Would using soil heating cables be an economic way of keeping plants frost
free in the winter? I am presuming that the heat will rise and keep the rest
of the plant warm. I would expect that not as much heat will be lost via the
top of the greenhouse because it will at least have a chance to heat up
something and some will get stored. Or is soil warming strictly for
propagation? Or does everyone just use heaters?
I know this sounds early to be asking but my cacti buying feet are itching
and so I need to sort out winter residences before buying too many to be
able to use windowl edges.

thanks
amber

Hi Amber,

You may consider building a bubble wrap dome inside the greenhouse. I used
this to good effect last winter in a large DIY propagator with heating
cables controlled by a lighting dimmer switch. If this is feasable, try to
arrange the roof, such that the condensation drips back into the soil (sand
in my case.) This is by far the most economic method I know.


"Amber Ormerod" wrote in message
...
Would using soil heating cables be an economic way of keeping plants frost
free in the winter? I am presuming that the heat will rise and keep the
rest
===============cut==========

Hope you used a special transformer. A dimmer gives pulses of mains voltage
that are a lethal as the straight mains.

Regards


"pronoun" a écrit dans le message de news:
...
Hi Amber,

You may consider building a bubble wrap dome inside the greenhouse. I
used
this to good effect last winter in a large DIY propagator with heating
cables controlled by a lighting dimmer switch. If this is feasable, try
to
arrange the roof, such that the condensation drips back into the soil
(sand
in my case.) This is by far the most economic method I know.


"Amber Ormerod" wrote in message
...
Would using soil heating cables be an economic way of keeping plants
frost
free in the winter? I am presuming that the heat will rise and keep the
rest
===============cut==========

In message , Chris R. Lee
writes
Hope you used a special transformer. A dimmer gives pulses of mains voltage
that are a lethal as the straight mains.

And why is this a problem?

AFAIK heating cables are mains voltage anyway - I have one in home made
propagator controlled by a rod thermostat control no transformer AFAIK
--
Chris French and Helen Johnson, Leeds
urg Suppliers and References FAQ:
http://www.familyfrench.co.uk/garden/urgfaq/index.html

"pronoun" wrote in message
...
Hi Amber,

You may consider building a bubble wrap dome inside the greenhouse. I
used
this to good effect last winter in a large DIY propagator with heating
cables controlled by a lighting dimmer switch. If this is feasable, try
to
arrange the roof, such that the condensation drips back into the soil
(sand
in my case.) This is by far the most economic method I know.

so the heated cables method won't end up with the bottom warm and the top
too cold?

"pronoun" wrote in message
...
Hi Amber,

You may consider building a bubble wrap dome inside the greenhouse.
I used
this to good effect last winter in a large DIY propagator with
heating
cables controlled by a lighting dimmer switch.

Unless I misunderstand you, you have a deadly system in mind, unless
you are using a transformer and low voltage cables.

[snip]

Franz

"Chris French and Helen Johnson"
wrote in message ...
In message , Chris R. Lee
writes
Hope you used a special transformer. A dimmer gives pulses of mains
voltage
that are a lethal as the straight mains.

And why is this a problem?

AFAIK heating cables are mains voltage anyway - I have one in home
made
propagator controlled by a rod thermostat control no transformer
AFAIK

Blimey

Franz

Hi Franz,

I'm still here--and it still works ok. You just need to make sure the
wattage rating of the dimmer exceeds that of the soil heating cable, and
also that the soil / sand stays damp to conduct the heat and avoid hotspots.
My cable is designed for this use at mains voltage. I admit the use of a
dimmer was my own idea--to save the cost of a thermostat. It would be best
to use a thermostat designed for the job. I think my cable was 40 feet
long. I fixed it to plastic fencing with nylon cable ties so that it kept a
snake like shape, and to prevent the coils touching when buried in the sand.
I would be more nervous of an electric blanket in bed. I may have a photo
somewhere--if your interested.

"Franz Heymann" wrote in message
...

"pronoun" wrote in message
...
Hi Amber,

You may consider building a bubble wrap dome inside the greenhouse.
I used
this to good effect last winter in a large DIY propagator with
heating
cables controlled by a lighting dimmer switch.

Unless I misunderstand you, you have a deadly system in mind, unless
you are using a transformer and low voltage cables.

[snip]

Franz

I think the idea of using a dimmer instead of a thermostat is false economy.
What you should be aiming for is a soil temp. of around 46-50f, with that
you can get away with an air temp of around 40f, or even down to 36f with
some plants.
You would be better using a time switch, but a thermostat is best as with a
hard frost you will want that extra time with the cable running on full to
maintain the temp.
At least with a timer you could give extra heat during the night, esp. from
around midnight to about 7am.
I wouldn't worry about a bublewrap tent, a single layer of polythene to form
a tent away from the glass will serve just as well, and if you have a fan
heater in there to keep the air frost free then you should do well.
Last winter I used a polythene tent inside a 24ftx 40ft tunnel. the tent was
7 ft in the centre and down to 5 ft at the sides. This cut the area being
heated down by around half, and meant I could get away with less powerful
heaters, and a lot less electric.
As spring came on I raised the tent till it was only reducing the air space
by about 15%.
One advantage of this was a great reduction in condensation as there was no
Cold film against the Warm air.
As the sun warmed the house I didn't have an insulated film (as you would
have with bubble wrap) keeping the heat away from the plants.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk

In message , Franz Heymann
writes

"Chris French and Helen Johnson"
wrote in message ...
In message , Chris R. Lee
writes
Hope you used a special transformer. A dimmer gives pulses of mains
voltage
that are a lethal as the straight mains.

And why is this a problem?

AFAIK heating cables are mains voltage anyway - I have one in home
made
propagator controlled by a rod thermostat control no transformer
AFAIK

Blimey

What's the problem here Franz? Soil warming cables, thermostats etc. all
standard kit intended for greenhouses - as is my mains electric heater,
and
--
Chris French and Helen Johnson, Leeds
urg Suppliers and References FAQ:
http://www.familyfrench.co.uk/garden/urgfaq/index.html

"Chris French and Helen Johnson"
wrote in message ...
In message , Franz Heymann
writes

"Chris French and Helen Johnson"

wrote in message ...
In message , Chris R.
Lee
writes
Hope you used a special transformer. A dimmer gives pulses of
mains
voltage
that are a lethal as the straight mains.

And why is this a problem?

AFAIK heating cables are mains voltage anyway - I have one in
home
made
propagator controlled by a rod thermostat control no transformer
AFAIK

Blimey

What's the problem here Franz? Soil warming cables, thermostats etc.
all
standard kit intended for greenhouses - as is my mains electric
heater,

I would not go near mains heating cables buried in damp earth. Full
stop.
Low voltage units are available for this obvious reason.

Franz

In message , Franz Heymann
writes

"Chris French and Helen Johnson"
wrote in message ...

What's the problem here Franz? Soil warming cables, thermostats etc.
all
standard kit intended for greenhouses - as is my mains electric
heater,

I would not go near mains heating cables buried in damp earth. Full
stop.

Fair enough, but AFAIAC they are safe. Obviously I would not put it in a
situation were I would be likely to damage it, - but otherwise I don't
see a problem. mine sits in the wooden propagator box in damp sand the
cable is insulated and sealed. If it was to develop a fault in the
insulation then it would just trip the RCD anyway.

Low voltage units are available for this obvious reason.

I guess they are, though I can't actually think
of ever seeing them on sale.
--
Chris French and Helen Johnson, Leeds
urg Suppliers and References FAQ:
http://www.familyfrench.co.uk/garden/urgfaq/index.html

"Chris French and Helen Johnson"
wrote in message ...
In message , Franz Heymann
writes

"Chris French and Helen Johnson"

wrote in message ...

What's the problem here Franz? Soil warming cables, thermostats
etc.
all
standard kit intended for greenhouses - as is my mains electric
heater,

I would not go near mains heating cables buried in damp earth.
Full
stop.

Fair enough, but AFAIAC they are safe. Obviously I would not put it
in a
situation were I would be likely to damage it, - but otherwise I
don't
see a problem. mine sits in the wooden propagator box in damp sand
the
cable is insulated and sealed. If it was to develop a fault in the
insulation then it would just trip the RCD anyway.

Only if the propagator itself is connected to earth.

Low voltage units are available for this obvious reason.

I guess they are, though I can't actually think
of ever seeing them on sale.

I used to have one when I still had a greenhouse. It ran at 12 volts
and used bare soft iron wires as the heating elements.

Franz

In message , Franz Heymann
writes

"Chris French and Helen Johnson"
wrote in message ...
but otherwise I
don't
see a problem. mine sits in the wooden propagator box in damp sand
the
cable is insulated and sealed. If it was to develop a fault in the
insulation then it would just trip the RCD anyway.

Only if the propagator itself is connected to earth.

And how would I earth a wooden propagator? :-)

The cable itself is earthed of course.

(though if you have mains electricity in a GH then yes I guess any metal
work such as staging etc. should be earth bonded
--
Chris French and Helen Johnson, Leeds
urg Suppliers and References FAQ:
http://www.familyfrench.co.uk/garden/urgfaq/index.html

"Chris French and Helen Johnson"
wrote in message ...
In message , Franz Heymann
writes

"Chris French and Helen Johnson"

wrote in message ...
but otherwise I
don't
see a problem. mine sits in the wooden propagator box in damp
sand
the
cable is insulated and sealed. If it was to develop a fault in
the
insulation then it would just trip the RCD anyway.

Only if the propagator itself is connected to earth.

And how would I earth a wooden propagator? :-)

Stick a metal peg into the damp soil and connect the peg to another
one driven into damp soil in the "real earth".

The cable itself is earthed of course.

That would not help you in this case, unless I misunderstand what you
mean by "the cable itself is earthed".

(though if you have mains electricity in a GH then yes I guess any
metal
work such as staging etc. should be earth bonded.

It would be good practice to do so.

Franz