baseboard sections toward the end get the "leftovers" from the baseboard sections toward the front. A larger delta T on the whole loop will mean that the baseboards at the supply end will be too hot, and those near the return end will be too cold.

absorbtu

There is one circulator and 3 loops

 with balancing valves, all sharing a common return in the living room. The largest loop is the living/kitchen/dining rooms at 150ft , smallest is the family/sun rooms at 110 ft and the bedroom loop is the middle one at 140 ft. The present delta t is around 40 and the comfort is there but I think the boiler gets up to 185 F to do the job.

Mark Eatherton

HMmmmm....

I smell trouble...



Too much BBR in series, and when you attempt to operate it at an even lower temperature, the problems will be magnified. If you can't break the loops into smaller segments, and parallel them, you might want to consider using a 4 way valve as a flow reversing valve, which changes quite a few dynamics, but will at least spread the heat around, causing a higher degree of comfort.



As the hot fluid works its way around the circuit, it gets cooler and cooler, and technically, the shortest boards are on the beginning and the longest boards on the end, but 40 degree delta T is 2 times as much as is normally designed for using non mod con equipment. Its not a major deal with a mod con, other than having cool rooms.



EDIT: After rereading your post, I see you gave lengths, and I assume that is piping lengths and not fin tube lengths. How much fin tube on each circuit?



As for pump, go with one of the variable speed, constant pressure circs. One pump, three zone control valves.



ME

absorbtu

The current system has

for the 150 ft in the loop has 45 ft fin tube, the 110 ft has 35 ft and the 140 has 45 ft of fin tube. In essence, each loop get robbed at the end. So the at lower temps coming out of a modcon boiler would magnify the problem. Can I manually balance the supply side since I have 3 ball valves one for each supply and add some fin tube at the ends of each loop to help eliviate the issue?

absorbtu

My current boiler is a Trianco Heatmaker II modified to 80,000 BTU output without modulation.

I think it is a condensing type of boiler though.

Mark Eatherton

A learning moment...

You have three parallel circuits. That is not the same as a series circuit, which your calculations would be correct for.



Generally speaking, you would size the pumps head to overcome the highest pressure drop circuit. Not the pressure drop of all three circuits added together. The required GPM is additive, but head is based on the highest pressure drop circuit alone.



You could add baseboard to the backs of the zones, or as I stated, put in a 4 way valve that would change the waters direction of flow every 10 minutes or so. This would require you to use a cylinder type of flow zone control valve if you ever intend to put in two more thermostats and zone control valves.



If you attempt to use the typical ball and seat arrangement zone valve, it will HAMMER if it is closing with flow going through it backwards.



I will go down to the basement PC and play with Siggies Hydronics Pro software and model your system to see what happens.



Stay tuned...



ME

Mark Eatherton

The results

I ran three different temperature scenarios to show you the affect of lowering the water temps, and a lst scenario with all bu the worst case zone flowing with a Grundfos 1542.



Increasing the flow from 3 GPM to 5 GPM on that zone only increases the BTUH output by 400 btuH. That is less than one human bodies output...at rest.



I also included a picture of the 4 way reverser in a RFH system.



ME

absorbtu

Would it be worth replumbing and going to 2 parallel

zones? I could reduce the total length of tubing by 65 ft and create a 175 ft living area zone and a 160 ft bedroom zone. I think 2 circulators rather than one with zone valves is a better choice unless the zone valves have improved since the 90's. The 140 F scenario you so generously computed doesn't look like it delivers enough BTU/hr. I am not sure how your software works, but it appears I don't have enough fin tube to run at 140 degrees. Is 140 degrees the optimum for the Viessmann? Also, what was the head calculation 11 ft at 6.xx GPM? My calculation by hand for 400 ft of 3/4" was over 30 ft using the Taco doc TD10 "selecting circulators". Isn't the head additive for the 3 loops?

CMadatMe

Vitodens 200

First I assuming you mean a WB2B-26 (There is no 9-26). Boiler cir sized by Viessmann Grundfoss UPS15-58 is based on a 40 degree delta-t across the boiler. The use of the low loss header takes the boilers head out of the equation. The installation of the low loss header sensor into the low loss header also disengages the boiler supply sensor. The boiler wants to make sure the water temp at the system side of the low loss header is what the system requires based on the outdoor reset/heating curve. Your indirect also gets piped on the boiler side not the system side and that circulator will be sized to get through the indirects head loss and the boilers. Generally a 15-58 is sufficient.



You can do what ever you want on the system side. The boiler does not care. It only cares about getting the required water temp and flow rate to the system side.



We generally zone our zones with zone valves and use a Alpha pump as a system pump. Also remember there is no "TT" on the VItodens boiler. You simply use a zone control for zone valves and wire the Alpha pump as the system pump. As soon as the LLH sensor senses water movement the boiler will fire.

absorbtu

I used to have zone valves but

they would last a couple of years and have to be replaced. That was the 90's so if they have improved, that would be the easiest method for my system. Thanks for the info on the pumps, it confirmed my choices. I am not sure what you mean by the "TT"? 

Do you know what the modulation curve is for the WB2B 26? In other words, at an outside temp of x degrees F, what does the boiler fire at? My understanding is for the unit to be efficient, it must condense at that happens at a lower temperature. If my system requires a higher temp to deliver the needed BTU's then, I am not at the higher efficiency for that bolier, right? I have a 2000 sqft home in zone 2 (Cleveland, OH) where the temps can go below zero a few days a year. I have 130 ft of fin tube total that seems to be OK with my current boiler but it delivers at above 180 degrees.

I just don't want to spend alot of money and not get the desired result. So I really appreciate your help.

CMadatMe

Water Temp is Just One Aspect

Water temp is just one aspect to condense. Rate of modulation also plays a role. The dew point is also dependent on CO. In other words it changes. at 9% CO the dew point is roughly 134 degrees. This is another reason why Lamda Pro Burner Technology in Vitodens has everyone beat. The boiler makes sure that dew point is consistent.  I don't know if the flash I attached will work, If you e-mail me I can send it to you. I will not attach so e-mail me and I will send you. I did attach a grpah that shows Vitodens 200 efficiencies based on water temp and rate of modulation.

Jean-David Beyer

Do you know what the modulation curve is for the WB2B 26?

If the WB2B 26 is anything like the W-M Ultra 3 boilers, the question is much too vague. For an Ultra 3, there are three thermostat inputs, and each one gets its own reset curve. Normally, an indirect hot water heater is attached to one of those inputs and does not get a reset curve.



For each of the others, the curve has 3 or four pieces. At an outdoor temperature greater that the Warm Weather Shutdown temperature, the boiler will not fire no matter what the thermostat asks for. But below the WWSD, the boiler follows the curve (assuming thermostat is calling for heat) First, the boiler output temperature is horizontal and is set at whatever the owner wishes. For me, it is 75F for my radiant slab. when it gets cold enough the curve slopes up. The breakpoint for me is at 56 F and it slopes up to 120F by the time it gets to 0F outdoors. After that, it is horizontal again and will not go any higher.



Around here, the design day is 14F, so the rest of the curve is in reserve except for the very cold days where I can get extra heat. These settings are such that it runs about 18 hours a day on very cold days. Right now, with it about 60F outside in the daytime, and 50F at night, it is running only about 4 hours a day with 77 degree water.



I assume that the boiler condenses when the return water is below 130F. This probably varies from boiler to boiler, depending on the gas composition and environmental air conditions. The colder the return water, the more condensing can take place. In other words, this boiler condenses all the time when heating my slab.



Upstairs uses oversized baseboards, so I run water through there between 110F and 135F. It probably condenses most of the time. The indirect hot water heater runs at 170F and returns around 150F, so very little condensing gets done, though some does while it is starting up.

CMadatMe

JD

Vitodens always goes to low fire first on start up. Boiler then looks at what is required and moves upward SLOWLY. Everyone else pretty much goes to 60% or even 100% and then backs down after about 45 seconds or so. Ala why the Triangle guys need to make sure they pri/sec the boilers. They go to 50% fire and then back down or go up.



I can also limit modulation if I wanted. Meaning if I don't want my boiler going to 100% I don't have to let it. So if your heat loss was let's say 60,000 and the boiler modulated between 31 and 93 I could limit modulation to 50%. In other words boiler would never see it's full output. I could bang between my low and 50% all day long.

Jean-David Beyer

I can also limit modulation if I wanted.

By default, my boiler modulates between 20% and 94%.  It is 80,000 BTU/hr input that is too big for my house, but the smallest Ultra 3 there is.  It is seriously suggested never to run it at less than 20%.



My upstairs zone really needs only about 6500 BTU/hr on a very cold day, so it tends to cycle rapidly (but not as fast as my old GE oil burner) if that is the only zone requesting heat. So I reduced the maximum firing rate for that zone to 55%. I hesitated to reduce it further because I do not know how the control board would react if the upper limit is lower that the temperature at which it starts (about 50%). I also widened the limits from +|- 5% to +7% | -8%. It does not fire long enough to see if this is enough yet (not very cold out, and the zone recovers too fast right now to measure these things), but it is clearly a step in the right direction.



Downstairs takes about 25,000 BTU/hr on a very cold day, so I cut the maximum rate to 90%. That zone worked pretty well last winter.



My biggest complaint (I used to design control systems) is that my control board is too impatient; it acts too quickly in response to inputs. I.e., if I thermostat calls for heat, it fires at about 50% and then if it does not heat up fast enough to reach the reset curve, it increases the firing rate. Similarly in the other direction.  But it does it too fast. In engineering terms, the feedback system is underdamped (damping ratio too low). It is not actually unstable, but it would work better with a higher damping ratio. Too bad I cannot control that, but I doubt a manufacturer would want a typical homeowner to get at such an adjustment if it were available.



I think it would be neat if all the control board designers could combine the best features of each. And have wider modulation ranges (but that is probably limited by burner design considerations).

CMadatMe

Similar but Different

Viessmann always starts at its low firing rate on fire. Trys to eliminate the short cycling on the intial call. I believe other mod/cons run about 45 secs to a minute at either high fire or 50% or so on start up and then they move to where they need to be. This could lead to a small zone short cycling. 



On the Vitodens 200 you can limit modulation of the heating separate from the DHW. I'm in the process of planning the change out of my boiler to a Vitodens 200. Heat loss is 45,000 but I am going to put in a boiler that will give me 93,000. I am going to limit modulation to 50% for my heating circuit for my design day. I am able to use 140 degree water at 0 degrees to heat my house. It way over radiated. In the spring when we tear down a few walls and redo the kitchen/dinning and entry will be changing out to Panel Rads.



I currently have 2 zones of heating. I am going to get rid of zoning and just let the boiler fly on outdoor reset. I am using the Vitotrol 300 which is an extenstion (remote control) of the boiler control. It will provide indoor feedback directly back to the boiler. The boiler will then be looking at outdoor temp, system supply water temp in the supply side of the LLH and indoor temp. This should give me a tool to really fine tune it in to what is going on in the house.



As you can see from the chart I posted above at 50% on my design day I will be at 95% efficiency. I will keep the modulation rate at 100% for DHW but will be playing around with it. Want to see how far a can bend output based on our hot water needs. I basically chose the boiler for DHW and not the heat loss.  



Viessmann takes the slow road to China approach to get to where it needs to be. Doesn't ramp fast. It coasts/creeps to where it needs to get.  I also think that the control by shutting down the boiler supply sensor and reading the supply temp in the low loss header helps. It doesn't cramp btu's where it does not need them. It wants to maintain a system temperature.

Gordan

Modulation

Chris, where do you get the information that the Triangle Tube Prestige, specifically, starts at 50% modulation? Their manual specifically states that after the flame stabilization period (which is a few seconds, not 45) the boiler goes to minimal modulation and then modulates up from there if needed.



I'd like to understand this because I'm planning to pipe up a TT directly, without pri-sec, taking advantage of the low pressure drop through its heat exchanger. Everything else that I've seen suggests that this should be a perfectly fine approach with the flow rates I'll be sending through it, especially since I'm using proportional zone flow control and not on-off, but I'm eager to learn if you're willing to share your sources.

Mark Eatherton

The Lochinvar Knight can be programmed to stand on its head and spit wooden nickels...

You can adjust the ramp up or down, and how long at what rate it runs before moving up or down, and the maximum fire rate if you so desire..



Having dealt with both the Vitodens logic and the Knight logic, I prefer the Knight logic over the Vito due to total flexibility.



Like a fine wine, they just keep getting better with age :-)



I am in the process of installing their smallest well hung model up at Hydronicahh...



ME

Gordan

Well hung?

I imagine that if it's that small, and that well hung, you shouldn't be allowed to program it to stand on its head or it might poke its own eye out!



Does the Knight use MCBA, too?

CMadatMe

Gordon

I called and posed the question to Triangle back in May.  My call was concerning what happens when guys don't pri/sec the boiler. I was specifically told that the boilers go to 50% of their modulation for 45 seconds before they decide in which direction they want to turn. It was specifically stated that by not piping pri/sec it could lead to short cycling.



I just read the install manual and your correct as to what it states in the manual. I was told differently directly by them. Again, was specifically told directly by them. 

CMadatMe

Haven't had the Pleasure

Of even tasting the Knight. Doesn't seem to be any representation in my market. Have seen some spec's for it on commerical quotes. Never had a rep say a peep about it. Is is not a Northeast boiler and more prevelant west of Hydronic Utopia .

Mark Eatherton

Spill czech on isle fore...

Just wanted to see if anyone would catch the typo ;-) Good catch, and better joke.



The Lochy uses the SIT, an Italian control, hence it is MUCH more flexible.



I LOVE the fact that I can tie my lap top into it and see whatever issues its been having, and with the new control, you can poll the last ten faults right off the machine without needing a PC.



I wish ALL the manufacturers were as good as Lochinvar. Every time I've made a suggestion, it was on the next boiler I purchased.



And rumor has it that they've got stuff coming down the pipe line that will knock your socks off :-)



Stay tuned.



ME

Gordan

Is there any chance...

...that they said "four-to-five" and not "forty-five"? :-)

Gordan

My socks stay on unless...

Let's see, what would I like? A wide modulation range to cover both DHW and space heating requirements. A combustion control system that actually senses what's going on and optimizes combustion quality. An ECM circulator that's controlled by the boiler control so that both burner and circulator modulation can respond to actual heat load. A good room temperature control with indoor feedback and programmable setback (for comfort as much as for savings.) A nice, efficient, durable, low-resistance heat exchanger so that you can pipe the boiler in line with the system and get the most delta-T for your buck.



And yeah, the ability to extensively tinker with any of these knobs.



And I'd like it all at commodity prices.



Most of these are features that Vitodenses of various guises have had to some degree. The 300 series, which is of course not available here, has just about everything except the low-resistance heat exchanger. And the commodity price. Oh, well.

CMadatMe

Nope

Specifically stated 45

Mark Eatherton

Socks on, socks off, socks on, socks off...

Here is a link that will walk you through their control programming manual. The meat of the controls starts around page 58 or 59.



http://www.lochinvar.com/_linefiles/KBII-I-O%20Rev%20A.pdf



All of your other wishes MIGHT be fulfilled in the near future Grasshopper :-)



Enjoy!



ME

Gordan

Me likey ramp delay

Definitely the degree of control over burner modulation is very nice. D'ya have any timelines on this new wonder of hydronic engineering that you're teasing about?

Mark Eatherton

I'd tell ya, but then....

I'd have to snuff ya, and that wouldn't be good for your business :-)



I really don't have a timeline that I can disclose. i just know they are working hard behind closed doors on a totally new product design to their long family of extremely efficient berlers.



I can't even disclose who told me :-(



Patience Grasshopper, patience :-) It will be worth the wait.



ME

Mark Eatherton

Eggzachary....

I ran the 140 temp to show the BIG difference in output. If your load matches the baseboards output a that point, then it will work. If not, you need to add baseboard to keep the condenser in the condensing mode.



A little secret. It is my experience that whatever load you "estimate" the loss to be, in real time, it will typically be half that amount.



As for splitting the loops in half, really not much advantage to doing that, other than using two pumps versus one, and zone valves really haven't changed much. They are electrical and mechanical and subject to failure, just like everything electrical and mechanical. They are easier to replace these days. Can do it without getting wet.



As I stated, in parallel circuits, the required head for purposes of selecting a pump is based on the worst case individual pressure drop, not the addition of head for all three circuits. Gallons are additive for all connected circuits, but head is based on worse case pressure drop. Circuits of less pressure drop will receive more flow than is necessary during combined calls, but not detrimental if properly sized and designed.



If you don't own Siggys book Modern Hydronic Heating yet, and yo are in the hydronic heating biz, you SHOULD buy it from Dans Book Store. It comes with demonstration software, and if you REALLY feel the need, you can purchase his professional version, which is what I used in doing your calcs. It is a great "What if" software program.



Must be run on a PC, or Bootcamp on a MAC.



G'Luck



ME

Gordan

It's always something like that, though...

There's always some new wonderful vaporware being designed that's going to make everything currently sold seem positively antediluvian. But you can't heat yourself on vapors... well, you can... if it's steam or if the vapors are flammable.



Thing is, if this thing is revolutionary then it's by definition unproven. :-) Its adoption will be helped some by the fact that it's put out by a large and well-regarded company, but even the Knight's market penetration isn't all that, and it's been around awhile.



Me, I'll wait until Apple puts out a boiler. It'll be the first forced hot air boiler ever, and everyone will just have to have one! :-)



Pardon the punchy commentary, it's not directed at you - merely at the human condition. I certainly understand and share the enthusiasm (even giddyness) experienced when beholding a product of excellent engineering.

Mark Eatherton

MacHeat....

I have one Macintosh lap top, and 4 PC lap tops, and the Mac get MUCH hotter than the PC's. They are all forced error at present, but I am working on a lap top heat exchanger to move the heat from my hot lap top to my cold behind and or feet.



And it will of course be hydronic based :-) 1/4" tubing, 1 watt pump, no expansion tank necessary. It will be controlled by, the lap top of course ;-)



More information on toasted leg syndrome....



http://news.cnet.com/8301-17938_105-20018459-1.html



My apologies to the original poster for hijack this thread...



ME