I have read through many threads on this forum and online and couldn't figure out a solution to my predicament. I imagine just like myself many will be interested in this.
I have a new built home with a 2 stage furnace, AC, humidifier and HRV. I am trying to automate some/all controls of the HRV. This home does not have traditional bathroom exhaust fans. All bathrooms exhausts are connected to the HRV. Problem is that often we forget to turn this fans on and humidity builds up. I was thinking of putting some sort of humidity sensor in the bathrooms and have it connect to the HRV to turn on the HRV fan.
coming to the HRV system, from what i can tell from the wiring it is independent of the furnace and AC. its a unit from CleanComfort brand. The main switch that controls the HRV is the VHP-TC10 and the bathrooms are controlled by VHP-T3.
if it helps, i recently had an ecobee installed as well. i have several zooz multi-sensors which i can use for measuring the humidity/temperature.
I am trying to figure out how to create any automation. I have looked into Z-wave relays (Zooz Multirelay, fibaro and qubino dry contact relays) but i can't figure out the wiring. I am also on the Hubitat C5 hub.
Any thoughts on ideas what to research on and any input is very much appreciated!
Ideally you want your HRV running most of the time in coordination with humidistatic control so you're only running it when the outside humidity is lower than inside to reduce high humidity and moisture in the home. Obviously there are exceptions depending on your location, but that is the general goal.
For whatever rules you make, you should have some defined goals, and a way to measure inside and outside humidity accurately.
For example I have mine run continuously as long as all the windows and doors are shut and the humidity outside is lower than inside. On hot summer days it turns off and just uses the AC unit.
I control my ERV (which is like an HRV as far as this discussion is concerned) using Hubitat. I completely disconnected the regular ventilation controls, so Hubitat does it all rather than providing an input into the existing ventilation controls. My ERV plugs into a regular 110 outlet, so I use a switchable plug (ZWave) to turn it on and off. Initially, I accomplished all of the control with rule machine. I have since written a zoning and ventilation Hubitat App. If you would like to take that approach, I will help you get your control logic right.
There is probably a way to interact with the existing controls. I am not familiar with the model numbers you mention. If they are like the ones in my house (that I bypassed), the bathroom controls have two wires that go to the central control and signal the need to turn on ventilation by connecting the two wires to each other. If you are handy with a multi-meter, you could experiment a little and verify that. You could use a relay like Zooz to do what the bathroom control does. It won't necessarily be easy to find a logical place to put the multirelay because I suspect both the bathroom control and central control are in electrical boxes with little room to spare. If you want to pursue that approach, a good starting point would be to take the controls out of the wall and post pictures of the wiring connections.
Doesn't have to interface just look at what controls are available and find a switch or a relay to interface. The logic is pretty easy to build in Hubitat once you have the interface device setup.
I disagree with this description of how an HRV should be operated. The primary function of an HRV is to bring fresh air into the house. The amount of fresh air needed is primarily based on how many people are in the house. The HRV should be operated as much as is required to bring in the amount of fresh air that is needed.
A side effect of operating an HRV is that it impacts indoor humidity. Specifically, it moves the indoor dewpoint toward the outdoor dewpoint. I don't like to control something based on its side effects.
A complication here is that, when the HRV exhausts from a bathroom, it can be used to replace the bathroom fan. The reason there is a control in the bathroom is so it can be used when a bathroom fan should be used. High humidity in the bathroom due to taking a shower is one of those occasions when a bath fan should be used. That has nothing to do with outdoor humidity.
There are multiple ways to duct an HRV. In some houses, the HRV ductwork is completely separate from the furnace ductwork. In that case, the controls should be completely separate. In other houses (like mine), the fresh air from the HRV is dumped into the return ducts of the furnace ductwork. There is some disagreement in the industry about whether the furnace and HRV need to be interlocked in those houses. In other words, whether the furnace blower needs to be turned on when the HRV is running.
In every case there's all kinds of loopholes and gotchas. In the south here in Texas the outside humidity is normally really high so we have to account for it. Someone living in Arizona probably doesn't really care about the Humidity. The number of people is just part of the equation too, square footage, CFM, occupancy, doors and windows open. In the end it comes down to what are your goals and requirements then design rules around those.
Folks, thanks so much for your inputs. This is very much appreciated.
I should have mentioned that i am up north from Canada and the temps here fluctuate between -35 and +35.
I do like the idea of disconnecting the HRV from the fan supplied fan controls. in that case, i suppose you cant run it on low speed. its just one constant speed. Did you set your ERV to continuous run?
My ERV does not have multiple speeds. To take advantage of multiple speeds, you would need to use something like a Zooz multirelay. Figuring out how to wire that would require delving into the documentation for the HRV but is likely not that complicated once you find the installation manual.
I suspect that there are a series of terminals that are connected to low voltage wiring from the controllers. If you take a picture of that and post it, I will help you figure out how to wire a Zooz ZEN16 up to it to control it.
Many many thanks for your suggestions and offer to help.
I just want to update on what I have done so far. It will likely help others as well. So I have simply added a zwave plug to the HRV plug. I have set the HRV to continuous run. On my main wall controller I have set it to "vent". This then allows me to turn on/off and run the HRV as I see fit.
I have placed 2 zooz multi-sensors in my bathrooms (prior to this i calibrated them by leaving them close to my ecobee thermostat and ensuring that the humidity the sensors read are close to the thermostat (play around with the offsets)).
Now I have two rules in the rule engine now. One to turn on the HRV zwave plug when humidity on the zooz sensors is over 55 and a second rule to turn off the HRV when it is less than equal to 55.
This works like a charm so far (I was on vacation so I didn't get a chance to do extensive testing but I am keeping a close eye on the system starting today). The issue with the zooz multisensors is that they run out of batteries every 4 to 6 months. So i have to keep an eye on that.
Quite frankly I am amazed by the simplicity of this solution. Since I have not modified any of the original HRV wiring, my warranty with the builder still stands.
On my to do list now is to create a mechanism (perhaps using a virtual switch) where I can turn on/off the HRV independent of the humidity related rules (sort of manual override). Once this is done I think the system will be perfect.
Once again folks thanks for all your suggestions. I will be tuning the system in the next months and through out the winter. I will post any questions and lessons learnt.
With these rules, you are basically running your HRV the way a bathroom fan should be run. However, an HRV is not just an expensive bathroom fan. The reason that the HRV is there is to provide fresh air to the entire house, which is needed regardless of whether the bathrooms are humid. To accomplish this, the HRV should run a fraction of every hour.
The rule I would recommend would run once per hour. It would:
Turn the HRV on. If Hubitat has a way of knowing when you have windows open, you may want to put this statement within a conditional block.
Wait 30 minutes (or some other duration based on how much ventilation your house needs). If Hubitat has a way of knowing how many people are home, you can calculate an appropriate duration instead of using a fixed number.
If (bathroom humidity is < 55%), then turn the HRV off
You could leave the rule in place that turns the HRV on when bathroom humidity is > 55%. I would get rid of the rule that turns it off when humidity goes below 55%.
Whether 55% is a good cut-off point depends on how humid your house is otherwise. Placing the sensor near the ceiling is better for sensing moisture due to showering.
