dba62 Posted December 8, 2017 Posted December 8, 2017 So I have roof coils for ice dam mitigation. I'd like to write a program to control the power for the coils. The problem is that the conditions aren't obvious. So I could do something like (excuse my crude program): if (snow today or snow tomorrow) then power on wait 72 hours else power off But that seems problematic. Perhaps there just isn't an awesome solution for this case. Thanks!
stusviews Posted December 8, 2017 Posted December 8, 2017 What are you using to determine if there's snow forthcoming? Also, what does your program control to turn the power on? If there is snow, then your program will turn something on, wait 72 hours and then stop. Power will not get turned off unless the condition evaluates as false (no snow), not even after 72 hours elapses. So, determine what you want to happen, when it will happen and when you want it to stop before creating the program. The post your writings
dba62 Posted December 9, 2017 Author Posted December 9, 2017 What are you using to determine if there's snow forthcoming? Also, what does your program control to turn the power on? If there is snow, then your program will turn something on, wait 72 hours and then stop. Power will not get turned off unless the condition evaluates as false (no snow), not even after 72 hours elapses. So, determine what you want to happen, when it will happen and when you want it to stop before creating the program. The post your writings I'm using the climate module. Power is controlled via Dual Band InlineLinc On/Off Switch. I agree with your analysis of the algorithm. The problem is that I don't have an input to tell if there is snow/ice on the roof. So I try to allow for this for leaving the roof heater on for 72 hours. My program (which is up and running) actually takes the temperature into account as well. So its: If Module 'Climate' Temperature < 38F AND ( Module 'Climate' 24h Snow > 0" Or Module 'Climate' Snow Tomorrow > 0" ) Then Set 'Basement Power' On Wait 72 hours Else Set 'Basement Power' Off I was hoping that someone else had already tackled this. Given the lack of a critical input, I'm not sure there is actually a good programmatic solution. For now, I'll let this program run and then tweak it as necessary or decide that this approach isn't going to work and just control the power manually.
Teken Posted December 9, 2017 Posted December 9, 2017 I would encourage you to test this out on a smaller and isolated scale. This way you can see first hand the cause and effect while reducing threats and hazards to you and the home. The best case you will waste a whole lot of energy and be lighter in the pocket book. Worst case you could burn down your house like a few others have in the past. As you correctly noted its important to have other independent system(s) that offer critical insight to the local weather, temperature, and reality there is indeed snow on the roof. What I can tell you is at the moment relying on the weather module in its current form isn't practical. Keeping in mind this assumes a few things like which station is being used and how accurate it is to your micro climate. Back in the day when the system updated every five minutes the data was at least timely. Now that its set to update every 30 minutes along with no easy method to select a micro weather station your whole project hinges and gambles upon that data being accurate and relevant. There have been a few good folks who have engaged me to do something similar and the only way they do this is with lots of checks and balances along with fail over protection. This involves the use of a PWS on site, IP Camera, 1-Wire sensors array, and programs that have been tested, validated, and proven over time to operate as expected. Please consider testing your project out on a small isolated system to validate it works as intended. Identify how long something takes to react and then adjust to compensate. You may find out quickly having 3rd party systems as noted up above is required to make a safe system operate. Lastly, it should be clearly noted the system must be taken off line when seasons change. On the surface this may sound very silly to state and would be expected. Sadly, that thing called life always gets in the way and as noted up above a few people have burned down their homes . . . Please be safe in this deployment Merry X-MAS . . .
KeviNH Posted December 9, 2017 Posted December 9, 2017 In my case, ice dam prevention isn't so much about the current rate of snowfall as it is about dealing with water coming off the roof while snow is melting --once snow has accumulated on the roof (melting all the snow as it falls is economically infeasible in Northern New England), then certain weather conditions, exacerbated by roof geometry and/or poor roof design) can lead to ice dams even if the living space is optimally insulated. Ice and Water Shield helps, I even replaced the most problematic roof with rolled steel roofing. So I have roof coils for ice dam mitigation. I'd like to write a program to control the power for the coils. But that seems problematic. Perhaps there just isn't an awesome solution for this case. I have heat tape for ice dam mitigation; it doesn't actually fully clear my roof of snow, but rather works to ensure there is a clear channel for water to make it off the roof instead of backing up behind an ice dam. Here's a link to the programs I use for controlling the heat tape: https://forum.universal-devices.com/topic/21363-weather-module-configuration-polling-interval/?do=findComment&comment=207798 I had a fair amount of trouble with this program before I realized that the climate module may cause re-evaluation of program conditions every time ISY polls for weather data, and that I needed to run the heat tape when there's snow on the roof and conditions make it likely to thaw and then freeze. I also added a variable to override the weather check, force heating even if weather doesn't meet the conditions.
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