Using burning alternative to get longer burns

[Kyle G]

We have a 6500 square foot green house. We fired up our Garn 11/20/10. And ever since we have had a lot of sleepless nights. Grant it we have 20 below weather at night sometimes. This is our only source of heat and I was was wondering if there are any tricks to get longer burns. One thing we recently just incorporated is making one bay cold crop at 50 degrees. And this bay is sealed up from the other 2 bays. Next year we plan on making 2 bays cold crop. Leaving only 1 bay for hot crop at 67 degrees. Until then me and my team are worn out. The green house does have a low R value but we have a shade curtain and it is sealed up as much as possible. Is there a way to use lava rocks or something you can do a last burn at midnight and then the rocks would maintain the heat for a few more hours? Please let me know soon. I can't afford to hire anyone else to do a night shift. We do love the garn and that it is eco friendly. We just need more sleep.

 

[leaddog]

Sounds to me that you need two garns. If you are useing all the btu's from one putting lava rocks won't help cause all they would be is storage and there isn't any btu's left to store. It sounds like you are having to continuos fire to keep going so the storage of water isn't doing you any good. You need more fire power so two would help.
leaddog

 

[pybyr]

How is the heat emitted into the greenhouses? I am guessing that it's by Modine-type radiator/ blowers that heat air and blow it around. That's inevitably going to leave you with hot air at the top of the greenhouse, where you'll have the greatest losses and it'll do the crop less good. I've heard of people putting radiant heat in/ under the growing medium as a way of getting heat to the growing plants with less heat use/ loss. I realize that that's something you probably can't do right away, but if you can find ways to make each BTU from the Garn go further, that'd gain you some shut-eye. Good luck.

PS, back when I was a teenager, I had a job where I became responsible for the heat, automated watering, etc. systems of a greenhouse operation. That house needed air circulation for other reasons (fungus on plant cuttings) and I improvised an air circulation system using a cast-off furnace centrifugal blower hooked into a plywood stack. That one pulled from the floor of the greenhouse and sent it out an inflated plastic film tube running lengthwise along the top of the hoop. In your case, as a band-aid, could you do something similar but pull from warm air at the top of the greenhouse and push it out down low- or put in some other arrangement to achieve the same result? It won't work a miracle by itself, but it might be one part of a multi-part solution.

 

[Frozen Canuck]

Agree with Leaddog, unless you have system/distribution or wood moisture content issues you are using all the btu's the system can provide. So you have basically two choices lower the load through insulation or a reduction in space heated or increase the btu's supplied. Perhaps if you wish to post a description of the distribution system (how you warm those plants) some of the members may be able to suggest improvements that may satisfy your needs without the expense of another heating unit. The green houses in my area are going now too but the btu needed per sq ft are ...huge to say the least. Best of luck.

 

[heaterman]

There is no better heat storage medium than water when it comes to soaking up and releasing btu's per pound.

If you can find a cheap 1000 gallon tank of some kind and graft it into the piping you could gain some storage capacity that way. It will give you longer off times assuming the your load is not so big that the Garn can't pick up the green houses + the additional storage. Sounds to me like you are at maximum output if you have a fire in the Garn continually.
What elevation are you at? That is going to have an effect on the actual output of the Garn (or any fuel burning device) also.

 

[Kyle G]

I am very impressed on how quick everyone has replied. We are using the blower radiator heaters. 6 of them 2 per bay. They do blow down and we have fans that circulate the heat also while the shade curtain holds down the heat. We also have the radiant floor tubing. We only have it set at 75 degrees since the plants are on the floor. We are at 7,800 feet above sea level. Our ranch is out in the open and it can get windy. So let me ask the rest of the Garn users. How often do you stoke your Garn? I know everyone has a different situation but im just curious. Also has any one tied in hot water Solar?
Thanks again for the responses. I will try to look into keeping the heat lower.

 

[Fred61]

Is your radiant floor tubing set in wet soil beneath the crops? If it is and there is nothing insulating it from the surrounding soil, you are trying to heating the whole state of Colorado. Your heat will be syphoned off faster than you can make it, even with 2 Garns.

 

[Como]

I am familiar with the San Luis Valley, it can get cold, really cold, a high alpine valley, used to drive through it on 285 to Durango during the winter.

What did you heat with before, I am inclined to wonder how you can keep a greenhouse going down there at this time of year, we are a bit higher but at 6 am it was -37, must have been getting on for that where you are last night.

-85 delta, 6500 sq ft, no R Value to think of, the heat load must be out of this world.

The only thing I could suggest is using hardwood, presumably you are burning aspen/pine?

 

[ISeeDeadBTUs]

One thing I enjoy more than wood . . . Plants!

First off, dumb question . . . How'd you heat it B4 the Garn?

 

[Kyle G]

no the tubing is set in concrete. We made the choice of concrete to control the bugs.
It partly me being stubborn and wanting to grow hot crops. Because then the whole space would have to be at least above 40.

 

[Kyle G]

This is our first year growing in the winter.
I bought the ranch in 2007. Built the green house in 2008.
Got water and electric in 2010 and started growing.
Then we finally decided on what to heat the green house with.
I like the fact its so eco friendly. So many G house people tried to talk me into propane.
We use pine. Very little cottonwood cause its free.
Next year we are getting mitigated pinon which is great.

 

[ISeeDeadBTUs]

Now. about those heat loss calculations you performed when you were planning this operation . . .

 

[woodsmaster]

Do you have insulation under the slab and around the perimiter ? Hardwood like oak, locast, ash, will give better burn times than pine.

 

[Rick Stanley]

Hi Kyle,
So far I only am heating my home with the Garn. We have plans to do a small greenhouse later, but not all winter, only for season extension. I have to hustle out to the boiler room pretty early in the morning to keep things warm around here when it gets down below zero. I AM burning hardwood, not the best, but it is hardwood. I can use water down to 150 degrees at 10 below.
My design load is 77000 btu/hr @ 30 below. Even a night when it gets down to only NEAR zero, when I pull probably 50000 btu/hr I can't languish long. But when you start punching your numbers into this baby http://www.littlegreenhouse.com/heat-calc.shtml
minus 30 outside----67 inside-----6500 sq ft it's clear that burn times aren't the issue.

Welcome to the forum!! Hang around here and these guys will help you straighten things out.

Rick

 

[Kyle G]

We did insulate the floor and perimeter footers. Unfortunately no oak here in our valley.
Im actually from Ohio and to get wood when I lived there all I would have to do is go in my back yard.
Now im on ranch land and there arent very many trees except for in the mountains.
Pinon is our hottest burn we have.
As far as calculations we did before we installed the garn. Thats why we chose the model we got.
It puts off 1 million BTUs! Our configuring came well below that.
Thanks Rick for giving that website I will check it out.

 

[Singed Eyebrows]

If you have the 3200 you already have 2 Garns BTU wise(the smaller Garns do not fire at 1 million btu). I would keep looking to insulate, Randy

 

[Como]

3200 has an hourly burn rate of 925,000

At sea level and using hardwood.

Garn do not have a factor for using soft wood and altitude, they do supply a high altitude fan.

I just used that calculator and came up with over 1m btus at -20.

The hourly burn rate is based on hourly refueling as I understand it. I seem to remember a prison that had a Garn and did operate it 24/7, but they had free labour.

 

[Kyle G]

I will continue to try to insulate and find any spots that are leaking heat.
Atleast in Colorado we have lots of sun shine, so day time burning is at a min.
I will prob have to create a night job unless coming up with another source of heat to help the garn..

 

[jebatty]

No way to turn a load of wood into more heat that it has. If you try for longer burns, you will get less btu output. Garn burn rate and rating is based on loading dry white oak, full load every 45-60 minutes. And if you need hot water, 160F+, you better keep that Garn in high burn continuously. You may need someone stoking it nearly all the time, or at least not much time available to do anything else. Garn's are not especially friendly for continuous high temp output.

 

[salecker]

Hi
If you don't have to burn as much during the day,then some big storage would get you a bit of cushion for nights.Given the numbers you are using it would have to be some big tanks.Some of the heating gurus should be able to help with actuall sizes and amount of BTU's stored.
Good Luck
Thomas

 

[Extremebison]

One suggestion to get you through this winter, maybe you can install a couple of wood stoves to get you through this winter. Stocked up at night to help supplement the Garn while you sleep and the morning.

I would look at insulation, it will pay you back time and time again, preventing heat loss would be easier and cheaper in the long run rather then trying to create more heat.

I'm no expert by any means but sealing up the green house will save you so much time and $ you'll be glad you splurged when you realize how little you need to heat the green house.

 

[Como]

I will continue to try to insulate and find any spots that are leaking heat.
Atleast in Colorado we have lots of sun shine, so day time burning is at a min.
I will prob have to create a night job unless coming up with another source of heat to help the garn..

I do not know what the economics are of greenhouse insulation and the crops you are growing.

Sounds like you could go through a cord a day in worst case scenario.

At current CO Propane prices propane costs me 7x more per btu than wood, I expect that to go up to 10x (has been there before). Obviously depends on how you are buying and processing your wood.

You are probably looking at a 500,000 btu Propane boiler for back up which are not cheap and would cost north of $10 an hour to run.

 

[Kyle G]

Good news! After putting in a new circulator pump and sealing many cracks and leaks in the shade curtain the garn seems to be holding its own. I still have more to seal but I think I might be getting to that point of burning at midnight and then at 6. Im going to test it tonight. What sucks is my family is sick and I have garn night.
Good news so far, I last stoked at 7 p.m. and the tank was at 170. My co worker came in at 9 15 p.m. She said the tank was at 185. I betcha my midnight burn is coming.
It is only -5 out right now. Last night got down to -30. We are having quit a artic blast.
Happy burning!
By the way we are growing Basil, Tomatoes, cucumbers, peppers, eggplants, strawberries, amongst many starter plants, flowers, house plants, and wheat grass in the 2 hot bays.
While in the cold Bay we are growing lettuce, Kale, and Chard.
It's great growing in Feb and having fresh greens for customers. I just wish my guys weren't so burnt out.

 

[Singed Eyebrows]

I was going to say "good" now your crop won't go to pot & you had to list what you were growing, lol. I'm getting hungry for a good salad though, Randy

 

[bpirger]

I have a Garn 1500 I use to heat the house. I burn only once a day, two loads of wood, i nabout 3-4 hours. One thing to keep in mind is that the temp on the sensors in the well on front of the Garn is not necessarily the temp of the water you are getting out of the Garn. There's a couple of threads on Garn stratification. WIthout a doubt, I have seen temp differences of about 30 degrees from the fron tpanel meter to what is actually coming out of the supply line on the Garn. Now, if you are burning continuously, I don't think this will happen much. But if the fire is out for an extended period, this stratification will start. Just something to keep in mind....monitoring the temp on the supply line might give more sense to the heat output you are feeling.

My other thought, and it sounds like you have done this, has to be loss due to air infiltration or similar....

Must be a wonderful thing to pick fresh veggies in Jan, after walking through the snow to get to the garden.