Boiler circ vs zone circ

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Old 01-19-16, 06:22 PM
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Boiler circ vs zone circ

Hi - I am about to add a seventh zone to my hot water heating system for a radiant floor. My existing system has 6 circulator pumps hooked up to a taco 6 zone control unit that takes the low voltage signal from the tstat and flips the relay to turn the circulator for each zone on. I also have a 1/8th hp circulator near the boiler on the return side and as far as I can tell that circ only connects electrically to the boiler and the line voltage - no connection to the control unit.

So to add a seventh zone my plumber want to use a circulator that is controlled directly from a 110v thermostat that turns it on and off - like a light switch would. This way I done have to add a control unit.

My question to him was what about the circulator on the return side of the boiler? Doesn't that have to come on whenever any of the zones turn on. He looked at me funny and said that circulator has nothing to do with it. Then he and u traced the wires and we both felt good knowing that it seems to be only controlled by the boiler.

So what does that circulator near the boiler do and does it need to be in sync with my new zone in any way?
 
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Old 01-19-16, 07:47 PM
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with out seeing your systems, it's hard to answer.
You Taco zone control panel with close the boier TT and make a call for heat.
While every boilers is different, the boiler will turn on the boiler circulator when there is a call at the boiler TT. Just adding a live voltage stat will not call the boiler TT, and if its the only zone calling there will be no boiler call and no heat.
Get a taco SR501, that can use a standard stat, control the circ and call the boiler
 
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Old 01-19-16, 08:23 PM
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I definitely agree with using the SR501 for your new zone.

It sounds like that circulator may be used for boiler bypass.
Maybe you can post a few pictures here of your setup. http://www.doityourself.com/forum/el...-pictures.html
 
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Old 01-20-16, 06:02 PM
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Here is a schematic of my system - this was actually a good exercise for me to get it on paper. Everything on this makes sense to me except why I need a larger circulator pumping towards the boiler on the return side. I thought the individual zone circulators come on as the TS calls for heat. And if I didn't know any better I would think my indirect water heater is simply treated as another heating zone.

So the question is - if I add a 7th zone for a radiant floor - do I need to make sure the return circulator turns on when that 7th circulator comes on. I'm still not sure what the difference is between getting a 110V thermostat that controls the circulator directly vs. getting a TACO SR501 and running a low voltage line from the thermostat.

Thanks!

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Last edited by PJmax; 01-20-16 at 07:51 PM. Reason: reoriented pic
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Old 01-20-16, 07:35 PM
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I too agree on using the 501 for the new zone. As far as the controls & boiler are concerned, your indirect IS just another heating zone.
 
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Old 01-20-16, 07:39 PM
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Not sure what it says in the boiler box. Looks like it could be munchkin. Either way if this is a mod/con or cast iron the piping is incorrect.
Why another zone? The more zones you add after a point the lower the boiler efficiency is. That boiler pump is not needed if this is a cast iron boiler and if it is a mod/con the piping is incorrect.
 
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Old 01-20-16, 07:46 PM
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Yep, seriously over pumped if its a cast iron boiler, and no bypass either.
If it's a mod-con, then you need some help.

If your doing radiant in floor, you will need a mix valve unless the entire heating zones are low temp.
 
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Old 01-20-16, 09:25 PM
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Yep it's a munchkin stainless hi efficiency condensing...

Seems that it has a single primary loop with a circ on the return side of the boiler and nothing more complicated than that.

So I should tell the plumber that using a control like a sr501 is the way to go?

Curious why the piping doesn't look right to the experts?
 
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Old 01-20-16, 11:44 PM
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Your system should look like DRAWING C2 page 27 http://www.htproducts.com/literature/lp-185.pdf
 
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Old 01-21-16, 05:56 AM
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There are many reasons why the piping is not right.
first , 7 circs will try to overflow the heat exchanger, causing higher head than needed in it, less efficency, and unpredicatable operation due to varying flow rates thru the boiler.
Second, if only one zone is on, and it's small then you will not meet min. flow rates. This can cause ketteling in the heat exchanger and can damage it, it will cause short cycling of the boiler which is hard on fuel and the mechanical components of the boiler.
Having hydraulic seperation allows the boiler to maintain a set, dependable flow rate.

Now with out a way to call the boiler on, how will zone 7 ensure that it will heat if it's the only call ?
We are alll going to tell you that you need to repipe the boiler as per manufactorers drawings, the sr501 is the least of the worries at this point
 
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Old 01-21-16, 06:11 AM
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So if I understand correctly I'm missing 2 things in my current design....

1 the return and supply should be connected to the main loop via 2 closely spaced Ts.

2. I need to add flow control valves after my zone circulators.

Otherwise I'm pretty sure I'm setup like the munchkin manual?
 
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Old 01-21-16, 06:31 AM
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See drawing 2C on pg 27.

This is there preferred piping, one thing it does do well is prioritize the DHW load.
You can use a relay and drop out the power to the Taco box(s) when there is a DHW call. Takes a bit of electrical knowledge to do.
 
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Old 01-21-16, 07:26 AM
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Very helpful thanks!

I went back down and looked at my setup again. I actual do have a connection between the return and supply sides that is very close together. I also see that my 6 zone taco controller has a low voltage line to the boiler.

So to add a 7th circulator like a taco sr501 - can I connect that to the 6 zone controller or do I have to connect it directly to the boiler? I figure it would be easier to extend the 6 zone controller than the boiler.

Any suggestion on mixing valve? This will be pex in a concrete bed over a subfloor on a second floor bath. About 100 sq ft.

Also - does it matter which return I used to mix with the supply going to the radiant circuit?
 
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Old 01-21-16, 03:27 PM
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if you wire the boiler terminals from the SR501 in PARRALLEL to the boiler terminals in the SR506, things will work fine.
As for the mix valve, there are many drawings online, but make sure that the return from the slab can flow back to the cold side of the mix valve or it will not work right.
 
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Old 01-21-16, 04:19 PM
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For any thing beyond XX out on each SR 50X to TT on boiler, see:
TACO Zone Control Wiring Guide[pdf]
 
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