"Screening" HE furnance vent in/outlets...Smart/dumb?

[Bsting]

Hello all. Thanks in advance, great forum for info to us homeowners...I already know the manuals say do not do it, but several professionals have offered differing opinions. So I want to state that I already know its wrong, but I have to do it anyway! I am in a high mice, bee, chipmunk, bird traffic area. I have placed a "PVC screen" over both pipes and am looking for advice on how stupid this actually is and if it will/can cause damage to my unit?

I have Lennox Elite G61 94% unit in Michigan. It is a brick ranch with a basement. The 2" vent in/out are about 12in up from the ground (I do get snow, but those pipes are as high as they could put them). Luckily, they are not in an area where drifts occur and usually no that high. Anyhoot...I know I would get mice or other creatures in there so I took a PVC drain (normally used for shower drains/utility sinks) and capped it off at first. This seemed to be fine on the outlet, but the inlet starting wistling so obviuosly not enough air getting in. I then took a 2" to 4" adapter, bought the 4" drain and capped it off (could have used the 2 to 6 but wanted to go as small as possible for looks). It all seems to be working great now. The 4" pipe with the PVC screen is much larger than the 2 so the surface area with the screening is probably about the same diameter as the original 2" without screen. Does anyone forsee any problems besides freezing--I say that because since it is a well heated basement, I think enough heat radiating from the walls and pipes will prevent a lot of the freezing (Im in zone 5). I know this got long, but thank you for all comments!!

[t527ed]

much greater chance of termination icing up with that mess on there than there is of a mouse, bee, bird or chipmunk causing a problem.

[tinknocker service tech]

first of the exhaust should be reduced to 1 1/2 with a 6in extension and should have no screen. This is so the exhaust is pushed away from the house and intake pipe

the intake should not have a screen either but i have had a few inspectors request them. You can go to a supply house and get pvc grilles that are designed for this applacation. They are designed for 3in or 2in and will fit inside a fitting or outside the pipe


i recconmend since it isnt reqired by the inspector then remove the screens you have and dont worry about it

or have your installer remove the termination that is there and replace it with a concentric kit and the problem is solved

[Bsting]

Thanks for the replies. My outlet does extend about 12in from the inlet, but is still 2 " PVC, not 1 1/2 like you suggested. I will check my install manual they left and see if it is code in my area...

I did put the PVC grilles on...When I attached them as is, the furnace was not getting enough air since I basically reduced the 2 in pipe down to 1"(approx) because the grille reduced the surface area. That is why I first expanded it to a 4" coupler, then put a 4" grille on, which in terms of surface area is probably about 2". That was my thinking anyway. Still want advice on whether or not this is wise or not. Have not heard of inspectors actually wanting screens or grilles in my area, as the Lennox guidelines state in bold letters NOT to put anything on the end, but I would have a mouse stinking up my basement if I didn't, as my neighbor already has.

[t527ed]

there is no way ANYTHING coming in those pipes is getting in your basement, it is a totally sealed system.

2 responses to your question along with the manufacturers install manual tell you not to do it.

if it causes a problem you have voided the approvals the furnace was designed with and its all on you............

[Milk man]

Make a cage to go over both sides out of 1' spare wire fence.

[SeattlePioneer]

I'd look at whether the installation standards permit you to elbow up and out of the snow/animal zone. That might be a simple and effective solution depending on the length of pipe and elbows in the system now.

[Milk man]

I pulled a lot of birds out of Carrier 58MXAs.

[Kevin Weaver]

I hope this G61 2 satge furnace is not over 70,000 btu. or the flues are short because 2" is small. When the pipes exit the home they can elbow uo and then raise the hieght of the termination. Possibly increase the termination to 3" then cut some metal wide spaced screen wire in a circle then insert into the termination elbow.

[Bsting]

Thank you to all for the advice. Interesting...It is an 88,000 BTU, and the pipes are only 2". I am no expert...but they leave the furnace at 2", convert to 4" for most of the run, and then exit as 2". Seems like it defies the laws of physics by decreasing down to 2", but according to the manual it looks like they know what they are doing, plus they are well respected in our community. I have to say I trust them 100%, however I cant but wonder now since these posts and others talk about vent diameters.

[keepyoucool2003]

A like someone else posted, it's a sealed combustion system, nothing is coming in. If that Lennox model is one of those where the intake pipe just drops into the sealed furnace cabinet, instead of directly into a combustion cabinet as with most makes its slightly different. (I haven't seen newer Lennox. Either way, it’s a completely sealed cabinet. If the terminations are installed correctly, with 90 at the outside of your house, there shouldn't be things getting in THE PIPE. I've had leaves make it to the inlet screen of the combustion chamber, that's it though. I've seen homeowners put large window screen on the inlet outside to prevent this. Never put anything on the outlet.

It’s not correct to change the pipe diameter twice. You leave the inducer at X", exit case, elbow, transition to X" and that size should be the entire pipe. Sounds to me like the run required larger than 2" but for some reason they didn't want to terminate with 2 1/2 so they got creative and reduced the friction rate by using 4" and terminate with 2". I would bet they didn’t want to make the holes bigger in the brick. That'd be one of those I just shake my head at.

[Bsting]

I appreciate the info again. You are probably correct with the brick being an issue, as it is a 2x6 wall with brick and a finished basement ceiling to boot. I hope it is ok anyway. I still defied Lennox's recommendations on not putting anything on the pipes because my neighbor has the same system and although mice could not get into the living space, they made it into the furnace and caused quite a "stink" if you know what I mean, and other problems as well. I think the future of these things is going to change just from reading blogs as numerous people are having troubles with animals getting in. To me, its like not capping your fireplace chimney--just a big hole in your house saying come on in.

I agree with you prob dont need it on the outlet, and that is the one that might ice up since it is pushing moist air and fumes, toxic to mice I am sure, constantly out. The inlet however, is drawing air actually inviting in mice looking for a warm spot to nest. Thanks again everyone.

[Milk man]

Put a large cage over both pipes. Use one inch square wire fence to make the cage.

It may not look the prettiest, but it will work. I've dug plenty of birds out of Carrier equipment.

I think someone has said that already.