Humidification and dehumidification controller for ISY?

[Plau]

My controller for humidification and dehumidification VICONIC (VH7200 Humidity Controller) is dead. Do you have any suggestions with which device compatible with ISY that he could be replaced?

[IndyMike]

Hello Plau,

 

I would be extremely cautious in trying to automate this setup. Your VH7200 is a rather capable device with built in protection to prevent damage to your equipment. This isn't easily replaced with standard automation devices. Without understanding your exact equipment type (heat pump, forced air/mechanical cooling, hydronic, etc,) it's impossible to recommend any replacement. Even if this were known, I would be hesitant to interface automation modules directly to your equipment. Without a lot of thought. they simply won't offer the protection that the VH7200 does.

 

A natural thought would be to replace your existing thermostat with one that included humidity control. There are communicating thermostats available that might be able to safely control your equipment. The fact that you have the VH7200 as a separate device indicates that the functionality is not built into your thermostat and you may not have the wires run to support a humidity control thermostat.

 

I have a lot of automation in my home. The furnace/AC/humidity is something that I leave to dedicated controllers that have the capability of properly controlling/protecting my expensive equipment.

[johnnyt]

I have a forced air furnace with a flow through bypass humidifier, AC, and a thermostat I can control with HomeSeer right now but plan to move it to ISY. I've successfully (after some tweaking for sure) automated humidification, dehumidification and general venting. I made sure where fail safe was needed that if the relay(s) involved were off due to failure or a blown fuse or whatever, no damage was done. I have one situation where I decided to override the furnace high speed trigger and I use the Normally Closed outputs on an IO Linc instead of Normally Open such that fan high speed is ON when the IO Linc relay is OFF. That fail safe is important during AC season.

 

I use the thermostat to lower my cool set point down when the humidity is high in summer but the temperature would not otherwise call for cooling (I don't have a dehumidify feature on my furnace/stat combo.)

 

You have to be careful using IO Lincs in scenes where it is reversed from the other ones but that's manageable (and will be using scenes when a bug is fixed in next release viewtopic.php?f=27&t=10499)

 

here's a thread on my HVAC related set up viewtopic.php?f=48&t=10174

 

and here's a post on humidifiying in particular viewtopic.php?f=27&t=10621&p=80841#p80841

[Plau]

I could use my thermostats Honeywell (prestige THX93..) that handles this case, but there is a limitation (not on the VH7200) , is the ability to drop below 40% humidity for the dehumidifier, I know that this can be dangerous, but here in Canada when the temperature drops below -30ºC sometimes I have to go down 35% humidity a couple of day (-22ºF I think) to prevent the water in the bottom of my Windows. Also i see on the viconic web site a zigbee versions but I'm not impressed with the reliability, almost 2 years and dead.

[johnnyt]

I don't know that dropping below 40% is dangerous. In fact at 0 F / -17.7 C the recommended humidity is 25% according to the guide that is on the humidistat that came with my furnace. It's not great for things like pianos, guitars, and sinuses (which is why you want a humidifier in the first place) but that's the proper humidity level to keep the air that's leaking out various holes in the winter from turning to water in the walls and, eventually, mold. I also think that if you didn't have a humidifier - or didn't run it as is probably the case in many households - you probably end up with humidity levels in the 15% range in many older poorly sealed houses from the drying effect of both the furnace and the cold air leaking in which tends to end up being very dry when it warms up to room temperature.

[IndyMike]

Plau,

 

Your Honeywell Prestige thermostat appears to have all the necessary controls for both dehumidification and humidification (internal humidity/external temp and humidity/ frost control). It seems like it could replace your VH7200 if you have the necessary wires run.

 

What type of dehumidification equipment are you using?

 

Note that if you are using the setback feature on your thermostat you will have problems @-22 outside. As your indoor air temp is decreasing the RH will be increasing. If you are using the setback at night, the indoor temp/RH is increasing at the same time that your window temps are decreasing. It's very difficult for any system to keep up with these changes. You need to compensate by keeping the RH low during your warm periods so it doesn't hit dew point (at your windows) during setback.

 

For your area, I'm not sure that is a economical tradeoff. Gar furnaces are far more efficient than mechanical dehumidifiers. It might pay to leave the temperature higher and run the dehumidifier less.

[johnnyt]

Good point, IndyMike, about the different humidity level at lower "set back" temp. I'll give my automation some thought around that. I don't use set back at night but do use it (a little) during the day.

 

Plau, if your house is older and leaky, when it's below about freezing (+/- depending on how much it leaks) dehumidification happens all the time when your humidifier is not running.

 

In Ontario and maybe Quebec and other places in Canada (and northern US?) if your house is newer (early 90's +) it was built air tight with either a Heat Recovery Ventilator (HRV) until about the mid 90's or a relatively big (150-200 CFM) bathroom fan with a "Vent" switch near the thermostat after the mid 90's.

 

If you have a newer air tight home you're supposed to run the fan or HRV to bring fresh air in so there's natural dehumidification happening with the need to bring in fresh air - and arguably no additional cost attributable to dehumidification unless you're overdoing it. I frankly don't know how much you need but I go for about 8 hours / day in spring, fall (when there's minimum "stack effect" venting your house naturally) and somewhat less in summer and winter. My HRV has dry contacts that I use to turn on to low or high IO Lincs.

 

I don't know the Viconic products or the Honeywell Prestige - do they control HRV's and bathroom fans?

[IndyMike]

In Ontario and maybe Quebec and other places in Canada (and northern US?) if your house is newer (early 90's +) it was built air tight with either a Heat Recovery Ventilator (HRV) until about the mid 90's or a relatively big (150-200 CFM) bathroom fan with a "Vent" switch near the thermostat after the mid 90's.

 

If you have a newer air tight home you're supposed to run the fan or HRV to bring fresh air in so there's natural dehumidification happening with the need to bring in fresh air - and arguably no additional cost attributable to dehumidification unless you're overdoing it. I frankly don't know how much you need but I go for about 8 hours / day in spring, fall (when there's minimum "stack effect" venting your house naturally) and somewhat less in summer and winter. My HRV has dry contacts that I use to turn on to low or high IO Lincs.

 

I don't know the Viconic products or the Honeywell Prestige - do they control HRV's and bathroom fans?

 

Hello johnnyt,

 

I was confused by your statement that HRV systems were "early 90's" while the large bath fans + makeup air were "mid 90's". I had thought that the HRV systems were the "latest and greatest" for providing ventilation (with the side benefit of winter humidity control) without increasing heating costs.

 

I currently use my bath fans + makeup air valves to "attempt" to control humidity in the winter (second floor runs 50% unless controlled). I was considering a HRV in an attempt to lower the heat load in winter. I'm having a very difficult time calculating the cost/benefit trade for the HRV (can't calculate the heating cost of running with makeup air). Is there something better? I've seen some reports of European fans that passively heat the incoming air, but they are expensive and have no numbers for humidity control.

 

IM

[johnnyt]

Hi IM,

 

My comment about the 90's for HRVs and mid 90's for bathroom fan was related to the building code. The builders lobbied hard when HRV's were added to the code in the early 90's and won, hence the change to the much cheaper bathroom fan idea. Maybe one can get an HRV in a current build but it's not minimum so probably costs extra. I do think they are the "latest and greatest" and would put one in if I had a house built today, but I confess to not knowing anything about makeup air valves and fans that passively heat the air.

 

I don't have much concrete data to help with your cost/benefit analysis of an HRV. I personally think they're worth it but I'm not totally motivated by the bottom line. It is kind of expensive where I am to have one installed (about $1200 for a "value" model - which is all you need IMO - and $2K+ for a higher end unit with fancy controls, 5 speeds, etc.) so not sure that the pay back period is particularly short. Maybe if you have an electric furnace but right now natural gas prices are really low...

 

I ended up replacing the original builder installed one myself a few years after we moved in. More on the reason why in a second but it cost about $900 2 years ago for all the pieces (plus my labor). I did get a slightly better unit (though not a high end one) and did a much better install job than an contractor would have, including putting in a high end backdraft damper http://www.tamtech.com/store/backdraft- ... tegory.asp.

 

I will mention that finding one with dry contact capability for HA control was a little hard. Not many vendors/models. I also had to find a reseller that didn't mind selling to a regular guy - I'm not an HVAC contractor and the whole industry seems to be kind of a racket up here. I've actually had to buy a lot of my HVAC stuff, like duct dampers, etc. from the US. Fortunately not the HRV though. I went with this line http://www.lifebreath.com/compare.php?id[]=26&id[]=27 (RNC10 in my case) from http://www.enmarsystems.com that I've had good after sales service from. I saved about $150 by not buying the control unit and a dehumidistat. (I might have to do something there when I sell the house if I don't leave the ISY behind.)

 

The main reason I replaced the builder one was because it had a heating element in the intake port, instead of a damper recirculation mechanism. I don't think they do that anymore but did in 1992 when my house was built. So in winter, a 1200W electric heating element was running probably most of the time that the HRV was running (I used an appliance linc to only run it a few hours a day). In my opinion, the heating element kills the business case entirely. Without having done the math, I think I would have been better off opening a window and letting the gas furnace do the work of heating the air than running the HRV. Heating my ~2300 sq ft house currently costs about $700/year (and winters are cold where I am). That wasn't always the case, of course, and may not always be the case in the future.

 

Hopefully some of this info helps. I always read / appreciate the advice you post to this forum.

 

By the way, what are makeup air valves?

[IndyMike]

Hello johnnyt,

 

Thank you for the clarification on your local code. I cringe whenever I hear the term "lobbyists". While it is possible that there were issues with the 90's vintage HRV's (your defrost heater as an example), I have a hard time believing they had your best interests in mind when they campaigned to change the code. A HRV would seem to be ideally suited to your area.

 

I do have co-workers that have HRV's with defrost heaters. They appear to function well in the milder climate of N. Indiana/S. Michigan. I can see where it could present an issue with your much colder climate.

 

Since you had a HRV installed during construction, I'm guessing that you have dedicated return/supply ducts throughout your home. In other words, your HRV system is separate from your Heating/Cooling air system.

 

I'm jealous. I'm running bath fans with makeup air vents in the basement (walkout). The air vents are similar to your back draft vents but reversed so they supply outside air to prevent negative pressure in the home. I live in an area where Radon gas is a problem (I've tested the house multiple times over the years) and need to prevent a negative pressure condition. As you stated, my system is analogous to turning on the fans and opening a window.

 

I would love to install a dedicated system, but simply don't have access to the walls/ceilings to be able to install one. That leaves the option of tying the HRV into my heating system. Unfortunately, my furnace is an older model with a fixed speed blower. It consumes ~1500W of power when running. That puts a big dent in the payback from the HRV. I've looked at this a number of times over the years and have always walked away in disgust. I really need my furnace to die (can't believe I wrote that) so I can replace it with a variable speed model.

 

At least I've been able to automate the bath fans using ISY so that the air exchanges occur at a regular rate or my choosing.

 

Thanks for sharing the information on your system. Glad to hear that it's working well for you.

 

IM

[arw01]

Ok guys, what's a HRV? Related in any way to whole house fans?

[johnnyt]

yep, they are whole house ventilators.

 

HRV = Heat Recovery Ventilator

ERV = Energy Recovery Ventilator - as well as recovering heat (or cool) that leaves the house it reduces the humidity coming in - more appropriate for hot climates that run AC most of the year.

EHV: not sure

 

Turns out I do also have a 4 inch vent to outside in the furnace room (no damper in it) to prevent negative pressure pulling flu gases back in (only a problem with hot water tank now but original furnace was not power vented either). Didn't know what they called that.

 

I wish our HRV was dedicated and pulling air from bathrooms, kitchen, etc. but it just pulls off the cold air plenum about 5 feet from the furnace and feeds new air back in close to the furnace. Obviously the lobbyists were able to get some profit maximizing concessions right from the beginning.

 

The furnace I have today has a DC motor and the fan is interlocked to run on low (about 50W) with the HRV. On a side note the furnace is actually plugged into a UPS with an extra battery as it only takes about 300 W on stage 1 heat and worse case 700W on stage 2 (not needed for maintaining the temp). When power goes out I set the stat back a degree or two and have heat for about half a day to a day or more without electricity depending how cold it is, of course. But I digress, so I'll leave it at that.

[johnnyt]

double post deleted

[IndyMike]

EHV: is either an Exothermic Heat Ventilator (haven't invented it yet) or a typo. I corrected my post to indicate a HRV.

[arw01]

Thank you gentleman. In my area, it would be nice to have a WHF or at least a way for the furnace fan to pull outside air directly after it cools enough outside to not run the heat pump and instead just change over the hot inside air for the cold outside air.

 

Currently I do that a bit with a kitchen fan and a bathroom fan and bedroom window fan to pull it in and the other two to push it out.

 

Alan

[IndyMike]

Hello again johnnyt,

 

More info on ventilation systems:

 

Nice article on using ERV's and HRV's: http://www.greenbuildingadvisor.com/blogs/dept/musings/are-hrvs-cost-effective

 

At the bottom of the article there are #'s for the relative savings for different locations in the US (johnnyt, you would likely use the Burlington Vermont #'s):http://www.greenbuildingadvisor.com/sites/default/files/Semmelhack%20HRV%20cost%20effectiveness%20table%201.jpg

 

From the chart above, I'm roughly in-line with the numbers posted for Chicago. I just re-tested my furnace blower. After subtracting out the "unneeded" loads (zone panel, vent dampers) it pulls 1100W in heat mode and 575W in low speed continuous mode. I think I'm stuck with my "open window" system until it dies. On the brighter side, I'll be in retirement sooner than I care to admit. I'll get another chance at this when we down-size.

 

Article on the "Lunos" through the wall heat recovery ventilators: http://www.greenbuildingadvisor.com/blogs/dept/musings/european-products-building-tight-homes

 

The Lunos fans go for $1200 for a pair and are rated at 17.6 CFM/Pair. My home would require 5 pair to meet ASHRAE standards. There is no current cost/benefit calculation ratio that would support using these in the States. The sad fact is these may make sense in Europe. On average, Europeans pay nearly 2x my local price for natural gas, and 3.5X the price for electricity. Add in the fact that the fans are "easy" retrofits for older homes and these could work for them.

 

IM