Looking for some advice here. I have a commercial greenhouse growing hydroponic edible herbs in Hinckley Minnesota. I installed a central boiler 6048 to help mitigate the cost of propane. The propane furnaces I installed as suggested when I bought the greenhouse were a 250,000 BTU and a 400,000 BTU propane furnace. I was spending upwards of $4000 a month on propane in the coldest months. I have since installed the boiler but am going through wood like its nobody's business. all I have access to currently for wood is a mix of green hardwood. I buy it in 8 foot lengths and cut it down to about 24 inch pieces splitting the bigger ones and leaving anything under 10 inches as rounds. I bought 4 120000 BTU heat exchangers. I built 2 wooden boxes 16 inches deep in a wedge fashion with 1/4 cage fans on each one. There are 2 heat exchangers back to back on each box. Running 1 inch lines on everything. I need to maintain a minimum of 65 degrees at night with a target day temp 75 to 80. My problem is even with that amount of exchangers I really am not seeing the heat I thought I would. Mainly due to the boiler not being able to keep up. If I recirculate water by passing exchangers it gets to 190 no problem. The second I flow through heat exchangers I can barely stay above 110 for water temp. I only get about 4 hours of burn time per full load of a 60 x 48" firebox. Then she's all ash. The dealer thought I would be filling it up to 4 times a day. I am filling 6 to 8 times a day. And I fill it FULL. Running 2 steibel 44gpm pumps right at boiler, one on supply and one on return. Lines configured reverse return style. The dealer really hasn't seemed to be any help with suggestions. Schematic of lines off of manifold and pic of one of the 2 heat exchanger boxes attached. This is my first attempt at anything boiler related. Thanks in advance for any advice or opinions. Mark
Also, please disregard all of the pex you see behind the exchanger. That is from a previous configuration. I now have it reverse return configuration as shown in attachment. And when I stated above "the suggested propane heaters. The company suggested 2 250k btu heaters. I upped one to 400k on my own. So the current exchangers I have in there should total 480k BTU output when water is 180 degrees.
I believe you have undersized the boiler for what you're trying to do. You have 4320 square feet of floor to heat. There's no insulation correct? An extra water storage tank to get more water hot may help you.
I have to wonder if your BTU output is limited by the greenness of the wood. You're spending much of the BTU capacity overcoming the latent heat of vaporization. I would invest in a couple of loads of seasoned wood and see if that improves matters. David
Definitely get some dried wood. Last year i burned wet wood from a semi load and struggled to get a good bed of coals or have anything leftover in the morning even all being red and white oak. Now i have dry pine and i can go twice as long. Dry wood makes a huge difference.
Is the temp dropping on the boiler? Is the water circulating fast enough? Its good if your supply water is going out at 190 degrees and coming back at 110. But whats the boiler doing at this point? Is the boiler temp dropping also? If not you may need to speed the water up. If it is dropping the boiler may be undersized
Specs Central Boiler 6048: Door . . . . . . . . . . . . . . . . . . . . . . . 23" x 31" Firebox . . . . . . . . . . . . . . . 60" x 48" x 36" Heat Transfer Area . . . . . . . . . . . 119 sq. ft. Weight . . . . . . . . . . . . . . . . . . . . . 2450 lbs. Water Capacity . . . . . . . . . . . . 393 Gallons Replaces up to 600 gallons of fuel oil per month. Dual Fuel Ready models available. 60 cuft firebox filled 6-8 times per day?
Wow thanks all. This forum is awesome and speedy. Yes I did have A TAD better luck with wood that was drier before but I feel that it wasn't enough to compensate the loss I am facing. Talking to an applications engineer flow should be adequate if not over what it needs to be as far as the plumbing goes. Just wonder if my cheaper heat exchangers are the culprit. I am thinking wood is the place to start and this summer invest in some seriously beefy heat exchangers. Plumbing flow is fine but heat exchanger coils might be too small limiting flow through them. Any suggestions for sources of large commercial grade heat exchangers?
Any more info or sources / pics on how this would be set up? Once I get through March I should be fine for the spring and can implement upgrades in the summer. Water barrels in line in the greenhouse?
Do you need "all" your space? Meaning, compartmentalize your green house, even with cardboard and move all your items to one end if possible. That would be the quick solution and only heat that portion of the green house.
Whoa! I can hardly imagine burning that amount of wood and am surprised that the boiler is even able to burn it that fast. When you say you get a mix of green hardwood, I'm betting quite a bit of it is oak. Yet, it is difficult to imagine oak or anything else burning up that quickly. No doubt what is happening is that almost all the energy being put out is going up that short stack. Contrary to what sales people will say, water does not burn well. The first thing that happens when you start burning a load of wood is evaporation of moisture. That has to be done in order to get the wood to burn. So by burning green wood, you just can not get the btu's that you need and no doubt that blower is running full time just to keep a flame going. One thing you could try if all you can get is green wood might be to try burning something like birch. You still won't squeeze all the heat out of the wood but will perhaps do much better than your present method. Good luck.
I'm afraid you are at max capacity already. Adding extra storage would only help if you had excess heat. If you are good during the day but running out over night this might help. If your just keeping up during the day you wont have the extra btu's to store
When it's sunny out it gets 65 during the day. Without any heat. So I think I may dive more into extra water this summer. That with seasoned wood and better exchangers hopefully I will see improvements. Anyone have any thoughts on upgrading my 1" lines to larger?
my guess is you dont need any larger pipe if you are getting the btu's out of the water. return water is 110 degrees. And your boiler temp is dropping.
Forgot to add on my post before I'm also not blowing tons and tons of smoke out the stack when it's burning with dry wood!
