I am trying to find out the best practices for inspecting a humidistat connected to a central AC system in Florida. For example, how should system be set for the humidistat to function, and how would one go about checking to see if it is working?
Any help would be appreciated.
To start, this is not an inspection requirement.
Next, you need to pick which (of several) systems you plan to inspect.
Learn how they operate.
Inspect their operation.
Then figure how you are going to make the stat call when it’s 90% rh in the summer…
Donald, first you have to know if the humidistat is wired in series or parallel. Talk to an AC guy about this.
Some need to be “on” to active the thermostat as the primary source and some need to be “off”. This can be a HUGE problem. Many times, the mold testing we do here is on the account of a humidistat being used improperly or failing.
I make sure they work as intended. I do not ensure 60% humidity is actually 60% humidity. I check to see if it clicks and activates and turns the system on and off.
That’s about it.
Pull the wires and stick your tong on it.LOL
I have found maybe 3 that were actually working. 99% haven’t been touched or cleaned in ages. I disclaim them mainly because of this. I just tell people, this is what you have, it hasen’t been cleaned since Reagan was president. IF you want it to work get it serviced.
They are very rarely even used anymore. People are more likely to leave the AC set at 78-80 degrees now when they are out of town instead of higher as they did in the past when most humidistats were installed. I know that does not really answer your question but that is a way of explaining it to your client that they should set a better temperature to control the environment. Russ would be correct though. You can test by seeing if it will activate the system but in no way is a guarantee on if it is completely accurate.
In the south i see no reason for them
Thanks for all the help, guys.
Best to disclaim it in your PIA. It will just add time to your routine and add needless liability unless you are an HVAC specialist.
If we are not an HVAC Specialist, why are we inspecting this stuff?
Why do we “Disclaim” things we are not required to do (or are not qualified to do)?
I pretty much always recommend that humidifiers be removed, for the reasons listed by Sean. Humidifiers need monthly maintenance, humidistats need to be adjusted whenever there is an outside temperature change (colder = lower settings). Its one of those, if I need to explain this stuff to you, you should not have a humidifier 
So I just say, have it removed unless a doctor or your piano tuner says you must have one, and then learn how to use it and keep it working (RTFM).
I certainly am not an HVAC “specialist”. I’m a generalist home inspector. Perhaps “disclaim” was the wrong word, but my PIA if full of a list of stuff I don’t do. Heat exchangers, humidifiers and de-humidifiers, water filters, etc. It’s called “limiting my liability”.
I don’t know how the winter air in Alberta is but it is dry as burst toast in MN and WI.
Humidifiers, if well managed can provide a great deal of comfort to occupants and allow lower temps in the home.
If you have wooden musical instruments the humidifier will help them stay more stable.
I advise clients to be careful to adjust the humidity level as the temp changes, to periodically change the dispersion media and tell them about more sophisticated humidistats that include an outdoor temp sensor to make more automatic.
I also tell them to pay attention to their windows on very cold days as condensation and frost will form on the lower corners of the windows and could damage the wood trim as it melts as the humidity is to high in the home.
I would never recommend their removal.
I bring an digital thermometer that also shows relative humidity with me when I inspect homes.
I find that the relative humidity is generally about 25% in winter in homes without humidifiers.
I also find that homes that do have humidifiers, the water reservoirs and drums are usually filled with slime and mineral deposits, and the rh is about 25%. There is something in the city water here that messes up humidifiers, and based on my observation, no one ever checks them or cleans them.
A home that had a newly installed humidifier, humidistat was set to 80, the windows had so much frost they were frozen shut, and there was frost in the attic.
Based on my actual experiences, I do not recommend humidifiers, because
a) they mostly don’t work, and so have zero effect on the actual humidity in the house.
b) if they do work, people who don’t understand relative humidity, which is just about everybody, can do a lot of damage to their homes.
c) cooking, breathing, daily showers, etc. keep a house in Edmonton in winter at a relative humidity of 25% without a humidifier, which is just about perfect for the house, most people can tolerate it, but may be hard on some people or pianos.
In hard water areas humidfiers should be supplied by softened water.
If I advised clients to install water softeners so they could install a crap humidifier from home depot I would be justifiably laughed out of town.
What is a crap humidifier?
Crap humidifiers are mounted on forced air furnaces or air handlers, hot air from the supply plenum blows though the humidifiier, where water is added by evaporating from a foam drum or some kind of plates or wick kept wet by capillary action. Water is added through a nasty saddle valve tapped into a water line. Water levels are maintained by some type of float. The system only works when a control calls for heat, an optional control may operate a damper that controls the flow of air through the humidifier when the furnace is running. Prices vary from 50 bucks to 200 bucks.
Even crappier are room humidifiers, but I don’t inspect those.
As I said, previously, which you totally ignored, my actual on site measurement here in my area shows that installed humidifiers usually do not make a difference compared to homes that do not have humidifiers, and that in all cases, the humidity is at an acceptable to ideal level to prevent condensation and mold problems, but may be too low for sensitive people or objects that can be adversely affected by low humidity.
As a ps here is an interesting article re this discussion
There isn’t a thing you wrote I can agree with.
It’s all about the right type of supply water and proper maintenance.
They never have been a set it forget it device.
LOL I didn’t expect less from you and your steel trap mind Michael, (sprung 40 years ago, and rusted shut)