Need some help to understand *Dehumid* / *Humid* in HVAC stat
Hi, I use Braeburn 5400 stat connected to my conventional 80% HVAC. I am planning to have a whole house humidifier installed. Doing some research, I found most of them come with their own stat, etc. Looking at my 5400 literature, I find some great options (since I also have the outdoor sensor installed) which i want to utilize. Wondering if you folks can help me understand a few things.
1. In installation manual, option #22 - Dehumidification fan speed control. Explanation given is: Feature accommodates either a normally open relay or a normally closed relay. Selects between Dehumidiﬁcation fan speed limiting off (NO), or on: D output normally active (NA) and D output normally inactive (NI).
What exactly should I be selecting? I've understood that during cooling periods, if it's high humid, stat will run cooling for a longer time and effectively try to lower the humidity levels, etc. but nevertheless don't understand what the above means and what should be the settings.
I might be installing a humidifier pretty soon. My furnace provides a 110V humidifier tap, activated when there's a heating call.
Question a: I would like to avoid installing the humidifier's own stat but rely on the settings of the Braeburn stat. Effectively, if the humidifier is connected into the 110V furnace tap can I assume that as and when my 5400 stat detects a need for humidification, it'll call the furnace to start, which in turn activates the humidifier, thus effectively I am controlling my home humidification completely using my 5400 without having to install the humidifier's own humistat. I also thus utilize some features provided by my 5400 using my outdoor sensor, which I have.
Question b: However, I also do see in 5400, there's a humidifier connection available. I wanted to know what's the use of that in conjunction to what I stated above?
Note: I am not planning to do a DIY on humidifier. However, it'll be terrific if I can know of the feasibility beforehand and how the wiring setup operates. I am getting some quotes, etc. from reputed HVAC professionals but some have stated evap, some drum, some fan-powered, some steam. I am on a tight budget. Against all that's above, if I know beforehand how to achieve the wiring along with pros and cons of humidifier, I can have a good discussion. I am in NJ, USA and in a small 1500 sq. ft 2 storied townhouse, built around 1960.
I will address your control concerns in a moment, but your first option to improve your indoor winter humidity levels might be to consider a trip to your hardware store. But before that, walk your townhouse and see if you have the following things:
For attic access hatches or pulldown stairs, several options exist to make them more airtight to the attic, but that is a great place to start to make your house less leaky (which is what lowers your indoor humidity levels in winter). That and weather sealing exterior doors, including any door that leads to an attached garage. Recessed lights require more caution for sealing so they do not become a fire hazard...at this juncture my energy audit friends here would chime in and state you ought to consider an energy audit including a blower door test to see where your structure is truly leaking air and has insulation gaps.
- Acess to an attic from inside the house, whether it be a set of pulldown stairs or the older "hatch" method
- Condition of all exterior door weatherstripping and door sweeps
- If townhouse has attached garage, check door to house weather sealing
- Recessed lights in the upstairs ceiling?
- Location of HVAC equipment...in attic, in the house, or in a basement/crawl space?
In short, the "tighter" a house is, the less problem you have controlling interior humdity in the house, year round, but particularly in winter. Some homes are tight enough that winter indoor humidity levels are controlled by careful mechanical ventilation. A 1960's townhouse may not be able to achieve that level of tightness, but it's not necessary that it does. You just want to consider helping your structure do a better job holding in the air you pay to heat and cool, and to humidity/dehumidify.
As for controlling a humidifier with its own stat vs. your Braeburn, it depends on the control sequence for each, well, control. I think you're favoring the Braeburn because of your outdoor temperature sensor, which could offer some form of reset control as outdoor air temperatures drop or rise. The idea behind this is to vary indoor humidity levels to keep your windows from sweating and to minimize excessively moist air from entering the attic when it is very cold outside. For the latter, making the ceiling below the attic as airtight as reasonably possible absolutely minimizes the attic condensation/frosting risk from maintaining higher indoor humidity levels in winter. For windows, either plastic film or double/triple pane units can handle that issue. Also consider what average indoor air humidity levels you want in winter, and at what point you feel the air is too dry.
See if your humidifier control also offers outdoor air reset; additionally weigh its control method against the Braeburn. You don't want the furnace to fire just to humidify the air if you choose a steam humidifier, but you do if you choose a wet drum or other non steam type of humidifier. Additionally, if you use a steam humidifier, the thermostat controlling both humidifier and furnace might be the way to go since the stat can call for the furnace to circulate the air on low speed to minimize draft risk when there is a no heat call but there is a humidity call.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.
The fact that the braeburn supports humidification without heat (18:IND), as well as outside air reset of the humidification setpoint (19:ON), you would probably want to go that route. Most likely, the included humidistat with the humidifier is just on-off, depending on the indoor RH, and would most likely only work while the furnace is running (if using the HUM output on the furnace controller).
First of all thanks. Let me address the pertinent points. HVAC is in basement, attic access is via a hatch, which I open and then use my own ladder. Thanks to you, I will shortly put an attic tent in addition to sealing of the attic from inside via removable duct tape good quality. The doors excellent and 1 door replaced. Basement I have verified and found to be in very good condition. The only 2 places I see are my windows and my exterior wall. The problem is these windows are double-pane up-down sliding and I feel few of them air leak in-between where the panes meet horizontally in the middle. I am trying to find a solution to fix this. The exterior walls, outside is real stucco and inside is plaster with a thin insulation in-between. Currently, blow-in insulation is my only option but it's prohibitive. What my neighbors tell me plaster's heat retention coupled with stucco is considerable and thus it's quite good enough.
I am scheduling an energy audit shortly but in the meantime, here's what my core question is. Assume stat determines the need for humidification. I believe it'll send power to my humidifier if it's connected to the stat's H terminal (24 VAC) and the humidifier itself is connected to 110V. This will start the humidifier but will the stat also kick start my furnace to make sure the humidifier is successful? What if my inside temp matches the set-point, in which case should it not start off my blower at least?
Sorry, didn't understand. So, I should say to my installer who's installing the humidifier to ensure connection from the humidifier's solenoid to be connected to my Braeburn's H terminal and subsequently I should go into the installer options to have the option 18 set to IND and option 19 set to ON ? BTW: I am planning to install a fan-powered humidifier. If this type of humidifier is not an option and the only way is to install for this functionality a steam powered one, please let me know. I was of the opinion that if I set option 18 to IND and have a fan powered humidifier installed and if there's NO call for a heating but just humidity, stat will at least trigger humidifier and start my furnace blower....
Originally Posted by CraziFuzzy
1 last thing. Just now had a talk with the installer. He gave me 2 options provided I know beforehand how the stat will behave. He doesn't have much exp. with Braeburn.
Anyways, option 1 is having the fan-powered 110V humidifier connected to a standard supply plug, but power to the plug is via a SPDT relay where the "H" terminals from stat is connected and the relay to the plug point. This way, as and when there's a humidity call, from "H" terminal stat will trigger the relay which activates power and humidifier turns on. The control of the solenoid of the humidifier is short via a wire nut.
Option 2: Is to connect the humidifier to it's dedicated power supply but the solenoid wires (Yellow) connected to the stat via a relay which has a 24 Vac coil and a single set of normally open contacts. What on Earth is this? Is this the same as the SPDT relay above? Just need to know and which will be the better option.
There are two styles of humidification, and as Braeburn calls them, they are INDependent, or DEPendent. Independent have their own source of heat to evaporate the water (like a steam fed humidifier). Dependent use the heat from your furnace (like a bypass humidifier). IND will only turn the H output on if humidity is low AND at least one stage of heating is on. DEP will turn on the H output and the fan output whenever humidity is low.
Originally Posted by wisepole
I'm not really getting the difference he's talking about. Do you know what humidifier he's installing? Not sure on the power repuirements without that information. Ultimately, you want the humidifier to be able to run when the 5400 tells it to. If the stat is controlled by seitching the 115V, then a relay is going to HAVE to be involved (the H output of the stat will be 24VAC).
Originally Posted by wisepole
DEP will turn on the H output and the fan output whenever humidity is low.
>> This is great, that means since I'm installing a fan-powered Honeywell humidifier, if the current indoor temp is at set point but stat determines there's a call for humidity it'll instruct the humidifier to start up and the furnace blower to run, without the explicit need for furnace heat to start up. Correct?
'Bout you other point, since it's a fan-powered humidifier after intense discussion with him what I understood is there's an option of either installing the relay at the 110V power side or at the solenoid side. In other words, humidifier is switched on via the 110V power outlet being activated consequent to the relay being triggered via the "H" terminal of the stat OR, the humidifier is constantly powered to 110V but the actual start of the same is when the solenoid triggers it, which is via the relay connected to the stat. Note: In 1st. case, i.e. relay at 110V side, the solenoid terminals are jumper connected.
I am good at electricity and understand wiring as such my thoughts are having the relay at the solenoid side makes more sense since that's how the humidifier is supposed to start up not by switching on/off the power supply to it.
Any advice - appreciated. Also, I just received feedback back from Braeburn tech support. I can only say good stuff about this company, they are VERY responsive. Don't really know why the company is not that widely used. Their products are cheap, 5-year warranty and for the price point yet to see a better featured consumer stat...
If the humidifier is designed to have 115V always supplied to it, and a 24VAC control signal to turn it on, and your thermostat provides said 24VAC signal, then I don't see a reason to NOT hook it up that way.
I think I will go for a better installer, it's just that this guy I believe should have understood these things...
BTW: This is for my personal knowledge, would you recommend any humidifier brand for example which wont cost me an arm and a leg and secondly should I be using hot or cold water?