IFC used on boiler loop

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Old 01-31-15, 11:02 PM
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Help with expansion tank location

Hi everyone.

Trying to locate best position for expansion tank. Image depicts tank on supply side before close tees with circulator on return side. Four zones depicted with circulators on supply side.

I guess the difficulty I'm having is simply that using the close tees am I really pumping away from the expansion tank no matter its location on what I want to call the boiler loop?

 
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Old 02-01-15, 09:51 AM
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Hi Boo,

What you have is correct.

I guess the difficulty I'm having is simply that using the close tees am I really pumping away from the expansion tank no matter its location on what I want to call the boiler loop?
Yes, you are.

Remember that the two loops are hydraulically separate. The flow and pressure diff in one loop does not affect the other.

You want to pump the SYSTEM away from the tank connection, which is what you are showing.

At least that's what I think I see in your graphic. That brown pipe from the tank is on the PRIMARY loop, which in this case is the SYSTEM loop. Your BOILER is on the SECONDARY loop. It sorta looks like that brown pipe intersects the boiler loop, but I think it's not the intent, just the drawing, yes?

Your water supply to the boiler should attach to the pipe between the tank and your air removal device, on the system (primary) loop.
 
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Old 02-01-15, 09:54 AM
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Wait... I just reread your post and looked more closely at the drawing.

You do NOT want the tank on the boiler loop.

You want it on the SYSTEM loop, upstream of the 4 circulators... between the system circulators and the close tees from the boiler.

I think what I thought is a brown 'pipe' is actually your air removal device? And that you have shown on the BOILER (SECONDARY) loop?
 
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Old 02-01-15, 10:12 AM
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Yes NJ Trooper, the brown pipe is my attempt at a Spirovent which the instruction manual indicates best placed close to the boiler where the water temp is highest. Had hoped the expansion tank would work there too.

Back to the drawing board. Thank you.
 
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Old 02-01-15, 10:15 AM
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Boo,
The general response is to put the pump after the expansion tank. This is called pumping away.
To begin with the expansion tank is the part of the system where is is no pressure change.
The reason to install the pump after the tank is to get more force through the the system. For example, your system pressure is 15psi so that's what's going into your pump but coming out on the discharge side is roughly 22psi so that's what you have going through your system for better performance for lack of a better description.
If you put your pump on the return side or before the ex. tank, it's still going to give you that 15 in & 22 out but it will be lost when it gets to the tank so you've lost the benefit of the pump.
Commercial systems have pumps on supply's forever, it's just becoming more prevalent now on residential systems.
For 50yrs. they've been on the return with no problems. The fact is most residential systems are so small it doesn't make a difference and the customer would never know the difference.
That being said, the expansion tank for the purpose of just doing it's job can be put anywhere in the system. Supply, return or even off the boiler as long as it's no isolated from the main system. In other words don't install it after a zone valve or something that can be shutoff between the boiler and the tank. It's only purpose is to accept the heated water to control the pressure. Same as an overflow container in a a car.
I know this is long but I hope it helps somewhat.
 
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Old 02-01-15, 10:29 AM
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the instruction manual indicates best placed close to the boiler where the water temp is highest. Had hoped the expansion tank would work there too.
Gotcha...

That's somewhat of a 'general' statement really, and in fact, right after the close tee, before the pumps, is still "close to the boiler".

for lack of a better description.
I wonder if this will clarify?

When you pump AWAY from the expansion tank (the PONPC (Point of No Pressure Change)) the differential pressure across the pump is ADDED TO the system pressure. This extra pressure tends to keep air bubbles smaller and they will not as easily get 'trapped' up in the radiators. It GREATLY aids in air removal.

If you pump TOWARD the tank, the pump's differntial pressure is SUBTRACTED FROM the system pressure. Bubbles get larger, and harder to move.
 
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Old 02-01-15, 10:38 AM
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Hi spott. Thanks that does help. It now makes me question if the boiler loop circulator actually supply's flow to the zone circulators? Is the boiler loop circulator even needed? If the boiler loop circulator is taken out of the picture then the zone circulators of course are all pumping away.
 
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Old 02-01-15, 10:45 AM
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Thanks NJ Trooper, makes me question the boiler loop circulator as well.
 
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Old 02-01-15, 10:55 AM
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Is the boiler loop circulator even needed?
ABSOLUTELY!

With close tees and primary/secondary piping, there will be almost NO FLOW through the boiler without a separate pump.

As I mentioned earlier, the two loops are HYDRAULICALLY SEPARATE. FLOW in ONE loop has next to zero affect on the flow in the other.

Think of it like this:

You have flow in the system from the system zone pumps. That's going round and round in the system loop... without the boiler pump, the same water would continue to circulate in the system.

The boiler pump is INJECTING the hot water into the system loop. At the same time it is pulling return water from the other tee.

Try to visualize the water flow with

EITHER / OR

BOTH

pumps running.

If only a system pump or pumps were running, what motive would the water have to flow into the boiler loop?
A: no motive, it wouldn't.

If only the boiler pump was running, would water get into the system?
A: no, it wouldn't. It would simply come out one tee and loop right back into the other. No motive for it to flow into system.

If BOTH pumps were running... hot water from boiler is mixed with the flow in the system.
 
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Old 02-01-15, 10:56 AM
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If you install with the tank between the system pumps and the boiler tees, you will be good to go, just as shown.
 
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Old 02-01-15, 11:01 AM
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By the way...

Make sure your piping is the correct size!

Up to 80K BTUH you can use 1" piping for the boiler loop. 1-1/4" if the boiler is bigger than that.

Have you done a heat loss estimate on the home? What criteria are you using to select your boiler size?

If you are running three pumped 3/4" zones, the 'common piping' between the supply and return manifolds should ideally be 1-1/4" pipe.

You could proabably 'sneak by' with 1" on that portion, but it's all about FLOW.

All three pumps will probably not be pumping at the same time very often, but when they DO the flow will be too much for 1" pipe.
 
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Old 02-01-15, 11:18 AM
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I should have been a little more careful in my description of removing the boiler loop circulator, also would have required removing the close tees so each zone then becomes a complete loop. Given that, do I really need the boiler loop?

I'll go dig up the heat loss numbers and post back.

Thanks again.
 
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Old 02-01-15, 11:37 AM
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Boo,
Is this a new system. Why are you setting up a primary/secondary system.
If you remove the boiler loop and just return your zones into a common return to the boiler you will not need the boiler loop pump at all.
Just leave the supply piping as is and bring back each zone into a common return and your good to go.
 
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Old 02-01-15, 11:43 AM
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would have required removing the close tees so each zone then becomes a complete loop. Given that, do I really need the boiler loop?
There are advantages to going with primary/secondary piping.

I would stick with it myself...

You haven't told us what boiler you are using, some require it. Please tell.
 
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Old 02-01-15, 11:46 AM
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Thank you both.

Boiler is 115K derated to 108K for elevation.

Current heat load is 89K and hoping to run a small zone to green house later to just keep above freezing. (Wouldn't even know how to calculate that load but probably not too large)

All main piping is 1-1/4, all zones are 3/4

It's a Viessmann 050 ECV
 
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Old 02-01-15, 11:52 AM
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Not a lot of piping diagram but also doesn't mention primary secondary requirement. However I would prefer that application.

http://ecomfort.com/PDF_files/Viessm...50-ECV_ISM.pdf
 
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Old 02-01-15, 12:39 PM
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spott, just saw your question about new system and primary secondary.

Yes it's new and now as I start thinking about putting this all together I'm wondering why I had convinced myself that I should use primary secondary.

Can you elaborate on the advantages NJ Trooper? I'm just looking for the simplest and easiest to maintain system I can come up with.

Thanks again.
 
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Old 02-01-15, 02:19 PM
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I'm wondering why I had convinced myself that I should use primary secondary.
You had a session of 'right mind'!

Can you elaborate on the advantages NJ Trooper? I'm just looking for the simplest and easiest to maintain system I can come up with.
Going primary/secondary IMHO is not any more difficult than directly piping it, and no difference in maintenance.

If it's maintenance you want to make easy, be sure to install adequate isolation valves... for example, for the expansion tank, so you don't have to drain the boiler to change it, or to adjust the air charge bi-annually. See the end of this for suggestions:

http://www.doityourself.com/forum/bo...sion-tank.html

Any of the 'maintenance items', such as pumps, air vents, tanks, etc, should be able to be isolated by valve for service without draining the system.

I think the biggest advantage is that the flow through the boiler can be maintained at optimum.

No matter how much flow is in the system, the flow through the boiler will remain the same. Your boiler should flow about EIGHT GPM roughly.

If you pipe direct, and one pump is running, you won't have enough flow... if all three pumps are running, there will be too much flow.

So primary/secondary isolates the boiler from the system in order that the correct flow will run through the boiler at all times.

It also provides some limited protection to the boiler from 'too cool' return water. Not a perfect solution to boiler protection, but at least SOME.

What type of heat emitters are in your home? Fin-Tube baseboard? Cast Iron anything?
 
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Old 02-01-15, 02:26 PM
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Not a lot of piping diagram but also doesn't mention primary secondary requirement.
Not a lot is an understatement... next to nothing is more realistic.

Veismann wants only trained professionals installing their equipment and as such they make the assumption that these professionals will know the details... the hows and whys... and apologies to those of you professionals that DO, the sad fact is that MOST DO NOT.

Good reading here:

primary-secondary_piping_tutorial

general-hydronics

charts-and-graphs

cast-iron-boilers
 
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Old 02-01-15, 03:01 PM
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I've seen that Laars paper before and was struck by how very similar it appears in writing style to the old B&G papers...

BUT:

I would like to point this out so there is no confusion, because IMHO Laars is confused about which loop is primary, and which is secondary.

The PRIMARY loop is ALWAYS the loop that flows through the RUN of the closely spaced tees.

The SECONDARY loop is ALWAYS the loop that flows in and out of the BULL of the closely spaced tees.

Some ppl believe that the BOILER loop is always the PRIMARY loop, but that is NOT true. The boiler loop CAN BE the primary loop, but it is MORE OFTEN on a SECONDARY loop, feeding the primary.

For example, see figure 5 on page 3. The boiler is in the PRIMARY loop.

See figure 13 on page 7. Those two boilers are BOTH on SECONDARY loops.

Figure 14 on page 8 is calling that big loop the SECONDARY, and it is NOT the secondary loop. The loop through the runs of the tees is ALWAYS a PRIMARY loop.

Pretty much everywhere in that paper they are incorrectly naming the primary and secondary loops. Other than that, it's very good information, so don't let the misnaming confuse you.

Figures 15 and 16 on pages 9 and 10 illustrate the pump's pressure differential that was discussed earlier, showing how pumping AWAY ADDS the differential pressure to the system and pumping TOWARD SUBTRACTS the differential.

Bell & Gossett seem to know which loop is which. Uhhh, they should... wasn't it they who more or less invented it? Specifically Mr. Gil Carlson ?

Gil Carlson, the late Director of Technical Services at Bell & Gossett, invented primary-secondary pumping as a way of providing adequate flow to all the units of a large heating system by dividing it into a set of smaller, easier to control sub-circuits, each one independent of the others.

This independence means that the action of a pump or control valve in one loop has little effect
on flow in another loop. The key to this flow independence is low head loss in the pipe that is common to both of the piping circuits.
 
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Old 02-01-15, 03:26 PM
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Gee... look at that!

Those diagrams on page 9 and 10 of the Laars document are EXACTLY the same ones that are in the B&G "How Hydronic Components... " document! Imagine that... blatant plagiarism !
 
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Old 02-01-15, 03:52 PM
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Thank you all so much. I see a fair bit of reading in my future later this evening.

Currently everything is fintube baseboard, still haven't made a final decision on the garage/shop as the floor is not yet pored so may go infloor but leaning more toward fintube rather than having to get into mixing valves etc.

I also want to have the option of tying in an outside wood boiler that I could swap back and forth to/from with simply closing a valve or two and maybe a switch or two.

One more question that the boiler loop gives me is: Would a boiler loop not be a cause of short cycling?
 
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Old 02-01-15, 04:12 PM
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I also want to have the option of tying in an outside wood boiler that I could swap back and forth to/from with simply closing a valve or two and maybe a switch or two.
The ideal solution is for the changeover to be completely seamless, without having to flip any switches or turn any valves.

Just start a fire and go... when wood boiler gets hot the other boiler is automatically turned off ...

If you are going to be using a NON-PRESSURIZED outdoor boiler, you will need a HEAT EXCHANGER to transfer the heat from that boiler to the indoor one... You can't just hook it in to the existing pipes.

You would be smart if you read up on that NOW and installed the necessary cut-ins and what-nots, so when it comes time to hook up the woody you aren't tearing out all of your existing piping. In other words, have a PLAN.


Would a boiler loop not be a cause of short cycling?
Uhhhh, no, it won't be a cause of short cycling. But I'm not real sure exactly what you are asking.

Short cycling is CAUSED by too big a boiler and too small an attached load.
 
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Old 02-01-15, 04:25 PM
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The stubs on the left end of my picture are for the future outside boiler tie in to a heat exchanger.

I guess to my thinking on the boiler loop, it seems as though the return temperature would come up to shut off temp considerably faster than with out the loop? Would that not cause the boiler to shut down and restart more often?
 
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Old 02-01-15, 05:05 PM
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The stubs on the left end of my picture are for the future outside boiler tie in to a heat exchanger.
OK, but how's that gonna work? Are you thinking of a valve on that vertical portion that you would close when using the wood boiler?

Installing ball valves with a plug in the end is preferable to just a stub. It means that when time comes to hook up, you don't need to cut anything, just pull the plug from the valve and thread in an adapter and off you go.

If I were to do this though, I would pipe the wood boiler such that it heats the gas boiler by pumping it's hot water through it. This way, all the existing zone controls would not need to be messed with, they would work as is. Gas boiler heated by wood boiler, hot water to home through gas boiler.
 
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Old 02-01-15, 05:19 PM
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I guess to my thinking on the boiler loop, it seems as though the return temperature would come up to shut off temp considerably faster than with out the loop? Would that not cause the boiler to shut down and restart more often?
Read through those things that HeatWorm posted... you'll see one of the B&G articles talks about the flow in the primary versus the flow in the secondary... what happens when one is more than the other, or vice versa.

Let's do some examples...

Let's say that you've got ONE zone calling and the system is pumping 4 GPM.

The boiler pump is running and pumping 8 GPM.

Of the 8 GPM that the boiler is pumping, FOUR will turn RIGHT and go to the SYSTEM.

The other 4 will turn LEFT and combine with the 4 coming back from the system so that 8 GPM goes back into the boiler.

The pipe BETWEEN THE TEES will be flowing 4 GPM in REVERSE of the system flow, from the right hand tee to the left hand tee.

OK with that so far?

Let's say a second zone kicks in ... now 2 are running and pumping 8 GPM in the system.

ALL EIGHT of the GPM in the boiler loop is going to turn RIGHT and go to the system.

ALL EIGHT of the GPM coming back from the system will go into the boiler return.

There will be ZERO GPM flowing between the two tees.

NOW, the third pump kicks in... and there is 12 GPM flowing in the system.

You STILL HAVE 8 GPM flowing in the boiler.

ALL EIGHT of the boiler GPM will turn RIGHT and go to the system.

EIGHT of the 12 GPM returning from the system will go back to the boiler.

The OTHER FOUR GPM coming back from the system will travel across the pipe between the tees, and combine with the EIGHT coming from the boiler ... to get back to 12 GPM.

So to answer your question directly...

It IS POSSIBLE that the boiler will 'short cycle' if only one zone is calling.

It's even possible that it will short cycle when 2 or 3 zones are calling... ESPECIALLY when the weather is warmer and the heat load is not as great.

BUT... this is NO DIFFERENT than if it were piped 'conventionally', because it all has to do with the BTUH OUTPUT of the boiler as compared to the BTUH LOAD of the system.

If at any particular time the home only requires 20K BTUH of heat (warmer weather), and the boiler is putting out 100K BTUH, there will be short cycles. Short of using a "MOD/CON" boiler, or a buffer tank and expensive and complicated controls, there's not much that can be done about that. Just something we have to live with. You aren't alone!
 
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Old 02-01-15, 08:35 PM
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NJ Trooper, thank you so much for the detailed description of how flow behaves across the tees. I must have read similar information a dozen times but it had never totally sunk in until reading your post.

The stubs will have ball valves so there would be no need to drain the system to work on the other portion. May never get to the outside boiler but will like to have the option to do so without too much trouble.

Thank you again.

I'll probably go with something like this.

 

Last edited by BooDaa; 02-01-15 at 10:56 PM.
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Old 02-02-15, 07:49 AM
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Put the Spirovent with th expansion tank. You don't need it on the boiler loop, you want to catch and release the air from the SUPPLY side.
 

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Old 02-02-15, 09:17 AM
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Yes that would work too. I'd still need to use a 90* and extend the tank out otherwise the entire assembly would have to be moved out because of the foundation ledge.

Thank you.
 
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Old 02-03-15, 12:09 PM
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Best Piping Practice: Air Separator should be located so that full system flow passes through it.

See Air Separation pp 13-16
TEH 1196B Air Management Sizing And Installation Instructions For Hydronic Heating/Cooling Systems [pdf]
 
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Old 02-03-15, 09:50 PM
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Thanks for that HeatWorm I think I may understand this now.

Raises another question though.

Would there be any minimum pipe length required between the close tees and the air separator?
 
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Old 02-04-15, 07:29 AM
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A spirovent 'type' of separator has no minimums, but the CSTs DO ...

Read through this:

Comfort Calc

Down the page a way is a diagram showing minimum/maximum distances for the CSTs.
 
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Old 02-04-15, 09:43 AM
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Thanks NJ Trooper, that covers it for me.
 
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Old 02-10-15, 04:42 PM
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IFC used on boiler loop

Hi everyone.

As I was dry fitting a few components today a couple of questions came to mind.

Should the internal flow check be left in the circulator on the boiler loop?

Will I have to connect the boiler loop circulator as a zone of its own?

Thank you so much.

 
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Old 02-10-15, 05:08 PM
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I don't believe there's any need for a flow check on the boiler loop.

The boiler loop pump should be wired to the controls such that it runs whenever the boiler is called for heat. There should be output from the boiler for same.
 
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Old 02-10-15, 06:14 PM
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Thanks NJ Trooper, I have the connection but thought that would go to the circulator control switch Taco SR506?

 
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Old 02-10-15, 06:38 PM
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What's the boiler model again? too lazy to scroll back...

That's the plan? 506 to run the zones?
 
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Old 02-10-15, 06:39 PM
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It's an ECV 050, yes 506 to circulator each zone.

http://ecomfort.com/PDF_files/Viessm...50-ECV_ISM.pdf
 
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Old 02-10-15, 06:48 PM
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check valves are required when other pumps are in the same loop.
 
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