OK to cut humidifier in side of A-coil box?

Subject says all... it's been unuually cold for the area here (DC-land, si ngle digits at night) and I stayed last night at my girlfriend's place whil e she was out of town. A while back I'd brought over a little weather stat ion thing for several reasons, and had always noticed that it was very dry in the wintertime. We've disconnected the dryer vent in an attempt to miti gate this (I know you're not supposed to do that but desperate times etc.) Last night it got down to single digits and the hygrometer was measuring 2 0% RH when I got up this morning. I guess the combo of only one person in the house and cold temps just dry everything out.
The house has an updraft natural gas furnace with a whole house A/C sitting on top of it. There's no room to install a typical humidifier like I'm us ed to seeing e.g. Aprilaire 700 between the A-coil and the ceiling. Would it be acceptable to just cut it right into the side of the A-coil box itsel f? This seems to be literally the only way to make this happen.
Or are there any other ideas for humidification (besides leaving a teapot o n all the time...)
Oddly, my place does have a humidifier that I serviced when I moved in, and never finished hooking back up (hack job by previous residents) and it nev er gets this dry...
thanks...
nate
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On Saturday, February 14, 2015 at 9:06:13 AM UTC-5, N8N wrote:

ile she was out of town. A while back I'd brought over a little weather st ation thing for several reasons, and had always noticed that it was very dr y in the wintertime. We've disconnected the dryer vent in an attempt to mi tigate this (I know you're not supposed to do that but desperate times etc. ) Last night it got down to single digits and the hygrometer was measuring 20% RH when I got up this morning. I guess the combo of only one person i n the house and cold temps just dry everything out.

used to seeing e.g. Aprilaire 700 between the A-coil and the ceiling. Woul d it be acceptable to just cut it right into the side of the A-coil box its elf? This seems to be literally the only way to make this happen.

ever gets this dry...

Typically today they are being installed on the cold air side with a duct running over to the hot side to bypass some air across it. That avoids the problem you describe. I had a relatively new Aprilaire powered model (760 I think) that doesn't used bypass air and it was mounted on the hot side of my old furnace. When I replaced the furnace, I put it back on the hot side. Not sure if I'd do that again. With the coil and plenum assembly sitting on the floor, it was possible to see where there was clearance and cut it. But today the plenum part is double walled with insulation in between. And instead of A coils the higher efficiency ones today, at least mine, had an N coil, ie an additional section. The humidifier will still fit, but without having it sitting, open, pre-install on the floor, I would not have attempted to cut a hole because there isn't much clearance, IDK if you could even figure it out, because once it's on the furnace, lines connected, not so easy to tell. Bottom line, much easier to put a bypass model on the cold side. Then you just need a hole anywhere on the hot side for the bypass duct. It can be up higher or over, etc where there is no coil to worry about.
Also, with it in the single digits, that 20% humidity isn't too far off. You want the humidity backed down as the outside temps decline. About 40% when it's 50F out, down to mabye 25% when it's in the single digits. Otherwise you can get condensation around windows, ceilings with recessed lights that damages paint, etc. When it'r real cold like that, better to err a little on the low side instead of getting it too high. I'd recommend getting one with an outdoor sensor that automatically does the adjustment. Highly recommend Aprilaire.
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trader_4 wrote:

700 model is pretty big in capacity, No need to over sizing it. Our house has 600 model. I'd stay clear of evaporator coil for maintenance reason.
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On Saturday, February 14, 2015 at 9:20:28 AM UTC-5, trader_4 wrote:
Just to add to what I previously posted, if it's really an A coil, one layer of metal to cut through, then I'd probably put it on the hot side. That's what I did with my old furnace. Recent experience is with an N coil, double thickness, insulation in the middle plenum.
If it;s single wall, A coil and you can visually verify where the coil is at or alternatively drill some small, very limited depth holes to probe and figure it out, then that's OK too.
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On 2/14/2015 6:33 PM, trader_4 wrote:

I'd not want to drill holes into an AC coil. Too easy to nick a refrigerant line, and let out the "freon".
To the OP, I think others have mentioned the hum typically goes on the return side. I'm not there to see the setup. But, cutting into an AC cased coil is a poor decision.
In my trailer, I've got a floor model humidifier, which takes about two gal of water per day. It's a bit of work, but easier than try to modify my duct work.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
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On Sunday, February 15, 2015 at 7:30:46 AM UTC-5, Stormin Mormon wrote:

I've honestly never seen a humidifier on the cold side, only on the hot sid e above the A-coil (if present.) Will that actually get enough water into the air to make a noticeable difference? One would think that air in the h igh 60s F will be less likely to draw in moisture than the output of a runn ing furnace...
nate
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On 2/19/2015 7:49 PM, N8N wrote:

(if present.) Will that actually get enough water into the air to make a noticeable difference? One would think that air in the high 60s F will be less likely to draw in moisture than the output of a running furnace...

I used to install them. There is a six inch round duct that goes from the hot air to the humidifier. Some air pumps in circles, but most of it goes into the structure. Yes, it works. There is a damper that needs to be closed for summer, open for winter.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
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On Thursday, February 19, 2015 at 8:24:56 PM UTC-5, Stormin Mormon wrote:

Ah, OK, after some more searching and that idea in my head I see what you mean now.
But then I still have the same issue; the only accessable point on the hot side to install the duct flange is the A-coil box...
nate
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On Saturday, February 21, 2015 at 8:00:45 AM UTC-5, N8N wrote:

No other hot side duct area near the furnace is accessible for a 6" round duct connection? That would be very strange. And you certainly can cut a hole in the section with the coil, as long as you ascertain where the coil is and isn't and make sure there is no way to hit it.
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On Saturday, February 21, 2015 at 8:13:01 AM UTC-5, trader_4 wrote:

Nope. Is very strange. Very tall updraft furnace, A-coil on top of it, th en there's maybe 6" of flex bellows and the duct disappears into the ceilin g. The ceiling in the mech. area is very low, probably hiding more ductwor k and plumbing, but I'm loath to cut into it as then that would turn into a Major Project(tm) and I've already done tons of stuff that'll never give a ny payback except to the actual owners... (but was kind of necessary, like fixing the arsed up handrails, replacing completely toasted receptacles, et c.)
nate
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On 2/21/2015 8:00 AM, N8N wrote:

duct flange is the A-coil box...

of the A coil, so you can see what's inside. They usually have 1/4 inch or so of fiberglass inside the sheet metal. I'd want to be super sure not to damage the coil. Also to be sure a future tech could get the coil out for service and cleaning.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
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wrote:

That's how mine was when we moved in and how the new furnace was done later on. So far, so good
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