This section is from the book "The Gardener's Monthly And Horticulturist V23", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I have yours of the 10th ult., and shall endeavor to meet the question as to the greater merits of steam heating above that of hot water. If I rightly recollect our conversation you put it about as follows: Why is it, that with the advantages claimed for steam over hot water it has been so perfectly dormant for so many years - since Loudon drew attention to steam as a practicable heating medium for horticultural structures? And why has nearly every attempt at utilizing it for the purpose failed completely? And lastly, wherein does my method which has proved thoroughly efficient throughout five seasons, differ from others that have been tried and abandoned?
To these queries I shall try to reply as briefly and pointedly as I can. I think the explanation to query No. 1, is that the necessary devices for the control of steam as a heating medium have been of comparatively late introduction; among these are foremost, next to an efficient generator (boiler) an automatic, and at the same time positive-acting device for the return of the condensation to the boiler, and next nearly as useful, if not as indispensable as the one just mentioned, a reliable damper regulator. After these there are other excellent arrangements either tending to greater perfection in economy of fuel or attention, such as pressure-regulators (for admitting steam at a low pressure to the heating pipes, while generating it in the boiler at a high pressure, the advantages of which any one familiar with steam is cognizant of), or the self-feeding device so well known in base burning stoves for doing away with the necessity of replenishing fuel oftener than every eight or ten hours.
My opinion as to the principal cause of the failures with steam heating, is that in every instance brought to my notice the pipes used have been entirely too small, generally one inch and even as low as three-quarter inches having been used to convey steam many hundreds of feet; the condensation going on in so small an area is so rapid, that in order to transmit any steam at all to any considerable distance, you have to do so at a very high pressure, which in itself is so great an evil as to stamp the whole thing a nuisance at once. It has been my practice to use two-inch, but in the houses at present under my personal supervision I have three-nch in use, a large lot of that size becoming available from a different use. I find the advantages important enough to recommend their use in preference to two-inch whenever first cost is not too great a consideration.
The present winter has certainly been a good one for thoroughly testing the merits of any heating apparatus, and the ease with which we have mantained from 60 to 65 degrees against 20 below zero out doors, was even a surprise to myself. It may perhaps be of some interest to yourself or others to learn that my efforts in this direction were caused by a serious mishap to my heating apparatus (smoke flues), late in November, 1876. To have placed hot water into my houses could not have been done under a month; my whole stock was in imminent danger of freezing, root and branch. Not unnaturally under the circumstances, I was willing to listen to any suggestion coming from my friend Mr. John H. McElroy, a well-known expert in mechanical and steam engineering, who proved conclusively to me, that all the objections I ever heard urged against the use of steam were based on errors in the construction of the apparatus. In short, I accepted his advice and assistance; the whole thing was finished in as many days as it would have taken we«ks to put in hot water, and for about one-half the cost of the latter, and it has worked from that day on to the greatest satisfaction in every particular, and I should here like to say, that if the horticultural world adopts, as I have no doubt it will, low pressure steam as a heating medium for greenhouses, in the near future, as a grateful release from the clumsy, expensive and wasteful method heretofore in use, its thanks for the blessing are due my friend Mac.
In conclusion I wish to say to yourself Mr. Henderson, and not as a mere compliment either, that it seems to me peculiarly your mission, especially in commercial floriculture, to advocate anything tending to simplify and cheapen the cost of operations, or to make the same productive of better results, (practically the same thing,) and I do not think there is a better field for progress just now in our line than the subject matter of this letter.
[We have been favored with this very interesting paper through Mr. Peter Henderson. - Ed. G. M.]
Since our first attempts to bring the subject of steam heating in glass structures into general notice, I have looked in vain for some information as to what was being accomplished in the matter, but save in the case of Mr. Bochman I have not been able to find anything. This subject is of such great importance to those interested in the heating of greenhouses that it should not be allowed to smoulder, but be pushed in such a way as to bring all to a knowledge of the efficiency of steam for their use. I know the old heads still shake a negative at the bare mention of the idea. Dangerous, too dry, too complicated, but to each of these we who have proved it can truthfully ejaculate, Nonsense! The antipathy to steam results from want of knowledge rather than from any experience gained from a trial of it, and I do hope Mr. Bochman will push the matter all he can, making himself sure of hearty sympathy and good wishes at this end of the line, while you, kind editor, can help us smugglers after truth, through your esteemed magazine - which can be made the dispenser of knowledge in this particular, as it is in so many others - and we trust you will give us all the facts, both for and against steam, of which you may become possessed.
Regarding a few details I must disagree with Mr. Bochman, though in the main we prove of the same opinion, and perhaps it would be best to to canvass our differences, with a view of finding whose plan is the better.
In the letter to Mr. Peter Henderson, which appeared in your April issue, Mr. B. responds to some queries. His first reply as to the comparative recency of introduction of steam governing devices, etc, I heartily indorse, but his reasons for the failures in the attempts to utilize steam - if I rightly understand him - I cannot altogether concede. What I wish to know is this: Does he use the two and three inch pipes as radiating surfaces, or merely to convey his steam to his radiators of smaller pipe? And does he mean to condemn the use of small pipes as impracticable?
We use one-inch pipes altogether for radiating, but convey the steam to them thro' larger pipes, the size of which varies with the amount of surface we wish to supply, and its distance from the boiler.
Moreover, we use steam at a pressure of from three to five pounds. We return our condensation direct to the boiler without the intervention of steam traps or any other device, and I think the cases are very few where anything of the kind is necessary.
In a general way the more simple the apparatus and the less complications we use the better.
Regarding the larger pipes, their cost is nearly double that of the smaller, and if the latter can be made quite as effective, this is surely a saving.
But to the main question. I am merely vindicating our faith when I say that we have this season taken out our last remaining hot water pipes, replacing them by one-inch steam pipes, which would seem to prove that after several years of trial we have learned that the latter is in all ways the best.