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Alternatively, you can run the incoming (hot) Pex pipe to a brazed plate heat exchanger
for your hot water heater – before running to your heat exchanger for your furnace. It is
usually about $175. In this case, you would only need 3 Pex lines running to your house,
which may save a little, if the furnace is going to be a long distance away. The downside
is that your pump on the furnace would have to run continuously (24/7), instead of cycling
on and off as needed. They don't use a lot of electricity (about 80 watts) but it is increased
wear and tear. Eliminating the built-in water coil reduces the cost of the furnace by $75.
Our system is a LOT better because you have accurate temperature control. You don’t
end up with scalding water as is possible with the external plate HE or side-arm.
Gas Hot Water Heater
For a gas heater, there is usually a plate than can be removed to gain access to the
tank itself (or cut an access hole). Simply mount the thermostat on the tank and
follow the other instructions for water hookup above.