A question for the engineers...

hot_rod

infrared video of indirect tank

I did film a tank as you mentioned. It was a stripped HTP SuperStor 20 gallon. The stainless did not like to have it's picture taken! I finally spray painted the one side of the tank flat black and it filmed ok.



I'm using that well traveled tank as my drainback tank now, the coil as the DHW source.



I powered it with a 120,000 Contender on DHW high fire. That small capacity tank heated very quickly with that much hp.



I'm not sure if I still have the software from Flir to view the tape. It stacks just as you would imagine, both loading and unloading.



hr

Glen

ahhhhhh

thank you for being kind in your scolding. I sit sore and corrected.



:-)

scott markle_2

How smart?

I once paired a smart 80 with a solo 60 because I wanted some extra drawdown from the small boiler. My expectation was that using such a large tank with so much HX surface area would give me a healthy delta. In reality I see a fairly low delta and get very little condensation during DHW demands, even with a cold tank, the return was surprisingly hot.



I'v noticed healthy condensation on the Viesmann indirects I'v installed and I attribute this to a generously sized coil placed at the very bottom of the tank. When I choose an indirect for a condensing boiler I'm looking at HX surface area because it's clear to me that this is the determinator if I want high efficiency on the DHW side of things. Since DHW is a fairly large part of (perhaps a third) of the overall btu demand in a modern house I believe it it's important not to ignore the condensing bonus.



I think the perception that the smart tank has an efficient heat exchanger because of large size,.. is flawed. I don't believe there are baffles directing the flow, my guess is that the way heat is moved through this "shell" is much the same as a cast iron radiator, natural convection. It's almost like a hydraulic decoupler, with the majority of the flow going in and out of the ports and then secondary convective currents picking up the heat and distributing it throughout the shell. Also if you have to move a volume of water that is grossly disproportionate to the btu transfer required (to get this turbulence) your wasting electricity and spending money on big pumps. Maybe this money would be better spent on a nice large coil at the bottom of a conventional indirect.



Because of it's unique design it's next to impossible to compare this tanks HX performance to a coil that sits in the coldest part of a conventional tank.



BTW- how to you effectively drain sediment from a tank like this?

Jean-David Beyer

I have a W-M Ultra-Plus 40.

As far as I can tell, it is the same as the Smart 40. Mine is made in Belgium; I do not know where the Triangle Tube ones are made. Both are tank within a tank type with the stainless steel inner tank being the one that contains the domestic hot water.



The inner tank is made like a concertina, so it can expand and contract a little. It probably does this as the relative pressure between the inside of the domestic tank and the boiler water in the outer tank changes. This movement is said to break off the scale that might form on the inner surfaces of the inner tank.



Now where do the scale particles go? They might go out the delivery pipe to the user of the hot water. Or they might settle to the bottom. Because the inner tank must be free to move, there cannot be a drain valve there that would let the sediment go.



"BTW- how to you effectively drain sediment from a tank like this?"



I think the way to do it is to turn off the boiler supply, and leave the cold water supply turned on. Then turn on the drain valve, with a suitable hose attached routed to a drain. If the drain valve was installed on the AUX outlet of the tank, there should be a dip tube on it that goes near the bottom of the tank. For the 80 gallon model, this dip tube will be 61 inches long. Makup water coming in the supply also has a dip tube, and the makeup water may disturb the scale at the bottom and it may be sucked out the drain dip tube. I have no idea how effective this is, but as far as this non-professional knows, this is the only way to do it.