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Strong NG smell at the discharge location.


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This morning I had an inspection on a home that had a HE furnace(about 6 years old) and a fan assisted NG water heater(3 years old). The discharge location was at the front wall of the home. The smell of natural gas was quite strong at the discharge location.

Haven't run in to this before. Could it be that one of the appliances isn't burning properly?

I am recommending that the furnace be serviced, I am just curious as to what other's may think is the cause.

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You should have a strong odor of unburned nat. gas and aldehydes (car exhaust smell) upon initial firing, and then it will usually clean up as it burns. The amount of smell will change depending on how many elbows in the vent pipe, length of pipe, etc.

I respond to odor calls (gas leak reports) weekly due to these high efficiency furnaces. It's usually nothing......

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Just to pick on terminology a bit. When you say fan assisted NG water heater, shouldn't it more accurately be called a direct vent water heater.

To say assisted implies that it relies on other methods as well such as natural drafting in addition to the fan assistance. While there are fan assisted natural draft furnaces, water heaters are either direct vent or natural draft.

At least I've never seen a fan assisted natural draft water heater.

For the record, I'm frequently less than accurate on my terminology and appreciate it when it gets pointed out.

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This morning I had an inspection on a home that had a HE furnace(about 6 years old) and a fan assisted NG water heater(3 years old). The discharge location was at the front wall of the home. The smell of natural gas was quite strong at the discharge location.

Haven't run in to this before. Could it be that one of the appliances isn't burning properly?

I am recommending that the furnace be serviced, I am just curious as to what other's may think is the cause.

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tn_201332704928_DSCN1024.jpg

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Trust your nose.

Remember Phillip's words...If it smells, it goes in the report.

Marc

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Just to pick on terminology a bit. When you say fan assisted NG water heater, shouldn't it more accurately be called a direct vent water heater.

"Direct vent" is associated with appliances that get all their combustion and dilution air from the exterior.

Water heaters are fan assisted, or sometimes called power vented. I use "power vented", as folks understand it quickly.

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Just to pick on terminology a bit. When you say fan assisted NG water heater, shouldn't it more accurately be called a direct vent water heater.

To say assisted implies that it relies on other methods as well such as natural drafting in addition to the fan assistance. While there are fan assisted natural draft furnaces, water heaters are either direct vent or natural draft.

At least I've never seen a fan assisted natural draft water heater.

For the record, I'm frequently less than accurate on my terminology and appreciate it when it gets pointed out.

There are fan-assisted natural draft water heaters that work very similar to how a Category 1 furnace with a draft inducer works. Google it.

However, I think Rob is referring to a power-vented natural gas water heater. Those are pretty common around here. They use a large PVC vent that passes out through the wall of the house. There is an exhaust fan on top that's interlocked to the burners.

It pulls it's combustion air from the interior. It's a good option for a location where there are two appliances close together and there's not much combustion air. He says the furnace was a category IV unit. The photo shows that the intake and exhaust pipes for that furnace are right next to each other and then the power vent from the water heater is discharging right over those.

I think it's likely that the Cat IV furnace is pulling in a lot of exhaust from that water heater whenever the water heater burner comes on and the fan kicks in and that's affecting how the furnace burns. I think he made the right call.

I've lightened up that photo below.

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ONE TEAM - ONE FIGHT!!!

Mike

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Just to pick on terminology a bit. When you say fan assisted NG water heater, shouldn't it more accurately be called a direct vent water heater.

"Direct vent" is associated with appliances that get all their combustion and dilution air from the exterior.

Water heaters are fan assisted, or sometimes called power vented. I use "power vented", as folks understand it quickly.

I have a direct vent furnace that pulls combustion air from the interior.

Wait, are you saying that in order for it to be called direct vent, it must pull combustion air from the exterior?

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Direct vent is associated with properly installed Cat IV setups, w/proper meaning two pipes, an intake and an exhaust.

Honestly, I don't know if pulling combustion air from the interior changes the terminology, but I would never call any furnace power vented.

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No,

It's still a Category IV furnace. It can draw combustion air from the interior if there is enough for the appliance. As I said, this is probably a situation where you have two appliances in a small area that wouldn't normally provide sufficient combustion air. They've equipped it with a Cat IV furnace that gets its combustion air from outside and they've equipped it with a power-vented water heater to ensure that there won't be any accidents caused by backdrafting associated with interior exhaust fans, fireplaces, etc.. Those water heaters seem to get the job done. Any backdrafting that overpowers the fan shuts them down. If the fan breaks down they won't light off.

What's so hard to understand about this setup? It's really very common out this way. I do think there is an issue with the proximity of those vents to one another though and I think Rob made the right call.

ONE TEAM - ONE FIGHT!!!

Mike

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I understand it fine. The question was about terminology, and if the term changed if it pulled combustion air from the interior.

I know it's OK to install a Cat IV where it gets it's combustion air from the interior. I just think folks that do it that way are troglodytes. [:-eyebrow

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