Modine with out a doubt.

I don't use a heater but if I did then I would choose Modine every time!!!!!

Chris, how do you know? ;)

Nathan,

That is the type I see around here all the time. Getting parts and getting one serviced would be an important consideration.

So perhaps better (more portable) advice would be 'buy whatever everyone else buys in your area'?

If you think about it even ACF cannot decide! They are offering both, so my way of thinking is ACF sells both, makes a profit on both and neither one of them causes them more customer complaints than the other one.

If you trust ACF's commercial judgment in offering both then neither is better/worse than the other. In the end it would be down to initial installed cost balanced against ease of service in the future.

As I said in this area the only small units like that I have seen are Modine so there must be someone local who maintains them.

Now, if I was asked "which heater would you buy for your greenhouse?" without being asked "Sterling or Modine" I would go for an L.B.White custom built greenhouse heater. However in this context it does not apply because their smallest unit is 120,000 Btu/h (get the plus and it will run at 65,000 Btu/h)

If I ever manage to make a living out of growing stuff then I will double the size of my greenhouse and I will be getting an L.B.White heating unit for it.

Conflicting answers? Yes, as I am now then the choice small heater would be Modine. A garage/shop/greenhouse heater.

Larger or commercial greenhouse? Then a greenhouse type greenhouse heater.

As an aside, you want any plants before I compost them? This season has been perfect for an unheated solar structure. The only time I had to use heat in there was when I was transplanting plugs. Because my hands got cold!!!!!

I don't think they'd make it through quarantine :-(

Chris:

After first posting an opinion based primarially upon name brand recognition, you followed later with a far more thoughtful one.

But you were correct in stating it to be conflicting, so I went for another; a professional opinion I thought you might be interested in learning.

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YOU WROTE: "If you think about it even ACF cannot decide! They are offering both, so my way of thinking is ACF sells both, makes a profit on both and neither one of them causes them more customer complaints than the other one."

AND: "If you trust ACF's commercial judgment in offering both then neither is better/worse than the other. In the end it would be down to initial installed cost balanced against ease of service in the future."

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You bet, and no, as much as I like their prices, I do NOT trust ACF to best judge what is most to MY benefit as opposed to THEIR bottom line.

That was why I came to this forum, to seek input from those with no financial interest in my decision.

However, your responses also gave me the right questions, without which there are rarely any right answers.

I contacted the long established H/AC contractor who installed our home H/AC system, and after he compared both heaters, his reccommendation was unequivical:

Sterling: better quality of construction, ease of access for cleaning and servicing the burners, local parts distribution all over the country, including one local to us, and last but not least: better energy efficiency with more heat and fan power.

In toto- so much more bang for pretty equal bucks as to make it no contest.

He did say that the Modines made for larger, commercial installations were very good, but had a very low opinion of the Hot Dawg model, made, he said, to capture the home market with a cheap unit.

So although I have made a different decision as your basic reccomendatiom, I still thank you, for your time and consideration, but mostly:

Your input forced me to THINK, and for that- I thank you most of all.

better energy efficiency with more heat and fan power.

If we are talking about electric heaters, then this is complete rubbish. For greenhouses, all electric heaters are 100% efficient.

Nathanhurst:

Both heaters operate on natural gas.

I am glad you got someone who knows about that size heater to help and advise you. My initial post was a "jump in and pick one" type of post because I couldn't believe your question sat there for 8 days without someone who has a gas heater helping you.

Then Nathan backed me into a corner and I had to explain why given that choice I picked one brand.

After that then I had to think about my dream greenhouse and research heaters. I am really glad you got help from a professional not a dreamer.

Enjoy your greenhouse.

Ah, ok. Well getting _unbiased_ professional advice is usually the best idea. (determining bias is left as an exercise :)

chris: I didn't mean to back you into a corner. I just like to be precise about things. Others might call it overly pedantisisticismical.

Nathanhurst:

No need to apologize for being precise. As it was my question, I am grateful for your insisting upon a rationale for an answer.

Chris:

You wanted to help, and you did. You responded, and set me onto the right track.

Thanks to you both, and keep checking the new posts.

I'm sure to come back with more questions.

Hummm... I believe I already do have another one to ponder: ground insulation, to fight the cold.

Three directions you can insulate in: inwards, downwards and outwards. All have advantages and disadvantages: inwards is probably the easiest - flatten the ground, put down some foam panels, pour on concrete or whatever.

outwards gives you the ground underneath the greenhouse as thermal mass - you instead put the foam around the site and cover with dirt or paving. Downside is that the gruond outside can't be dug in, but you get lots of earth as thermal mass for free. If you put a raised bed on the surface you could dig in that, but be warned that the bed will freeze much more readily in winter (might be good for a tomato bed, if soil freezing kills nematodes?)

Downwards is the most work, but gives you the benefits of both other techniques - you get ground thermal store, plus ability to dig in the garden outside, at the cost of having to dig a trench to the required depth on the border.

Standard insulations are polystyrene foam, polyisocyanurate foam, straw and air gaps. PS foam is the cheapest, polyiso is resistant to higher temperatures, but this is not going to be an issue on the ground, straw is hard to do properly and tends to rot (but if you have a regular supply it can work well with either of the on ground approaches, redone each year. Air gaps are generally too much work.

Nathanhurst:

I never thought of the ground as a thermal mass, perhaps because our frost level is 30 inches deep, but what you wrote makes sense.

I printed out your message, to give to my husband.

However, in our area, drainage is vital too.

Just about anywere within 100 miles of Chicago is on hydric soil, so foam panels on the ground outside of the GH would need to be sloped away from it, but that wouldn't be a big problem.

Lots to think about. Thanks.

Hi birdwidow -- sounds like you are getting the same greenhouse I am leaning strongly toward!

I would like to keep in touch with you as you go along, if you don't mind? I don't know that much, and hope that I don't make too many mistakes -- it's always easier to have someone go before you! :)

my email is plant.babies@gmail.com

IF you plan to take pics, I'd love to see them. For some reason I can't see pics posted directly on Gardenweb, but Links work ok.

:)
regards,
D.

They are both high quality heaters. Modine does a great job marketing their Hot Dawg product. Sterling has a unit specific to greenhouses which is all stainless steel. Visit the link for more info. I would choose either, and base it on price.

Here is a link that might be useful: Greenhouse Heaters

I have a Sterling that has been trouble free for 6 years.
I bought it brand new so I hope it keeps going for many more years.

I was surprised to see my old post back in play after 2 years, but as it is, I'll report.

The Sterling outperformed expectations and contrary to some cautions about having such a powerful unit, it maintained my desired 72 deg. temp throughout our bitter cold winter for a fairly cheap cost and if it turned on/off more than a smaller one might have, thermocouplers are cheap and should be replaced regularly in any case. Mainly, it kept the GH warm, and I reared a lot of delicate tropical fish in it, while the bitter winds blew.

We calculated that it added no more than $300.00 to our heating bills for the entire season and possibly less, as my husband also ran a gas heater in the tractor shed for most of January, and it is not only far larger than the GH, it's also not as well insulated.

He plans to open up the Sterling next week for a through spring cleaning. Then we will shut it down for the season and cover it with a wall AC unit cover. I honestly don't know if such a precaution is truly necessary, but reason that in winter, when it's operating, dampness isn't an issue as it dries itself, but when shut down it might be and protecting it from water spray is so easy to do.

Nevertheless, regardless of brand, my husband the Great Depression reared farmer who can squeeze the last drop of life out of any machinery has always contended that with proper preventative maintenance, just about any gas furnace can be kept operational, literally forever.

So when he performs the annual PM routine, it will also be wiped clean inside and out, the exterior checked for any nicks that could engender rust and if any are found will be attended to, then it will be waxed, sealed against damp and hopefully; will both operate perfectly and look good- for many, many winters to come.