Heating a greenhouse with poly lines connected to a propane water heater?

[onerha]

I'm trying to figure out a way to heat my hoop houses... it's a couple 12x20' heavy duty car ports end to end with greenhouse fabric over the top. I'm worried about the weather for the next few months getting too cold at night (2400' elevation).

What i'm thinking is, getting a cheap propane water heater, running one 3/4" or 1" black poly (or pex or whatever would be best) through the raised beds (maybe 6" under the surface) and then draining into an olive barrel to be reused again. Setting a timer to kick a pump on every hour between 11pm and 5am (or whatever interval it would end up being to keep it warm enough).

My thinking is that the hot water running through the tubes would keep the roots nice and warm and the soil would capture and store the heat as well, hopefully helping to maintain a bit more even of a temperature.

I'm working with very little electricity available... hopefully will have a nice batter bank to power the pump and timer...

My main questions would be:

1. is the main concern with the colder weather the roots or the exposed part of the plant freezing?

2. Any recommendations on a pump size or line size?

3. Do you think that a 3.4 gpm water heater would heat enough water to fill the tubes? Since there are three rows of raised beds I'd probably run one line through the middle perpendicular to the beds and have a line T off in each direction down the bed.

4. I'm also debating stretching another piece of green house fabric over the top of the plants, maybe at about 6' (where the carport starts to angle up to the peak) so that the heat would be trapped lower to the plants

5.Does anyone know if the propane heater exhausts carbon dioxide or carbon monoxide? If it's carbon monoxide, does that help the plants at all? If the propane water heater would also double as a co2 generator it might serve double purposes...

 

[GP73LPC]

the plants will be affected before the roots... the ground retains heat much, much more than the air around the plant....

i don't have an answer for you, but am interested in what ideas people may have...

incandescent lighting can provide heat, but with a photo-periodic plant that is probably not an option...

 

[Hydro-Soil]

1. The main concern is the exposed parts of the plant freezing. Given a warm root zone, plants can grow up through snow and survive mild frosts. Too cold and you'll still get frost damage as the cells in the leaves burst from the water freezing in them.

2. No real clue but would guess around 1/2" - 3/4". You'll want to insulate the pipes between the beds to reduce heat loss and have a strong enough pump to exchange out every half hour?? You'll have to do some tests....

3. Don't know but I highly recommend plumbing the return directly into the heater mains inlet... this way it keeps recirculating and the heater is constantly trying to maintain the temp.

4. Yes, lowering the amount of space that needs to stay warm will help, as well as give an extra barrier between the outside air.

A forced air propane heater can be rented from most rental outlets and the plants won't mind the extra co2 for a bit. Just remember that you're looking to take the chill off, not turn it sub-tropical.

Good luck with it and....

Stay Safe!

 

[2uptown]

to help keep the heat in at night pick yourself up a magni-clear inground pool solar blanket. a 30 x 50 will run you about $350 to $400 delivered. its 14 mil. thick and resembles a huge piece of bubble wrap. it will keep in the heat better than anything else out there. i simply attach mine over the poly cover. no need to take it off during the day, just face the bubble side against your poly to prevent any unwanted snags. as far as the geo-thermal idea i run a propane pool heater to 1 1/2 inch galvanived pipe on 12" centers at the bottom of my raised beds. you can find pool heaters that do not require any power to operate besides the pump to circulate the water. the pump is the killer..... my system is a closed loop set at 60*. the heater turns on and off as it senses the temp of the water. i can keep my 100' x 8' x 2' raised bed 60* all winter long running a 100,000 btu propane pool heater. once its set up it works incredibly well and efficient. yes you will burn some propane but who doesnt at 3500' in norcal during the winter. get your self a propane generator to run your water pump and you are all set for a huge winter harvest or better yet garden year round. anyways your on the right track, good luck...

 

[onerha]

Thanks for the reply.

1. it shouldn't be getting too cold outside so i would think between the greenhouse itself and a warmed root area, that the temperature near the plants would hopefully stay above freezing (thats the main purpose of what i'm trying to accomplish obviously.

2. my raised beds are approx 3' wide, 1' deep. would you guess a single line down the middle would be sufficient or would you loop it through each bed twice?

3. My thinking with returning the water to a reservoir is that it would also act as a heat sink, albeit that probably wouldn't help too much and the size of the olive barrel inside the greenhouse may be an issue. Perhaps a closed loop is best.

4. thats what i figured.

5. any idea if the exhause is carbon mon/di oxide?

 

[2uptown]

i think propane creates co2 but not entirely certain. just thinking of the co2 burners the indoor folks use. i love to burn propane, my generator, my heaters, my stove, my shower..... dam im hooked on propane. i have no grid power so its either propane or diesel......

 

[joe fresh]

yes propane burning makes co2, so does natural gas....not only safe for plants, but they love it, just be sure the co2 levels dont get too high, 1800-2000 ppm is absolute max otherwise the stoma will close up and the plant will stop to transpire

 

[onerha]

good call on the bubble wrap pool cover... do you think it'd let enough light through for starts as well?

Are you able to do a green house cycle through winter using your heating method? I've thought about that before since the daylight is so short, if you could veg indoor to a foot or so and then just transfer to the greenhouse for flower since the daylight is near or less than 12/12.

Do you think the pool heater is necessary? 1 1/2" pipe seems nice but seems like it could be overkill to me... (at least with my sized greenhouse?) The propane water heaters are quite less expensive than a pool heater but also do quite a bit less water.

 

[2uptown]

the pool cover will let in plenty of light, just make sure you get the magni-clear brand/style. oh yes and order the clear and not the blue ;0 i can and i have ran my greenhouses year round. did i mention im at 3500' in norcal. the biggest problem with vegging indoors then moving them out to the green house is the temp/conditions. i have seen it time and time again when the temps/conditions are not spot on from veg inside to the greenhouse the plants go into shock and the yields, quality go to poop. just nail the transition and you will be surprised on how well you will do. in regards to the propane water heater are you thinking about the floor standing models in say a typical home? if you are those particular models heat water fairly slow and will not work to keep your raised beds warm. the only other option i have seen work well is a tank less hot water heater from bosch. the model to get has what they call a hydro-ignition. it requires no power to operate but instead senses the flow of water to ignite. get a pump that does no more then 10 gallons an hour and you should be fine. of course the length of pipe in your raised beds will effect the heating capabilities. definatly run a closed loop system. it might take a few days to heat up your beds at first but then you will be able to maintain the temps fairly easy. if this is something you plan on doing year in and year out then i would highly recommend insulating your raised beds from the ground. you can do this by getting sheets of insulation from home depot. they come in different thicknesses and sizes i believe. i went with the 1 1/2 inch 4'x8'. i placed them on the inside of the raised beds on the ground and placed my planting mix on top of it. doing that alone will help tons. i think its made of styrafoam or something. i do not know if it harms plants but i have seen no ill effects in years of usage. i am an organic grower and had issues with burying styrafoam in my garden. i figure if it takes thousands of years to break down then i should be all right. i will remove it before i die or sell the place, i promise:}

 

[onerha]

does the pool cover heat the green house when the sun is up? Like does it make it TOO hot?

Correct, I would use a bosch style on demand heater with the hydro light. Most of those heaters produce 3.4 gallons of hot water a minute... they usually need a flow of 1.5 (or so) per minute in order to ignite. But in any case, yeah a nice and slow pump to ciruclate the water.

It's nto a year round thing... just mainly for the next couple weeks. The raised beds are elevated off the ground already so it wouldn't be too hard to slide some insulation under them... My concern would be drainage I guess... It obviously works fine for you though.

I'd rather avoid the cost of one of those pool heaters... (I almost lucked out and found a used on on craigslist but it's for natural gas and not propane - $275).

You say you have seen this setup work with an ondemand water heater? Do you know if they used steel pipes or just a pex or poly?

 

[2uptown]

the pool cover keeps the heat in, i have not seen increased temps while the sun is out. usually i need to vent during the day to keep my temps/humidity in check. the on demand system used 1/2" pex.

 

[Midnight]

Have you ever tried heat tape? You bury it in the soil, works off of 120v and uses around 500 watts (100 foot cable).

http://www.charleysgreenhouse.com/8...ng-Cable-100-ft----Variable---P5595--100-.htm

 

[supermanlives]

i installed hydronic heating in all my greenhouses. farmtek .com for all your needs. but i had a 300 gal tank. i moved tho and sold my business. worked great tho . mine was wood fired closed system. i heated the air,water and soil. i might have some pics in my old gallery

 

[joe fresh]

why not use solar to heat? initial cost may be a bit more but after that its free heat
[YOUTUBEIF]EEWD6D7Vwbg&feature=fvsr[/YOUTUBEIF]

 

[onerha]

Have you ever tried heat tape? You bury it in the soil, works off of 120v and uses around 500 watts (100 foot cable).

http://www.charleysgreenhouse.com/8...ng-Cable-100-ft----Variable---P5595--100-.htm

This might be a good solution for city folks, or the people that run the loud ass diesel generators... but it's not an option for me! 500 watts is more than i run my entire house on!

 

[GP73LPC]

why not use solar to heat? initial cost may be a bit more but after that its free heat
[YOUTUBEIF]EEWD6D7Vwbg&feature=fvsr[/YOUTUBEIF]

link no good...

i would like to see this video however...

 

[onerha]

@supermanlives: I believe what i'm attempting to create IS a DIY version of hydronic heating. I'd run PEX or similiar tubing in a closed loop to an on-demand propane hot water heater. Every XX minutes a small recirculating pump would kick in and move the water around, thus activating the hot water heater, keeping the water warm as well as the raised beds the tubes are in.

@joefresh: can you elaborate a bit on solar heating? The link in the youtube video doesn't work.

 

[onerha]

Another thing just popped into my head... I dont actually do the starts in the raised beds... Raised beds are for light dep, once the full season ladies go outside... the starts will actually be in 3 or 5 gallon plastic bags sitting on top of the raised beds.... uptown (or anyone else) do you think this heating method of running hot water through the raised beds themselves would still work?

 

[2uptown]

so the question is will the warmth of the raised beds keep the root zone of the potted plants from getting too cold. of course. by simply raising a potted plant off the floor, on say a pallet in a heated greenhouse will in effect keep the root mass warmer.

 

[supermanlives]

i would make holes in the beds and set the pots in them . then the temps will be better. dont just sit em on top. welll thats my advise . been there. i might have some pics of my gh setup in my gallery . i aint sure as i cant view my old gallery anymore. for best results i would wire in a temp sensor. then you would be set. they make plug and play ones. farmtek.com for all your needs