I had an Aprilaire 500 humidifier professionally installed. The humidifier appears to be installed correctly and appears to operate properly when triggered, but I can't seem to keep the thing running long enough to make any impact on the humidity level in the house. The humidistat installed on the return duct is reading 45%+ RH at which point it turns the humidifier off. The actual humidity level in all areas of the house is reading 20-23% on another portable humidity monitor. The outdoor air temperature sensor is properly connected to the humidistat and is on the east side of the house.
Any thoughts on why there might be such a large variance between the humidistat's RH calculation and the actual humidity levels in the house? Based on what I have read online and in the manual, the humidifier control is doing its job turning the humidifier off when the humidistat reads 45% (based on the settings I have dialed up). I just don't know why it's reading so high when the house is as dry as it is. I have even tried placing the portable humidity monitor directly outside the grill of the main return duct. There is still a 25% variance in readings between that monitor and the RH monitor on the humidistat.
Other factors that may or may not make a difference: outside air temperature is approx. 27 degrees F, AHU/humidifier/furnace is installed (hanging) in an uninsulated garage (approx 38 F currently), indoor air temperature is approx. 68 F, humidistat is installed in the center of a 6 foot, uninsulated return duct.
Thanks folks. Any thoughts you could provide will be helpful.
It sounds like the outside air sensor is resetting the setpoint to keep condensation on windows from forming, Does it explain in your paperwork how that works?
It sounds like the outside air sensor is resetting the setpoint to keep condensation on windows from forming, Does it explain in your paperwork how that works?
Thank you for your response. That is correct. The manual explains that it uses the outdoor temp to calculate a target RH% for your home to prevent condensation. Based on my dial setting (7/highest), a table in the manual shows that it targets 45% relative humidity in the house when the temperature is 30F outside. The display on the humidistat show the RH% calculation it is measuring in the return air duct to which it is affixed. It is currently showing/reading/calculating 47% RH in the return air duct. Other sensors I have show that the humidity level in the house is 24%. My nose agrees with the 24% reading.
I feel that because the humidistat is currently reading 47% RH that it is purposely not activating the humidifier. The problem I have is with the 47% RH reading. That does not accurately reflect the level of humidity in the house. There is a green led on the display that shows when the humidifier is activated. I can get it to run if I activate the "test" feature, so I feel confident that it works. I think the high, erroneous reading on the humidistat is keeping it from turning on.
DOGBOY, looks like I need one more post in order to post links. Hope this one puts me over the threshold.
buford, thank you... I will check the install and see how easy that is. I don't believe the guy caulked the hole in the wall, but I haven't inspected it from the outside.
Unfortunately the sensor is sealed from the outside. It would be difficult to remove and reinstall unless I had another sensor to replace it with. Sorry about that.
If the humidifier is set up to run only when the blower is running in heat mode, as many of them are - it's obviously only going to run when the furnace runs. Control voltage will not even be sitting at the humidistat if the furnace isn't running.
We'd need the make and model of the furnace and then the documentation for the model to be sure. But if your furnace only runs so much (perhaps oversized a bit) and it is, in fact, set up as I described - that might be the issue.
Just a thought.
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Should have taken that return flex off the other side and then used hard pipe down to the return.Would have made for a better looking and a heck of a lot easier to service.
@buford, haha. That is my spring project. This joker blocked both the control panel and the furnace filter with the flex duct. Luckily I had just changed the filter.
@hurtinhvac, thanks! According to the documentation, this humidifier IS only supposed to operate when the furnace is running, so you may be on to something. I will try to monitor the frequency of furnace activation and watch the humidifier LED at those times.
Is it straight electric or do you have a heat pump outside?
And yes, most here will take exception to the manner in which it was installed - using flex duct and hanging it cross country right in front of everything. Brace yourself for a few more comments.
Is the Religious Right to blame for Christianity's decline?
They argued that, as the Religious Right became increasingly visible and militant, it became associated with Christianity itself. And if being a Christian meant being associated with the likes of Jerry Falwell, many people—especially political moderates and liberals—decided to simply stop identifying as Christians altogether.
You should have seen the initial install. The outdoor temperature sensor was shoved behind the pegboard you see in the pic (not run outdoors), and the humidifier drain tubing rollercoastered its way over to the condensate drain, secured by duct tape. On the return visit they sent their senior tech who assured my wife that nothing could be done about the bypass ducting blocking the control panel/filter. It is a sad install, but I spent over $ already in labor and parts, and I just want to get this thing working properly without spending any more money. If there's some safety concern with the ducting, I would gladly call them back out. But at this point, I would rather not deal with them again.
Last edited by beenthere; 03-01-2015 at 06:16 PM.
Reason: Price
Sadly, I understand. No safety concerns; just performance (flex duct does not permit airflow as well as hard pipe), appearance and serviceability.
Oh BTW, specific prices are not allowed here going forward. No big deal - a moderator will probably be along to remove just that portion of your previous post.
Is the Religious Right to blame for Christianity's decline?
They argued that, as the Religious Right became increasingly visible and militant, it became associated with Christianity itself. And if being a Christian meant being associated with the likes of Jerry Falwell, many people—especially political moderates and liberals—decided to simply stop identifying as Christians altogether.
Sorry to say getting it working properly and spending no $ just isn't going to happen
Will that unit ever work as you wish or as you were told I don’t know. Unfortunately as you've found out just slapping it on the duct is not the solution. Size means a lot, size of the heating system, size of the ducts, size of the humidifier etc. Call a new contractor and start over.
Johnny, its not going to cost a lot to fix this. It might be worth having a tech come and verify the wiring and operation, and if you send this same pic to the co that does come out, maybe the said tech knows sheetmetal and could bring what is needed to get you fixed up. Did not find where you are at, but a heat might be worthwhile depending on your location, elec rates and how long you plan on staying there.
Thanks for your responses everyone. I probably will just take buford's advice and send the pic to a tech to see if they can correct the issues.
Also, what beenthere mentioned makes total sense. If the humidistat is not getting a proper reading on the temperature of the return air, it would make sense that it throws the RH calculation off. I may be able to throw a temperature sensor inside that duct and see how the cold garage is affecting that reading. Along those lines... would there be any other benefits to insulating that return trunk? I will probably insulate the whole garage at some point, but that's a few years out. $$$! I live in the lower mid-atlantic, so we do get some extreme cold/hots every once in a while.
Thanks again, everyone! And sorry about that dollar figure and the gigantic photo.