How to Install a Primary Heat Loop

Radiant floor hot water heating systems heat water which travels through heat-exchanging pipes throughout the home. The heat radiates out of the piping, warms the room directly above and the cool water returns to the water heater before it's sent back out into the home. When using an on-demand water heater, the volume of water passing through the unit affects the heater's efficiency. To make sure the volume of water remains consistent, installers use a primary loop that heats the water and a secondary loop which draws heated water from the primary and circulates the water through the home.

Copper plumbing, including pipes and assorted fittings
Propane torch
Plumbing solder
Pipe hangers
Cordless drill, with assorted drill and driver bits
Cement wall anchors
1 5/8 inch all-purpose screws
1 sheet 3/4-inch plywood
Builder's saw
On-demand water heater
Temperature gauge
Pressure gauge
Pressure relief valve
Water pump
Shut off valves

Instructions

- 1
  Mount a sheet of 3/4-inch plywood to the basement wall with cement wall anchors or all-purpose screws. This area serves as the central location for all the devices included in the primary loop.
- 2
  Mount the on-demand heating unit onto the plywood. Mount the unit at the point that is the farthest away from the rest of the house. For example, if your mechanical room is at the north end of the house, mount the heater toward the north end of the plywood, so all the plumbing leads southward, toward the home.
- 3
  Connect copper plumbing pipes to the outbound side of the heating unit. Connect the pressure relief valve, the T fitting and the temperature gauge in this initial line. Then, connect this copper line to the double-legged, T-shaped intersection between the primary and secondary loops. Leave the nipples on both ends of the secondary loop open at this time.
- 4
  Connect a copper line which returns back toward the on demand heater from the intersection between the primary and secondary loops. Install the pump, shutoff valves and pressure gauge in this loop in this order, then connect this pipe to the inbound side of the on demand heating element.

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