Following talk of GSHPs... what's the best (DIY or "professional") way of
measuring the frost line during Winter and/or monitoring ground temps at
different depths? I'd like to get an idea of how useful a GSHP would be
around here and how deep the loops would need to be (figured I'd ask now
in case it's best to set something up before the ground actually freezes!).

Ideas on a postcard. Or just save paper and say here.

cheers

Jules

Jules wrote:

what's the best (DIY or "professional") way of
measuring the frost line during Winter and/or monitoring ground temps at
different depths?

Make a string of 1WIRE temperature sensors spaced a few inches apart,
and bury it, you'd have to give some though to waterproofing it, pot the
individual sensors in epoxy? seal the lot in some heatshrink tube?

On Fri, 17 Jul 2009 19:40:11 +0100, Andy Burns wrote:

Jules wrote:

what's the best (DIY or "professional") way of
measuring the frost line during Winter and/or monitoring ground temps at
different depths?

Make a string of 1WIRE temperature sensors spaced a few inches apart,
and bury it, you'd have to give some though to waterproofing it, pot the
individual sensors in epoxy? seal the lot in some heatshrink tube?

True... I was thinking along those lines, but not liking the need to have
sensors all over the place. As you say though, I can probably just make up
a 'rope' with them at different depths and that should be quite neat. My
only worry there is whether whatever I seal them in will somehow distort
the readings.

cheers

Jules

On Jul 20, 1:34*pm, Jules
wrote:
My only worry there is whether whatever I seal them in will
somehow distort the readings.

Temperature-delta per unit time is pretty minimal.
Insulation is not perfect, it just slows the rate of change & may miss
transients.

Since we are talking about evaluating GSHP at depth in soil, pretty
immaterial.

Would be more useful to know you have "nothing else down there".
Going thro the local gas main is rather novel... GasSHP :-)

On Mon, 20 Jul 2009 07:34:29 -0500, Jules wrote:
On Fri, 17 Jul 2009 19:40:11 +0100, Andy Burns wrote:

Jules wrote:

what's the best (DIY or "professional") way of
measuring the frost line during Winter and/or monitoring ground temps at
different depths?

Make a string of 1WIRE temperature sensors spaced a few inches apart,
and bury it, you'd have to give some though to waterproofing it, pot the
individual sensors in epoxy? seal the lot in some heatshrink tube?

True... I was thinking along those lines, but not liking the need to have
sensors all over the place. As you say though, I can probably just make up
a 'rope' with them at different depths and that should be quite neat. My
only worry there is whether whatever I seal them in will somehow distort
the readings.

I did something similar with my fishpond (not measuring the frostline, but
the temperature at various depths, to see how the little blighters fared
during the winter).
I used LM335 sensors - cheaper and less hassle than 1-wire jobs, as these
output a voltage of 10mV/degree[1] so you can just attach them to a DVM.
I sealed these with bathroom caulk to keep out the water and it worked very
well. The temperatures won't vary at all fast, so there should never be a
gradient across the caulk. Also these sensors take very little current
so the self-heating is negilible.

However, for the frost line, what you'll really measure is how deep the
frost penetrated *that* *year*. If you need this info to base the depth
of foundations on (as opposed to simply wishing to know for your own reasons)
How much of a margin you add for bad winters is a matter of judgement.

[1] when powered, the voltage "output" is really the voltage drop across
the device, which is temperature sensitive and remarkably linear.

On Mon, 20 Jul 2009 06:57:40 -0700, js.b1 wrote:

On Jul 20, 1:34Â*pm, Jules
wrote:
My only worry there is whether whatever I seal them in will
somehow distort the readings.

Temperature-delta per unit time is pretty minimal.
Insulation is not perfect, it just slows the rate of change & may miss
transients.

Ta - makes sense

Would be more useful to know you have "nothing else down there".
Going thro the local gas main is rather novel... GasSHP :-)

Around here there's an online service where you can request a (free)
site survey - they'll then contact the relevant folks (telecomms, power
etc.) who'll come out and mark out where all of their stuff is for you. It
all works rather well (just been through it prior to planting some trees
out front - 48hr turnaround, which isn't bad).

No gas main or water main here; gas is via an LPG tank and water's via a
drilled well - although it's still useful to avoid digging through the
lines

It gets too cold around here for ASHP to work, but I believe GSHP is
possible given a big enough / deep enough loop.

cheers

Jules

On Fri, 17 Jul 2009 09:06:29 -0500, Jules wrote:

Following talk of GSHPs... what's the best (DIY or "professional") way
of measuring the frost line during Winter and/or monitoring ground temps
at different depths?

Think about it water pipes are below 750 mm mainly to prevent
freezing.
The temperature at that depth will vary very little summer to winter,
what temp it varies about will depend on where you are.

30cm averages:

http://www.metoffice.gov.uk/climate/...ukmapavge.html

--
Cheers
Dave.

In message o.uk, Dave
Liquorice writes
On Fri, 17 Jul 2009 09:06:29 -0500, Jules wrote:

Following talk of GSHPs... what's the best (DIY or "professional") way
of measuring the frost line during Winter and/or monitoring ground temps
at different depths?

Think about it water pipes are below 750 mm mainly to prevent
freezing.
The temperature at that depth will vary very little summer to winter,
what temp it varies about will depend on where you are.

30cm averages:

http://www.metoffice.gov.uk/climate/...ukmapavge.html

That's neat!

My lowest average 300mm soil temp. is 4-5deg.C in February. If someone
cares to remind me, I'll measure river water temps. for the same month.

regards


--
Tim Lamb

On Thu, 23 Jul 2009 09:22:23 +0100, Tim Lamb wrote:

30cm averages:

http://www.metoffice.gov.uk/climate/...ukmapavge.html

That's neat!

My lowest average 300mm soil temp. is 4-5deg.C in February.

Might be be worth trying to find 100cm temperatures, they are
recorded but my quick search didn't produce those. 30cm temps vary
quite a bit summer/winter and are of interest to growers. Down at
100cm the temp is higher (in the winter) than 30cm and is much more
stable summer/winter.

The EA might have river water temps from their monitor stations,
though generally they are more intrested in flow rates than temp.

--
Cheers
Dave.