Author Topic: Greenhouse heater  (Read 7218 times)


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Greenhouse heater
« on: December 22, 2020, 10:00:19 pm »
So I know the norm with any forum is to have a bunch of read time and not be that newbie. But I can’t find anything on the net about heating a greenhouse with a waste oil furnace. I found some YouTube videos but didn’t find them super helpful.

Here’s the skinny-

Wife and I are opening a large scale nursery/greenhouse retail business. I’m currently heating her 30x40 propagation greenhouse with natural gas and that thing runs constantly!

I want to explore waste oil to heat our 4,000 sq ft greenhouse that’s being put up this spring.

I spoke with linaire today and they said the ducted units don’t put off a smell or oil residue. Is that true? I can’t have a greenhouse full of plants get nasty.

2nd question— I live in a rural area and a lot of the shops burn their own oil. Is it hard finding used oil? I have an in with the local Walmart and I’m going to see if I can get theirs. But it’s doubtful.

3rd part— can a linair system burn waste cooking oil? I understand it needs to be well filtered. But it says in the instructions that they don’t recommend cooking oil. Reasons other than epa regulations? I feel like I could get cooking oil easier than motor oil with all the fast food joints around here.

Also, am I going to be working on this thing constantly? Being a greenhouse if it went down it would be bad. I plan on putting in a backup LP unit but if it were to go down when it’s 10 degrees outside for a week it would cost me $250-400 a day to heat it with LP. So I don’t really want a system that will go down.

If you couldn’t tell I’m a newbie to waste oil.


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Re: Greenhouse heater
« Reply #1 on: January 09, 2021, 10:17:50 pm »

I have no knowledge or interest in commercial heaters. I build all my own burners and have helped a few people now convert heaters for heating greenhouses. I remember one guy in canada that simply replaced the gas burner in his existing heater with one of my design oil burners and it worked perfectly. He saved a literal fortune on LPG and it was a real boost to his family business. they also extened their growing season of summer crops all year round and that was a boost because they were the only fresh supplier for hundred miles around.

His brother owned a Truck service centre so had a great supply of oil . He took some from other places as well as word got around so it was never an issue for them.

I don't know if the commercial units use a heat exchanger or are direct heating, I would suspect the former so as not to fill the greenhouse with CO2. If they use a HE as likley, the combustion products never get into the greenhouse, it's just the air going in, being heated and going out so no way for it to be contaminated.

That said, my burners run on an oversupply oxygen principal so burn clean as the eye can see and the only smell is that of warm air and donuts as I prefer Veg oil myself. There may be some very fine ash but id tend to think that would work as a fertiliser for the plants than be harmful or detrimental if it was discharged into the GH.

The guy I helped in Canada bled some of the combustion gasses into the GH to raise the Co2 Levels instead of using the compressed gas he had been before. Hooked up his existing computer control and just used a damper in the flue to bleed off some of the gasses  up near one of the fans to disperse it around. Last I heard from the guy he had taken over the farm next door and expanded the operation and had a guy part time looking after the oil handling and fuelling the burners which he said was worth while 50X over.

I don't know how hard it is to find oil in your area.  I can get an endless supply of Veg or engine oil.  People I talk to around the world have different experiences and rules and overbearing and stupid regulations often mandated by vested interests such as the cowboy  grease collectors.  The BIGGEST determining factor I see is how big the persons balls are looking for the stuff.  If one is going to worry about any BS licences and regulations and get all pedantic about following " codes"  then it's plainly not going to work for these people.  Likewise if one is too timid to ask and push to secure supplys, disappointment will also follow.

I rarely ask for oil because I understand the other side. It's a waste product and a detriment to restaurants and they just want it disposed of in a way that won't come back and bite them on the arse nor think they have the problem taken care of only to find they have bins full of the stuff.  Much the same with workshops and engine oil.  I remember going to a favourite strip of restaurants where I just used to go and get the oil and this guy coming out and asking if I was taking the oil. I said yes and he shot his hand out and thanked me. Next thing he lead me next door and was speaking to the guy in Chinese whom also seemed very happy and said will you take my friend oil too? He opened a shed and there was over 1000L sitting in drums and it was all beautiful stuff.  Veg oilers Christmas and Birthday with a winning lottery ticket all thrown in.  never had ANYONE complain about me " Stealing " their oil as some of the soft of heart and head put it but I sure have had a lot of people thank me!

As I have always said, sales Skills is an invaluable life skill and been very helpful to me in this regard. When I have asked for oil mainly in the early days, I have frequently been told the place had a collector already.  Probably true but from the  other persons POV, they don't want to be left hanging with the stuff or have problems so easier to say no.
My reply was to look forlorn, say something like, " The collectors get it all and leave none for anyone else" and then ask if they would give me or allow me to get a bit of it. This changes the dynamic because they can then give you " Some" and have the safety net of not burning ( pardon the pun) their regular pickup and disposal service. Of course a "BIT" is open to interpretation and I took all the good stuff they had leaving the dregs and fat at the bottom for the collector.  Never had a problem with that either.

Another thing that's an angle is a lot of collectors come at inconvenient times. Pulling up trucks in sight of patrons, making noise, smell and often wanting staff to move cars.  they never see me. I come late at night when they have gone home or early in the morning before they get there and there is no problem, no mess and their  drums are never near full. You quickly get an idea of their output and know how often to go back.  Can be worth a comment, " do the collectors come reliably and at convenient times because I'm happy to come and you'll never see me or have to worry about me being reliable."

This line " Could I have a Bit?"  worked really well for me with about 8 out of 10 saying yes.  If you have young kids or can borrow some, take them with you and order some takeaway and strike up a conversation.  Many people are fascinated with the story and excited to be a part of it. Have some pics on your phone to show them your setup.  One of my best referrals was a local club I went to with friends for Dinner. Spotted a pile of drums out the back and at the end had a conversation with the manager.  They didn't believe I was running my car on veg oil till I pulled round to pick up the tins and they could small the exhaust.  The whole staff was out there to see the car that was running on cooking oil.
Next thing the lady is ringing me saying she knows someone that has a restaurant that they are having trouble getting rid of oil and then she knew a bloke and within a month I have 6 new places giving it to me.  I got quite a few free meals out of that too as the people were so happy I was taking it away for them and fixing a big problem they had been dealing with they wanted to thank me and make it worth my while.  I felt they were helping me and they felt the same so it was good all round.

If you get a place, take them round some of your produce now and then as a think you. Might even turn them into customers.

Again, know nothing about commercial systems but in my experience, Veg can be slightly harder to burn than engine oil although I'm so used to veg I tend to have to get my head round engine oil. Not that I like it much. Black, stinking, staining filth that is so much harder to clean up than veg. Get it on your hands and you can wash and shower  and it's still there for days.  For Veg I clean up with Potasium or Sodium hydroxide ( drain cleaner or soap base) and all good. I do get WVO from my brother in law whom has a battle ship size boar and saves it for me ( haven't got the heart to tell him I don't really want it) and the other occasional well meaning person so I do run it now and then and do notice the difference.  Burned properly, one does get the same warm air aroma only although from what I have seen, the ash content is slightly greater.

The burning characteristics of WMO and WVO are different but it should be possible to Tune the burner in the air fuel ratio to burn veg better.  The problem the manufacturers are probably worried about with veg is likley gelling.  It will thicken up much more in the cold than engine oil.  Ways around this, mix in some Kero/ jet fuel or even Turps  and it will lower the gel point and keep it a lot thinner. I would NOT recommend any aromatic like Petrol  though that gives off a vapor.  The guy that used it in his greenhouse had a couple of "Day" tanks so the oil was pumped in and allowed to warm up before that tank was switched to so the oil was of a pretty consistent viscosity even though he was using engine oil.   

I would also not advise mixing engine oil and Veg UNLESS you do a test batch in a bottle of the same ratio you intend to use.  Shake it up and let it settle at least the time it would be in your tank, double to be safe and see how it goes.  SOME combinations will separate or even glug up and cause fallout and some are fine. There are a lot of different veg oils, corn, canola, sunflower, etc and mixtures there of just as there are different additives in motor oil and other things that may be present such as transmission oil.... which is an EXCELLENT fuel if you can get it from a transmission shop.  Doesn't gel like veg in fact stays thin past freezing far as I know, easy to clean up, easy to pump around and burns well. See what you have and how they react before Mixing or put a stirring arrangement in your tank to stop it settling out.

How much maintence really depends on what you have and how it's set up.  I would have zero fears about running one of my burners non stop for a month or pretty much indefinitely.  They have NO build-up what so ever so the only thing might be the HE might need a bit of a blow out or brushing down depending on what type it was and if it caught any ash Build-up. Other than that, While there is power to run the blower and pump and fuel in the tank, the thing should run untouched till it burns through. From experience I can say that's going to take years.

From what I have read of Commercial burners they do require periodic maintence so look up what that is. Most of them have pumps and nozzles which wear and clag up so see what the servicing intervals are and what can be done by the user.  Should be pretty simple from vids I have watched though.

I have converted a couple of gas water and Spa heaters to oil just by removing the gas burner and putting in one of my oil burners.  Only thing to watch is you don't overpower them which is real easy to do.  I can blast 500KW  easily in the space of a 100 Kw burner so the challenge for me is keeping the output LOW enough.
At a pinch, you could make your own heater by simply putting the burner at one end of the greenhouse, running some Pipe above it and along to the far end of the greenhouse and having your fans blowing on the pipe along the way to take the heat off and then exit the gasses out the far end of the structure.   Duct the blower intake from outside to stop blowing your heated air away and increase efficiency. Then again if you need outside air circulation.... maybe utilise the energy the fan uses to help with that.  You would probably want to Check the pipe every so often for fine ash build up and you could probably clean it by shoving a compressed air line down there Or letting a leaf blower run a while. If you put the pipe in sections with sleeves so you could take each length apart, even easier.

You can Look on YT for my user name and see the laughable Vids I made but they do have a lot of serious how to infor including how to build very simple and effective burners.  A LOT of people have done them now for all sorts of things.  I think the last one a guy showed me was for making cement and drying sand, another guy in Argentina used one in place of the gas dryer for grain, countless in workshops and garages and some even for heating water in pools and Places like resorts with high heat demands.

I have just done a spa heater I got for free because the electronic controls were shot. The Heat exchanger itself was fine so I removed the gas burner and controls, put in a oil burner that uses a timed pump for fuel supply and oif course has fixed airflow from the fan and that's it.
You may be able to find something similar to convert and remove any risk or fear you may have of it not working.

Chances are though like a lot of other people you might Improve or build a bigger one but you won't be disappointed especially in the hugely lower running costs and profitability your business will have without this major expense.



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Re: Greenhouse heater
« Reply #2 on: January 09, 2021, 10:56:30 pm »

One other thing to add to the already long and boring rant is something I'd probably do thats a little out the box but could be a LOT better way to go.


Don't burn the fuel in a burner just for heat, Burn it in an engine driving a Generator.
You pull the waste heat out the cooling and exhaust system and get the power as a bonus. You can feed that back to offset your power usage or divert it to resistance heating where you could say heat water to circulate back around at night to eliminate running the engine unattended.

This is a very efficient way of going about things and has the potential to be cheaper than a commercial burner if you can source an engine or 2 at the right price.  All you really want is something that will meet your heating needs which can easily be worked out and is mechanically instead of electronically injected.  Most diesels pre 2000 are like this and a lot of newer ones still are as well although less now due to emissions. May also be possible to fit an old pump on a new core.

The only drawback to this idea is your fuel needs to be filtered  better.   Burners don't need much more than straining though a couple of layers of cloth to get the chunky bits out, engines need much cleaner fuel.  That's not at all a problem is you set up right.  I can process 200L of oil in as little as 30 Min for veg, a LOT quicker for engine oil. Instead of a 200L drum I use for processing which meets my needs, would be no problem to upsize to a 1000L IBC and scaled up wouldn't take much longer to process that with bigger pumps and more filtering.

My costs to filter about 2500L of oil are around $10. $8 for a filter I change pre emptively anyway and I over allow a couple of bucks for power. That's cheap fuel and well worth my time.  Just built a processor for my mate whom has a tree felling business to run all his machinery in the yard on.  He's very happy with how it's going and the savings he's making.  His mechanic spends about 10 min in the morning loading the processor and switches it off at whatever point later on.  If he has time he will spend another 10 min pumping the finished oil out and reloading the processor and  setting it going again. It does not need a minutes hands on time in between.
If he has the time He may reload several times and if hes busy he doesn't touch it.  They have a reserve now so works real nice.

You could make a LOT of power with the amount of heat I envision you will need so it may be possible to sell any excess back to your utility and make a second income stream there.  Other way is use the power for heating and you could downsize the setup accordingly.
Crunch the numbers, find out the info and see which works best for you.

The only other thing I would strongly suggest with doing this is run a very basic water injection system.  I was banging on about this 20 years ago and basically being called an idiot.  Now I look on the veg fuel forums and everyone recommends it as a basic part of of veg fuelling.
Water injection keeps any residues and build-ups at bay and keeps the engine clean. The biggest danger with waste oil is incomplete combustion that causes the rings over time to coke up and stick which results in the engine loosing compression and needing  to be torn down.

Water injection prevents this 110% guaranteed. Many ignorants scoff at the idea of putting water down the intake of an engine but it was done on loads of high performance piston aircraft, ships and many other applications. BWM even put it on their cars for a while about 10 years ago.  It has a lot of benefits but the one thing often touted that it will not do is better fuel consumption.  It will keep engines clean, stop detonation, stop pistons melting in high load situations, add power ( that and the meltdown prevention was the main thing it was used for in aircraft )  and is a great all rounder preventative of problems.

You do NOT need some expensive 500PSI commercial system that sprays a micro mist fog as touted by the guys making systems for go fast vehicles, just a constant metered drip into the intake is all that is needed for cleaning purposes.  In my vehicle I do all sorts of things that should have killed the engine years ago from high boost and fuelling to running straight oil all year round and NEVER had a problem.  If that was just luck I would have won the lottery 10 times by now but seeing I haven't, must be the WI working. I also add alcohol to the water to give the thing a big power boost but you would of course not need that although it is effective for Cleaning out used engines that haven't had the WI treatment before a lot faster.

If done right, you don't NEED WI with waste oil fueling but  given you can set it up for literally $20-30 and the safety net and benefits it provides with virtually zero running cost, I think a person would be mad not to put it on an oil burning engine. More people use it just for diesel fueled anyway. All the high performance truck and tractor pullers out there use them and Banks performance parts have a heap of systems and I think Holley does too. 

Anyway, something else You might like to look into that's a bit left of centre but entirely doable. There are commercial co gen systems out there so you could compare the features and benefits and costs of these to a commercial heater system or  DIY it would would be not much more than moving the radiator  of the engine to inside the green house and tieing in the electrical side wherever you wanted to use that.