Boiler feed and returns

KBP&H_3

Why do most gas boilers and some oil have the feed and return on the same side so that the water can travel up the first section and exit. Why wouldn"t we want to flow the water from the bottom of one side to the opposite top of the other, creating flow across all sections>  when small zones it's hard to believe the furtherst section is getting much water. Any ideas? 

Ron Jr._3

Good question .

We use 2 different brands that have the supply and return in the same section . Seems like water might bypass the other sections if you have 3 or 4 007s pumping at once ! But the boilers seem to run just fine set up like this .

KBP&H_3

90 views, one response?

With the quality of installer on this board, only one idea?

KBP&H_3

90 views, one response?

With the quality of installers on this board, only one idea?

LarryC

What is the velocity of the water coming into the boiler?

DISCLAIMER : NOT A HEATING PROFESSIONAL, JUST AN ELECTRICAL ENGINEER WITH AN INTEREST IN HEATING SYSTEMS.



What is the velocity of the water coming into the boiler?



I suspect that the momentum carries the incoming water past the first section, well before it begins the move up the various sections.  Plus, once the water is in the boiler, it probably slows down to the point where convection driven flow is the major driver of the fluid currents.  The sections with the greatest delta T, top to bottom, are the ones that will greatest (albeit small) vertical currents.  Once the vertical moving water hits the top of the sections, they will spread out to all posible directions.  The strongest currents ( high delta T) will over power the slower currents (low delta T) and a dynamic equalibrium will be reached. 



There is probably less friction drawing the water from the top of the sections than pulling water thru the closest section, therefore the majority of the water will come from the multiple sections, not just the closest section.



Using your minds eye, which is easier, pulling all of the water thru a single tall skinny section or multiple smaller amounts of water thru multiple sections?



Larry

KBP&H_3

Different Scenario"s

As most boiler's operate under different scenario"s during the course of heating the water,  it would seem to me that the longest route thru the boiler sections would create the most turbulence and more even heating of the block and water. However, most gas blocks have the supply and return in the same end sections. The opposite end section has no openings to connect to.



 A few boiler companies praise their length of water passage thru the boiler and a few newer blocks have anti-stratification design built in. 



I'd really like to order a block with separate tappings in each section with a thermistor to check out different water flow ( zones operating ) to see what actually happens, The new I-Pad has a thermal camera built in it. but I don"t know if it is accurate enough to give 10" differences in a 150" environment> 



Really have to wonder what actually happens in there>  

Things mostly alway's work ,  but what does that actually mean?

kcopp

its a interesting ....

thought. Probably more for the the boiler engineers than the installers. Your observations make sense but  common sense is not always the norm. Buderus 115's have a 1.25" supply and a 1" return... you would think they would be the same. Especially on the 5 section where the BTU output is 136k...