Fresh air intake question

Newly installed high efficient furnace drawing fresh air from the basement utility room and crawlspace.

Isn’t there something about being a certain distance from the gas water heater?

Yipper needs to be at least 10 feet separation

For combustion air?

I thought that was for the return air.

10’ separation is not possible in most utility closets .
I see them almost touching all the time however Charlie may have gotten confused by the question and been thinking return venting as follows below…

**311.3(6.3©)Return-air inlets shall not be located within ten (10) feet (3,048 mm) from any appliance firebox or draft diverter in the same enclosed room or confined space.

So any firebox with an opening into the interior within 10 feet and in the same room as a return is considered hazardous.**

My concern is always with air intakes on cat 4 units that are not utilizing air from the exterior in tight places with lack of ventilation or a different pressure zone.

see below…
(source unknown)

**1) Exterior air, in the winter, is colder and denser. It therefore has a slightly higher oxygen content and the HE furnaces are designed to use the extra oxygen and burn cleaner, therefore, more efficiently.

  1. By taking combustion air from the interior, you lower the air pressure inside and create a negative pressure condition in the house. This strains the furnace to get more air and also leads to more cold air leaks into the house.

Finally, why would you want to take interior air, that you have already spent money heating, and send it out the furnace? Think the old style fireplaces, with the combustion and draft air coming from the interior, vs. the newer type fireplaces with a sealed hearth and an exterior combustion air vent out the back of the chimney.

Last but not least you are drawing chemicals from the air into your components.**

Nice Bob! I guess I will have to start saying (Unknown source too) This is getting retarded. I am sure Charley new about the 10 foot rule and was referring to the shared air.

That would probably be my least concern. The basement/crawlspace is an unconditioned space.

What troubles me is a high-efficiency condensing furnace installed:
without the fresh air intake hooked up.
No trap on the condensate drain.
Auxiliary drain is open. Both the un-trapped drain and the open fitting discharging air into the unconditioned space (resulting in building depressurization).
The condensate drain dumps on the floor (next to the dehumidifier). :?:

Obviously an installation by “I have my head up my *** HVAC specialists”.

Did anyone else notice the upwards sloped drain pipe?

The picture shows combustion air not fresh air. Combustion air should come from outside ideally, but some AHJs will allow it to be taken from inside if the furnace is not in an enclosed furnace room and the building is not overly tight. From what I can see in the pic if the furnace is inside the building envelope it is a code question, refer to AHJ. If it is in unconditioned space there is no issue, provided there is ventilation

Fresh air is outside air ducted directly into the return air duct, and is used to pressurize the building or replace exhausted air. A fresh air intake should be located on the outside somewhere where it will not get contaminated by exhausts or vents.

The ‘ten foot’ rule is about return air openings in the return air duct which can not be within 10 feet of the furnace if the furnace is in an open conditioned space, such as an undeveloped basement. Return air intakes are not permitted inside an enclosed furnace room.

Ya I F up I was thinking return air not combustion air I was trying to get out the door 75 miles to first job:mrgreen:

Best advice is to check manufacturer.
Some allow intake from indoors and others do not.

I always recommend external combustion air .

Sample installation manual… begin reading bottom page 10…

Jeff ,the one in question is a cat 4.

So is the one in my link…

What’s your point???

Did you bother to read the first few paragraphs?

Not to mention the wye also…

I caught the “no trap” and the “condensate drain missing the hole”.

Thanks David

Above and to the left of the furnace. I caught that and an active leak behind it.

Thanks Juan

Yes, I used the wrong terminology. Combustion air was my concern.

This utility room was in the unfinished basement approximately 11’x10’ with a hollow core door separating the finished portion of the basement. The attached crawlspace was only about 6’x8’ with no exterior ventilation.

Thanks Erik

Thanks for the rest of the responses. Good informational reading Jeffrey.

“always recommend external combustion air” thanks Bob.

So how does the air know not to come in the intake when the system isn’t running, but the door is open for people to come in and out?

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