Primary Tee Direction with Low Loss Header Secondary

colinbarry

Hello, I’m a long time lurker!

Question on Tee direction for primary secondary plumbing.

I would like to emulate this layout (borrowed from caleffi) however I’d like to confirm it is correct. I will be using only one boiler and would like two headers coming off the primary loop. In every other example it seems like primary loops always go through the “run” of the tees and the secondary is flows from the “bull” of the closely spaced tees. The diagram shows the opposite. Does the low loss header have to go through the run to decrease turbulence?

Snowmelt

I know what you’re talking about, if you go to the Weil McLain sights there done the same way as the same was as the diagram above, I even think navien does it this way also.

hot_rod

It always been up to interpretation which loop is the primary. Is it the loop with the boilers within?

The key to primary secondary is the properly installed closely spaced tees

Although a buffer tank or separator/ low loss header also accomplish primary secondary function.

It’s mostly about the “generous” size that allows two direction flow in that short section, header, or tank

colinbarry

Is there a minimum distance rule (like 6 pipe lengths) between the closely spaced primary tees and the secondary branches? Thanks for your help

Ironman

Primary flow is from left to right in the diagram.

hot_rod

closer the better, a close nipple

colinbarry

Thanks for your help, this website is a great resource.

JR_NH

Hello,

I've been researching this too and haven't been able to come to a definitive answer or rule of thumb. Let's say the boiler loop is always considered the primary. Is there a rule of thumb for which direction the tee's are assembled?

Tee'ing out from the primary boiler loop or tee'ing in from the secondary heating loop? Does it depend on the flow rate for each loop?

I primarily design radiant snowmelting systems. Most of the systems I design are based on a shared boiler system with a heat exchanger separating the snowmelt glycol loop. However, sometimes I am dealing with a dedicated boiler and want to make sure the P&ID diagrams I present clients will work, or that I at least solidly understand the concepts.

I have been a long time lurker and finally registered. Thanks!

hot_rod

Two different ways to pipe injection, direct or reverse
This tekmar info may Help
http://www.tekmarcontrols.com/images/_literature/365_d_06.pdf

Tinman

The confusion is common. With customers, I refer to them as the boiler loop and the system loop without identifying which is primary and which is secondary.

JR_NH

Let me add two visual aids to my question. Maybe it has been answered and I am overthinking it!

The attached pictures show two different tee piping arrangements. The snowmelt loop will have a higher flow rate than the boiler loop. Also, this is the only "secondary" loop/heating load.

Which would be correct, A or B?

Note: the drawings are not to scale so the spacing and pipe lengths aren't relative to proper sizing guidelines.

hot_rod

What type of boiler if it is a non condensing type you need boiler return temperature protection

If a mod con you have minimum flow requirements and adjust for any glycol mix for pump sizing

JR_NH

99% of the time ModCon boilers. Which closely spaced tee orientation would be correct?

hot_rod

Why not use a hydraulic separator? Air, dirt, magnetic and hydraulic in one https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_15_na.pdf

Gordy

^and time saver.

colinbarry

JR NH i was the original poster so I wanted to follow-up. I ended up piping mine like “A”, but i have a cast iron atmospheric boiler that is in the primary loop. If it were a modcon I would pipe it like “B” because the boiler loop is secondary to the primary loop.

hot_rod

Drawing A is what I consider a primary loop with the boiler in that primary loop. Pipe size and circulator selection need to be correct to move the required gpm

The secondary loop circulator pulls the required gpm from that primary loop.

There are a handful of ways to pipe primary secondary piping. All methods have advantages and disadvantages

JR_NH

I would prefer designing with a hydraulic separator as I think it's the simplest and most elegant solution. In cases where, for whatever reason, I would need to use closely spaced tee's I want to make sure I have sound design and logic.

Thanks for the feedback.

Garfield

In Both A and B is the flow going the wrong direction? The closely spaced Tees are making the fluid flow the opposite way of the primary loop. Is this relevant? Thanks