Snowmelt options

hot_rod

to connect the boilers and snowmelt. This could provide just enough blending to prevent the extreme cold from hitting the boiler? And a air purger, sediment tap, etc.

hot rod

Rocky_3

Flat plate or buffer tank?

Scenario: 150' X 40' snowmelt in Fairbanks, Alaska. Will be used as a fabrication platform for a local pipe fabricating company. They are using 3 Munchkin mod/con's. Currently they have them piped direct. No Heat X-changer between snowmelt system and boilers. I told them no dice. Can you imagine -25 degree glycol hitting those things? Ouch. This will be basically be an "on-off" system. They will flip a switch when they want the snow melt to come on. Am afraid a simple flatplate heat exchanger will freeze up on the boiler side of the system as they do not want to run glycol on the boiler side of the system. Efficiency loss I guess. How about an indirect used as a "buffer" so to speak? Cold glycol hits a large thermal mass to temper it? Anyone used an indirect in this application?

Any info is appreciated,
Thanks
Rocky

Weezbo

Good Thinking ,Rocky.

it sounds like they are looking for a run to destruction strategy, it would be better to put the ball back in their court with requiring the manufacturers specifications of the equipment when used in that manner *~/:)

Rich L.

Max Delta T

I've been told with Mod-Con boilers the greater the delta T the more efficient the heat transfer. I realize this is a substantial TD but won't that just make this system run that much more efficiently? Sorry if this is a dumb question but am I missing something here?

Still learning! Rich L

Rocky_3

\"Ice water\" return

The manufacturer's rep was closed on Friday. I called them just to verify that you could not bring sub-freezing glycol solutions back to the boiler. I believe "low temperature" return for condensing is not the same as "REALLY low temperature" returns . Unfortunately, I could not find any piping diagrams in their installation manual dealing with snow melt applications. Will have to wait until Monday to actually verify if sub-zero returns are allowed in their boilers. My gut feeling is that they are not. Just can't see -20 glycol hitting a boiler.

Regards,
Rocky

hot_rod

How will the HX protect against ice cold

return temperatures? Won't the same temperature be seen across the HX? Unless you use some type of buffer tank or injection mix system....

At a 50% glycol mix the head increases by 50% and the btu output decrease is about 30%. If these are accounted for, and the boiler HX gets adequate flow as per the manufacturers spec, I think the boiler could see the cold fluid just fine??

Unless the fluid turns to a solid

I'd highly recommend a good quality multi-metal glycol. Blended with DI water of course and added to a cleaned system.

hot rod

Mark Eatherton

I'm not aware of any low end limitations for snowmelt and modcon

boilers. I have numerous Munchie 399's out there doing direct, and the biggest problem we have had is the internal freeze safe protection firing the boilers during periods of non use, trying to keep the controls cabinet above freezing. Only problem with that is we have one relay powering both the boiler pump AND the distribution pump, so there are times we're heating up the driveway trying to keep the controls vestibule warm. It was recommended to me that we put a small light bulb inside the vestibule to keep the sensor from seeing cold temperatures. It was my recommendation that they allow us access to the SIT control logic and allow us to turn the freeze protection OFF when necessary.

Personally, I think that all modcons would LOVE to see return water temps that low. Just make certain you have adequate condensate neutralization stations and redundant pumps if necessary, cause there will be a river of condensate rolling out of them puppies.

I know Dale Picard with Radiant Engineering did some LARGE Viessmann boilers (Vertomats) direct to snowmelt operations at a fire training facility in Alaska, and as I remember, they did it direct.

Other than fluid viscosity (like SYRUP) and the control issues I mentioned, I don't think it would be an issue. But you'd best get it from the hoss's mouth, depending on who's hoss you're riding:-)

ME

Rocky_3

That floors me!

I would have never thought a boiler, even a modcon, could handle those type of temps. That's why I come to "The Wall"! Will verify with Munchkin on monday as to their thoughts on this. Granted, if we can push a 50/50 mix of twenty below glycol right to the boilers, wow, they may need to increase the size of their floor drain to handle the condensate!

Thanks for the info, as always.

Regards,
Rocky

Mike T., Swampeast MO

X amount of fuel can only produce Y amount of condensate, and nice low-temp radiant space heating systems can already get painfully close to 100% condensate recovery, so you won't have to increase the size of the floor drain...

How though do you handle the changing viscosity from "like corn syrup" at -40 to to nearly water-like when the system is up to temp while still ensuring flow through the HX is neither too low, nor too high? Perhaps a good use for VS circulators modulating on delta-t?

troy_8

Snow melt

I also have installed many munchkin snowmelt jobs direct . They work great. I have always used a boiler pump piped to primary secondary piping. It is essential to maintain flow through the boiler. They condense a lot of fluid. We have two EVO 599s piped to 8000 sq. ft. of snow melt and common vented through a 6" pvc pipe. That is a sight to see when it runs. You get a 15' plume shooting up and then streaming across the sky like a locomotive. I think wirsbo and probably Tekmar have a snowmelt control that will bring the temp. up slowly and also allow the boiler to maintain a min. temp. if you desire. Sorry I don't remember the model numbers.

Rich L.

Hydro seperator

If he doesn't want to run glycol through the boilers but does in the snowmelt loops a hydro seperator won't accomplish that.

Joe Billow_6

Rich,

I think that the radiation can be a HX, separating the glycol, or the actual snowmelt panel. The hydro separator is being placed in to boost return temp.

Rocky_3

I called Munchkin today,

They said I could do a direct return to the boilers. Just with the 50/50 glycol mix make sure the pump can push the right gpm, and that the boilers can handle the load do to glcyol de-rating. I had already told the shop to install a Caleffi Hydro-Separator to facilitate the P/S, air and dirt elimination when I looked at the job on Friday. Hopefully, the Hydro-Sep will also provide a little mixing to temper the water coming back to the boilers so it won't be so viscous. I really want to see what these boilers do when -20 degree glycol hits them this winter. I still like my "indirect-as-a-heat-exchanger/buffer-tank" idea so as to be able to run minimal glycol in the boiler side of the system, and still run -20 degree, 50/50 mix glycol in the system side of things, without either freezing up a flat-plate, or, running the cold, viscous glycol directly through the boilers.
Like I said, hopefully the Hydro-Sep will provide a little tempering and "de-viscifying" (new word I just invented);)

Will let you all know how it works when they flip the switch,
Regards,
Rocky