Cast Iron Boiler w/ Flate Plate Pool Heater

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for a load that large to keep the boiler in the condensing mode for extended periods.

The best way is a mixing device or return protection mechanism. Primary secondary alone will not assure you have adequate return protection.

You need a means to watch and adjust that return temperature to the boiler.

tekmar controls, injection mixing, 3 way thermostatic valves are a few options.

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Paul MacDougall

Will a flat plate heat exchanger for a pool cause damage to a convention cast iron boiler due to condensate? Return water temps are below 140* during the first start up of the day for about 5 hours. Would primary secondary pumping be a solution to prevent pre-mature cast iron failure?