Choosing your radiant heat manifold

How does a Radiant Heat Manifold works?

Manifolds (also known as Radiant Heat Manifold) are used to distribute and collect the water circulating in the radiant heating system. Radiant heat PEX manifolds have a double structure: Supply Manifold and Return Manifold. Supply manifold serves as the input manifold, distributing the hot water from the boiler to its various outlets. These outlets are connected to the various PEX loops delivering hot water to the PEX tubing layout. As hot water circulates through the floor PEX layout and cools off, it returns back to the Return Manifold. The Return Manifold serves as a collector and directs the cold water to the heat source.

We categorize radiant heat manifolds based on the number of outlets on the structure. Typically, manifolds have between 2 to 12 pairs of outlet. We sometimes refer to outlets as ports, branches or loops. A circuit is a PEX circulation loop, referring to a closed PEX layout connecting to the Supply and Return manifold ports.

A zone is made of one or several circuits. The zone PEX layout usually refers to a single area or space which may be controlled by an independent thermostat.

Ecosolaris Manifold

Components associated to radiant heat manifolds.

Manifolds are delivered with a range of components which insure proper operation and reliability. Let’s review this list:

Flowmeters

There devices are scaled-readers allowing to monitor the volume water flowing through the radiant manifold’s outlets. Flowmeters are used to balance the flow of water in the various circuits. The visible part of a flowmeter is an engineered plastic graduated cylinder. You will see a flowmeter on each manifold port. Inside the cylinder a float indicates the water flow rate in the specific PEX loop connected to the manifold port. Water flow rate is graduated in Gallons per minute (GPM). Although non-essential, a manifold without flowmeters makes it very difficult to balance water flow in the various circuits of the system.

Balancing valves

These valves allow to manually regulate the water flow inside the manifold. Each manifold outlet has its own valve, allowing increasing or reducing the flow through the loop. These adjustments are done to adjust the flow of hot water in the individual loops, consequently impacting on the temperature of that specific zone. These outlets adjustments have an impact on the entire heat flow of the manifold and its distribution, by modifying heat distribution in all the loops.

Air Vents

Air vents are used to eliminate air accumulated inside the circuits. This component is essential on radiant heating manifolds. Most modern manifolds have an automatic air vents. The air vents will automatically bleed the air, as it accumulates. In a standard configuration, the manifold must be located at a higher position that the PEX circuits. The air will accumulate by gravity in the manifold and will become available for bleeding. If this configuration is not possible and the manifold is located below the PEX circuits, other types of purging mechanisms are required. It is recommended to have a pair of air vents, one on each manifold. This allows to obtain a more flexible unit, in term of installation.

Isolation ball valves

Thes valves are used to shut-off the water circulation in the supply and return lines. Standard ball valves (red and blue) are used, offering Πturn handle. Standard ball valve has one end with a union-type connection to be attached to the manifold. The other end is a 1 inch NTP female inlet.

Drain Valves

Drain valves are used to drain the radiant heating system, during the scheduled maintenance. These valves allow an easier purge and fill of the system.

Thermometers

A namifold is equipped with 2 thermometers. They are positionned on the return and the supply manifolds. They allow to measure the water temperature coming out from the boiler and moving through the various floor loops and compare it with the water returning to the manifold. The delta (the difference between the hot water leavng the manifold and the cooler water returning to the boiler) is an indication how well your system is operating. Your installer will be able to indicate the best configuration for optimal heating performance.