Primary/Secondary looping for multi-temperatures

PipeJr

Hello All, this is my very first post and first go @ setting up a multi-temperature system.




Primary loop Circulator -
Taco 007 (7.82 gpm; Head Added 10.51ft; Diff. Press 4.43)

Secondary loop Circulator(s) -
Taco 0014 (10.06 gpm; Head Added 16.34; Diff. Press 6.89)
Taco 008 (7.82 gpm; Head Added 10.51ft; Diff. Press 4.43)

-Issue-
When stat calls for heat in Secondary loop(s) (middle or top manifold) primary loop and secondary zone loop circulators start. Heat is properly mixed thru 4-way set point; HOWEVER temperature between post mix valve gauge and manifold gauge is different (-40 degrees).

Is the primary loop circulator on the wrong side of the T's (could they be fighting each other), incorrect type of flow check valve, incorrect zone circulator (system has 22-25 psi)?

All constructive input and questions are welcome. (Have lots of data)

STEVEusaPA

You have 3 circulators installed upside down, they should be rotated.

Gordy

Yes they don’t like that.

Edit: However I believe you can orient them as such so long as system psi is 20, or more? I don’t know why it’s that high though. Best to have motor horizontal. Gets air out of the volute much easier.

Gordy

There should only be one circ for the primary loop. Then all zones come off secondary loop in order of temperature demand hottest to coolest.

The way you have it with two circs involved in the primary loop the flows are not predictable, or consistent depending on when, and how often that high temp zone comes in line.

Gordy

Caleffi has an idronics educational series free to download. This covers hydraulic separation.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_1_0.pdf

EBEBRATT-Ed

I'll take a stab at a few things:

primary loop pump is much lower gpm than secondary pumps. This will make the water flow backwards through the "cross over bridge" and probably cause your temperature to be different from what you expect.

The tees to your high temp zone are incorrectly oriented to the primary loop and incorrectly oriented to your radiant loop low temperature zone

Paul48

That should be a physical impossibility. Does your 80* manifold feel hot to the touch? If it does, I'd suggest that gauge is wrong. Eighty degrees is tepid at best. There should be an obvious difference.

Gordy

In a properly piped P/S system shouldn’t matter if flows between primary, and secondary are different. They are hydraulically seperated.

The high temp loop is not piped right. You should only have one circ in the primary loop. You essentially have two. The way it is piped with the high temp loop circ dumping in down stream of the primary loop circulator inside the primary loop. This essentially renders the primary loop concept useless.

Any zones off the secondary loop need to be teed off the secondary loop, or another set of closely spaced tees off the primary loop.


To the OP are you saying you are getting 120 after mixing valve then 80 at the temp gauge on the supply manifold, and then 80 on the return manifold?

PipeJr

Hmm, I see your/my confusion. Let me use this simple diagram of this setup. First I would like to address your questions in order.

STEVEusaPA - Orientation (upside down) ? Do you mean Vertical not horizontal like they are? or do you mean rotated so motor is to the side of the pipe?

Gordy - see last response.

EBEBRATT-Ed - Great point about the T orientation to the primary loop. I tried tying into the existing setup to create the primary loop. see simple diagram

Paul48 - hmm. that's what the gauges say... and tested ok.

Gordy
1. They are horizontal or maybe this is the same statement as Steve.
2. Technically there is only (1) one Circulator in the Primary; I will tempt to address this using simple diagram
3. Caleffi - fantastic paper; thanks!!!
4. This by far was the most insightful comment; unfortunately I'm a little confused as you can see. With my current setup could you give me a simple sketch that would give me the proper piping layout?

Simple Diagrams:


Original piping setup-


Current piping setup-
* I've closed off High Temp zones with no successful change in temperature flow (back to thinking its the circulating pump for the manifold zones; aka incorrect orientation) Is there a recommended pump that is built for that orientation?

Paul48

Purge the air out of them. And, as said, rotate those circulators, or they will burn up. Air gets trapped in the bearings, that way.

PipeJr

System was purged using city water. I'm still not making much sense of your orientation? Do you mean rotate so the motor is on the side of the pipe path?

Paul48

Install the circulators per the manufacturers instructions. There's only 2 ways I can think of, that would allow for 120* before a circulator and 80* after a circulator. A broken gauge, or no circulation. In the case of no circulation, you could be getting some convective flow to the 120*gauge.

PipeJr

I'm using Taco equipment, this is what they say:


Here's what I've found from searching other equipment manufacturers.

PipeJr

Bell & Gossett is much more thorough with there instructions!! Kudos...
I will try tomorrow and post results.

BTW: does anyone know how to flip the mechanisms around on a 4-way mixing valve? It seems that Taco also likes to design to the left <...

Gordy

Motor shaft should be horizontal. Right now they are vertical.

Gordy

PipeJr said:

Hmm, I see your/my confusion. Let me use this simple diagram of this setup. First I would like to address your questions in order.

STEVEusaPA - Orientation (upside down) ? Do you mean Vertical not horizontal like they are? or do you mean rotated so motor is to the side of the pipe?

Gordy - see last response.

EBEBRATT-Ed - Great point about the T orientation to the primary loop. I tried tying into the existing setup to create the primary loop. see simple diagram

Paul48 - hmm. that's what the gauges say... and tested ok.

Gordy
1. They are horizontal or maybe this is the same statement as Steve.
2. Technically there is only (1) one Circulator in the Primary; I will tempt to address this using simple diagram
3. Caleffi - fantastic paper; thanks!!!
4. This by far was the most insightful comment; unfortunately I'm a little confused as you can see. With my current setup could you give me a simple sketch that would give me the proper piping layout?

Simple Diagrams:


Original piping setup-


Current piping setup-
* I've closed off High Temp zones with no successful change in temperature flow (back to thinking its the circulating pump for the manifold zones; aka incorrect orientation) Is there a recommended pump that is built for that orientation?

Plumbed that way, Your high temp zone does not allow itself to be hydraulically decoupled from the primary loop. This may, or may not be the problem with your radiant loops. It will create issues with the system when certain zones call together.

However I don't see how you can get 80 supply, and 80 return. With 120 water. Unless the radiant room temp is 80 degrees allowing for zero delta t supply, and return, or zero flow with the ambient in the boiler room is 80 degrees.

I'm thinking air may be your issue.

Gordy

The proper way is to have two closely spaced ts upstream of your radiant loops. Then the cooler return dumps back in upstream of your radiant loops. So instead of 180 hitting the supply t of the radiant its 160 maybe.

Gordy

Another note your HT zone is branched with 1 1/4", and 3/4" yet comes back as one 1 1/4" . Where before there was a seperate return, and circ for each.

hot_rod

Gordy said:

Yes they don’t like that.

Edit: However I believe you can orient them as such so long as system psi is 20, or more? I don’t know why it’s that high though. Best to have motor horizontal. Gets air out of the volute much easier.

Not sure why Taco shows vertical motor, it seems to confuse some users? 20 psi fill is not a common pressure on residential systems, it would also require and upsized expansion tank if you start with a 20 psi cold.

hot_rod

You have an unusual combo of P/S with a parallel loop. That is sometimes done when that parallel loop is an indirect for example and only runs when other zones are off. Essentially giving full temperature and possibly output to the high temperature load.

If all those circulators are running at the same time you loose your hydraulic separation.

Looks like you also have your P/S connection as a reverse injection?

A few repiping details would give you a more predictable piping system.

Paul48

@hot rod
That adds some confusion. He's working with the 4-way, and has it piped per the instructions, on the secondary side, anyway. Evidently the valve may be installed backwards?

Gordy

He has 120 after mixing, and then mysteriously looses 40 degrees after the circ. About 2' maybe 3.

hot_rod

What happens to temperatures on the mixed loop when zone 1, the parallal loop is not operating, do temperatures change?

Paul48

His supply manifold temp is 80*, and his return manifold temp is 80*.

PipeJr

FYI... My High temp zone has demand and the boiler loop circulator is wired to same relay as larger manifold circulator.

Ok got it!!! Indeed having the circs in that position and airlock was the problem.

Now time to tweak..

I'm getting the proper flow and heat thru my larger (lower) manifold; as expected 180 F to 4-way > 130 F to larger manifold return @ 120 F !!!

Having trouble getting the flow thru the smaller (top) manifold??

I'm thinking of changing the piping layout.. Based off of your guys suggestions and reading much more about hydraulic separation... What do you guys think of this sketch? Each Circ will be controlled by individual stat...


Here is some more information that I had found in regards to P/S calculations.
https://www.slideshare.net/illinoisashrae/hydronic-basics-primarysecondardy-pumping

Gordy

Now your talking. I thought it was air. If you didn't rotate your pumps it could happen again.

Gordy

The top loop may be getting robbed if both loops are operating at the same time. Have you tried just the top loop?

PipeJr

Is the thermal trap post 4-way necessary if I rework piping as latest diagram?

PipeJr

Gordy said:

Now your talking. I thought it was air. If you didn't rotate your pumps it could happen again.

@Gordy it was a mixture of both orientation and air

Paul48

Forget the loop around the low temp loops. It won't work.

Gordy

The orientation has nothing to do with how well the pump moves water. It will move water in that position. However air gets trapped in the volume, and impedes flow, and kills the bearings.

Gordy

The theory of higher pressure is it shrinks air bubbles to help move them along, and keeps oxygen in solution.

Paul48

I believe your smaller manifold is losing the battle. You have 2 pumped supply manifolds going to a single return manifold.

PipeJr

Paul48 said:

Forget the loop around the low temp loops. It won't work.

@Paul48 so your suggesting something like this?

Gordy

Yeah ditch that. I was looking at the high temp loop.

Gordy

What is the required Gpm for the calculated load to each manifold?

PipeJr

Paul48 said:

I believe your smaller manifold is losing the battle. You have 2 pumped supply manifolds going to a single return manifold.

why would that make a difference? Theory says they return to the same position...?

Paul48

Yes, but the manifolds may be an issue, as I said. Maybe some of the others will weigh in on their thoughts.

PipeJr

Ok here are the stats for the BTU I'm tempting to achieve.

PipeJr

In short 10 gpm sum for 6 loop mani. 2 gpm for 2 loop mani.; still not sure why separating return would make a difference?

Paul48

I theorize that they are pumping against each other. The larger circ is creating so much head in the return manifold it's stifling the smaller circ. Try running the smaller by itself and see if you get a different response.