I suspect that my problem with high humidity levels in the summertime have been caused by two separate issues i) a blocked condensate pan drain, which keeps condensate water removed from the indoor air from the air conditioning evaporator recirculating in the indoor air stream, and ii) my Venmar ERV furnace fan interlock - which keeps the furnace fan running even when the air conditioner cycles end, not allowing the evaporator coil condensation enough time to drip down into the condensate pan and into the floor drain. Consequently, this condensate water just gets re-evaporated into the fan coil airstream, and back into the indoor air. Net result - buildup of humidity inside the house. I needed a way to independently control the ventilation ERV, the furnace fan, and timed with the air conditioning cycles, and the only thermostat that I found that would do that, and also independantly control humidifying, is the Honeywell Prestige 2.0 IAQ thermostat.
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| Honeywell Prestige 2.0 IAQ Kit with EIM, Outdoor Wireless Temperature and Humidity Sensor, and Duct Temperature Sensors |
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| Honeywell Redlink Internet Gateway |
I also require central control of the humidifier in the winter time. This lead me to look at the latest generation of smart thermostats - in an attempt to get better control over the HVAC in my home, and address my air quality issues. I found that the Nest thermostat doesn't have the capability to intelligently control ventilation, it only has a single output to control humidification, but has the ability to control the air conditioning to control de-humidification. Similar situation with the Ecobee 3 thermostat. Finally, I found the Honeywell Prestige 2.0 IAQ thermostat - with the equipment interface module, it has three customizable user outputs that can control ventilation (ERV/HRV), humidification, whole house dehumidification, and a fresh air intake damper. So - following my research, I ordered Honeywell Prestige IAQ thermostat kit with return and supply duct temperature guages, outdoor wireless temperture and humidity sensor, and the equipment interface module. In addition, I picked up the Redlink internet gateway, which allows me to control the whole system from my smartphone or tablet, even when away from home.
Installing the system may seem a bit complicated, but in practice, it's not much harder than installing a standard thermostat. The Prestige 2.0 thermostat that installed in your living space on the wall - is actually just a wireless controller for the system - like a small tablet computer. There are no relays inside this thermostat, just a small backup battery to retain settings during power failures, and two contacts for 24VAC power. The Equipment Interface Module, which installs close to your furnace / HVAC sysem, has all the relays and switching, connects to all the HVAC equipment using standard 24VAC hard wired controls, and connects wirelessly to the wall mounted thermostat in your living space. The nice thing about this architecture is that it is very easy to wire up additional elements to the Prestige thermostat system - temperature sensors, furnace / fan coil unit, ventilation system (HRV or ERV), whole house humidifier, whole house dehumidifier, an optional duct zone control system, etc) and the multitude of wired connections are all made close to the equipment, and don't all have to be run through your walls to your wall mounted thermostat. Very easy to wire up, very easy to add additional system components, and very easy to integrate the operation of everything using the smart thermostat.
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| The back of the Honeywell Prestige IAQ Thermostat. Note the button type backup battery in the top right corner, and the power connection posts in the center. |
This thermostat is small - slightly smaller than a dual electrical switch wallplate. Whatever you are replacing with this was probably larger, and you'll probably have some drywall patching and painting to do to make it look right. If you don't want to get into paint - there is an accessory backplate that covers the old thermostat hole. I went for the cleanest install possible, and did my patching and painting.
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| Thermostat powered up, while still sanding and patching the old thermostat space. |
Since the thermostat communicates with the EIM wirelessly, all the thermostat needs for connections is red and black - 24VAC and Common.
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| Wallplate is nice and small, terminals are a bit fussy. |
Installing the Equipment Interface Module (EIM) is fairly straightforward. Find a suitable mounting place close to your furnace or fan coil, and mount it vertically. I found a good spot on the return ductwork just above my fan coil.
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| Cable tie holes make wire management fairly simple. |
The connections you make here are your typical HVAC control connections - up to 4 stages of heating / 2 stages of cooling for heat pump systems, or 3 stages of heating / 2 stages of cooling for conventional system. It has power connections for running to the wall mounted Prestige Thermostat, 4 wired sensor inputs, for temperature sensors or switches, 3 control outputs for user defined applications - such as whole house humidification, dehumidification, fresh air damper and / or ventilation HRV / ERV.
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| Once installed - lots of wires running to the EIM - 2 temperature sensors wires, humidifier control and humidifier damper, ventilation ERV control, power to thermostat, control to fan coil unit. |
I found this system to be really well thought out, well architected, and logical. The EIM installs close to your equipment - and is designed to interface with all the control wires required even for a complex, multi-zone system. All the wiring is close to the equipment, so control wire runs are short and simple. You're only sending power to the thermostat, and all the switching is done close to the equipment. The thermostat communicates over a wireless protocol called Redlink - designed by Honeywell for low power consumption and reliability. The system also communicates with an outdoor temperature and humidity sensor which gives lots of control flexibility for things like ventilation, heat pump balancing and lockout control, fresh air intake damper options, and controling ventilation considering the outdoor humidity levels. You'll have to get a copy of the manual and installers guide to get a real good idea of everything that this thermostat can do - it is quite impressive. I should say here that this hasn't been designed for homeowner installation - it should probably be installed by a HVAC technician, especially if you are not familiar with HVAC controls and systems.
Controlling your ventilation HRV / ERV. I had a Venmar ERV installed when we renovated and moved into our home three years ago. Since our home has central ventilation, three zones of ductwork, our Venmar was installed to draw air from three separate places on each level of the house (three bathrooms), but the fresh air distribution runs into the fan coil return ductwork, and must be circulated by the furnace. So - the Venmar was set up (properly) with a furnace fan interlock, to force the furnace fan to run when the ventilation is running. We were running the ventilation constantly, and therfore, that forced the furnace fan to run constantly. A 3/4 HP blower fan running 24/7, 365 days a year draws a lot of power. At $0.094 / kW-hr, this blower fan was consuming almost $1,100 a year of electricity. This lead me to my first major system upgrade, the
retrofit of an Evergreen IM electronically commutated motor. However, this furnace fan interlock would force the furnace blower to run - right through the end of air conditioning cycles - which has the effect of preventing condensed humidity on the evaporator coils from draining to the floor drain (and humidifying your air in the summer). So - I was getting high humidity levels in my home in the summer. You can set up the Prestige IAQ thermostat to force the blower fan off at the end of an air conditioning cycle - even if there is other demands to have the fan continue - giving time for this condensed humidity to drain away. However, for this to work, the ERV has to be controlled by the EIM / Prestige Thermostat. If you keep the furnace interlock connected directly to your green fan wire - it will still override the EIM / Prestige system. It is very simple to have the EIM control the Venmar - two wire dry contact from the EIM to the override terminal in the Venmar connection box, and now the EIM / Prestige thermostat is controlling the Venmar. I took my Venmar controller down from the wall above my old thermostat, and mounted it on the duct next to the EIM just in case I ever decide to control the Venmar independantly for any reason. I could have just left it uninstalled. I have three Venmar boost switches installed in each of my bathrooms - they will still force the Venmar to run, but I removed the furnace fan blower interlock, so when the boost switch in a bathroom calls the Venmar to run, it doesn't force the blower fan to run. It will still evacuate bathroom smell / humidity out of the house, the return air will just be pushed into the return ductwork by the Venmar fan.
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| On the Venmar AVS Duo 1.9 - shorting the OC and OL terminals forces the Venmar to run at high speed. This does not affect normal operation of any pushbutton switches you have installed on the same terminals. |
The kit comes with two temperature sensors designed to be installed in your supply and return ductwork to perform routine temperature rise logging and system performance evaluation. The system is called Delta T Alerts and Diagnostics. The installation manual provides clear instructions where to place the sensors in your ductwork in relation to any bypass ducts, humidifiers, zone splits, etc. Once installed in your ducts, they are wired to any 2 of the 4 sensor inputs - S1, S2, S3 and S4. Once added, you need to configure them in the system through the installer setup menu on the Prestige thermostat. Take note on the packaging whether they are 10kohm or 20kohm sensors - you'll need to specify this in the setup. Once installed, you can run temperature differential tests, and you can also download historical performance logs detailing the delta t of the system, with the indoor and outdoor temperature and humidity data. This is great for analyzing the performance of a heat pump, and setting lockout temperatures. You can also set alert ranges - for example, if delta T on air conditioning or heat pumping drops below a certain threshold, that could indicate loss of refrigerant or a dirty indoor or outdoor coil, and put an alert on the thermostat advising the owner to take action. Very nice feature.
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| Testing equipment to determine baseline temperature rise. With this information, you can set alerts. |
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| Testing temparature rise on emergency backup heat. |
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| Checking performance logs - note min and max delta T recorded for the specified interval. |
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| You can also download all the historical performance logs onto a USB key - for analysis in a spreadsheet on your computer. |
The completed installation, the EIM is on the top right corner mounted on the return duct:
I really like this instalation - I really appreciate the information provided on the thermostat screen. I like being able to see at a glance the indoor and outdoor temperature and humidity. The Nest thermostat has a nice industrial design, but for my needs, I appreciate the compact but useful screen display.
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| Nice density of information - and you can set the screen colour and backlighting to about a dozen different colors, or any intensity level you wish. |
The smartphone application is also quite useful, but I think I'll make that the subject of another post. Ask any questions you would like and I'll try to answer.
