Outdoor Boiler Water-to-Water Plate Heat Exchanger

A plate-to-plate heat exchanger is used to transfer heat from one hot water source to another without mixing of the water. Three common examples of this in the outdoor wood boiler industry are as follows:

1. A plate exchanger enables an outdoor boiler to provide domestic hot water. The plate exchanger is configured to pre-heat the water going into the domestic hot water heater. The plate exchanger allows outdoor boiler water to heat the domestic potable water WITHOUT MIXING these fluids. After all, nobody wants outdoor boiler water (that contains anti-corrosion chemicals) to come out the kitchen sink faucet or shower head!

2. A plate exchanger enables an outdoor boiler to provide indoor heating of buildings heated by an indoor boiler with baseboard radiant tubing. The plate exchanger is configured to increase the temp of the return water (from house loops) before going into the indoor boiler. The plate exchanger isolates the outdoor boiler water from the water in the indoor boiler system for two reasons: (i.) First, the indoor system is pressurized and must never be unpressurized because that would allow for corrosion damage to destroy the indoor boiler, and (ii.) Outdoor boiler systems are open to the atmosphere and can have sediment in them; accordingly, the water in an outdoor boiler system should not be allowed to pass through, and potentially clog up or otherwise damage the indoor loops.

3. A plate exchanger enables an outdoor boiler to provide indoor heating of buildings heated by an indoor boiler with in-floor tubing radiant heat. The plate exchanger is configured before the in-floor loop manifold to increase the temp of the return water (from in-floor loops) before going into the manifold. The plate exchanger isolates the outdoor boiler water from the water in the in-floor system for three reasons: (i.) First, the in-floor system often contains antifreeze, particularly for the in-floor tubes of a cement floor of an out-building. This is commonly used to protect the in-floor cement from freeze damage in the case of a prolonged period without heat in cold temps. This antifreeze solution needs to be isolated from the outdoor boiler water, and that is accomplished using a plate heat exchanger. (ii.) Second, an in-floor system ALWAYS must be set at temperatures much lower than the outdoor boiler. In-floor systems in cement floors normally must not be heated to temps above 120 degrees F. In-floor systems in hardwood floors normally max out at 115 degrees F. Outdoor boiler water, however, must never drop below 140 degrees F, otherwise damage will result to the outdoor boiler. Therefore, a plate heat exchanger is used to isolate both fluids so they can operate at different temperatures. (iii.) Third, outdoor boiler systems are open to the atmosphere and can have sediment in them; accordingly, the water in an outdoor boiler system should not be allowed to pass through, and potentially clog up or otherwise damage the in-floor radiant loops.

316 stainless steel plates. Plate to plate heat exchangers have a nominal size of 5” x 12”. The number of plates varies based on the btu transfer requirements, but we have the following sizes available:

20 Plate - Most often used for heating domestic hot water. NOTE: It has 1" MPT connections for both the domestic side and the outdoor wood boiler side. BTU transfer = 80,000.

30 Plate - Often used for heat exchange interface between an outdoor boiler and an indoor boiler system (baseboard radiant or in-floor systems) for buildings under 2,500 square feet in size with 8-foot ceilings. 1" connections. BTU transfer = 120,000.

40 Plate - Often used for heat exchange interface between an outdoor boiler and an indoor boiler system (baseboard radiant or in-floor systems) for buildings between 2,500 and 4,000 square feet in size with 8-foot ceilings. 1" connections. BTU transfer = 160,000.

50 Plate - Often used for heat exchange interface between an outdoor boiler and an indoor boiler system (baseboard radiant or in-floor systems) for buildings between 4,000 and 6,000 square feet in size with 8-foot ceilings. 1" connections. BTU transfer = 200,000.

60 Plate - Often used for large and specialty heat exchange needs with BTU transfer = 240,000. 1-1/4" connections.

80 Plate - Often used for large and specialty heat exchange needs with BTU transfer = 320,000. 1-1/4" connections.

100 Plate - Often used for large and specialty heat exchange needs with BTU transfer = 400,000. 1-1/4" connections.

Most imports are smaller at 4" x 10" or other sizes. Because of this they have from 7.6% to 26% less heat transfer area. They often use an lower grade of stainless steel (304) for the plates. Be sure to check when comparing.


Made with 316 Stainless plates for long life. Ports are 306 stainless.