Low Speed AC Fan Dehumidification - Honeywell Prestige 2.0 Thermostat and Evergreen IM ECM Variable Speed Fan Motor

Now that summer is just about here - I've been working on fine tuning my summer dehumidification as part of my indoor air quality project. One of the issues that I'm working on resolving has been a faint musty odour in the house particularly in the summertime. Last summer I was dealing with 60% relative humidity (RH) levels in the house - even with the air conditioning running, and a small 18 litre/day humidifier running in the basement.

Honeywell Prestige 2.0 IAQ Thermostat - With low speed fan AC dehumidification - and the RH right at the setpoint - 45%

I'm running a 4 ton thermopump with a large Lennox fan coil unit in the basement. The system heats well in the winter, cools well in the summer, but the single speed 3/4 hp blower was consuming a fair bit of energy running 24/7 so that I could keep the heat recovery ventilator (HRV) to try to deal with the musty odour. I've done a couple significant upgrades to the system since last summer; i) upgrading the 3/4 hp split capacitor single speed blower motor to an electronically commutated (ECM) permanent magnet varable speed Evergreern IM blower motor - which is much more efficient at full speed, and magnitudes more efficient when running in low speed circulation mode; and ii) installing a Honeywell Prestige 2.0 IAQ Thermostat and Equipment Interface Module (EIM) to manage all aspects of HVAC control - especially to control humidification and dehumidification in conjunction with the heating and cooling system.

The Honeywell Prestige 2.0 IAQ thermostat has a control option for dehumidification using the low speed fan option of an air handler / air conditioner with a multiple or variable speed motor. There are three user defined outputs on the EIM that can be set up and customized using the configuration tools on the Prestige 2.0 IAQ thermostat. One of these outputs controls my HRV. A second output controls my new Honeywell Truease Bypass Humidifier and Damper, and the third output was unused. Since my humidity levels were running a bit better than last summer, but still higher than I wanted (52 to 55% RH) I decided to try configuring the third output to slow the blower speed down when air conditioning - Low Speed AC Fan Dehumidification - as a way of getting the humidity level indoors between 45 and 50% RH. The theory behind low speed AC fan dehumidification is pretty simple - by slowing the airspeed across the evaporator coil - this allows the evaporator coil to run a little bit colder, increasing the temperature differential of the return air and the evaporator coil, and improving the quantity of condensate on the evaporator coil.

So - the Evergreen IM motor uses speed "taps" that sense control voltage (24VAC) for the various HVAC functions - such as 1st, 2nd, 3rd stage heating / cooling, emergency heating, etc. and allows you to configure the motor to run different speed ranges for different heating and cooling functions to optimize the performance of your fan coil / thermopump combination. My configuration is described at the followling link - but simply, I had thermopump heating or cooling running at high blower speed, electric backup heat running at medium high speed, and HRV / circulation running at low blower speed. The control connection is simple - the Evergreen IM high speed "tap" which is the yellow control wire is connected to the first stage thermopump compressor control wire ("Y") from the thermostat (or EIM with the Prestige 2.0 IAQ). Since the Evergreen IM speed always defaults to low speed whenever it doesn't receive a higher speed control signal from any of its speed taps - all that is required to switch the fan to low speed when the thermopump compressor is running is to interrupt the speed tap on the Evergreen IM motor connected to the "Y" control wire. I thought I would have to install a small control relay to interrupt the speed tap, but the Honeywell EIM user outputs for low speed fan dehumidification is software configurable as a normally open or a normally closed relay. So - run the speed trap through the EIM user input - configure the relay as normally closed - and when the thermostat calls for dehumidification - it will interrupt the speed tap on the first stage compressor and force the fan to low speed operation. Since I already had a pair of unused wires running between my fan coil control box and the EIM - I didn't have to run any new wire, just make the user output connections at the EIM, and wire the pair in between the Evergreen IM speed tap, and the "Y" connections on my furnace. Simple.

One of the nice features of the Honeywell Prestige is the Equipment Interface Module (EIM) - Instead of all connections being made at the Thermostat in the living area of the home - all the connections are made at the EIM installed at the furnace or air handling equipment - and the Thermostat only requires power - control is all wireless between the thermostat and the EIM. 

Conclusion

So - how does it work? In a word - excellent. It took about a day for the average RH to drop from the 55% range to 49 / 50%, and then after the second day it's been running at my setpoint - 45% - during the day (when there is enough solar energy hitting the house that the air conditioning is running during the day). At night, the RH will drift up towards 49% because the outdoor temperatures are just a bit higher than the indoor temperatures, but this will improve as the summer gets hotter in the evenings. I shouldn't have any trouble now keeping my indoor humidity level below 50%, and I didn't have to resort to purchasing a larger dehumidifier, or a whole house dehumidifier.

I have to say that I still really appreciate the Evergreen IM variable speed blower motor - the HVAC system in the house runs silently most of the time now, and I still really like the Honeywell Prestige 2.0 IAQ thermostat - I like the display and integrated humidity control, I like that it controls my HRV and I don't need a separate, uncoordinated HRV control on the wall, and I like the continuous outdoor temperature and humidity display, along with the indoor temperature and humidity display. I also appreciate the ability to monitor and change the thermostat settings from anywhere - inside or away from the home,  using my smartphone and the Honeywell Total Connect Comfort app. (I still intent to write a post about this app.)

Now that the house has been below 50% RH for a few days since making this upgrade - I've noticed a reduction in the musty odour. It's not completely gone yet - we'll see how this evolves, but I'm thinking of adding a UV lamp to the ductwork to further improve the indoor air quality.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. 

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House Freeze Alarm / Furnace Failure Alarm / Pipe Freeze Alert

This is another feature that can be added to an Insteon / Universal Devices ISY994i system - a freeze alert to warn of a furnace failure, to prevent pipes freezing or other damage in cold weather. I negotiated an insurance rebate with this capability added to my system, so it's worth considering and looking into.

I had some unused inputs on an EZIO2x4 Input Output module, and was looking for a simple way to add a freeze alarm. I also had an unused Honeywell CT3500 digital thermostat, with single stage heating and cooling functions. This was very quick and simple to set up, starting with the installation of the thermostat next to my automation panel in my mechanical room in the basement. The Honeywell CT3500 runs off battery power - and the internal relays are switched on battery power as well - so you don't need to provide the thermostat with 24VAC to provide the dry contact capability.

Install the digital thermostat at a convenient location. Note the wiring connections - R and W connections give you a dry contact output for the heating activation of the Thermostat.

With the thermostat installed, and a dry contact wire pair connected to the R and W (Heat) terminals - it was time to install the thermostat face, and program the thermostat. I programmed the thermostat so that it would always return to the programmed temperature setting if anyone (kids) play with the setpoint keys on the face of the thermostat. The CT3500 can be set as low as 4.5 degrees C - but in my case I decided to give myself a bit more warning and programmed the heat setting on the thermostat to 7 degrees C. 

CT3500 thermostat programmed to provide heat at 7 degreex C - Label added to face of thermostat indicating function of the thermostat and a reminder to replace the batteries once a year. 

On the automation side, you have to have an input contact interface to your Insteon network. You could use a Smarthome IOLink, an EZIO module from Smartenit with input capability - the EZIO2x4, the EZIO6I, or the EZIO8SA. In my case, I had free inputs on an EZIO2x4 2 Relay 4 Input Insteon module.

The EZIO2x4 has four inputs per device - 2 inputs are dry contacts, and 2 inputs are digital / analog inputs that need to be configured for your application. Since my dry contact inputs were already being used for smoke detector and alarm interfaces - I had to use one of the digital inputs for this function.

The instructions for the EZIO2x4 advise you to use a pull up resister in order to convert a digital input to a dry contact input. Some research on the Smartenit forums provided some additional detail - you should use a 6000 to 10000 ohm resistor - connected between the 5V and the I3 or I4 terminals - in order to avoid drawing too much current from the 5V terminal. Then - your dry contact connects between the common terminal and the I3 or I4 terminal. Here's what the connection looks like with the pull up resistor:

Using a pullup resistor to protect the 5V terminal on the EZIO2x4 from overcurrent, when using inputs 3 or 4 as dry contact inputs.

On other thing I learned on the forums - that if you are not using the digital inputs on these EZIO modules - you should ground the input to keep them from floating, and initiating unneeded Insteon traffic on your network. If you look at the photo above, that's what the green wire is used for - shorting the I4 input to the common terminal. 

Once the thermostat has been programmed, it's time to program your ISY-994i. I set up a new notification message - House Freeze Alert - and created a new program to check the status of the I3 input on this EZIO2x4. Whenever the input changes to "On" that indicates that the thermostat has called for heat - indicating a temperature inside the house of less than 7 degrees Celcius. In that case - I have the ISY-994i send me an email to my email address, and a text message to my phone with the Freeze alert message. 

You could also tie this functionality to a monitored home alarm system - simply by using one of the output contacts on the EZIO2x4 to trigger a zone on your home alarm. Your alarm company could configure this zone to warn of the house freezing - and initiate a call out.

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Lennox Elite Series Thermostat Settings Optimization for Air Source Heat Pump Energy Efficiency

My new house came equipped with a Lennox X4147 Elite Series thermostat - a fairly high end touchscreen unit that can control up to three stages of heating and two stages of cooling. Last weekend I upgraded the Fan Coil unit's blower motor to an Evergreen IM electronically commutated motor to help increase the efficiency of the system. While testing the system, I was noticing how quickly the thermostat would call for emergency / auxiliary heat. If I increased the setpoint by 1/2 degree Celcius, the thermostat would shut off the heat pump demand, and call for emergency 2nd stage heating - in my case electric strip heating in the fan coil unit. This heat will cost 2 or 3 times as much as heat from the heat pump will cost (equivalent to the Coefficient of Performace of the heat pump performance at a particular exterior temperature, interior temperature, and airflow across the indoor evaporator coil). So - I started looking into the thermostat settings to see how I could avoid the emergency / auxiliary heating from kicking in so soon.

A little research lead me to the balance point settings on thermostats for heat pump systems. In order to be able to set the balance point - the thermostat needs to know the exterior temperature - to be able to know when to lock out the emergency heating, and when to lock out the thermopump. Setting these lockout temperatures can allow the thermostat to control when the emergency heating is engaged - so you're only using pure electric (or gas / oil) heat when the temperature is too low outside for the heat pump to make up the entire heating demand. This will improve the overall system efficiency - especially in the start and end of the heating season, when the exterior temperatures are still warm enough for the heat pump to deliver sufficient heating to the house.

There are a few ways that a thermostat can detect the external temperature. In the case of the Lennox X4147 - you need to install an external temperature sensor - the X4148 pictured below:

The Lennox X4148 Temperature Sensor and Bracket

The other method is to use an internet enabled thermostat, that can get the external temperature from an internet data source. The Nest thermostat is an example of a thermostat that doesn't require an external temperature sensor.

Since I already had a decent thermostat, I picked up the temperature sensor on Ebay for a reasonable price, and did the installation this morning. The instructions recommend that you use a separate, shielded cable for the temperature sensor installation, in order to minimize interference with other cables. It took me about an hour to route a signal cable out to a foundation wall through the basement.

Pulling a second, separate cable for the temperature sensor.

The temperture sensor pulled outside. I'll have to spend some time pulling this to a better location, out of direct sunlight and where the sensor could be buried with snow in the winter time. 

The final steps were to connect the cables, and program the thermostat to recognize the external temperature sensor.

The temperature sensor connects to the S1 and S2 terminals.

 Once the sensor is installed, wired, you can reinstall the thermostat face, and power up the system. Prior to engaging the heat pump or heating system, you'll need to program the thermostat to recognize the temperature sensor. You'll need to get into the setpoint programming interface - you can download the installer manual from the Internet for the full instructions.

Change installer setup number 340 to "2" in order to recognize the external temperature sensor and use it to control heat pump lockout settings. 

You can then  adjust your lockout settings for electric heat and the thermopump. Some caution is warranted here - you should check the specifications for your heat pump, and find a reasonable balance point based on the heat pump performance curve, and how well insulated / sealed your home is. You'll have to note the performance of the system in order to verify you have the correct balance point set. If you note when in ambient temperatures around the balance point you've selected your heat pump is not making enough heat for the interior temperature to meet the thermostat setpoing, you may need to adjust the balance point higher. You can research "Setting Heat Pump Balance Point" on the internet to find some further information on the thermodynamics on this. The Nest thermostat webside has a very good description on the relationship between balance point, and energy consumption.

I'm looking forward to reporting how this upgrade works with respect to energy consumption and performance. I'll provide updates over the coming weeks. 

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions.

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Building a New House or Doing a Renovation, with Home Automation in Mind?

Here is what I would set out as a specification for your electrician:

1. Put in the deepest wall switch boxes that are readily available for your wall thickness. Some of the modern Insteon devices are getting quite large now that they contain wireless mesh net antennae ("Dual-band") circuitry, and the Insteon Switchlinc On/Off Relay switch - which you would use for all wall switches that don't require dimming circuitry, are now rated to switch 17 Amps / 1 HP / 1800W. The downside to this high current capacity is that it's supplied with 12 gauge leads - large, require larger maretes to make connections, and less flexible. So it becomes a chore to install these and try to stuff the wires and connections behind it. So - deep switch boxes will make this easier.

2. Always feed the switch box first - and everywhere there is a wall switch control. In my current house - this rule is 75% respected - except for most of the closets, where the circuit is fed from the ceiling light octagonal box, and a two wire 14 gauge cable (14/2) is sent down to the switch box. So - if you want to install an automated switch - you're in trouble because there is no neutral wire in the switch box. There are ways around this - Insteon sells a dimmer switch that doesn't require a neutral wire, but not a relay switch which is required for flourescent fixtures and some LED fixtures.

3. Make sure there are a good number of blank or spare breaker spaces. This makes it easy to add a double breaker to install a phase coupling powerline communications module (for better powerline signalling - e.g. Insteon), and a spare outlet for the installation of your powerline modem (PLM) right next to the panel for the best possible comminications with your Insteon devices located across your house.

4. Have your garage door opener wires - from the door sensors and wall mount controls to the opener location - run in the wall behind the drywall. This will ensure a nice neat setup without any surface mount wires. Have your electrician install an outlet in the ceiling of your garage, close to the opener. If you want to have the lockout limit switch to avoid garage door activation when the door is bolted, you can run those wires behind the drywall also.

5. Wiring for 120V wired smoke detectors - if the code in your area only calls for one smoke detector on each floor of the residence, consider upgrading the wiring to include one smoke detector per floor, plus one smoke detector in each sleeping room. The wired smoke detectors can then be interfaced to your home alarm system and your home automation system using interconnection relays like the Kidde SM120X.

6. Cabling - You can run structured cableways throughout your house for future expansion requirements, which is certainly a good idea, but for some reason the structured cable tubing is really overpriced. For short runs within walls - I've used ordinary shop vac or sump pump tubing - which is about 10 times less expensive, but it is not plenum rated for fire safty - it should not be run within ventilation ducts or in open ventilation spaces above modular ceilings. Here's a short list of cables you may wish to consider running in your walls before closing up drywall:

• Smoke detectors - 110V with signal wire - every level of the house plus one in every sleeping room;
• Network Cat 6 cable;
• Video RG6 cable for classic cable / digital cable / PVRs;
• Video surveillance. Sure, you can get wireless IP cameras, but you still have to get power to them. Power over ethernet is one option - run Cat 6 cable to camera locations, or plan for regular analog output cameras (which are much cheaper) and run a combination video signal / power cable. Front door, back door, garage, a few eaves of your house to watch your driveway, yard, etc. 
• Alarm system - see below - panels, keypads, motion detectors, sirens;
• Automation of roller blinds and shades - run cables to window corners for future upgrades;
• Telephone (Cat 4, 5 or 6) - plan where your cordless phone base station will be - run a Cat 5 cable to that location, and also plan for a UPS protected outlet at that location so when the power goes out, your cordless phones still work;

7. Alignment of boxes - you can check out my post on Wall Acne - but I would certainly try to plan for and enforce coordination between the various contractors that are installing anything on the walls, such as:

• Alarm contractor - panels, keypads, motion detectors, sirens, etc;
• Electrician - lighting, outlets and switches;
• Network - Cat 5/6 internet cabling, telephone cabling, coax cable, etc. 
• HVAC - thermostats and controls for ventilation - humidity control, etc. Note that the thermostat has to be placed in a central location in the home, that you`ll need thermostat cabling to the furnace / mechanical room, and also keep in mind that modern intelligent recovery thermostats for heat pump systems require a separate cable running from the thermostat to an appropriate exterior location under a roof eave for outdoor temperature measurement.
• Other items such as smoke detectors and CO (carbon monoxide) detectors. 

You'll end up with fewer wallplates and wall acne issues if you can use separator plates to double up electrical and low voltage in the same wall box. I've done this to combine telephone / internet cabling with electrical outlets, and wall switches with low voltage ventilation controls. You just need a wall box with a metal separation plate - your electrician will be able to help out with this. The trick, however, is that you'll need to direct your electrician to install the double boxes with separation plates before your network cable and HVAC installation takes place, so it requires some planning. 

Note the metal separation plate running down the center of this box, separating low voltage on the right, from line voltage (110V AC) on the left.

In a retrofit situation, you can add a surface mount media frame next to a standard simple outlet. It takes some adjustment to get the hole centers aligned to fit a double wallplate correctly, but it ends up being neater than having two boxes in close proximity on the wall.

Another example - telephone and internet next to outlet using surface mount media frame

Combination Electrical Box / Low Voltage Media Frame - These are tough to install in a renovation - easier to install in new construction

Venmar air exchanger control on the right, Insteon Light Switch on the Left.

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Dealing with Wall Acne

This has been one of my pet peeves during the renovation of our last two homes - wall acne. I don't know how widespread this term is, but I use that to describe when you have a bundle of different switches, thermostats, and controls placed haphazardly in the same zone of the house, with no regard for esthetics. A few examples follow.:

Thermostat, 24V Legacy Automation Lighting Control with 8 Switches, Closet Switch. The light switches are aligned horizontally, the thermostat doesn't line up with anything.

The problem with wall acne is that it takes time, skill and patience to correct it. In the thermostat example above, I set out to correct the misalignment. There are other posts in this blog which discuss my legacy automation controller and the 24V switches - these have been all changed out for Insteon Switchlinc switches, keypads and dimmers. In this case - I doubled up the wall switch box for the closet light switch to accommodate the Insteon Switchlinc Keypad. The thermostat was moved in line vertically above the light switch and Insteon Keypad, and the new air exchanger control was added above the thermostat.

Doubling up the closet light switch to accommodate the Insteon Keypad.

Thermostat moved to vertical alignment

The completed alignment, Insteon Keypad installed with closet light switch, thermostat and air exchanger controls aligned vertically. 

Garage Door Controls - Door opener and Legacy 24V Lighting Control. Why doesn't the garage door opener line up either horizontally or vertically?

On to the garage switches. Besides the alignment, I was bothered by the surface run garage door opener wire, and the lack of a thermostat for my two 4000W wall heaters. Running the thermostat wire down through the wall, and incorporating the garage door opener control wires in the wall necessitated a few drywal cutouts to help with fishing the wire past a structural beam.

Aligning the controls with the light switch, and running the wires behind the drywall.

Finished product - Insteon Switchlinc Switch, Thermostat, and Garage Door Opener control all aligned vertically, with wires hidden. 

Maybe I'm a bit fussy about this, but I really don't think so. If some forethought is given to the various trades involved in house construction, and control wires are run behind the drywall during construction (such as the garage door control wires), then this should never be an issue in new construction. But I think the time spent solving the issue is well spent.

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