Thread: more ventilation for mid effience unit

Should the room that this furnace and water heater are in have more ventilation that is currently provided?

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Originally Posted by cory nystul

Should the room that this furnace and water heater are in have more ventilation that is currently provided?

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Maybe but the main concern to me is the lack of fire separation between the garage and house as well as the garage and common attic. Where is the separation? There should be a virtually air tight 1/2" drywall separation between the garage (which I assume is just outside the doors to the closet) and the house and its attic.

If that is not a garage, ignore the above.
The only way to know if the ventilation is correct is to run the numbers using the BTU input of the gas fired appliances vs the size of the vent openings. Remember to reduce the amount of ventilation based on the louvered vents... Use the "Net Free Area" of the vents.

Originally Posted by Jim Luttrall

Maybe but the main concern to me is the lack of fire separation between the garage and house as well as the garage and common attic. Where is the separation? There should be a virtually air tight 1/2" drywall separation between the garage (which I assume is just outside the doors to the closet) and the house and its attic.

The inside of the room was sheet rocked. Am i not seeing something???

Originally Posted by cory nystul

The inside of the room was sheet rocked. Am i not seeing something???

Yes. Combustion air is being sucked from the garage.

Looks like two openings between the garage and the mechanical closet, albeit the lower opening seems kinda small.

There is also an opening in the floor in front of the furnace ...

Not sure those openings are properly sized, but they are there.

I suspect that if those doors were replaced with louvered doors the combustion air question would go away.

The closet does appear to be drywalled, if done properly then that would be the fire separation between the garage and the hose.

Then there is the missing sediment trap at the water heater ... the installer probably thought that was a sediment trap - but it isn't.

Originally Posted by Jerry Peck

Then there is the missing sediment trap at the water heater ... the installer probably thought that was a sediment trap - but it isn't.

Wasted a perfectly good elbow.

Originally Posted by Vern Heiler

Wasted a perfectly good elbow.

Elbows fine, its that 'spot o' tea' which was wasted.

Originally Posted by John Kogel

Yes. Combustion air is being sucked from the garage.

What is wrong with that?

Originally Posted by Jerry Peck

Elbows fine, its that 'spot o' tea' which was wasted.

#1. Remove elbow.
#2. Move T" to where elbow was and install on side.
#3. Put elbow back on truck.

Originally Posted by Vern Heiler

#1. Remove elbow.
#2. Move T" to where elbow was and install on side.
#3. Put elbow back on truck.

Got it!

Okay, with that I will agree with the wasted elbow ...

... except that if the elbow is wasted, then other items are also wasted because the entire connection could be reconfigured even more so that the one correct sediment trap for the furnace served both the furnace and the water heater, in which case the tee is also wasted (and the elbow may be needed).

Originally Posted by Jerry Peck

Got it!

Okay, with that I will agree with the wasted elbow ...

... except that if the elbow is wasted, then other items are also wasted because the entire connection could be reconfigured even more so that the one correct sediment trap for the furnace served both the furnace and the water heater, in which case the tee is also wasted (and the elbow may be needed).

Sediment trap needs to be after the shutoff valve. Do you want both the furnace and water heater on the same shutoff?

Originally Posted by Vern Heiler

Sediment trap needs to be after the shutoff valve. Do you want both the furnace and water heater on the same shutoff?

Nothing prohibits using one service valve for two side-by-side appliances like that, and the sediment trap would serve both appliances.

Originally Posted by Jerry Peck

Nothing prohibits using one service valve for two side-by-side appliances like that, and the sediment trap would serve both appliances.

I did not say it was prohibited; I said "Do you want..."

I see three louvered grills and I bet there is another in the ceiling of the closet to match the smaller coming from the crawl space (at least I think it would connect with the crawl space). My theory is if it looks squirrelly it probably is. It at least deserves a second look. If they are taking combustion air from the attic or if they did not seal around the metal duct passing through the ceiling, then it is wrong due to breaching the fire separation. Either take combustion air from the attic or the garage but not both.

Originally Posted by Vern Heiler

I did not say it was prohibited; I said "Do you want..."

I know you didn't say it was prohibited, that was my PC way of saying 'why not want it that way' ...

... could increase the safety factor when working on one of the adjacent gas appliances.

The only drawback I thought of would be having the heat off temporarily while replacing the water heater ... "temporarily" ... meaning that it should not be a problem.

Originally Posted by Scott Patterson

What is wrong with that?

Nothing, really. Just thought if you allow for air coming in both lower and one large upper, there should be enough air. The upper vent can supply air if air is needed, and expel air when it is not needed.

Originally Posted by cory nystul

Should the room that this furnace and water heater are in have more ventilation that is currently provided?

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It does look like they made provisions for combustion air but shouldn't that water heater be 18" off of the garage floor?

As far as combustion/dilution/make up air grate sizes are concerned, Gas Code Standards will list the minimum size at 100 sq. in. net free each an can go up from there depending on total BTUs of both appliances. That equates to about a 12x12 metal grate, at 75% net free area.

Originally Posted by Vern Heiler

#1. Remove elbow.
#2. Move T" to where elbow was and install on side.
#3. Put elbow back on truck.

I see sediment traps (usually called drip legs around here) installed as in the photo weekly and on approved installations. As crimes go in this business, this one is a minor misdemeanor. sediment trap.jpg

[QUOTE=cory nystul;253096]Should the room that this furnace and water heater are in have more ventilation that is currently provided?

Cory, Heater for the home- What I am seeing is that the natural gas shut off valve should be located before the flex line. The make up air requirement for combustion appliances in a confined space require 1sq. inch per 1,000 BTU, as per Code Check 2nd, page 135 Table #3. Review the sq footage of the garage is also needed. There is not enough make up air openings for these 2 natural gas fired appliances located in a closet. Louver type doors would solve the problem. Flame and Vapor Inclosed Recovery (FVIR) newer water heaters can be installed lower than 18" from the floor. The exhaust stacks are not pictured to allow a full view or allow additional comments. One problem with FVIR construction becomes the dust that can and does clog the make up air/flame arrestor plate over time, dogs (hair) being kept in the garage is a general cause.

Originally Posted by Lon Henderson

I see sediment traps (usually called drip legs around here) installed as in the photo weekly and on approved installations. As crimes go in this business, this one is a minor misdemeanor. sediment trap.jpg

Hi Lon; Sediment traps (dirt legs) were not installed in my area for many years as the AHJ's were telling everyone they were not needed because the gas from Piedmont Gas was soooo clean. The problem is that the mfg. installation instructions always require one be installed. The way I explain it to my customers is that if there is a fire, and the mfg. rep comes and sees no sediment trap, the only thing the rep. will say is "take me to the airport, I'm done!" So for $5 in parts and 15min. work we can take away there get out of jail free card. Sediment traps and drip legs are two different things that look much the same but have different functions.