90+% furnace exhaust vent icing?

[tikimonster]

Love this site, I've learned a lot just reading. I'm getting bids for a new furnace and AC in my rambler (yes, the late 50's model shoebox.) Since I'm in Minnesota, I figure the high efficiency furnace is the better option, with maybe a 13 SEER AC unit.

I'm still wavering on variable speed fans and which brand, Lennox, Bryant or Trane. From what I've read here, any of those brands should be fine. But one thing I've been told bothers me.

One salesman said that the high efficiency furnace exhaust vents A) freeze over unless you inspect them daily and B) attract small animals to come in and die, and the vents cannot be covered in any fashion! This guy also said that the PVC pipes would be sticking out about a foot from the house (and had photos!)

Now this guy was real high pressure and he is definately NOT getting my business (despite doing a manual J calc, about the only thing I liked about him), but I am quite concerned that I may be stuck with a furnace that will never allow me to leave for a day (or even a week, as another dealer told me. Funny, they were both Lennox dealers.)

So how about it, pros? Do the high efficiency furnaces have exhaust vent icing issues? If there is an issue, is it specific to Lennox, or do all models have the same problem? Or was this just a line to try to push an 80% unit on me?

Thanks for all the info on this site!

[james mo]

90% furnace venting issues are similar with most brands, but icing issues are usually due to improper installation. I would never recommend a device of any kind for a home that needed daily attention and you have to believe that a furnace manufacturer would not expect you to buy one. We have very few issues with venting if furnaces are vented properly. Sometimes, a wasp nest ends up in the intake and has to be cleared, but this isn't a constant problem. This will usually happen in the summer and be noticed when the furnace is first turned on...like during maintenance.

[mayguy]

LOL wow.. Where in MN are you from?? I am in Rochester.. Those Lennox guys must be scared of the 90's???? I'd look at someone else.

The only time I've had problems with ice build in in the vent is

-Screen was used on the intake (a foggy cold winter night)
-Intake was too low to the ground.
-the exhaust was put in wrong (blowing down to the ground) and the intake was sucking up high.


As for animals, I had not had that happen to me for a service call..


Trane has a nice BAYVENT that pretty much makes it looking good on the side of the home.

Also, if the white PVC bothers you, it can be painted.

Go variable speed.. You'd be glad you did.


Check with your gas company (Xcel) and see what type of rebate you can get.. I got $200 from Aquila.

Also 13/14 SEER is about all you want to go for in MN.

[Jultzya]

I see you had a salesman and not a tech at your home.

The only furnace I would recommend you going with would be a high efficient furnace!!!

If properly installed and maintained, you will have years of reliable performance!

The venting doesn't have to be a FOOT away from the home and you can install SS (stainless steel) large screens in the PVC piping.

There are little concerns with freezing and rodents, if the piping is properly installed.

[docholiday]

Well, the screen is one way to make it freeze, even with 1/2" screen.

[Black Adder]

I usually put a heavy piece of fishing wire through the vent outlets to stop any birds flying in. I have seen several units with birds in the inducer fan but other than that I have not seen any other animals (wasps excluded) in the vents. As for icing if the piping is installed as per manufacturer specs and sloped correctly it should not be an issue.

[beenthere]

You can use a concentric vent, its only a couple inches deep, and they look nicer then the 2 pipes.

[MikeJ]

Mice nest in intake of Lennox Pulse furnace. Came all the way in to inducer motor and died after birth along with mother. Solution: style of house limited location of pipes. Homeowner then landscaped with some stones and bricks which createda path right up to pipe, mice walked in.

Bird in inducer wheel-dead, head crushed. Homeowner liked birds enough to put a 4'x4' covered bird feeder about 10' from pvc location. Birds would land in shrubs, dumbs ones went spelunking two years in a row. HO moved feeder far away and problem went away.

Bird nest in intake pipe. Exit of pipes was 10' off of ground on front of house. House one block from White Bear Lake, few trees around. Used nitrogen and "blew" nest from house to middle of yard. 2nd time this happened. I recommended removing pipe or doing gooseneck, don't know what final solution was. I never found out why bumblebees liked Pulse units. Almost always remove a couple from the intake chamber during service calls. They don't do any harm, just get in there and croak. They are ground nesters tho.

I've removed birds, squirrels, and nests from chimneys of old style furnaces and boilers. Some birds sit on top and get overcome with exhaust, fall in and die.

The number of service calls for iced over pvc pipes is not that common but it does happen. Worst time is with a large snow fall or when drifting happens. Homeowners are not always aware of what those pipes do and even blow snow up against them. Rare but it happens. Another time is when we get that type of morning where it is below freezing and damp. Hoar frost can build up. Also, when an intake is too close or downwind from the exhaust, or in a corner. Intake frosts inside of the pvc from sucking in moist exhaust air. Finally completely blocks pipe.

I have removed screens that froze over and stopped the unit from running. Some manufacturers say they are ok. If used, the screen should be at least 1/2" squares and the squares should be angled so they look like an 'X'.

Trane has a nice bayvent. Worked on a couple of those three years ago. Seems our installers didn't think it mattered if they got assembled tight. A gap in the two pieces caused a water buildup in this space and the ice grew like a glacier till it blocked the vent.

I have seen pvc that got knocked loose and the homeowner knew about it but didn't think it mattered until one night the unit would not keep up. It would start and stop, then go into lockout. Found out that the unit was intaking the exhaust and couldn't run due to lack of oxygen. So why not check an A/C prior to the season and a furnace piping regularly? Kids put rocks in them, mothers put easter eggs (plastic) in them (yep, sucked it right into the furnace top where there is a screen. It blocked air flow. Renters hang clothes from gas pipe and pvc pipe. During first few run times of furnace do your own inspection. No water should drip from exhaust pipe connections and slope should be noticeable, 1/4in per foot at least. Specs are in manual.

If I had a high efficiency unit, I would probably want to build a 2' x 2' screened box over mine. I would probably at least cover the pipes during the off season and remove prior to fall check up, just like I would lay a piece of 3/4" plywood over the top of a condenser during the winter. I would look into a Trane and a good company to install it but I think Lennox and Carrier are also good units. I would go with extended warranties and I would read the manual cover to cover seven times too.

I would also make sure that the pvc inside of the home does not have any sags and does not exceed the manufacturers specifications. I have been out on a few of these problems also. Amazing how much water collects when it looks like it 'only sags' a little. I have pulled debris out of the Lennox rubber exhaust boot more than a few times each winter. And, wonder why some engineer decided that he could reduce the size of the drain hole that much just to insert a nickel piece of plastic to connect a hose to. Do they not lay awake at night and rethink their days activities? They should.

Maintenance is your responsibility and if it means that you have to check doors and water faucets etc, before you leave for vacation or trips, so be it. Add furnace and water heater to your list. Remove shrubs from area of pvc or keep them far enough away. Get used to 'seeing' problems before they hit your pocket book.

I have seen some winters where there is a spike in service calls due to no gas. Seems under certain conditions the outside gas meter regulator diaphram 'freezes up'. Only a gas company technician can tell you exactly why. Last one was I believe three yrs ago. Many calls over a two day period when temps went down over twenty below. (Pays to keep this in mind).

Keep bedroom windows cracked open an inch or so during the winter.

Mn born and raised. East metro serviceman for ten years.

Why not follow up with what you chose and how the install went?

[Edited by MikeJ on 09-07-2005 at 09:12 AM]

[Jultzya]

Originally posted by MikeJ
I have seen some winters where there is a spike in service calls due to no gas. Seems under certain conditions the outside gas meter regulator diaphram 'freezes up'. Only a gas company technician can tell you exactly why.

Keep bedroom windows cracked open an inch or so during the winter.

Freeze ups due to moisture.

And the last comment is only masking a real problem. There should be no reason for a window to have to be open!

[Toolpusher]

LENNOX,

I would recommend a G61mpv, 2stage 90% gas furnace rated at 94%.
And scale back on the a/c, install a 10 or 12 seer.
A 10 seer unit with the variable speed drive furnace will give over 11 seer.

Your not in a high a/c climate,
You use a/c but not like some places in the us, that rely on it 6 to 9 months.
They would be more apt to need a 13 or 15 seer.

You'll save enough on the a/c to upgrade to the variable speed 2 stage furnace.

You'll get more use from the heat, then you will the a/c.
So focus on the cheaper gas and more comfort that the G61 will provide.

Just my 2 pennies,
Now I'm sure I'll be blasted.

[beenthere]

Ok, I'll bite, why keep the bedroom window open an inch or 2.

Kinda defeats the purpose of buying better windows.

[docholiday]

defeats the purpose of having a furnace where you live!

[amickracing]

Open the windows so you don't get hot from your trusty furnace running ;-) lol

[beenthere]

Originally posted by docholiday
defeats the purpose of having a furnace where you live!

LOL... It sure would.

[Christheheatingdude]

Living and working in a northern climate such as yours (I am in northern michigan) almost all the furnaces we put in are 90+. As long as the manufacturers instructions are followed you should have no trouble with the venting of the furnace.
Animals are another concern, cant control what they do. But I have not had any calls involving pests in pvc vent. Though I have had some involving 80% furnaces, one involved more bats than I ever care to see again.
Screens are another matter...we do not install them here, because of the potential for unwanted service calls.

I would definetly consider the 2 stage variable speed furnace.

I have heard Trane is coming out with a three stage as well, but I will wait til it is actually in stock at the distributor before I get excited about it.

[beenthere]

York is suppose to come out with their mod furnace this winter.

[tikimonster]

Wow! Lots of great info here, thanks! I'm in the Twin Cities metro. I don't know if the salesman is afraid of the 90+ efficiency furnaces, or was trying to dump his 80% stock and ensure some repeat business as prices increase. Needless to say, he struck out on both counts.

Since all the reps I've talked to plan to vent through the rim joists, I figured regular winter inspection was a must. I already check my dryer vent in the winter to make sure it is open. It only makes sense to ensure that an exhaust vent is open, CO can kill! The PVC itself doesn't bother me, it was the "hanging out a foot, haven for animals, and having to chip ice off it daily" part that I didn't like.

I inspect for wasps and bees after some "surprise tenants" moved in shortly after I did. I do worry about other wee creatures, we have some brazen chipmunks in the neighborhood. If we don't go with the Trane unit, or concentric venting (not sure if Lennox or Bryant offer that), I may have to consider some summer screening and add another item to the fall maintenance list.

Some of those incidents are scary, it's hard to believe people can be so dumb! Easter eggs and laundry on an exhaust vent???? Brother! And I do plan to read the manual, several times. My father always said, don't get it if you won't take the time to understand it!

I'll have to consider the 10 SEER AC, everyone defaulted to the higher SEER units. Maybe because of the utility rebates. It would be nice if money was no problem, but if money was no problem..... I may go with the variable speed blower, it is more expensive but sounds like it's worth it. Winter is our major season, so it makes sense to spend more on the furnace and not the AC.

I have one more rep coming in (recommended by a friend), and then it's "bite the bullet" time. I'll let you know how it all turns out. Thanks again for all the wonderful info! You people are GREAT!

[Wirenut]

A properly installed high eff furnace will not have problems with vent iceing. I have had my Lennox 90+ furnace several years and have had only one problem with the vent. 3 years ago we had a very large snow and the intake was covered with snow!! My furnace has a roof termination also the vent is near the highest portion of the house. With more than two feet of snow the intake became covered and the furnace locked out! With that much snow up there it was time to remove some anyway.

[MikeJ]

Originally posted by beenthere
Ok, I'll bite, why keep the bedroom window open an inch or 2.

Kinda defeats the purpose of buying better windows.

Nope, you don't get the answer that easily. Find a grandparent or great grandparent and ask if they still do this. If so, ask them why. This advice has been passed down in my family for several generations and is why I don't seal all the leaks in my old house. I would rather the house breathe a little. I have a boiler also.

[beenthere]

My parents, and grandparents have all passed on some time ago.

So I can't ask them till i do also.

my grandma on my das side cooked with a wood stove.