Bosch combi

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  #41  
Old 11-22-12, 02:34 PM
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One more thing...

I did not use check valves. Page 58 here. They show one for each zone and one after the circ.

What are the ramifications of not installing these???

http://www.bosch-climate.us/files/20...al_07.2011.pdf
 
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  #42  
Old 11-22-12, 02:56 PM
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Those are flow checks (a.k.a. flo control valves), normally used to prevent gravity flow. I don't see why they are needed when there are zone valves. They would run up the cost.
 
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Old 11-22-12, 02:58 PM
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gil beat me!

I'm not sure I understand the need for check valves when there are zone valves...

I also would not go to the trouble (and expense) of placing valves either side of the ZVs. How often does one really have to change out a ZV valve body?

You put the ZVs on the supply side?
 
  #44  
Old 11-22-12, 03:47 PM
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I wonder if there is some kind of German mentality at work here. Of course, if the seemingly unnecessary valves are supplied by the field installer, the cost doesn't come out of Bosch's pocket. But, still, it seems strange.
 
  #45  
Old 11-22-12, 03:51 PM
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Yes ZV on the supply... Im not a total idiot...LOL. Well thats how I been piping them for as long as I been doing it.

http://www.doityourself.com/forum/at...icture-031.jpg

I wonder if it has someting to do with the internal pump. Can it lift the disks in the ZV''s

It is a variable speed internal pump and was preset to 3. I reduced it to 2. BB is about 7 ft above combi circ.

Chart here

Page 64 fig 65 for combi 4 gpm on # 2 is good for 9 ft head? Do I want 4 gpm? Possibly I should have left it on 3?

http://www.doityourself.com/forum/at...icture-031.jpg
 
  #46  
Old 11-22-12, 04:07 PM
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I wonder if it has someting to do with the internal pump. Can it lift the disks in the ZV''s
I don't see how. It's hydraulically separated from the system.

Besides, if it was strong enough to lift the ZV open, it would certainly be strong enough to squeeze past the check valve.

I'm thinking that whoever drew that diagram drew the one for PUMPS first, and forgot to take the check valves out.
 
  #47  
Old 11-22-12, 04:10 PM
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I'm still musing over the whole idea behind wall-hung combi units with everything jamed inside the cabinet - like a 409 big block V8 crammed in a Malibu.

Could it be that in Europe or Asia, the connections between the combi and the field piping are mechanical/electrical quick disconnects? And when there is a problem, factory servicemen take the combi back to the factory, maybe slapping in a loaner? That might fit Japanese mentality (where the notion of an independent plumber fixing your Toto toilet is unheard of and possibly illegal); not sure about Germans. Just a thought.
 
  #48  
Old 11-22-12, 04:10 PM
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Page 64 fig 65 for combi 4 gpm on # 2 is good for 9 ft head? Do I want 4 gpm? Possibly I should have left it on 3?
I don't know how restrictive the HX on that boiler is. Do they give a spec for it?

Do they quote a 'minimum boiler flow' spec?

I wonder if since as TO has mentioned, there may be some delta T sensing going on inside, and since a higher pump speed would reduce DT, and the pump was preset to 3, if maybe it should be on 3 ?
 
  #49  
Old 11-22-12, 04:18 PM
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But TO says these units like a higher delta t....Like 30f of so. Yes????

Did you even look at the pump curve Troop? Dont make me come over there....LOL

And how about my taco 403 question???

Geez cant get good help here.......
 
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Old 11-22-12, 07:22 PM
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I haven't looked at the manual, but aren't all those piping diagrams merely suggestions? I think there is an expectation of the installer to know enough to leave things out or add them in if needed. If I recall correctly, that's how the drawings for my Burnham are. They have zone controls all over the place. They also show the bypass in every drawing, but if you RTFM, they tell you when you should use a bypass.
 
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