Split single loop boiler radiant slab into a primary w/ seocndary

Ben Greenfield

Hello All,



I have a 3 buildings. Building one has the boiler which travels 40' in buried insulated 1" pex. This feeds Buildiing 2 which has a 12 loop manifold with only 10 loops used. Each loop is 1/2" pex-al-pex no loop is greater then 220' feet.



In Building 2 I'm going take the 1" Pex from the boiler and create a primary circuit.



The first supply 3/4"tee will be for building 2's existing 12 loop manifold. The current set-up has an unknown way mixing valve to mix return water with supply and then a taco 11-f4.



On the primary circuit 7" inches from the first supply tee I will place



The second supply 3/4" supply tee will have a 3 way mixing valve to mix return water A circulator with autoadapt and a 90' run of 3/4" id of pex-al-pex to a 2 loop low water temperature baseboard system.



On the primary circuit somewhere before the boiler return tee I will place the return tee for the radiant slab and the return tee for the radiant baseboard.



Finally the controller I have has 8 relays and 12 sensors.



I'm looking for advice on the layout of the primary and secondary circuits supply and returns. As well as boiler supply and returns to the primary circuit.



How many mixing valves of what type would make the most sense. I can think of lots of places to put mixing valves but maybe it becomes excessive at some point.



Thanks,



Ben

STEVEusaPA

missing info..

Don't quite follow.  Building 1 has the boiler, building 2 receives the 1" pex.  What about building 3?  How big are these buildings? Are they apartments or individual houses?

First, of course, you need a heat loss to determine the load to each building.  The main question is how many btu's do you need to each building?  This will determine pipe sizing and flow rates, and temperature to each loop (or manifold) After this is decided, then you need to answer some more questions.

What kind of boiler do you have/ or plan on using, and how many btu's will it provide.

What are the loops doing, and how do you need them controlled?

How far is building 3?

Do you need/want domestic hot water?

How is the whole system controlled.

After you figure out all this, for starters, then you can design the piping.

But a shorter answer, if it were me, and after all the math and design work was done, would be basically a district heating scenario:

A boiler loop in the centrally most located building, if possible, with boiler protection for low water return temperatures (if needed for a non-condensing boiler).  A well insulated loop from the boiler, around to all 3 buildings (this will be your primary loop).  Has to be big enough to send all the required btu's, for all 3 buildings. Closely spaced tee's in each building, with injection circulator/bridge in each bldg.  Then, in each building, the secondary loop (with sensor of course) feeding the manifolds.  All controlled with proper Tekmar controls.  All manifolds would have balancing valves.

Second way, depending on logistics and piping requirements would be:

Boiler loop in one building.  Closely spaced tee's (3 sets, properly sized), one for each building.  Then in each building, same as above--injection loop, feeding manifolds.

If it's 3 larger buildings, why not a boiler in each one?  Or size the load for multiple boilers in one building.

Supply some more info and we'll have more advice