Humidifiers and Dehumidifiers - Parched House

Hi, everybody & best of the New Year to you.

I have a Honeywell 365 unit installed on the supply side of my primary 5-ton Frigidaire dual fuel system--on the plenum beside the A-frame. The house is 3,300 sq ft. of conditioned space with several high ceilings (18 feet in one room) and a lot of large windows. (There is a second, smaller system for upstairs, but it doesn't run much in the winter.) I recently had a reputable company reconfigure my main supply duct and add a second return to balance out the system. The system is balanced, according to this firm, although there seems to be a fair amount of positive pressure where the Honewell is mounted, perhaps due to the 90-degree bend the ductwork takes immediately above it. (I really don't know how much pressure there's supposed to be at that point.)

On their recommendation, I ran a 1/4" hot water line to the humidifier, thoroughly cleaned the unit and installed a new water panel. It appears to be working properly and now does an adequate job humidifying the house when the temperature is moderate and (I believe) the unit is operating mostly in heat pump mode. It keeps humidity up at about 40% under those conditions.

However, when it's really cold, like today, the HVAC system is running on gas pretty much all night and much of the daylight hours if it's cloudy outside. At times like this, the humidity in the house drops to around 30%. So, I'm guessing the gas-fired system is overwhelming the Honeywell.

Is there anything I can do to improve this? I've tried increasing the set point on the humidistat, but that hasn't helped--it runs pretty much whenever the fan is on.

Should I add a second humidifier? I do have limited options as to where I can install a second unit. There is horizontal ductwork available on both the supply and return sides, but not much to work with vertically. If I need to add a second unit or replace the Honeywell, what should I consider?

I'd appreciate any thoughts.

Thanks

angus

Is the humidistat the old style manual or newer one that has an outdoor sensor?

What are the temps outside at 30%?

The 360 on an upflow furnace or horizontal furnace?

thanks for the reply Jay11J

the humidistat is the duct-mounted automatic version -- i believe it's an H1008A1008 and it's properly located on the return duct. however, i've never installed the outdoor sensor. i guess i didn't think that having an outdoor sensor would matter much because the humidifier seems to be on whenever the blower is on and it's not up to the job running full-time as is.

outside temps lately have been in the upper 20s, low 30s during the day and teens at night. last night, it dropped to 7 here on signal mountain. outside humidity during this time, I believe, has been 35% to 45%.

the furnace is an upflow. however the ceiling is only about 7 feet high in our basement and the duct has to make a 90 degree turn immediately above the plenem. (maybe telling you more here than is necessary, but trying to think of everything.)

thanks again for your help.

angus

the humidistat is the duct-mounted automatic version -- i believe it's an H1008A1008 and it's properly located on the return duct. however, i've never installed the outdoor sensor.
That model of humidistat will adj the humidity as needed.. So an outdoor sensor is not needed.

so the colder it is, the humidistat will "turn" down the humidity to advoid any moister on cold spots, and wet windows.

Jay, could you amplify on that for me, please?

I would think that if this humidistat were restricting the humidity because it's cold outside, that it would shut off occasionally while the hvac unit is running. it doesn't; it runs literally whenever the fans running. and, as it runs, it's not able to get the humidity much above 30%.

am i missing something?

thnx

angus

Ok, Forgive me, I didn't see the part you said it runs pretty much non stop.

Do you have a fresh air pipe tied into the return duct work, or ERV (Air exchanger)?

Lot of recess lights?

Hey, nothing to forgive!!! I just appreciate your help.

No fresh air pipe or exchange pipe. I've seen a picture of your set up and wonder if it's a better way to go.

We do have a lot of recessed lights, but we only use them a few hours a day in the evening when we're home. Would they be a factor in that case?

thanks again

angus

The photo of my bypass, and thinking that may help? It could help, but I'm not sure to be honest with you.

Recess lights can be a problem in some home.. Lot of time the wrong type are put in, and they leak like crazy, so the heat is being sucked up into them like a chimney, and the air is coming into the home and drying it out.

If you are able to go up in the attic and see them to see it's an air tight can/box, then should be OK then.

AHA! I see how you're saying they could add to heat loss. (I thought you might have been saying that running a lot of lights dries out the air in the house.) In our case, about 25 cans lead to unconditioned space above--the rest would be in the floor for the second story. Something to check on.

thanks again

angus

Yeah.. if you got 25 cans that is not sealed well, for sure you are going to have the issues you are seeing.

Well, it's been a year since I started this thread and it's still dry in my house (<30% with the humidifier running whenever the furnace fan is on). I've neglected this long enough and I'd like to fix it this time.

The problem is the same as described below. The powered Honeywell 360 doesn't seem to have enough fan power to overcome the static pressure on the supply side. The unit is installed correctly and it has a new water jacket.

I'm thinking of replacing this unit with a Trane/Aprilaire bypass unit mounted on the return duct.

I hate to throw away my investment in the Honeywell, so before I replace it, I've been thinking of trying to reduce the static pressure by setting the fan speed lower on the Frigidaire FG6RC (120,000 btu) furnace.

What's the consensus on trying that and, assuming it's OK, could someone walk me through how to make the wiring changes to reduce the fan speed?

Thanks!

angus

Did you go up to the lights or into the attic to see if your can lights are air tight?

Before we mess with the blower speed, we need to take two temps reading.. One at the air filter in the return, and above the furnace.

Report those numbers back to me.. Also, look at the model# sticker for temp rise on it.

I'm very sure the cans, themselves, leak air. They are all covered, however, with at least R-30 blown insulation--probably over R 40 in some rooms.

I'll take those measurements and post them as soon as I get back in town.

Thank you, Jay.

angus

I'm very sure the cans, themselves, leak air. They are all covered, however, with at least R-30 blown insulation--probably over R 40 in some rooms.
The blown insulation is not going to stop the air flow. It just a blanket to help keep the house warm. When you take your blanket, you can still breath though it.