On Jan 4, 10:20*am, brooklyn1 wrote:
Pavel314 wrote:
brooklyn1 wrote:
Phisherman wrote:
Pavel314 wrote:

Just to clarify the question, here's my original post to the home
improvement group:

We have a small greenhouse attached to the south side of our home.
It's 14' X 12' with a shed roof tapering from 10' on the house side
to
6'. Roughly 1,400 cubic feet. It's a 2x4 frame with double-walled
polycarbonate sheeting, 10mm for the roof and 6mm for the sides.
We're
in Maryland, near Baltimore, so it rarely gets below the mid-teens in
the winter.

We heat it with a 220V electric heater, 5,600 watts and 19,110 BTUh
rating. This generally keeps it at the 50 degrees the plants require
but occasionally my wife puts on a 110V supplimental heater on cold
nights.

The power hasn't failed in the winter since we got the greenhouse but
it's probably only a matter of time. I was thinking of getting a
kerosene heater as back-up to the electrical heaters. Home Depot has
a
23,000 BTU heater for $129 which seems to fit our needs. Could I use
home heating oil for this or would it be better to stick with pure
kerosene?

I was wondering about a propane heater; would that be more efficient
than kerosene? We have a propane ball/tank for some other
applications
which aren't used in the winter.

Paul

Some plants will refuse to bloom or struggle with growth if there is
too much propane, natural gas, or petroleum vapors in the air.

That would depend on concentrations, heating a greenhouse would never
reach such concentrations due to the fact that rarely are greenhouses
anywhere near airtight.

Electric heating makes more sense, safer, cleaner and expensive.

True, electric heating is typically expensive.

Kerosene heaters are not recommended due to increase of fire risk.

Kerosene space heaters are never safe, they also pump soot into the
air.

Gas is typically the least costly fuel and as to fumes from combustion
there is no reason that combustion needs to take place inside the
greenhouse... a gas hot water heater can be placed outside with hot
water baseboard piped in, with a thermostatically controlled
circulator. *Which fuel to choose is primarilly based on climate, in
warm climes where heat is needed only occasionally then inexpensive
electric heaters may be the way to go but in colder climes the cost of
a gas heater will quickly pay for itself.

Good point. I was thinking of building some sort of outside enclosure
for the propane burner and transferring the heat inside. I was
thinking more of convection than hot water as this would just be for
emergency use.

Explain emergency use. *If you mean for only very occasional use then
gas is probably not the best solution. *For occasional periods of low
temperature a radiant electric heater would be more than sufficient
and requires no installation whatsoever (except to plug it in) and no
pilot light to deal with, just set the thermostat and forget it. *More
than any other factor climate determines what system to employ. *The
only other point I'll make is that with a greenhouse I'd not try any
*iffy* system, you only get one chance at a cold spell with plants and
they're all gone, and then there was never any reason to have a
greenhouse at all. *Whether gas or electric I'd also install a low
temperature alarm... they are very inexpensive (~$30-$100) depending
on type, some will simply turn on a lamp and/or a bell while more
expensive units will also dial your phone number so a prerecorded
message can alert you that your plants are about to recieve frostbite.
And since you are already using electric and you are satisfied then
during cold snaps simply add another electric heater. *But if you're
concerned with power outages than obviously you need a back up that
requires no electricity (or use a generator). *I suppose in extreme
emergency you can resort to a kerosene space heater but I'd definitely
use clean/filtered kerosene made especially for a wick type heater.
During the '70s oil shortage I used a kero space heater for a while,
they are awful filthy things and dangerous... if you decide to go that
route I'd recommend monitoring it often while in use, they don't have
a thermostat and the wicks are prone to flare ups that will generate
excessive heat. *If your greenhouse is important to you and you intend
to use electric heaters in your climate, and you are prone to power
outages of any duration then I'd strongly recommend having a portable
generator on hand, it will cost a bit more initially but I think
that's a far better solution than kerosene. *If you are prone to power
outages of duration then you really should have a whole house
generator permanently installed, it can run off your propane.- Hide quoted text -

- Show quoted text -

By emergency, I mean if the power goes off and our electric heaters
stop working. I have a generator for the pump, refrigerator and
furnace, but it's only 5,500 watts and the greenhouse heater is 5,000
watts. A propane heater would be a cheaper alternative to buying
another generator for a rare outage.

Paul