Re: greenhouse-tomatoes: Wood boiler system

[Debra Otwell <tomato59@bellsouth.net>]

greenhouse-tomatoes - an email list for growers of greenhouse tomatoes.
Sent by Debra Otwell <tomato59@bellsouth.net>.
-

David Blanchard wrote:

> greenhouse-tomatoes - an email list for growers of greenhouse tomatoes.
> Sent by "David Blanchard" <flyingpondfarm@pivot.net>.
> -
>
> Hello, I have been heating a tomato greenhouse in Maine (producing 
> tomatoes March through November) with a wood boiler for four years. I 
> run 180 degree water through unit heaters to heat the air, and 110 
> degree water through PEX tubing under the plants (tubing is 3/4" 
> diameter). The way you get two temperatures off one boiler is to use 
> two different piping circuits. The high temp circuit for the unit 
> heaters uses water straight from the boiler. The low temp circuit 
> incorporates a thermostatic mixing valve, which mixes just enough 180 
> degree water with the warm return water from the circuit to maintain 
> the desired temperature, in this case 110 degrees.
>
> There are a lot of design considerations, such as circulator pump 
> size, tubing type and diameter, flow rate, tubing spacing, etc. which 
> will differ from greenhouse to greenhouse. An excellent starting place 
> for information is the ATTRA publication "Root Zone Heating for 
> Greenhouse Crops", available free on the ATTRA website at attra.org. 
> In designing my system I also used the book "Radiant Floor Heating" by 
> R. Dodge Woodson, published by McGraw-Hill in 1999, and a booklet from 
> the New Jersey Extension Service entitled "Soil Heating Systems for 
> Greenhouse Production", published by Rutgers University in 1996.
>
> Tomatoes and other heat-loving crops like cucumbers and basil really 
> thrive with bottom heat.
>
> Here in Maine, the economics of wood versus oil looks like this: 
> 100,000 BTU's from oil costs $1.79 (oil@ $2.50/gal., 140,000 
> BTU/gal.); 100,000 BTU's from wood costs $0.38 (hardwood logs 
> delivered @$90/cord, 24,000,000 BTU/cord). Of course there's labor 
> involved with wood, and you have to take that into consideration.
>
> I hope you find this info helpful.
>
> Dave Blanchard
> Flying Pond Farm
> Vienna, Maine
> ----- Original Message ----- From: "Debra Otwell" 
> <tomato59@bellsouth.net>
> To: <greenhouse-tomatoes@Lists.MsState.Edu>
> Sent: Friday, August 11, 2006 1:24 PM
> Subject: greenhouse-tomatoes: Wood boiler system
>
>
>
> > greenhouse-tomatoes - an email list for growers of greenhouse tomatoes.
> > Sent by Debra Otwell <tomato59@bellsouth.net>.
> > -
> >
> > I am considering converting from diesel forced air heat in my tomato 
> > greenhouses to wood burning boiler system.  If I run heat under my 
> > plant containers what type and size of pipe should I use, and what 
> > temp. should the water be?  The boiler I am looking at will heat up 
> > to 180degrees, this temp. would be good for the heat 
> > exchangers/radiators, but I feel would be too hot for root zone 
> > heating.  I cannot find much info. on the web, and thought someone in 
> > our mail list could help.  Thanks! 
Dave, Can you give me a ball park figure on how much wood you would use 
for a crop. I know it is a lot colder in Maine but it would give me an 
idea.  I live in North Louisiana with average winter night temps. in the 
upper 30's low 40's but we do have some 15-20 degree nights.  I have 
talked to many boiler companies and no one can even begin to tell me how 
much wood I might use.  I don't want to come up short in the middle of 
the crop.   Thanks for the info. everyone and keep it coming! 
Debbie Otwell