This might help:
http://www.extension.umn.edu/distrib...ng/dk7284.html
In the planning stages of designing a new home in Florida. Will be using heat pumps with VS air handlers (possibly Carrier Infinity system). Would like to install an ERV for fresh air. I am a commercial HVAC engineer so I understand how they work and would like to place the exhaust portion in the bathrooms in lieu of using regular bath exhaust fans.
My question is what is the best way to control an ERV for residential applications? I know the incoming fresh air is not completely cooled/dehumidified so they need to connect to the air handler for additional cooling/dehumidificaiton. Therefore they should be interlocked with the air handler so that it only operates when the air handler is on.
What if the air handler is not running and we need exhaust in the bathroom (i.e. cool times of the year, taking a shower, etc)? Can an overide switch be installed in each bathroom to operate the ERV when ventilation is needed? Or is it better to use separate bath exhaust fans and only connect the ERV directly to the air handler?
Also, what brand ERV's are recommended? I noticed Carrier makes residential models? Are they any good?
Thanks!
This might help:
http://www.extension.umn.edu/distrib...ng/dk7284.html
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Progressive thinking. ERVs in your climate are not very common. You have several exhaust fans that need makeup air when used. The clothes drier, kitchen hood, and bathfans are most common. Homes in wet climates depressurized forces moisture into the walls where the high moisture air has the potiential to condense. Most prefer fresh makeup air for that pressurizes the home plus providing make-up air for the exhaust fans forcing dry out through the cavities. During most of the year, the small temperature difference between inside and outside air reduces the savings potiential of the ERV.
Green grass climate homes have many months that the outside dew point is high without enough cooling load to remove the moisture from fresh air and occupants. Supplemental dehumidification is necessary to maintain <50% RH even with an ERV. Most now are skipping the ERV because low savings and maintaince. Instead they are using the ventilating dehumidifier which manage the delivery of the fresh air to the home and maintain <50% RH when the a/c is unable.
A high SEER a/c combined with the ventilating dehu makes a simple install and provides fresh, filtered air when the home is occupied, and maintains <50%RH with or without a/c operation. I work for and suggest the Ultra-Aire. There are others like Honeywell, Rheem, Goodman etc.
If you decide to use the ERV, I suggest on using dehumidifier for damp cool weather.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
i believe renewaire has a timer system that places a push button control in several rooms. you push the button a certain number of times for a certain length of run time (1 time for 20 minutes, etc). For instance, to take a 10 minute shower, walk in the room, hit the button once and the unit shuts down on its own 20 minutes later.
I am an old HRV/ERV salesman. I thought they were the only way, that was 20 years ago.
Consider what happens when an ERV operates while showering. The damp air is slow exhausted through the core. The fresh air being brought in is humidified by the exhaust air. Some of the exiting moisture comes back in. But not too worry. The bigger problem is that connecting 3-4 exhaust points to an ERV exhausting 120 cfm of air is only 30 cfm from each area. This is not enough. Much better off with a good 100 cfm fan from each shower to get the moisture out.
If you are going to have all the bells and whistles, get good bath fans, an erv, and a small whole house dehumidifier. The next level down and more practical is good bath fans with a whole house ventilating dehumidifier. You need whole house dehumidifier as a minimum to provide <50%RH during low/no cooling load conditions while fresh air is entering the home and occupants are present. The ERVs are not very effective at removing mositure, <40% under ideal conditions.
I tried what you are going to do several times. Never could keep the homes dry during cool wet weather. The dehumidifier maintains <50%RH regardless what the conditions are.
Regard TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
I was actually planning on using a 200 cfm ERV with 100 cfm each from two bathroom. Florida Mech. Code requires a minimum of 50 cfm of exhaust per toilet and shower.
I like the idea of using a Carrer ERV because of the integrated controls in the Infinity system. I am a big proponent of keeping it simple.
Funny, yet true story. I worked for this guy 25+ years ago that during his new home addition had 1400 CFM exhaust fans installed in each and every bathroom, you all but needed a seat belt to sit on the can
Seriously though have you weighed the cost verses the Bennie's? Sounds like a lot for 2 crappers and what 2 people? Not seeing the advantage/purpose here.
Using Ebay as a guide, a whole house dehumifier appears to roughly 2x the cost to of an ERV. You then still have to install bath fans.
Still going back to what you have here, 2 crappers right? So the house cannot be that big, I mean not like a mansion or something, right?
I am still trying to figure out why you think you are going to have all these humidity issues and what not.
I realize you're in the PE biz and I am similar field, but are you sure you're not over thinking this whole thing here?
Seriously if you want a commercial app in you're 2 crapper homestead (would not know why) but, I could could hook you up with someone capable, assuming you do not have these connections currently?
House will be 3700 sq. feet, two story. Total of 3 baths (one downstairs, two up). Was going to install ERV on upstairs system. I was originally thinking about using a 200 cfm ERV so I could eliminate the upstairs bath fans. 100 cfm of exhaust for each bathroom (50 for toilet and 50 for shower as required per code).
This is a great opportunity to learn about fresh air ventilation with ERVs. YOu assume that operating an ERV is going to reduce indoor moisture. When you operate the erv, 200 cfm of exhaust from a bathrooms does not remove any moisture from the incoming air. Mainly wet exiting air transfers moisture to the incomming air if the incoming air is drier. Ventilating when the bathrooms are dry will be only slightly better. ERVs tansfer about 40% of the sensible/latent difference when the exiting air is <50%RH. This leave 60% of the excess moisture in the air. Keep in mind that as the home gets a fresh air change the home is wetter after the first air change. After a day of ventilation, the air inside the home will be as wet as outside. But have fun. During low/no cooling load conditions, you will some dehumidification to maintain <50%RH in a well ventilated home. You can add a small whole house dehumidifier after you have proved if the ERV will do the job or not. One more kicker is that clothes driers/kitchen hoods/bathfan exhaust air while sucking in wet through the walls. Using make-up air ventilation provides make-up air for the exhaust devices and puts a little positive pressure on the home, keeping out damp infiltrating air.
You will be as supprised as I was after I tried the same thing on several homes. It took a good researcher to prove to me that I was making the homes wet with my good ventilation. Monitor the home. Keep us posted.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
I think I am going to take your advice and seriously look at a whole house ventilating dehumidifier. For 3700 sq. feet, should I look at using one Ultra-Aire XT150H for the whole house or should I look at using two smaller 70H/90H's? I will have three heat pumps systems. One for down stairs, one for upstairs and one for the bonus room over the garage.
florida_pe,
I live in the Tampa area myself and have a similar property (2 level, 2800 sq/ft, built in late 2009). I am having a very hard time locating a contractor who not only will install a ventilation system or ERV, but one who seems to know how to install it correctly. The only quote I've gotten was from a company who installs ConsERV units, but the gentleman stated they would use existing ductwork for both the supply and exhaust from in the house. Based on my research, this is incorrect and will cause improper operation. Every other place I've called just won't do it.
Anyway, I was wondering if you'd let me know what you decide to go with and, if you're having someone install it for you, who is performing the work. If you're installing it yourself, would you be willing to do a residential install at a market price?
I was leaning more toward an ERV. It looks like Bryant, Carrier, and Venmar produce the most efficient systems (based on TRE ratings from HVI) and they do at least some de-humidification. I'm not a PE like some of you are (network engineer here) so I may be getting some of this wrong.
If you don't mind, please email me (whalenkcj .at. gmail.com) once you figure out what you're choosing to go with.
Thank you. =]
Appreciate your consideration.
The size of the dehumidifier depends on the amount of fresh air infiltration/ventilation, the number of occupants, the size of the home, and the %RH you want.
Extreme air tight homes provide real control of the amount of fresh air and allow using less dehumidification than leaky homes. Assuming 150 cfm of fresh as a max with 5 occupants max and <50%RH suggests that 150 pint/day of dehumidification is plenty of capacity.
If your air handlers that service the open partof the home and master bedroom, are located in way that you can split the fresh dry air between them, one dehu will do. If the key handlers not near by, I suggest two smaller units. Two 70 pints UA 70s located near each of the air handlers. If you feel you want the home very dry and or more fresh air on any occasion, consider a couple 90s or a 90 and 70, as an extreme three 70s could be considered.
Follow our recommendations of fresh air inlets, independent central returns to the dehus and discharging the dry, fresh air into the a/c supply. The install manual is on the thermastor web site.
If you use one 150 pint dehu and your home is occupied <40% of the weekday, consider using the a CO2 contoller to provide fresh air when the home is not occupied and/or the wind is blowing enough that you do not need fresh air. This type of controller will reduce the fresh air needs. This eliminates over ventilating, which saves a lot of energy.
Stay in touch, I am willing to help.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
The research post is a good one. Keep in mind that while ervs reduce the moisture put into the home while exhausting <50%RH air, +60% of moisture in the outside air is blown into the home. As the exhaust air %RH rises, the amount outside moisture blown into the home, increase significantly.
After a day of several air changes without dehumidification, the exhaust air is as damp as the outside, resulting in outside humid air being blown into the home.
At a minimum, you need supplemental dehumidification to maintain <50%RH exhaust air to allow the erv to remove a minor amount of moisture from the outside air. Another consideration, is to provide makeup air for the exhaust air for your clothes drier, kitchen hood, and bath fans. A ventilating dehu provides make-up air pressurizing the home keeps moisture from infiltrating and provides the make-up air for exhaust devices.
I am in Cape Coral today with 69^F, 95%RH with rain. My home is 74^F,47%RH with adequate fresh air change and the dehu cycling on/off. No cooling load for several days. This is what is all about. ERV would need supplemental dehumidification.
Keep us posted.
Regards TB
Last edited by teddy bear; 01-06-2011 at 09:54 AM. Reason: added a thought
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
What is the fresh air ventilation capacity of the Ultra-Aire XT150H? How many cfm's?
The XT moves +300 cfm of air. Any portion of the total air can be outside air. Normally we suggest connecting a 6" flex duct from outside with an electric damper to the fresh air inlet. When the fresh air is desired, the damper is opened and the fan operated. A second flow control damper allows the desired cfm of fresh air from outside. The balance of the air through the XT comes from inside the home, is blended with the outside air, filtered, and retuned to the home. When the inside %RH goes above the desired level, the dehu will operate independent of the fresh air.
For more fresh air, a larger fresh air duct is suggested. In some situations, a 10" fresh air inlet is used with a damper in the inside and outside return duct. This allows upto 100% outside air if desired.
We are having great dehu weather lately. This morning, 65^F,90%RH outside. Inside 70^F, 48% RH with 70 cfm of fresh make-up air and two occupants. We have had mixed weather this month with outdoor dew points from 40^F-70^F.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
How much heat do I need to accommodate for in the load calcs from these ventilating dehumidifiers?
Usually, you specify typical cfm of fresh air infiltration when doing Manual J load programs. Using 100 cfm of fresh air at your max cooling load temps is enough. When the cooling loads at their highest, the a/c has excess latent cooling capacity to remove the moisture from 100 cfm of damp fresh air and the moisture from the occupants. As the cooling load subsides and the a/c starts cycling, like overnites/rainydays, the dehumidifier will maintain 50%RH. The heat added is about 1,500 btus per lbs. moisture removed. Removing 4 lbs.per hour could be 9,000 btus per hour but the a/c is not operating at max capacity. Therefore do not add additional cooling capacity for the load of the dehumidifier, only the cfm of fresh air ventilation at the design temps in your area which should be part of your manual J load calcs. As an extreme, most suggest limiting fresh air infiltration loads from wind/infiltration/ventilation to an air change in 3-4 hours. I suggest setting the make-up fresh air ventilation to an air change in 5-6 hours when the home is routinely occupied.
Hope this answers the question.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"