Humidistat turns on A/C?

[Winterpegger]

Hello,

I live in a newly built house which has a forced-air natural gas heating system. Aside from the digital thermostat, there is also a humidistat mounted on the wall. I've been told that the humidistat controls a fan which exchanges humid indoor air for dryer outdoor air. I've also installed a central air conditioner over the summer (install done by an HVAC contractor). Given that it is winter, I'm noticing that with the humidistat turned on to control the humidity in the house, the air conditioner fan also turns on whenever the humidistat kicks in.

Is it just the fan operating, or is the air conditioner unit actually operating and lowering the indoor temperature?

I've also noticed that the refrigerant line that runs from the A/C unit into the furnance duct/coils get all covered with a layer of frost.

Is this normal, or is it a wiring error of some sort by the HVAC contractor?

[Duane Bozarth]

...

Sounds buggered for winter-time operation. I'd think in the winter normally the humidstat would be controlling a humidifier to raise interior humidity and it should, of course, be tied into the fan so you don't dump water (mist) in a noncirculating system.

But, the frosting makes it sound like the A/C may be running which is probably not what you want...

[BGBevill]

You tell us.

Well, on second thought, it does appear to be running.

No, it is not normal. Around here, we have to add humidity to the indoor air in the winter, but it could be different where you live. Normally, the a/c removes moisture in the summer and a humidifier is used to add moisture in the winter. Call your contractor and address your questions to him.

Bobby

[Bubba]

The humidistat should control a Humidifier. Nothing else. I cant see the air conditioning compressor working from here when the outdoor fan runs. Only you can tell us that. The A/C compressor nor the A/C outdoor fan should NOT be running in the winter NOR when the humidistat is turned up. Youve got some messed up wiring and obviously no one has checked out your system in your newly built house. You'd do yourself a favor by getting them or a Good hvac company back out and have them check everything over including settings, air flows, temps etc. etc. Bubba

[Edwin Pawlowski]

Depends. A humidistat is just that. It control humidity. While it would be very unusual for most of us to want to decrease the humidity in winter, there are certain applications to do just that. I know of a couple of printing plants where humidity control for the paper was more important than temperature control. It was not unusual to run the AC system and the heater in order to lower the humidity.

Perhaps the OP lives in a very humid region. There is always an exception.

[nicksanspam]

Wrong. It should control a DEhumidifier.

Nick

[David Martel]

Winter,

It sounds to me as if your AC or it's connection to the humidistat may need adjustment. From your post it sounds as if you originally had a heater and a humidifier. You added AC recently and the installer wired this to the humidistat and thermostat. Now the humidifier is putting moisture into your dry winter air and this moisture is setting off the AC, which functions as a dehumidifier. For now go to your breaker box and turn off the AC. See what this does. Call the AC installer about fixing this, this is probably warranty work.

Dave M.

[Dave Morrison]

Actually it should control some type of humidity control device(s). Can't see it from here, it may add or subtract moisture from your environment. The system I have installed will add humidity any time of the year and turn the inside fan on to distribute it as needed. (Autoflo steam). Call your hvac contractor to diagnose AND explain your systems operation. Dave

[winterpegger]

Hello All, Thanks for the replies.

The humidistat is mainly used to de-humidify the house. Where I'm living, the temperature gets quite cold and the houses are tightly sealed. So to avoid excess moisture from day-to-day activities such cooking, showering, even breathing, building up inside the house, dryer air is brought in through the central exhaust system to replace the more humid air inside the house. I do not have a heat exchanger.

I believe this is normally done through only a central exhaust fan. But since this is the first time I've lived in a house with a central exhaust system, I wasn't sure if the humidistat was supposed to turn the A/C on as well.

Is there any way that I can tell if the condenser is running? As previously posted, I can see the refridgerant line being frosted up as well as the A/C fan running. And I'm not sure if the cool air being pumped through the registers is simply the cold outside air or if it's as a result of the condenser working.

Based on the above, do you still believe that this is a wiring error of some sort?

[trader4]

This sounds whacko to me. First, there is the notion that you can build up a lot of excess humidity that needs to be removed in even a relatively tightly sealed house in a cold winter climate. Activites like cooking and breathing add a minimal amount. The only significant amount on that list in my experience is showering and that humidity is usually only a problem only if it's confined to the bathroom. A simple bathroom fan run for a few mins fixes that. An average house has all the humidity sources on your list and the humidity is still low enough in cold winters that people add humidifiers to raise the humidity.

Then, if you're lowering the humidity by bringing in cold winter outside air without a heat exchanger you're just throwing money out the window. It's going to take quite a bit of outside air to achieve any significant reduction in humidity. And why then, is you're housed tightly sealed? To tightly seal a house requires mork work, more cost, and then you put in a system that blows cold outside air into the house to reduce humidity? If the house is that tightly sealed, then the correct system is one with a heat exchanger and that is typically used to bring in fresh air, not lower humidity.

[nicksanspam]

An absolutely airtight house will build up humidity in wintertime until water vapor condenses on windows. Winter humidification is a mistake.

No need for that, if the house is sufficiently airtight.

How much? :-)

Nick

[Bubba]

Try posting some names and model numbers of the furnace, AC, humidifier, humidistats, energy recover units, fresh air exchangers or just whatever the heck you have because none of your posts are making any sense anymore. Then, maybe we can help you Bubba

[JustCallMe Norman]

'Given that it is winter, I'm noticing that with the humidistat turned on to control the humidity in the house, the air conditioner fan also turns on whenever the humidistat kicks in. Is it just the fan operating, or is the air conditioner unit actually operating and lowering the indoor temperature? I've also noticed that the refrigerant line that runs from the A/C unit into the furnance duct/coils get all covered with a layer of frost. Is this normal, or is it a wiring error of some sort by the HVAC contractor? '

Your (residential) A/C system is NOT set up for winter operation and you will damage the compressor in the unit. Dont run the a/c below outside temp of 60 f. You need to find out why the a/c is running in the winter. Not good. Dont delay.

[Greg]

Humidistats usually do turn on the A/C. They assume it is summer. Where is all the humidity coming from?

[nicksanspam]

Makes perfect sense, with the AC turned off in wintertime.

Nick

[trader4]

"An absolutely airtight house will build up humidity in wintertime until water vapor condenses on windows. Winter humidification is a mistake. "

Yeah college boy, and how many of those does one typically find in the real world? Did the OP say he had an absolutely airtight house? You're lack of real world experience and common sense is obvious.

"How much? :-)"

Why don't you go solve some differential equations for us and let us know.

[trader4]

You know, I used to think from your posts that you were just some kind of academic, without practical experience or common sense, caught up in the wonders of saving energy, no matter how impractical. Now, it's quite obvious you're a complete idiot.

The OP has a system where he claims to have a house that's tightly sealed. So, the house was built with considerable additonal cost to keep air out to save energy. Then, to control humidity, he says he has a system that just blows cold winter outside air in to the house, without a heat exchanger. And now you tell us that makes perfect sense to you. You, the guy who complains that adding a humidifier to a home wastes energy, has no problem with blowing cold air needlessly into a home. You might as well be opening windows in the middle of winter, it would be just as effective. And isn't it rather strange that if his system makes perfect sense, no one else on here, including HVAC pro's, can figure out what he's talking about?

[Red Neckerson]

Better than being a complete a-hole......

[nicksanspam]

Not many in the US, vs our Canadian friend's. That's another mistake.

Another mistake is to imagine that it takes less heat energy to humidify a house than the energy saved by turning the thermostat down 2 F for equal comfort. That only works if you live in an airtight house without much insulation, eg an old oil tank in Barrow, Alaska :-)

Winter humidification typically consumes 10X more energy than it "saves."

Nick (again repeating obvious truths to people who will not listen.)

[Red Neckerson]

Well, to stop the static shocks, bloddy noses and itchy skin, running my humidifier may cost me a total of an extra 50 cents per month. Well worth it if you ask me....