air supply inlet jargon

[Glevin]

What is the difference between non-mechanical and mechanical air supply?

I am investigating purchasing a tankless water heater. When deciding location, horizontal vent location appears to be a big issue.

The distance between the "HVAC air supply inlet" and the "water heaters concentric, combustion air inlet" differs between mechanical and non-mechanical systems.

My HVAC unit is in the basement. I have a duct (?fresh air?) going from outside to the return plenum before the filter. Would this be considered a non-mechanical air supply inlet system?

Thank you.

[lynn comstock]

What is the difference between non-mechanical and mechanical air supply? (Grill or duct open to outside air with no fan vs same thing with a fan that operates while the water heater is being used and a saftey that detects airflow to prove that combustion air is working.)I am investigating purchasing a tankless water heater. When deciding location, horizontal vent location appears to be a big issue.

The distance between the "HVAC air supply inlet" and the "water heaters concentric, combustion air inlet" differs between mechanical and non-mechanical systems. (Beats me)

My HVAC unit is in the basement. I have a duct (?fresh air?) going from outside to the return plenum before the filter. Would this be considered a non-mechanical air supply inlet system? (Yes, for ventilation of your home; No, as far as the water heater is concerned.)Thank you.

The instuction manual for the heater model number should provide lots of pictures, warnings and other information for you. Check online.

[hvacvegas]

What is the difference between non-mechanical and mechanical air supply?
A mechanical air supply is piping hooked up to a motor.
Non-mechanical is not hooked up to a motor.
I am investigating purchasing a tankless water heater. When deciding location, horizontal vent location appears to be a big issue.
That it is
The distance between the "HVAC air supply inlet" and the "water heaters concentric, combustion air inlet" differs between mechanical and non-mechanical systems.
YepMy HVAC unit is in the basement. I have a duct (?fresh air?) going from outside to the return plenum before the filter. Would this be considered a non-mechanical air supply inlet system?

I would consider that a mechanically induced inlet, because a mechanical device bring air through that pipe.

Thank you.

A mechanical induced inlet would be that fresh air inlet, because the blower motor in the furnace is mechanically sucking air from the outside to the inside.

A typical non-mechanically induced inlet, would be a combustion air for a 80% furnace. Metal pipe that runs to the floor and stops, is open, and not hooked up to any type of motor to suck the air in.


whos going to install the equitment for you? I would suggest for these water heaters, having a pro do it. There's special things involved in these installs. It's not a standard water heater install at all.

[lynn comstock]

• You need a separate, dedicated mechanical combustion air inlet for the water heater. The selection of a correct blower and necessary duct cannot be made in this forum.
• Be advised that a tankless water heater will need a much larger gas supply line that a tank water heater and possibly to your home. That is another pro job. Compare the BTU input ratings.
• Most jurisdictions also require a mechanical permit and safety inspection for very good reasons.
• Otherwise put some serious inslation on the tanked water heater
• Consider a water heater with forced draft combustion venting. (80 to 95% efficient.)

[Glevin]

Thanks for all your professional input.

To Lynn and Vegas, I will be hiring professionals. Thanks for your concern on safety in this area.

Vegas, thank you for answering my question directly. Now I know it is a mechanical inlet. I now know how far away my tankless water heater venting needs to be. You were very helpful.