# Small propane heater for greenhouse



## extrafu (Dec 11, 2018)

Hello,

I have a greenhouse which is attached to my garage. The greenhouse is 24' x 16' and its insulation is quite high (R38 walls, double-glazed poly, etc.).

During winter time, as we are located in Quebec, Canada, it's getting pretty chilly in there. We only want to maintain the temperature to like 5-10 Celcius - and not heat the thing at 35C.

I am looking for a small propane-based heater, vented ideally. The electricity consumption should also be quite low because we are entirely off-grid.

Any recommendations?

Thanks a lot!


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## DAKSY (Dec 11, 2018)

Are so far "Off-Grid that you will have to travel to fill your LP tanks?
If not, talk to the LP Delivery company. They can probably recommend 
a unit that will meet your needs...maybe install it correctly, too...


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## Gasjetruss04 (Dec 11, 2018)

Rinnai Direct vent is your answer. They have 4 size heaters that modulate heat.


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## Gasjetruss04 (Dec 11, 2018)

I just installed one in a Florida room. The couple was ecstatic how well this medium unit heated and efficient. The stainless vent is attractive and awesome technology.


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## extrafu (Dec 11, 2018)

@DAKSY Thanks for your reply. I've got a 500 gallons propane tank so delivery here is once per year 

@Gasjetruss04 Also thanks. I've looked into the Rinnai models. What I fear is the oxydation of the unit - being in a green house the humidity is high and potentially acidic too.


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## Gasjetruss04 (Dec 11, 2018)

extrafu said:


> @DAKSY Thanks for your reply. I've got a 500 gallons propane tank so delivery here is once per year
> 
> @Gasjetruss04 Also thanks. I've looked into the Rinnai models. What I fear is the oxydation of the unit - being in a green house the humidity is high and potentially acidic too.


Not sure seeing they already are a condensing heater with all stainless components. And the acidity of the condensate is quite high.


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## DAKSY (Dec 11, 2018)

extrafu said:


> @DAKSY Thanks for your reply. I've got a 500 gallons propane tank so delivery here is once per year
> 
> @Gasjetruss04 Also thanks. I've looked into the Rinnai models. What I fear is the oxydation of the unit - being in a green house the humidity is high and potentially acidic too.




If there is no exposed, unprotected metal, I don't think oxidation will be an issue.
DV Units draw combustion air FROM & exhaust TO the outside.
It's a sealed combustion system...


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## extrafu (Dec 11, 2018)

Ok thanks for your replies guys. I'll try to look at a wall hung one.


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## wooduser (Dec 11, 2018)

I'm ALMOST ready to recommend a small unvented heater,  which would also contribute the water vapor from burning the gas to keeping the greenhouse space  humid.


You might even be able to get away with a camp style unvented heater mounted on a tank of propane inside the greenhouse  ---perhaps a couple of them and you could decide how many to operate based on weather conditions.

But I don't know if unvented heaters are approved by the manufacturers for such locations,  and the danger from poor combustion and carbon monoxide hazards might be elevated in such a use....


What sort of BTU input do you figure you need?


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## extrafu (Dec 12, 2018)

@wooduser Many thanks for your reply.

I've so far experimented two products, all propane based with for now, a BBQ propane tank. First, a 15-20K BTU tank top heater. It wasn't really efficient in heating the greenhouse unless it was running for many many hours. Plus, the smell was disgusting. Then I purchased a 140K BTU forced air heater (portable, for construction sites). That thing is insane - very noisy and it heats the whole thing in 5 mins but still, it smells a tiny bit.

So I think I would be looking at something in-between, maybe 30K to 40K BTU.

Note that I do NOT plan to install this myself, I'll ask for a professional. But, I want to recommend products to him.

Thanks,


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## wooduser (Dec 13, 2018)

Just guessing,  but the smell from the heater was probably due to chemicals contaminating the combustion air.  You could test that theory by moving the heater into a space with good clean air and see if the odor goes away.

But that suggests that unvented equipment is not a good idea for your needs.

I would suppose that if you look through an index to gardening magazines or a book on greenhouses,  the issue of suitable means of heating them would be discussed in some detail.  That might be a good place to look for advice.

I've seen lots of greenhouses heated by hanging unit heaters vented out the top of the greenhouse.


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## k0wtz (Dec 15, 2018)

extrafu said:


> @DAKSY Thanks for your reply. I've got a 500 gallons propane tank so delivery here is once per year
> 
> @Gasjetruss04 Also thanks. I've looked into the Rinnai models. What I fear is the oxydation of the unit - being in a green house the humidity is high and potentially acidic too.





extrafu said:


> @wooduser Many thanks for your reply.
> 
> I've so far experimented two products, all propane based with for now, a BBQ propane tank. First, a 15-20K BTU tank top heater. It wasn't really efficient in heating the greenhouse unless it was running for many many hours. Plus, the smell was disgusting. Then I purchased a 140K BTU forced air heater (portable, for construction sites). That thing is insane - very noisy and it heats the whole thing in 5 mins but still, it smells a tiny bit.
> 
> ...


I can just about bet trying to heat it with propane is going to be expensive.  I guess it depends if you are planning to sell some plants to help your utility expense.  Maybe an industrial type hung heater with blower will be your answer like a warehouse uses and vented!


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## wooduser (Dec 15, 2018)

<<@Gasjetruss04 Also thanks. I've looked into the Rinnai models. What I fear is the oxydation of the unit - being in a green house the humidity is high and potentially acidic too.



That's a good point.  The very moist air typically air,  often contaminated with chemicals and such,  is bound to be hard on heat exchangers,  even ones that are vented.  Indeed,  the unit heater's I've seen in greenhouses tend to look rather down at the heals.

But that's probably inevitable in such an environment.

You might try looking up in gardening magazines and such to see how others heat their greenhouses.  There may be some useful ideas out there someplace.


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## extrafu (Dec 18, 2018)

My propane installer recommended me a Sterling GG 30. Looks pretty OK.


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## KeithO (Jan 3, 2019)

Radiant tube type garage heater maybe ?   Vents outside, used in shops and manufacturing facilities.  Cheap.  Can buy at your local big box DIY store, install yourself and save money...


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