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Author Topic: Updated Photos! - Greenhouse Ideas - DIY Solar Panel - Construction Photos  (Read 2354 times)

Kevin Jones

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Cooler weather is here and I need to be thinking about keeping my plants alive for the winter.
I'm building a new greenhouse in my backyard (to add to my plant menagerie... this make 3 GHs so far!) and was hoping to get some suggestions for an electric heater.
Here are the basic facts:
Location: Tuscaloosa in West central Alabama...Zone 7B - 8a... we get some temps in the teens every now and then.
The greenhouse is 240 sq ft.
I am not trying to create a tropical climate all winter... just keep temps above freezing on those really cold days/nights.
Needs to be electric.
For now... Service is provided with extension cords from garage/house back porch.
In the past I have used a couple of milk-house style heaters in my other GHs to keep the temps above freezing.

They work OK.

This is basically an inner-city neighborhood... so there are a few zoning restrictions I have to obey.
Primarily height, square footage and property-line setbacks.
But the city has been pretty helpful.

It's not a huge GH... 20ft X 12. Still under construction as time allows
Shed style pitched roof - 12 ft on high north side - 8 ft on low south side.
PT lumber - Screws - Simpson Strong Ties.

Here's a few construction pix:
 
Pre fab wall units:


Now with roof rafters and end-walls:


Today I start working on the doors.

Thanks for any input.

Kevin





« Last Edit: December 06, 2019, 09:40:42 AM by Kevin Jones »

Jack, Nipomo

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Re: Greenhouse Heater Suggestions?
« Reply #1 on: November 09, 2019, 12:17:26 PM »
We don't have your cold temps, but have you considered heat pads.  Mine keeps the soil (pots) warm and therefore the greenhouse.  Thermostat turns on at 40 degrees.

Kevin Jones

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Re: Greenhouse Heater Suggestions?
« Reply #2 on: November 09, 2019, 01:21:15 PM »
Theoretically I like the idea...
I have a small heating pad I use for bottom heat when I am germinating a small batch of seed.
It's about 1 ft by 2 ft.
If we are talking about the same thing... it might be cost-prohibitive for my budget to heat my whole greenhouse with it.

Thanks. 
Kevin


SeaWalnut

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Re: Greenhouse Heater Suggestions?
« Reply #3 on: November 09, 2019, 04:17:01 PM »
If you use electricity to heat then dont use electric heaters but instead use a heat pump ( an air conditioned used to heat).
Electric heaters are rated to 95 % efficiency maximum but the air conditioner has up to 400% percent efficiency.
That means you get 4 kw of heat with one kw of electric power consumed by the AC.
This efficiency drops if outside its too cold and at minus 15C  ,the efficiency of the AC is same as that of the resistance heaters.
You will need to heat the greenhouse mostly at night.

SeaWalnut

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Re: Greenhouse Heater Suggestions?
« Reply #4 on: November 09, 2019, 04:37:53 PM »
Here is a link with that 400% efficiency .https://www.heatpumpkeymark.com/about/why-heat-pumps/
So with a heat pump( an air conditioner unit used on heating) you will get up to 4 times more heat for the same monney compared to any electric resistance or induction ,heating device.
I will use a rocket stove on wood to heat my greenhouse but if i were to go electric ,then i would have installed an old air conditioner unit and use it for heating.

brian

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Re: Greenhouse Heater Suggestions?
« Reply #5 on: November 09, 2019, 07:14:13 PM »
If you are using a single 115v line via extension cord you dont have a lot of options.  Any generic 1500watt space heater will consume an entire 15 or 20amp circuit.  Make sure to use a heavy gauge extension cord or at best you will lose a lot of heat through the extension cord or at worst cause a fire hazard.  If you can run a 230v line on a double pole breaker you can get a lot more heat from the same wire gauge.  Not sure how feasible that is for you.

I highly recommend getting a “mr heater” that attaches to a 20lb grill propane tank in case you have a power failure or the electric heater cant keep up.  These put out a *lot* of heat compared to the electric space heater and can run for 24hrs even on low if you start with a full tank.  I keep four of them as emergency backup heat.  They are really cheap to purchase
« Last Edit: November 09, 2019, 07:26:53 PM by brian »

Alejandro45

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Re: Greenhouse Heater Suggestions?
« Reply #6 on: November 09, 2019, 11:09:57 PM »
For such a small space and being stuck with extension cords I would use 1 or two oil filled radiators on wheels. Set both on the lowest setting and go from there. Cheap easy to get and can store them away or use them in your house. Also the don’t dry out the air and I have seen some pretty efficient models.

Kevin Jones

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Re: Greenhouse Heater Suggestions?
« Reply #7 on: November 10, 2019, 05:49:08 AM »
It's not a huge GH... 20ft X 12. Still under construction as time allows
Shed style pitched roof - 12 ft on high north side - 8 ft on low south side:






Kevin

brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #8 on: November 10, 2019, 09:22:26 AM »
I think you are gonna need more heat.  I had a similar size greenhouse but only one face was glazed, the rest insulated, and I used two of those space heaters - each on their own circuit.  Even so I had to run propane supplemental heat on colder nights.

It gets to zero degrees F or below here in pennsylvania, so might not be so bad for you, but I doubt a single  1500 heater is going to be enough

brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #9 on: November 10, 2019, 09:27:03 AM »
Also you could insulate the north wall instead of glazing it.  Or get some foam board insulation and put them in place only in winter

Kevin Jones

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #10 on: November 10, 2019, 12:00:45 PM »
You are correct sir.... the north wall will not be glazed.
I figured 2 heaters on separate circuits... until I figure out something else better.

Kevin

brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #11 on: November 10, 2019, 12:20:55 PM »
You should be in good shape then, good luck.

I still recommend a propane backup, though, just in case

Kevin Jones

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #12 on: November 10, 2019, 01:51:14 PM »
Are there any toxic issues with CO2 and Carbon monoxide?

kj


brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #13 on: November 10, 2019, 02:52:50 PM »
Not if its burning cleanly.  Ive been inside my greenhouse countless times after unvented heaters ran all night and no issues.  I got a carbon monoxide alarm and its never shown significant levels, also got a co2 sensor and highest ive seen is 6k ppm which is well under OSHAs unsafe workplace level of 10k

Kevin Jones

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #14 on: November 10, 2019, 03:42:48 PM »
Good to know.

kj


spaugh

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #15 on: November 10, 2019, 06:11:07 PM »
I like the heat pump idea Kevin.  9000 or 12000 BTU mini split units are really cheap.  You can run the 9000 on a 15 amp circuit. 

I would dig a trench and run four #10 wires and and 230v 30amp run to the GH.  Then you can run all kinds of junk.
Brad Spaugh

Kevin Jones

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #16 on: November 11, 2019, 08:02:35 AM »
I agree... and if money were no object... the heat pump would be the way to go.
I may have to put that on my wish list for the future.
Tomorrow... we are expecting temps in the low 20s... so for now I will prep for that.
Thanks.

Kevin

brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #17 on: November 11, 2019, 11:36:19 AM »
If you are mainly concerned about not allowing subfreezing temps I'm not sure how much a heat pump will benefit as it reverts to resistative heating around freezing.  If you were trying to maintain 50F or something like that when it is 35-45F it might be good... not sure I have never acutally used one. 

Two of those portable heaters is good because in my experience their thermometers are very unreliable, having two helps even out the heat

forumfool

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #18 on: November 11, 2019, 01:30:09 PM »
Could just hook them up to thermocube wouldn’t have to worry about turning on/off

brian

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #19 on: November 11, 2019, 01:34:15 PM »
That's awesome, thanks for posting this forumfool.  I didn't realize such a simple/cheap device existed.

https://www.amazon.com/Farm-Innovators-TC-3-Thermostatically-Controlled/dp/B0006U2HD2

Mark in Texas

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #20 on: November 11, 2019, 03:32:37 PM »
Used an unvented natural gas for years.  Excellent heaters.

No way would I go with electric.

https://garden.org/thread/view/96330/Southern-Burner-Greenhouse-Heater/

I hope those studs are treated for ground contact! 

spaugh

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #21 on: November 11, 2019, 03:42:38 PM »
If you are mainly concerned about not allowing subfreezing temps I'm not sure how much a heat pump will benefit as it reverts to resistative heating around freezing.  If you were trying to maintain 50F or something like that when it is 35-45F it might be good... not sure I have never acutally used one. 

Two of those portable heaters is good because in my experience their thermometers are very unreliable, having two helps even out the heat

Brian, you are right they dont work in freezing temps.  It totally slipped my mind but this is correct.  We use a mini split in our garage but it never freezes here! 

Bad idea on the heat pump!  I would still run power to the GH though even if you end up with propane heating.  Running fans, and grow lamps in winter is really nice.

Brad
Brad Spaugh

Kevin Jones

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #22 on: November 11, 2019, 05:23:17 PM »
Every stick is pressure treated.
I have a solar panel and lithium battery/inverter system I will be installing for a LED low power DC lighting system.
Plus I gotta have tunes!

Kevin


SeaWalnut

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #23 on: November 11, 2019, 06:12:10 PM »
Newer air conditioned used to heat ,like Daikin LV ,is efficient up to minus 20 C outdoor.http://www.southshorehvac.ca/cold-weather-and-your-heat-pump/
In usda zone 7 where you get a minimum of minus 18C in the coldest winter ,this heat pump will work at full efficiency.
It is more expensive than resistance heating but the electric bill will be a lot cheaper  and the air conditioner will probably pay for itself in only a winter season.
It has thermostat included in it and if you can get one from used ( second hand) then it will be dirt cheap.
Even in zone 6 and 5 its still better than resistance heating because you can save a lot of monney from electric bills until you get minus 15-20 C.
Initially i wanted to heat my greenhouse with an air conditioner( cheaper one,not Daikin) used as a heat pump and i have a big water well where i wanted to install the condenser ( the outdoor part of the air conditioner).
Because in the well there is no freezing ,it would have been 400 percent efficient all the time even if id live on zone 3-4.

In colder zones even if the efficiency drops by half you still get only half of the electric bill that you get with resistance heating.
« Last Edit: November 11, 2019, 06:15:20 PM by SeaWalnut »

scashaggy

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Re: Greenhouse Heater Suggestions - Plus construction Photos
« Reply #24 on: November 11, 2019, 08:03:29 PM »
I don't know anything about heat (I'm in Miami); but have you considered a kerosene heater?  As stated, I don't know pros/cons, just throwing it out there.

 

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