Why does EK want bypass valve partially closed?

rynoheat

I have a System 2000 EK1. It's been great and is working well. I've been reading the manual and other documents just to understand how it works better.

I noticed that in the current installation manual they say to set the bypass valve(the one that also feeds the plate heat exchanger) to 1/2 open. That made me realize that I opened it all the way when I flushed my basement zone last year.

So I initially set that valve to 1/2 open, but I have the classic manager with the dual aquastat (that delays opening the zone valves until the water is hot to avoid condesation). In the classic manager manual that describes this, it says:

"Completely open the by-pass valve on the boiler. Throttle returns to maintain a return mix temperature on start-up at least shower water temperature (110F). Valves 1” and larger - 2/3 closed. Tag valve “Leave valve only X turns open.” (the valve is 1/2")

I'd assume the discrepancy between the two directions is because I have the older manager with the aquastat, but I'm a bit confused on this wording.

What should I be doing to find the right position for that valve? I've put it at a little more than half open and it seems like the return temps are above 110 shortly after the burner starts, but I don't know what the goal is.

Why is having the valve partially closed necessary/desirable? I'd think you'd want it as open as possible to heat the plate exchanger and thus DHW faster.

Thanks

(PS This is a great forum. A lot of smart folks discussing technical things in an intelligent and civil way)

Big Ed_4

They want to maintain minimum boiler temperature to prevent the combustion from condensing . Which is not good .. The delay open on zone valves gives it a chance from a cold start to heat up to minimum temp , I use 120* . Adjust the system bypass if needed . Depends on the size of the boiler and system load , as well of the size of the bypass ..

Perfect adjustment would be a constant slow increase in boiler temperature . … I would assume the boiler was sized for the hot water load , so the boiler would be bigger than needed for the heating load … Now the longer the cycle the better .

I would first set it to wide open and raise all the zones on a cold start …

SuperTech

Its to slow the flow through the plate heat exchanger for better heat exchange across the plate heat exchanger.

It's not a bypass. It's a globe valve for throttling flow

rynoheat

>Its to slow the flow through the plate heat exchanger for better heat exchange across the plate heat exchanger.

That makes sense, thanks.

Robertw

EK uses that valve to achieve the delta t we need for proper domestic hot water heating. We like a 35 degree drop across the plate exchanger when the domestic circulator is running. The slower the flow the higher the delta t. This adjustment can change over time as the plate exchanger calcifies.

Throttling the return valves would slow the flow back to the boiler, especially on high mass systems, To keep the manager from opening and closing the zone valves due to boiler water temps dropping into condensing temperature range.

Rob W

Energy Kinetics

rynoheat

Thanks Rob, that's what I was looking for. I'll put some temperature probes on there and dial it in.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1817062#Comment_1817062

Actually the opposite, the faster the flow through a HX the greater the heat exchange. It is hard to over-pump a plate HX. But too slow (grossly oversized plate HX, the channel velocity drops, heat exchange suffers.

This "speed" concept for heat exchange is true regardless of solar collectors, fin tube, air handlers, boilers, etc.

Slowing the flow never increases heat transfer. 500X F X delta T. The hydronic formula, heep increasing F and output increases.

Here is what it looks like in a fin tube circuit. If you use the HX manufacturers design software you can run the flow options also.

Screenshot 2024-10-31 at 4.58.16 PM.png

Screenshot 2024-10-31 at 5.04.41 PM.png

rynoheat

https://forum.heatinghelp.com/discussion/comment/1817398#Comment_1817398

That was my initial instinct, but I don't know much about this stuff so I accepted SuperTech's explanation.

I still don't really understand the "why" part of Rob's explanation, but I understood the "how" part. Interestingly I had to open the valve considerably more than 1/2 way to get it to that 35 degree delta t across the heat exchanger. I'm guessing that means my heat exchanger is getting less efficient than it was new.