Generally, a direct vent must be next to an outside wall or be connected to a chimney that extends 2-4 feet above roof peak (all gases and fumes from the burner will vent naturally). A power vent is used when the unit is put inside the home in a closet or on an interior wall. It must have venting to an outside wall and must have a blower fan to remove gases from the water heater so they don't back up into the house.
a direct vent water heater is more fuel efficient (cost's less to operate). aside from that there isn't much difference, aside from not needing a double wall flue through the roof on a standard gas water heater.
The difference between a mobile gas water heater and a standard gas water heater is that a MH unit will use an outside air intake for combustion. That is the most important difference.
Heater produsces - heat recovery finds heat and reuses it
A block heater is not standard equipment.A block heater is not standard equipment.
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The cost difference between a tankless water heater and a traditional tank water heater is typically higher upfront for a tankless water heater, but it can be more cost-effective in the long run due to energy savings and longer lifespan.
There really isn't except that a commercial model may have more failsafe features.
In a directly heated cathode, the filament is the cathode and emits the electrons. In an indirectly heated cathode, the filament or heater heats a separate metal cathode electrode which emits the electrons.
With a direct fired system the airflow goes directly over the flame. An indirect fired air heater has a heat exchanger that the air passes over. Indirect units provides heat without contamination from combustion by-products.
A standard cartridge heater usually requires between 1000 and 11,500 watts to run. They run on 120 or 240 volts and one can find more information on the Chromalox website.
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yes there are direct vent gas water heater available Absolutely NOT