Chinook Wind (ME)

hr

I toyed with direct piping like that onn the Weil Ultra i did this week for a snowmelt. i wondered that I would get adequate flow through the HX when the glycol get real cold, and thick. I know all the manufactures indicate P/S for snowmelt. Maybe just paranoid about flow through their boiler, although the modulation feature should in essense protect until the flow is adequate.

Sure would be a nice clean, simple install to pipe boiler to snowmelt loops. Need to size the pump to the boiler spec and the snowmelt spec, of course. and use the glycol % pump factor! Thanks for trying it first :)

hot rod

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Mark Eatherton1

Powered by a 399,000 Munchkin

I commisioned this new snowmelt system last week. Its a 3000 square foot driveway snowmelt system. It was stone cold when I started it and the combuystion analyzer sat at 99% forever. There was a RIVER of condensate coming from the boiler.

In an effort to assist getting all air back to the seperator, I closed the ball valve between the secondary takeoffs. The delta T went from 25 degrees with it open, to 32 degrees with it closed. I'm tending to agree with montain man Mike from Swampeast Missouri. These puppies LOVE to see that extremely cold return, and by going P/S, it defeats the purpose of keeping the return water as cool as possible.

I left the ball valve closed.



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bob_25

head

Mark, aren't you putting the primary pump in series with each of the secondary pumps when you close that valve? What's your head then? Have you ever tried pulling a vaccum on a system before you fill it? Try it sometime. Good hydronicing. bob

Wayco Wayne_2

Hey Mark

Way cool job, in more ways than one. How far down can the 399 modulate? 30% or lower. I was asked to price a job for an existing warehouse radiant floor using one and I opted for 2 boilers instead because I thought I could modulate lower that way and squeeze a little more efficiency on moderate temp days. Now I'm intrigued with the 399. Who knows, maybe someday. WW

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Mark Eatherton1

Yes Bob...

pumps in series do ADD their head together. But as proven by the delta T, it didn't make much difference. If I hadn't piped the system P/S, I would have to have had either one MONGO pump, or two in series. Essentially, thats what I ended up with. 2 oo12's in series (2 are in parallel).

ME

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Mark Eatherton1

Wayne...

I'm not positive on teh lower end modulating capabilites, but I think it may be 20% (5 distinct stages of modulation in transition). The boiler was an easy plug-n-play. Fired right up first time. It's SO cool to watch this thing modulate.

ME

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Mark Eatherton1

HR...

I'm sure the controller monitors the delta T, and if it becomes to much, it does something about it, I'm just not sure WHAT it does. In my experience, the factory calls out some pretty conservative flow rate requirements (20 deg delta T) on their equipment, knowing all along that the real life experience is going to be ALL over the board. I know with my T-50, that I'm supposed to be flowing at 5 guppies per minute, and I'm flowing at 2 and things are perking right along. THe delta T varies as a function of the outdoor temperature, and loads imparted by the TRV's in my system. The boiler just modulates around its dictated set point.

I've asked for an interpretation of the blocking codes that the controller generates and will share them with you all as I receive them.

It appears as though the second half of this boiler is ALL condensor. You can look into the combustion chamber and can see the target wall in the middle of the heat exchanger assembly. The burner is covered with a fire proof sock like assembly. It's IS quite the deal...

ME

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Mike T., Swampeast MO

"The delta T varies as a function of the outdoor temperature, and loads imparted by the TRV's in my system."

AMEN!!!!!

"In my experience, the factory calls out some pretty conservative flow rate requirements (20 deg delta T) on their equipment, knowing all along that the real life experience is going to be ALL over the board." [emphasis added]

AMEN BROTHER!!!!

Just watch out that your flow doesn't get too low and don't forget those HX cleaning requirements!!!! (IMHO the two are highly related.)

Kal Row

WM modulates it, but...

glycol gets pretty thick and you can get stagnate pockets in the HX, and cause uneven even expansion of the HX, especially aluminum which moves like greased lightning, if you don’t pipe it primary injection like WM's diagram, you kill the warranty, and how much more is a second pump’s electricity - big deal - why take the chance

Mike T., Swampeast MO

By The Way

With your TRVs you CAN engineer the reset curve for nearly constant delta-t regardless of outside temp.

Mark Eatherton1

Kal's correct...

it is more important to follow the manufacturers installation guidelines as opposed to following your gut feeling. However (and there's ALWAYS a however waiting out there to jump up and take notice:-)), I think these heat exchangers are much more forgiving than the manufacturers would have us belive. If not, I'm sure they'll jump in here and let us know.

I looked at this snoweater two ways, one, with the system operating as a true P/S system, the boiler fluid temperature came up much faster, which theoretically would have raised the supply water temps going to the slab faster, thereby decreasing the amount of time for snow to melt, but the boiler was operating less efficienctly because of elevated return temperatures, or secondly, with the boiler "seeing" the lowest return water temperature, the "overall" efficiency of the "system" remained extremely high.

For my money, the second scenario makes my gut feel better for some reason. I guess thats where, as Duncan Wilson would say, "The rubber meets the road"...

The first scenario reminds me of slipping the clutch. It keeps the engine reved up, but it wastes energy. In scenario two, the clutch is fully engaged, the engine is fully loaded and all output is going DIRECTLY to the load, and the load is going directly to the engine. Solid connection.

But, then again, what do I know??? I'm just some stinkin' hot water plumber out here roaming wildly on the plains of Colorado playing games with other peoples equipment:-)

ME

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jerry scharf_2

you guys made me do it

Mark and Mike,

I had never thought about a ball valve between the tees on the P/S attachment point. It's only three valves and a flow check to build this in to the near boiler piping, so I can't see why not to do it. It won't be conclusive as it's only a single case, but it should give some interesting information.

jerry

Weezbo

i Like it

thats one way to move some stubborn glycol:))oops shhh...did i say that:)

Kal Row

i am not sure the heat is being lost...

just going into the system slower - with a slipping clutch - the motion is lost and the fuel wasted, whereas unless your primary loop has major parasitic looses, the heated water is just going around in a circle until it gets to impart it's heat to the secondary

so exept for the slower heat transfer speed and the extra 90watts for the second circulator - dont know whats the big deal, and this way, the boiler will cycle less - which is always a good thing - condensing or not

i know - your gut tells you simpler is better, less is more - i hear ya - i just love fancy shmancy systems - like that cool "quick pump" mixing box from buderus
http://www.buderus.net/Portals/0/Lit-Quick-Fit Sell Sheet1.pdf

Mike T., Swampeast MO

Flywheels and Torque Converters

Hate to have to keep giving background in different threads...

Gravity conversion system with TRVs on ALL radiators, constant circulation, outdoor reset and radiant floor loops tapped into mains without any additional form of control.

Traditional iron boiler with mechanical outdoor reset produced a "flywheel" of sorts in the mains. Don't forget those radiant loops--they ensure some flow at ALL times.

Like most reset controls, this one has a cut-in and a cut-off point. ±5° fixed for mine, but I'm sure others are different--important thing is that actual setpoint was a "floating" ideal.

REGARDLESS of outside temperature, it took the same amount of boiler power to add 10° worth of "spin" to the flywheel. The problem was that MUCH of that spin left via the flue--most terribly in warmer weather.

Try to think of the heating mains (it's a two-pipe system of course) as the "primary" with all of the branches making up the "secondary".

In this condition and in warmer weather, the mains were like an automatic transmission when you're "holding" yourself on a hill without moving--something we all know we should NEVER do...

As the weather cooled, you started to move, but the torque converter was ALWAYS in fluid drive--only a portion of it's primary spin was being transferred to the drive wheels (secondary or radiators).

Because the speed of the drive wheels (secondary or radiators) was FIXED, the system was FORCED to loose it's extra spin through the primary (boiler and mains)!!!

Now add a Vitodens. (Sorry, but I can't afford additional modulating boilers for added comparisons...)

What happens?

The boiler does its UTMOST to exactly maintain the desired supply temperature--no ups, no downs. RIGHT THERE! It LEARNS how to do this FOR THIS (AND ANY) PARTICULAR SYSTEM!

Again, remember those BIG mains with all of their water. They make a GREAT flywheel.

It's STILL an automatic transmission with torque converter but instead of relying solely on fluid drive which ALWAYS "slips" a bit, it can LOCK the converter into "direct mechanical" drive where force in equals force out.

The primary (boiler and mains) becomes a nearly perfect flywheel delivering JUST the amount of energy required to the secondary (radiators and floors)!!! There is NO EXTRA SPIN that must be driven out through the boiler!

hr

What goes into a tee...

must come out of a tee P/S wise. That concept has been pounded in my head for years! :)Seems to me if the P/S and the secondaries are piped (sized) and pumped to move the entire load of the system, and or the output of the boiler, the P/S should give up BTUs to the system at the same rate as a loop through the boiler only??

I think what is happening in your case Mark is the two mongo pumps in series, with the ball valve closed is moving things much faster than the two pumps hydrauliclly isolated in the P/S arrangement???

I have yet to see a boiler, properly or slightly oversized, overrun a snowmelt slab. That 30° slab can suck huge amounts of BTUs. The bottleneck is usually the distribution side.

I'm still not with you 100% on the P/S not moving the BTUs as quickly as the boiler loop only. EXCEPT for the two pumps acting as one. Are the both pumps exactly the same size?

Watts Radiant has always piped their hydro panels with the ball valve between the tees on the primary loop. Mainly for ease of purge reasons. You MUST provide check protection on BOTH those secondary takeoffs (S&R) or risk ghost flow. The pressure drop between the takeoffs in a P/S can never be zero, and the more distance or components i.e. a ball valve, even a 100% valve, will present a pressure drop. And the tendenancy to cause small trickle flow through the secondaries. Not a problem in a snowmelt like yours obviously, but in a heating application it can cause some control and overheat problems. Ever so slowly sometimes, but certainly possible.

hot rod

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Kal Row

not a perfect comparison in me's case

yes there is slip, but the slip manifests itself as a time delay, as there is very little loss up the flue in a condensing boiler thats off, and the secondary in the radiant mintube world is not holding enough water for too much conductive looses, just cover his picture with a couple of lengths of rubertex and you’re done

doing away with the p/s ie "locking the torque converter" as you say, is putting an un-necessary cycle load on the HX - in the case of WM's aluminum for sure, and to a lesser degree in the vie$$mann or the munchkin -

on the other hand, maybe you're right, with the current fuel costs, maybe the HX really is sacrificial – start it up and deliver exactly the amount of heat needed then lock it down!!! – screw it’s life, cause in ten years or less, “ya aint gona wana” own anything made today

Mike T., Swampeast MO

Why would you say that continuously producing just the amount of required heat results in a "sacrificial" HX in any condensing, modulating boiler?

In the case of the Vitodens, there doesn't seem anything I could do to stop this type of operation even if I wanted. Surely it wasn't endowed with the abilities of modulating the air-fuel mix and learning over time just for geek appeal.

Kal Row

the vie$$smann is unique....

in that the HX is pretty hardy stainless, and takes a beating, and it is actually recovering the radiant energy from that dome combustion screen, so a slower flow through the HX is in order - and while stainless is not as good a match for really low temp returns as aluminum is, (indeed in a 110/90 slab sys, the ULTRA comes out a few points more efficient), nevertheless, the really really slow combustion on the vie$$smann is, and i'll bet, they are producing the lowest oxides of nitrogen of the bunch as well - so in the vidoden, a direct to radiant, is a better piping strategy, that fact perhaps, makes the dollar signs in the name, a mark for savings in your case