Closely Spaced tees - Hydraulic Separation

solpanc

Based on what I have studied closely spaced tees makes that circuit only see itself. Therefore in order to get water from the main pipe you must have a pump pushing water towards the tees. I attached images from Modern Hydronics Book. In image 737 there is no pump pushing towards the boiler circuit. Wouldnt that make the boiler just heat the water it "Sees" and not the water from the whole system. In image 635 there is circ c5 that pushes water to the closely spaced tees (which I understand).

Is this an exception when the boiler is the circuit?
Does the other pumps in the system force other water into the boiler circuit?

Thank you in advance.

Zman

This is a good question. I see a lot of systems where folks are installing unnecessary circs because they don't understand this.

In this drawing, each zone circ is creating flow , not only through the zone, but also through the common piping that passes by the boiler loops closely spaced tee's. Because each zone has a check valve, the water has no choice but to follow this path.

hot_rod

The closely spaced tees serve a few purposes. They separate the primary from secondary piping, hydraulically speaking.

They also allow for two directional flow, depending on the flow rates in the two circuit.

With P/S or hydraulic separators one of three conditions are possible. Flow is equal in both circuits, flow can be greater in primary, or flow can be greater in secondary.

You want the secondary circs to pump away from the tees on then primary loop, as those drawings show.

The main point is you need closely spaced tees, or a hydraulic separator to have a true primary secondary piping arrangement.

Many drawings and rooms are described as P/S but without that separation they really are not P/S.

In Idronics 19 we wanted to show about 17 of the most commonly seen piping errors and try to explain then dynamics of the correct vs mis-piped systems. You will see a good example of "morphed" versions or failed attempts at P/S.


http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_19_na.pdf