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VeryChilly 12-21-2011 12:26 PM

Humidifier making my furnace struggle to achieve 68deg
I installed a honeywell he220a humidifier today here in 45deg SF.

This cheap o humidifier was first choice cos this is a rental house and Im tired of waking up with my tongue stuck to the roof of my mouth.

Anyway used insulated 7' ducting (6") to hook a tap to the humidifier and ran it tonight. The humidity is getting there, but the volume flow rate is down (probably because of the bypassed air) and the heater just cannot heat the house up.

Its a Carrier 58ctx mounted in the really cold attic that has a lot of vents to the outside for some reason.

Its only 45k BTU and this is a 12 sqft house, but it is not well insulated and the wood floor acts like a refridgerator.

Before my marvelous install it could heat the place to 72deg without much difficulty and would run every 10 to 15 mins. Tonight it is struggling to make 68deg.

I removed the small (one inch thick) amount of insulation from the top of supply plenum. I did this to install the take off, whIch is just bare metal and I did not insulate it. Since this is the hotest area of the ducting the tem difference is the greatest and I suspect some heat loss is happeneing here, but I don't know how significant that is.

Next suspect is this humidifier. The "design" basically just flows cold water through a mesh screen at a fair clip and the bypass air pulls it into suspension. The excess water runs down a drain tube. This is not just a tiny tricle! so I am wondering if I am in fact cooling the heated air substantailly with cold water enough to cause this issue? Obviously it takes some enegry to evaporate water, but 45k BTU running constantly?

I could plumb hot water to this thing, but then I am heating large quantities of hot water most of which goes down the drain and the heat loss from the coper pipe to the humidifier would probably be north of 80%.


BlueBSH 12-21-2011 03:13 PM

seems odd that it would have a hard time, water shouldn't cool air that much, assuming the water isn't super cooled (below freezing and still in a liquid state) it should make the hot air feel "warmer" even at a cooler temp due to the humidity, do you know what the relative humidity of the house is? you could have it at 70 degrees with a very low RH and it could feel cold, have it at 68 which a high humidity and feel hot

VeryChilly 12-21-2011 03:40 PM

good point. Yes the house feels warmer at 68 than aty 70 with the humidity, but the humidity is still low (<15%).

BlueBSH 12-21-2011 03:43 PM


Originally Posted by VeryChilly (Post 799604)
good point. Yes the house feels warmer at 68 than aty 70 with the humidity, but the humidity is still low (<15%).

less then 15%? where are you located at? thats pretty low humidity

biggles 12-21-2011 04:27 PM

with that cold attic how true/tight is the return to the unit and the vents to the outside are you descriding supply ducts down into the space and if that humidifier is sitting in that cold attic its cooling the heated air

biggles 12-21-2011 05:00 PM

the bypass air is mixing with the discharge air or actually suckimg on the supply is that mounted on the return ducted to the supply...

VeryChilly 12-21-2011 08:35 PM

yes its sucking on the supply side, thats how it is designed. The question what to do :)
Should I reduce the airflow to the humidifier, insulate the supply and return plenums as much as possible, reduce the water flow thru the humidifier...

Im just not sure where so much heat is going?

BlueBSH 12-21-2011 08:53 PM

do you have any lines running to the outside of the building? if so there is a chance its pulling "fresh air" from outside which is causing the temp drop... you generally dont want to have a fresh air vent open during the cold days, like an HRV / ERV ventalation system or a duct that goes out with a damper on it..

VeryChilly 12-21-2011 09:09 PM

lines running outside????
No. This is a closed heating loft furnace. The supply and return vents are all in the house ceilings.

I mention the loft venting cos its darn cold up there. There is no insulation above the heater is all...

REP 12-21-2011 11:28 PM

OK,first the house needs time to get acclimated to humidity.That means walls ,cieling,carpet furniture,bedding ,just everything needs to pick up humidity before the air gets to a steady state.
Second anything and everything that could be insulated.Thats just common sense.
Third the bypassed air should not be stealing any heat from the process.I noticed some "differant" requiements in the gas pressure section.You need a manometer to monkey around with gas pressure.You should first see what tempature rise you should be getting before you even have anybody adjust the gas pressure if needed.
If you installed your humidifier with a real valve instead of one of those laughable saddle valves you will be able to neck down the water flow.If a saddle valve you will most likely just get a leak if you try to adjust the water.

VeryChilly 12-22-2011 01:55 AM

Yes. Insulate everything. There are two giant (surface area) thin steel plenums on each end of the heater that are mostly uninsulated. The fan section of the heater is uninsulated and has a large flat floor to chill the air. I intend to wrap all that in R30 tomorrow. Im nut sure if the heater section nees to be insulated but I will add stff some under that section and put a layer on top to be sure.

The flex pipe leading to all the ceiling vents is very well insulated. They did a good job with that. I'm going to put another 5 rolls of R30 up there tomorrow and make double sure tho.

I did not do that half a$$ed saddle valve. There is a shutoff valve feeding the heater so I undid the heater cold feed and insterted a 3/4 T. Today I bought a water pressure regulator that adjusts all the way down to a couple of pounds I think. That did the trick with the water flow. Now its just a drop or two.

Since I have not insulated yet, I can tell that the water flow is not the problem.

I am goign to block half of the 6" bypass tube inside the humidifier and see if that helps.

I am not sure why the attic needs substantial ventillation. It has several 12"x4" vents where the roof meets the ceiling around the perimieter ofthe house and two even bigger ones up near the top of the V. Im thinking of just blocking them with R30. What harm can that do?

yuri 12-22-2011 05:51 AM

air and moisture will leak into the attic as hot air rises. this moisture needs to be vented or else the insulation will get wet and useless.

Marty S. 12-22-2011 06:02 AM

Humidifiers are not air tight so you're sucking in cold attic air. Silicone and tape all air leaks then replace the insulation you removed. What's the plan to keep the water line from freezing?

yuri 12-22-2011 06:11 AM

and the drain line from freezing? if that happens it will overflow damage insulation and leak thru the ceiling.

45deg SF = san francisco? maybe it stays above freezing there?

VeryChilly 12-22-2011 12:43 PM

>What's the plan to keep the water line from freezing?
Does not freeze here, if it did, the heater would be running all night so water would go thro the pipe and probably would not freeze.

Sucking in cold air from the attic
Yes. What I am not sure about is how much is leaking. I cannot feel it for example. I used sheet metal screws all around the tap (speediboot) and the humidifier body to try to prevent that but i did not tape or use sealant.

Can you use duct tape on the hot supply side o a heater plenum (the tap is on the top surface)?

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