Documenting my attempt to cut my energy usage in half.

Friday, July 1, 2011

A Home Built Heat Pump / Energy Usage Monitor

A couple of years ago I bought a small robot kit for my kid to experiment with from a company called Parallax.  Along with the robot I bought a couple extra of their Stamp chips just to play around with.  After a couple of months the "this is interesting" factor wore off and I moved on to something else.  Last summer (2010) after working in the attic one day I wondered how hot it got up there and thought about the possibility of putting a temperature sensor in the attic that I could monitor remotely.   Already having a BS2P from Parallax on hand, I connected a Dallas Semiconductor DS18B20 to it and wrote a small program to log the data to my PC every 15 minutes.   After a few days, I started wondering how the outside temperature affected the attic temperature and added some more code to log the outside temperature as well (a year worth of data is here at BuildItSolar).  I then added an additional sensor in the crawl space and not knowing where I was going with it, put the project on the back burner.

The Birth Of My Home Monitor

In Dec 2010 I ran across BuildItSolar and Gary's Half Program and I soon knew where I was going with those few temperature sensors.  The project needed to grow.  A lot.  After looking at a couple of options for chips/circuit boards to monitor multiple 1-wire temperature sensors, I decided to just keep on using the Parallax BS2P's since I had them on hand.  Personally, I've not used the Arduino yet, but from what I've read I'm sure it would be more than capable of doing what I've implemented. 

What I'm Monitoring

I now have 16 temperature sensors installed around the house with most of them monitoring what my two Water Furnace ground source heat pumps are doing.  Here's a run down of where the sensor are located:

UpstairsLogging Time
AtticEvery 15 minutes
OutsideEvery 15 minutes
HP Supply AirEvery 1 min when HP On
HP Return AirEvery 1 min when HP On
HP Desuperheater OutEvery 1 min when HP On
HP Desuperheater InEvery 1 min when HP On
HP Earth Loop OutEvery 1 min when HP On
HP Earth Loop InEvery 1 min when HP On

DownstairsLogging Time
Crawl SpaceEvery 15 minutes
Hot Water TankEvery 1 minute
HP Supply AirEvery 1 min when HP On
HP Return AirEvery 1 min when HP On
HP Desuperheater OutEvery 1 min when HP On
HP Desuperheater InEvery 1 min when HP On
HP Earth Loop OutEvery 1 min when HP On
HP Earth Loop InEvery 1 min when HP On

I also have 7 sensors that detect when the different zones for each heat pump come on.  The upstairs heat pump has 3 zones and the downstairs heat pump has 4 zones.  Detecting when the heat pumps are on allows me to log the heat pump temperature sensors only when they have meaningful data.

When I received and installed my TED 5000 in Jan 2011 I quickly found out that the load profiling software didn't work quite as well as I wanted it to.  To fix that problem I added the ability to retrieve all of the "seconds" data from the TED 5000 and save it to disk and I wrote my own functions to do the load profiling.  Since I have all the data locally now, I generate all the usage graphs within my monitor program and rarely look at the TED web console anymore.

I now have a fairly complete energy picture of my house and can see not only how much electricity is being used and what's using it but can also see how well things are working.  It also gives me the ability to log some baseline data so that when I do make changes I can actually see if it makes a difference.




3 comments:

  1. Workin on some similar projects. Impressed you were able to get so many DS1820 interfaced to a Basic stamp. Have you published that program? I use 1-wire buttons.

    My son did a high school science project on "effects of roof construction on solar gain". We found that the most cost effective way to decrease solar gain was to use a radiant heat barrier.

    But now I'd like to heat domestic hot water with attic air. I have a project in progres.

    Do you have an email address?
    James Jones md, phd
    Jacksonville Fl

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  2. No I haven't published the program anywhere. The code for the stamp is fairly simple. The home monitor program really controls everything at it tells the stamp what sensor to poll and when. The BS2P just listens for a command, reads the appropriate sensor and sends back the raw temp reading along with the status of all the zone dampers. The 1-wire network is configured as a star (which isn't ideal) and presented some issues getting it to function correctly.

    Please send any notes about your DHW/Attic Air project to Gary at BuildItSolar

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  3. Great post! Me and my husband have recently been investigating heat pumps for our home. The main reason for this is because I heard that the heat dispersing properties could eliviate the usual outbursts of excema I get from tradational skirting radiators, so far it's been successful!

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