Kitchen Gas Appliances - Gas Dryer Venting II

I looked at all the posts to see if anybody had addressed this one, and it looks like Tom Bartco did on a couple counts, but here goes.

Today we bought a new gas dryer and it warns that we MUST use a 4" vent. However, like most homes in this area, there is only a 3" vent going from the garage to the roof of this 30-year old single story house, I believe.

I saw one comment that you use the same size vent as that on the back of the dryer and I also saw the comment about running a new vent along the floor of the garage. The latter might be better than ripping out the walls and going over the kitchen door and behind the water heater to run a bigger vent, but it would be quite inconvenient.

What about just adapting the 4" vent on the dryer to the 3" vent in the wall. Am I going to damage the dryer? Cause a fire hazard? It doesn't sound like a carbon monoxide problem from what I gather.

Any ideas or should we bite the bullet and accommodate the new vent size?

Thanks much,
John

Hi:John

I would not recommend you downsize the dryer exhaust vent. As you mentioned, it is a good idea to bite the bullet and install the 4 inch vent.

Dryers have a powerful exhaust fan. Based on the air flow of these fans is the control over burner flame characteristics, drying times, safety, etc.

Changing the vent size, over a long distance run, will alter the above mentioned and adversely effect normal operation and final drying results.

As a professional, I have seen this installation method. The customer, having no means of comparison, was unaware that this one inch vent size reduction had any effect until the vent was removed or upsized.

Bite the bullet. Install the dryer correctly. You'll be glad you did and possibilty not void your warranty either.

Until you have this done, hang the vent tube out a nearby door or window. Plastic vent tubing is okay to use too.

Good Luck,
TomBartco
Natural Gas Energy Technician and Consultant.

TomBartco

OK. You convinced me of what I was afraid of and we ripped out the wall around the 3" vent pipe and my wife, who is a bit more limber than I, spent an hour chipping away at a couple 2x4's in the ceiling until we got a slightly squashed 4" vent pipe through the hole. Squashed 4" to about 3 3/8, so it ended up about 4.5" wide. My calculations indicate we only lost about 5% of the potential volume and are at about 95% of a 4" round vent, versus about 56% if we had gone with 3" like many of our neighbors.

Since it looks like we still have a 3" opening above the roof, though, we'll probably need to have that final piece replaced, right?

Does it sound like we got everything right if we replace the vent opening on the roof?

Thanks for everything. I may tackle that range next, but I'm not sure which wire nuts the appliance guy changed last time that made everything work again.

By the way, a Homer at Home Depot told me not to worry about the 3" vent, just get an adapter. Then one today said dryers have weak little fans and might have trouble pushing the air straight up to the roof. It's only 10'. That should be OK, shouldn't it?

Thanks,
John

Hi:John

The ten foot straight up run shouldn't be any problem but that vent reduction would be. I would suggest you also replace the roof vent.

I read from your second posting you have gotten yet another conflicting statement regarding a dryer exhaust vent size. An adapter is not the answer here.

If the dryers manufacturer figured a 3 inch vent was all that was needed, they would build the unit with that size vent pipe, if for no other reason but to save money.

Good Luck,
TomBartco