digital thermostat- which one is best??

I am feeling overwhelmed!!

I am reading that digital thermostats are the way to go because they have a smaller range. (instead of 3 - 5 degrees - they are accurate/can be set to maintain within 1 - 1.5 degrees of set temp).
But I can't really find much except ones that are meant to be in a house. I am thinking that the moisture inside a greenhouse would cause this type to rust and fail.

what type and manufacture have you found to be workable...which to avoid.

any help appreciated...

it is about to get cold... need to figure this out...SOON!!

thanks...:-))

Can't help you on the digital ones, but I would think a 3-5 degree range of accuracy should be fine for a greenhouse. I would recommend buying one that's designed for greenhouses, all the greenhouse supply places sell them. I don't have one so I can't recommend a specific brand unfortunately.

thank you ecrane... maybe I am over doing it. Do you try to heat your greenhouse during the winter?

I do, I have an electric heater, but I just never bothered with the thermostat. The first few days that I'm using the heater, I turn it to a setting that I think will be OK, then I check the temps in the greenhouse first thing in the morning, if it's too low or too high then I turn the heater up or down. (by too high I mean warmer than it needs to be to keep the plants happy, it's just wasting energy then) If I lived in a colder climate I'd probably invest in a thermostat, but I think one that controls to within 5 degrees would be fine.

thanks ecrane..

I am probably over thinking this. I do that sometimes.... I hear that 1-2 degree control is best.....so that is what I go for.... rather than just being happy with what works!! lol
thanks!!

Were you hearing that for greenhouses, of for thermostats for your house? I've heard that for thermostats for the house, that way it keeps the temperature more consistent inside which makes you more comfortable and I think it saves a little on energy costs too. For a greenhouse there's certainly nothing wrong with having the tighter temperature control, so if you can find something designed for greenhouses at a price you can afford there's no reason not to buy one with better control. But if you're going to have to spend twice as much or get a thermostat that's not designed for outdoor use in order to achieve it, it's not worth it, the 3-5 degree control will keep your plants perfectly happy.

merrydancer, I'm wondering what kind of heater you are using, gas or electric?

There is a very simple easy-to-use (and set up) for electric heaters at Greenhouse Megastore. You just plug it into an outlet then plug your electric heater into the back of it...Voila! (ecrane, you might want to check it out, too, just in case you feel the need to someday get a thermostat.)

http://www.greenhousemegastore.com/searchprods.asp

If you have a gas/propane heater you should feel perfectly comfortable with a Honeywell dial type. The one I've been using is going on 8 years old and has never failed me yet. Plus they are made of anodized metal (non-rusting), plastic dial (non-rusting) and your typical inside workings (mercury tube/balance bar). I suppose a search for a Honeywell site will find you one or you can just go to Lowes or Home Depot and pick one up in the heater section.

As for the 3-5 degree difference, don't worry about it. You can easily get around any temperature variation by manual adjusting until your get it where you want it. (By the way, you're going to have a natural temp difference throughout your g-house no matter what; some spots will be hotter than others, some cooler, some sunnier, etc.) What is easy to do is set your thermostat at 50º, when the heater is turned off by your thermostat check the temp at the far end of your greenhouse (or behind the heater or other important area). If the temperature there is only 45 then adjust your thermostat to 55º, then check various areas again, making adjustments to the thermostat as you go.

Happy Growing!
Shoe

I have thermostats like the first one Horseshoe describes, on my electric heater and my exhaust fan. I bought them at kkontrols.com:
http://kkontrols.com/

They work great, and did not require me to ask my patient husband to do any more wiring. (I can plug things in myself, lol!) The plastic cover flips up so you can set the dial to the temperature you want, and they seem very sturdy. I ordered late one night, and they shipped my order before I had my morning coffee the next day. Whoosh!

I ordered mine with a long 20 ft cord ($5 extra) so I could put the thermostat just where I wanted it (hanging at the level where my plants are, above the benches.)

Here is a pic of the thermostat end. When my heater and fan come on by themselves at the temperature I set...it's like magic! :-)
Sheri

...and here is a pic showing the plug. This plug goes into your outlet, and your heater plugs into the back of the thermostat plug. I admit I like simple stuff!

oldmudhorse, I have two of those thermostats, one for each heater. Right now, though, one is wired backwards, as it operated my exhaust fan this summer. If you take the cover plate off, you can access the wiring. This way, it closes the circuit when the temp rises, instead of cools. It's just a matter of switching two wires.

I'm not sure why you'd want to run the heater and the exhaust fan at the same time, though. I don't use my exhaust fan in the winter, at all. It gets covered with plastic, as do the auto-louvers..

Eggs, that idea might have worked for me. I did have to switch the two wires, as you said, to set one up for my exhaust fan. (Merrydancer, it was simple since they send a good big diagram.)

This is my first winter with a greenhouse so I don't know how late in the season I'll be using my exhaust fan here. So far I'm still running the fan during some days here to keep it under 93° in there (desert climate) and I've run the heater a few nights as well to keep it at 45°. I think this is going to be an awkward time of year for me...days too hot, nights too cold.

Anyway, nervousness won out, so I ordered three thermostats...one for the exhaust fan, and one for each of my two 1500w heaters. I would love to know how you set the thermostats for your heaters...I can't figure out if I should set each of them to 45°, or set them at two different temps so one kicks on before the other.

As you can tell I'm not very intuitive about this stuff. How do you do yours?

I'm zone 5b/6a, so it's *much* different, here. That being said, I was concerned about costs. We regularly get temps in single digits, to below zero in mid-winter, and some daytime highs may not get out of the single digits. I originally set my thermostats to 50 degrees. I figured that to be the minimum temp for my most sensitive plants. That first month's electric bill was only about $15 higher than normal, so I kicked the temps up to 60. During the coldest months, I had it set to 70, and only saw about a $25 increase over or normal electric bill.

It was the first year with the greenhouse, and due to some gaps at the joints of the framing, I had quite a bit of heat loss. The coldest it got was probably 49 inside the greenhouse. This summer, I went over every square inch of the structure, sealing all of the holes with silicone. As I said, right now I only have one thermostat set up for heating, so there's only one heater in there. I have it set for 50 degrees. We've had a few mornings in the upper twenties, and the coldest it's been in the greenhouse has been 55. =)

I see no need to set the temps higher than 50. The sun heats the structure during the day to about 80. I'm only concerned with using the heater(s) to keep the low temp. The end of January, through February, is our coldest time, here. I expect to have an easier time this winter, keeping temps in there, after sealing the gaps. It may still struggle, during those times. If so, I'll kick up the thermostats to compensate, as best I can.

I'd find the temperature range for the most sensitive plant that you want to winter-over, and either set it at that temp, or slightly above.

HTH,
Eggs

Eggs, that is helpful.

I am glad I don't have your colder temps (especially for my first greenhouse winter.) I'm concerned about my electric bills too. Fortunately my succulents (most) are OK down to around 40°, so I'll set both heater thermostats for 45°-48° and see how brave I get as the bills come in. The wimpy plants can always be moved back indoors to the laundry room if necessary...

Thanks again, may your gaps be gone forever. :-)
Sheri

I also shoot for 50-ish temperatures. Most nights last winter my heater kept things around 50-55. We had a really cold spell in January where it got down to about 35 inside the GH for a few nights (my greenhouse was built on a hill, so the end that was propped up to keep things level had some pretty good size air gaps that I didn't do a good job of plugging up!) No damage whatsoever during that time, everything came through just fine (although if it had been 35 in there all winter, I don't think the plants would have been quite as happy!).

This year I moved the greenhouse up on my deck where it's level and I sealed all the panels in with silicone caulk, so I'm hoping for a more energy efficient heating experience! Last year was my first winter in this house and we had such unusually cold weather, I have no idea how much of my ridiculously high energy bill was due to the greenhouse heater vs the furnace that was keeping me warm, I think most of it was the furnace because my house has terrible insulation.

i have thermostats from FarmTek that are just a little less spendy
http://www.farmtek.com/farm/supplies/prod1;ft1_thermostats_controllers-ft1_thermostats;pgcr2095.html
http://davesgarden.com/community/forums/t/653298/
i use one for 2 electric heaters and the other for a summer fan which i have not needed here
because the the automatic vents work just great
http://davesgarden.com/community/forums/p.php?pid=3006983

Dick

I thought I would need a thermostat
but I now have two 1500 watt electric oil heaters
Each is the cheap type which sells for under $50

I leave them both on set at one setting melow max temperature
they seem to be doing just what I wanted without any additional thermostat

the picture is output from my $40 "Wireless Data Logger" which is a discontinued
temperature and humidity device from LaCrosse

more explanation on the chart I just posted
1. the top line (purple) is a sensor inside the greenhouse
2. the other two lines are from sensors outside
the red line in the back yard 20 ' from the greenhouse
the green line in the front yard

notice that the greenhouse is between 52 degrees and 80 degrees
while outside it is between 35 degrees and 82 degrees

the evaporative cooler is running at the hotest time when the greenhouse is in full sun
in the early afternoon

the cooler shuts off when the greenhouse is shaded from the sun by the house about 3 pm