[Greenbuilding] ERV's

[sat jiwan ikle-khalsa]

To GB list, 
A few questions about HRV/ERV operation (and obligations of the installer)....

In renovating our house, we made it much tighter, and ordered an ERV (Aprilaire supplied by HVAC contractor) to tie in with the new ductwork and heat pump.  I had lengthy email conversations with the HVAC system designer, telling him how I have a corn stove to provide most of the heat and hopefully will not need to run the A/C much in summer.  So he was largely putting in a system that hopefully won't get used much, but if we sell our house, a non-corn stove user will  still have a good traditional system.  At one point, he had said that the air handler is so efficient, i should just run the fan on low _all the time_ even if the heating or cooling isn't on. But I'm not too keen on having something that's ON ALL THE TIME.

(Anyone else have experience using an ERV without needing to run a whole house air handler? and/or with primary heat being a wood/corn stove or passive solar?)

During system installation the ERV was forgotten and put in late. The guys working that day had never done one and I had to read the manual with them to do it "right".  When installing they put a power outlet in the conditioned attic where the ERV unit is so it could be plugged in.  

So currently it's winter, and we're not running the heat pump for heat.  A couple times just to test it, I have run the heat (and HAD TO CRAWL into the attic in order to plug and unplug the ERV).  I assume that there's no sense running the ERV without running the air handler, otherwise I'd just be filling my return duct with fresh air, but the output of the ERV would not be sufficient to move that air all the way to the basement and back out to the supply registers.

So a couple things i want to ask the HVAC company (and just want to know what i should demand or expect they do):

1. install (at the least) a switch not in the attic so i can control the ERV on or off.
2. connect the very fancy heat pump controls to the ERV so that it only runs any time the air handler runs.
3. set up a timed system that turns the air handler and ERV on at periodic intervals without a heating or cooling signal from the thermostat. (adjustable by me if/when the season dictates open windows and no need for the ERV)
4. I was told that the ERV could act as a whole house dehumidifier in the summer as well, so I want to know what I need to do to achieve that. (there's a humidity sensor on the system controls and a humidifier on the air handler). according to the Lifebreath FAQs referenced, it seems my limited use during cooling season would recommend an HRV, that my ERV wont serve well as a dehumidifier, though may serve a new owner better ho uses the heat pump more for heating and cooling.

I think someone on this list mentioned having some kind of timer/interval for running their ERV. (not sure if it was Ward).  Could you or someone tell me more about that? (any special controls needed? how to tie in with forced air ducts air handler?)

note: we live outside of Washington DC. and have moderate heating and cooling loads. (not so much cooling for us since we choose to mostly sweat out the summer).

thanks,
-sat jiwan

~ ~ ~ ~ please use my permanent email address: satjiwan at alumni.brandeis.edu ~ ~ ~ ~ 



Some of my recent projects:
green house renovation photos:  http://www.flickr.com/photos/satjiwan
Save Our Sky - corn stove cooperative - http://www.saveoursky.com



> >I have mine on a cycle that runs 20 minutes of every hour on low 
> speed and I find that keeps the humidity in check. 
> 
> You mean keeps humidity low in the summer, or keeps it high in the
> winter?  

There is some more detailed info on HRV vs ERV on Lifebreath's site at
 
http://www.lifebreath.com/en_tfaq/FAQ-ERV.pdf
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