Panic time

The sun can raise the temperature of a greenhouse well above the outdoor temperature, but after the sun goes down, the inside and outside temperatures converge. This time of year when the lows are a few degrees either side of freezing, that is a problem unless you take countermeasures. There are all sorts of things you can try that don't require electricity, and if you are interested do a Google search on "greenhouse heating methods." But I opted for the electricity. We haven't had a hard freeze in southern Montana yet (unusual), and the little heater I bought for the greenhouse has been able to keep up with the 30-something outdoor temperatures, maintaining 41-42 degrees inside. (Fahrenheit of course.)

A side benefit of the AC Infinity fan I have installed is it has an app that (in addition to controlling the fan) allows me to monitor the temperature and humidity remotely. I have gotten in the habit of checking the app frequently, particularly as the weather has gotten cooler. This morning at 4:25 AM, it showed the temperature plunging from 41 degrees to 37 degrees a few minutes later. It didn't go back up, which I took as a sure sign that the heating system had chosen that moment to fail. It bottomed out at 35.8 degrees at 6:01 AM. It was a clear day so the temperature started rising in the greenhouse after the sun rose at 7:35 AM. Most (but not all) of my current plants are cold tolerant. Fortunately, there was no apparent damage even to those that are less hardy.

I quickly determined that the heater itself was still operational, but the separate thermostat controller had failed. The display still worked and I was able to cycle through the options, but it simply would not turn on the heater. So I removed the controller and plugged the heater directly into the outlet. Temperature control via the analog dial is complete guesswork, and I have it set on 1.5. I will monitor the temperature tonight with the AC Infinity app and might have to take a midnight ride if it turns out that it is set too low. I have ordered a new controller, different brand of course, but it won't be here until next Thursday.

This is a picture of the Chinese-made Buyplus heater, controller (the green item), and a stand-alone digital thermometer that came in the package. I ordered them about two months ago and the Amazon return window ended after a month. So far I have been happy with the heater itself, and the digital thermometer is handy in that it gives me the 24-hour high and low, but the controller failure makes it impossible to recommend this package.

Update Oct. 18: The analog setting of 1.5 kept the temperature from dipping below 37.2 degrees last night when the outside temperature reached 32. I bumped it to just over 2.0 and will see if that will maintain above 40 degrees until I get the new controller. Also, I put the stand-alone thermometer outside on the north side of the greenhouse. AC Infinity already tells me the high and low temperatures inside, so this will report what is happening outside.

Update Oct. 20: The new setting has kept the temperature no lower than 41.7 the past two nights. I'm wondering if I should leave this heater as-is, and hook the new controller when it comes to a second heater set a few degrees lower as an emergency backup. Less than three months into my greenhouse experience I've already had technology failures of the ventilation fan and the heater controller. A backup heater seems like a good idea.