Venmar (Vanee/Broan) ERV / HVAC controller output


I may not have explained it as clearly as I could have – I have things working much better now. I have things pretty well automated with all the features that @k-d was wanting.

The key was to have a solid feedback control so you know the HRV reached the state you are asking for. Ironically, I already had the Venmar smart controller that was described above. I finally got a chance to sit down and take a picture so you could see it for yourself. I have a ton of ESP8266s around the house, but in this case, since the addition of the Bluetooth proxies, I have amazing performance with the Switchbot, and ask you all highlighted, i still want my finger to be able to reach up and manually command the HRV.

Figure 1: My setup, (there is an extension cord that happens to hide the Power Meter that the HRV is plugged into).

The problem that I solved is the feedback system to know the state that the HRV is in. (ie., did my command achieve the desired effect. Well, I achieved that by attaching a powermeter as the power source for the HRV. So I can see the power drawn by the HRV, and can use the power level to map to commanded state.

For example,
3 W (+/- 1 W) = Off,
25 W = Min
51 W = Med
78 W = Max

So, as you can imagine, this was a classic use of a state machine, because the switchbot has to reach the desired command by cycling through the various states by pressing buttons to move in one direction through the statemachine. For a while, I thought about adding two more additional switchbots to command TURBO and AUTO, but because I already have the system designed in HA to feedback on both interior Particulate Matter and CO2, rarely does the system ever need to get to Max. As people come and go, the system brings the CO2 down, and goes from Max, to Med, and to Min, etc. (the only problem, is that going DOWN requires half a dozen button pushes, but because there is a built in dwell timer in the Venmar control, it doesn’t mistake the intermediate states as actual commands). The good news, is that when there is a sudden source of pollution, the system reacts going from Low to Med to High because it only takes one or two switch bot “clicks”. I also have this integrated into my Ecobee, so I can also push one the circulating fan to also filter the air through our very effective American Standard filter.

Also - get this, as I’ve owned this thing for nearly a year with this arrangement, I’ve been able to detect when my filters are getting plugged. I’ve only done this by visually checking how much the power in a given state has creeped up → but I can see making that more robust a future project. (I also started hand making HEPA filters because the MERV filters from Venmar are a ripoff where I live. I was able to build a bunch from one 3M filter.

Anyway, I’m really happy with this, so I’ve started to tear up my Node Red code, and use some new state machine blocks I found throughout the community.

In closing, I think within another year we can have a really robust integration of these Venmar HRVs despite the company being unsupportive.

Figure 2: One of my summary dashboards showing the Air quality control system.

The SCD30 is in the basement sauna, the Portable CO2 is a box I made to take to various locations that is on our top floor. The system controls off the Average (light blue).


Did your HRV arrive yet?

Nice! Glad that seems to be working well for you.

Have you noticed that this power stays consistent? My ERV will fluctuate sometimes regardless of what mode it’s in. My MIN mode actually draws more power than my “medium” unbalanced/slightly positive pressure mode which I thought was strange. I was considering putting some CT clamps to measure each fan individually but that seemed like overkill…

I guess as power draw increases at the same setting, you can tell your filters are plugged after a certain point?

Ha, I thought the same thing and ended up adding an inline filter box (CFB series from HvacQuick) due to this cost and removed the filter in the ERV. Fits a 14x14x4 filter for greater dust holding capacity, lower pressure drop, less filter bypass hopefully (my ERV core was getting pretty dirty), and I think I can get a MERV14 from Nordic Pure - haven’t found anything better. Insulating it was the fun part, used styrofoam and can foam but I think it came out OK!


I’m also interested in the discussion and potential reverse engineering projects here. I’ll share what (little) I know and have found, as well as my ERV/controller setup.

I have a Broan ERV, model ERV200TE. It’s part of the Broan HE series which has corresponding Venmar and VanEE models as listed below:

  • Broan: ERV200TE, ERV250TE, HRV200TE, HRV250TE
  • Venmar: X24 ERV ECM, X30 ERV ECM, X24 HRV ECM & X30 HRV ECM
  • VanEE: G2400E ECM, G3000E ECM, G2400H ECM & G3000H ECM

All of these models have a single Broan/Venmar/VanEE controller listed as their only compatible controller:

  • Broan: VT9W
  • Venmar: X-Touch Mod. no. 40455
  • VanEE: Gold-Touch Mod. no. 40355

This controller has 4 wires, Y/B/R/G. A 2015 post in a separate home automation forum identified a different 4-wire controller from the same manufacturer with B as ground, Y as +12VDC, G as control, and R as unknown. That post also stated that the unit was controlled via resistance between the G and B terminals. Unfortunately, that doesn’t seem to be the case for the VT9W model as I tested a number of resistors between the G and B terminals and none of them had any effect on the ERV. My guess (/hope) is that these 4 wires are similar to the D+/D- configuration listed previously in this thread and that methods to reverse engineer that communication could work for my unit, as well.

The VT9W controller has a “Smart” mode that relies on outdoor temperature and indoor humidity to regulate exchange speed and damper operation. This works fairly well (though I would prefer more configurable control) except for one concern: This summer, the outdoor PM levels have gotten dangerously high at times due to Canadian wildfires. Awhile ago, I confirmed with Broan technical support that cutting power to the unit would leave the dampers in whatever state they were in when the power was lost, which means that using a smart switch wouldn’t work to block PM ingress. For now, I’ve also resorted to just using a Switchbot to manually toggling the Menu button multiple times in a row in order to cycle the unit to the “Off” mode that closes the dampers. I’m similarly using a power monitoring smart plug to verify which mode the unit is in (esp32 is monitoring indoor humidity to verify unit operation, too).

I’m not thrilled with the Switchbot approach because there doesn’t seem to be any sort of confirmation available that the “press” message gets received and executed. For my scenario, since I need to press the Mode button multiple times in succession, if any of those presses gets missed, then the state of the ERV effectively becomes unknown to Home Assistant until I go down to the unit and manually correct it.

In recent years, Broan has introduced a “Overture” system of sensors and controls, some of which are listed as compatible with my ERV200TE model. However, when I looked into it more, I found that the “compatibility” is simply via the high-speed override option. Here’s the wiring schematic for the Overture system smart plug:
My unit matches the bottom diagram, but both work the same way - closing the circuit between the OC/OL or 12V/OVR terminals turns on Turbo/high speed until the circuit is broken again. I may look into achieving the same thing with a Shelly1 relay (which could also be powered by the 12V from the ventilator). This method is only an override, however, because the unit reverts to it’s previous operation when the circuit is broken, so this option is pretty limited.

All I really need is a wired, non-Switchbot method that turns the unit on to low speed and off in such a way that the dampers are closed when off. Between that missing piece, the Shelly1 override option, and the smart plug power monitoring, I think I’d be covered, but unfortunately, I haven’t found it yet.

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All I really need is a wired, non-Switchbot method that turns the unit on to low speed and off in such a way that the dampers are closed when off. Between that missing piece, the Shelly1 override option, and the smart plug power monitoring, I think I’d be covered, but unfortunately, I haven’t found it yet.

If you are OK with the options being “off” or “min” you should be able to do that via the HVAC contacts - if you close the “Vent” contact and the unit is configured appropriately it goes into min speed mode, and if you open it up it goes back into standby.

Downside is you can’t get back into “Auto” without interacting physically with the device, but maybe you can mitigate that with the Switchbot? See my post here: Venmar (Vanee/Broan) ERV / HVAC controller output - #18 by k-d

You’re right, though I think the override goes to “max” speed rather than “min”. Most of the time, I’d want the unit continuously circulating at low speed with high speed only used for specific situations.

My setup now is technically workable with the Switchbot but I’m definitely interested in something better, I just have yet to find it.

You’re right, though I think the override goes to “max” speed rather than “min”

I think this is configurable, at least it is on my unit:

Unless you are talking about OVR - which is also somewhat configurable:

Ah, this must be a difference in capabilities then. Commenting the OC/OL terminals on my unit sets it to high speed only, no other choice.

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After testing the Switchbot approach, I’ve determined that it won’t work for me and my ERV200TE unit & VT9W controller. Cycling through the various modes doesn’t necessarily change the wattage draw since some modes may not immediately activate the blowers (e.g. 20 min/hr & Smart). Plus, sending repeated commands to the Switchbot is a pretty bad experience because they don’t seem to queue and some will drop unexpectedly, leading to a very unreliable experience. So I’m back at square one - able to call a Turbo/high speed override with the OC/OL terminals, but no way to reliably manually turn the unit off or to low speed.

Hey folks, I’m new to home assistant and am just getting started with the platform and I’m getting close to putting some time into getting my Venmar AVS integrated. I’m going to use this thread to capture my thoughts and maybe give some ideas to those also fooling around

I found this document which may help.

It looked like some folks were trying to hack the serial communications. I was doing some cursory research and it looks like there is a protocol called BACnet which ASHRAE defines for building automation and control. Reading some docs on this got me think why enginner a new solution for your consumer product?

I am wondering if the device uses BACnet over RS485 serial. The BACStat II controller uses a very similar 4 wire configuration but on 24v. And it has a Net+ and Net- terminals.

Needless to say, I going to dive into this once my renovation settles down. I appreciate the work other have done researching and digging.

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Great work, thanks for sharing this! Using something that’s modbus-like but not quite modbus would align with my earlier investigation here: Venmar (Vanee/Broan) ERV / HVAC controller output - #9 by k-d

Doing a little searching for BACnet-related libraries and found

I also found this tool: Which may be worth an attempted investigation. If I get bored, I may take a look myself as well.

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I also think it’s interesting that the Advanced Wall control has a Bluetooth Low Energy chip in it but there is no mention of it in the manuals anywhere

Another fun document:

RS485 - What Are Possible RS485 Polarity Issues - Chipkin Automation Systems

Wow I didnt expect that you guys continue to work on my thread! Have you been able to test the BACnet thing ? 2 years ago I end up by use the OVR relay on the ERV with and NodeMcu to HA… but this is a bit limitate the setting.

It’s going to be a while for me - just got the drywall up and painted so hacking the serial on the HRV is pretty low on the wife-unit’s list of things to be done.

Even just using a 12v relay like a Shelly for controlling override is LIGHTYEARS ahead of the advanced wall control given what we can do in HA for AQI monitoring/triggering. I would rather have a ventilator that can only run full gas when the AQI in the house is bad or when the humidity is high or when the bathroom is occupied than have a “smart” wall control that I can’t control with automation.

I will hack this thing - it’s just going to be a while. :slight_smile:

Count me as another interested lurker. I’m considering the Broan B210E75RS unit and am planning to buy the Auto and the Bath controllers. It would definitely be nicer if I could directly control power on/off and speed more directly.

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Well kids, I got some bad news today - an engineer at Venmar got back to me after I asked bluntly if the protocol used was Modbus or BACnet. He told me it was a proprietary protocol.

Besides trying to convince him to lose his job and give me the protocol, this hack job just got WAY harder.

My rs485 snooping stuff is in the mail and we will see where it leads me, if not to glory than at least to unproductive busy work.

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FYI I have one of those push button 20/40/60 min timers on my Venmar/Vanee HRV to enable turbo mode. The timer circuit board uses a push button on the board which can be toggled using a relay. This way I can trigger turbo mode from any device using an isolated relay and not worry about fragging an expensive control board on my HRV.

It wasn’t clear to me that anyone has confirmed that this is indeed using RS-485. I just received a VTSPEEDW control to go with my new B160E75RT. After removing the controller PCB screws and examining the other side of the board I can confirm that we are dealing with RS-485. There is a chip labelled HVD72 which is a SN65HVD72 RS-485 transceiver.

The processor is a STM32F030C8T6.

That side of the board also reveals labels for RX/TX/GND which is likely 3.3V level RS-232. Perhaps this is a “console” port that might provide some useful output.

It will be awhile before I can attempt to analyze the protocol.


Anyone make any additional progress with this? Looks like these AI series ERVs integrate with their new overture platform which has smart home integrations. Wonder if getting one of these is the ticket to getting it connected up.