As mentioned before I have a branch of the heating system that is
slightly at risk of freezing - UFH and an air blower in the conservatory.

I was considering Sentinel X500 which is propylene glycol based, but
thought people might be interested in some pros and cons I've discovered
during research:

Pros:

1) Obviously, reduction in freezing point. Protection to -6C at 20%
dilution.


Cons:

1) Not cheap - would cost £100 to add 20% to a moderately sized house
system;

2) Read reports that it can result in leaks due to lower surface tension
(valve stems, any joint that has a tiny flaw that otherwise holds water);

3) Worcester Bosch on the 42CDi Nat Gas, tell me I can only dose to a
maximum of 20%. I asked because I noticed that auto air bleed bottle
vents specify = 30% glycol.

4) Sentinel specify a minimum dosing of 20% as it contains the
inhibitors too;

5) Question of toxicity if the DHW heat exchanger ever leaks.



So given how little protection (-6C) I can get, I'm cancelling that idea
and getting some modes made (when I connect the UFH and add the auto
bleed vents) to add local isolation inside the house and extra drain
cocks to make it easy to dry out that part of the system with a wet+dry
vacuum.


I'll be doing some detailed measurements this winter on how cold the
pipework gets relative to outside (it is adjacent to the house wall or
under screed. Former, together with wind protection, does buy an
envelope of protection and the screed will slow the rate of cooling of
buried pipes.


So what I expect is that most of the time, when heating is running, it
will be fine.

If we happen to go away for 1-2 weeks in January/February, a quick local
drain down might be in order.

"Tim Watts" wrote in message
...

As mentioned before I have a branch of the heating system that is slightly
at risk of freezing - UFH and an air blower in the conservatory.

I was considering Sentinel X500 which is propylene glycol based, but
thought people might be interested in some pros and cons I've discovered
during research:

Pros:

1) Obviously, reduction in freezing point. Protection to -6C at 20%
dilution.


Cons:

1) Not cheap - would cost £100 to add 20% to a moderately sized house
system;

2) Read reports that it can result in leaks due to lower surface tension
(valve stems, any joint that has a tiny flaw that otherwise holds water);

3) Worcester Bosch on the 42CDi Nat Gas, tell me I can only dose to a
maximum of 20%. I asked because I noticed that auto air bleed bottle vents
specify = 30% glycol.

4) Sentinel specify a minimum dosing of 20% as it contains the inhibitors
too;

5) Question of toxicity if the DHW heat exchanger ever leaks.



So given how little protection (-6C) I can get, I'm cancelling that idea
and getting some modes made (when I connect the UFH and add the auto bleed
vents) to add local isolation inside the house and extra drain cocks to
make it easy to dry out that part of the system with a wet+dry vacuum.


I'll be doing some detailed measurements this winter on how cold the
pipework gets relative to outside (it is adjacent to the house wall or
under screed. Former, together with wind protection, does buy an envelope
of protection and the screed will slow the rate of cooling of buried pipes.


So what I expect is that most of the time, when heating is running, it will
be fine.

If we happen to go away for 1-2 weeks in January/February, a quick local
drain down might be in order.

Or electric trace heating. I have a run of pipe in a shed that regularly
froze until I put trace heating tape round it. TLC sell a kit that is
reasonably priced and has a blimp thermostat that fixes to the pipe and
comes on close to freezing - works a treat so far

Andrew

On Monday, 20 November 2017 11:21:58 UTC, Andrew Mawson wrote:
"Tim Watts" wrote in message
...

As mentioned before I have a branch of the heating system that is slightly
at risk of freezing - UFH and an air blower in the conservatory.

I was considering Sentinel X500 which is propylene glycol based, but
thought people might be interested in some pros and cons I've discovered
during research:

Or electric trace heating. I have a run of pipe in a shed that regularly
froze until I put trace heating tape round it. TLC sell a kit that is
reasonably priced and has a blimp thermostat that fixes to the pipe and
comes on close to freezing - works a treat so far

Andrew

You might be able to use the UFH pipe itself as the heating element, with a transformer with 1 or 2 turns on. Saves digging it all up!


NT

On 20/11/17 11:22, Andrew Mawson wrote:
"Tim Watts"Â* wrote in message
...

As mentioned before I have a branch of the heating system that is
slightly at risk of freezing - UFH and an air blower in the conservatory.

I was considering Sentinel X500 which is propylene glycol based, but
thought people might be interested in some pros and cons I've
discovered during research:

Pros:

1) Obviously, reduction in freezing point. Protection to -6C at 20%
dilution.


Cons:

1) Not cheap - would cost £100 to add 20% to a moderately sized house
system;

2) Read reports that it can result in leaks due to lower surface
tension (valve stems, any joint that has a tiny flaw that otherwise
holds water);

3) Worcester Bosch on the 42CDi Nat Gas, tell me I can only dose to a
maximum of 20%. I asked because I noticed that auto air bleed bottle
vents specify = 30% glycol.

4) Sentinel specify a minimum dosing of 20% as it contains the
inhibitors too;

5) Question of toxicity if the DHW heat exchanger ever leaks.



So given how little protection (-6C) I can get, I'm cancelling that
idea and getting some modes made (when I connect the UFH and add the
auto bleed vents) to add local isolation inside the house and extra
drain cocks to make it easy to dry out that part of the system with a
wet+dry vacuum.


I'll be doing some detailed measurements this winter on how cold the
pipework gets relative to outside (it is adjacent to the house wall or
under screed. Former, together with wind protection, does buy an
envelope of protection and the screed will slow the rate of cooling of
buried pipes.


So what I expect is that most of the time, when heating is running, it
will be fine.

If we happen to go away for 1-2 weeks in January/February, a quick
local drain down might be in order.

Or electric trace heating. I have a run of pipe in a shed that regularly
froze until I put trace heating tape round it. TLC sell a kit that is
reasonably priced and has a blimp thermostat that fixes to the pipe and
comes on close to freezing - works a treat so far

Andrew



The only problem with that is the Myson itself - it has a myriad pipes
and fins inside and is probably the only or at least the first bit that
would freeze

On Monday, 20 November 2017 14:36:45 UTC, Tim Watts wrote:
On 20/11/17 11:22, Andrew Mawson wrote:
"Tim Watts"Â* wrote in message
...

If we happen to go away for 1-2 weeks in January/February, a quick
local drain down might be in order.

Or electric trace heating. I have a run of pipe in a shed that regularly
froze until I put trace heating tape round it. TLC sell a kit that is
reasonably priced and has a blimp thermostat that fixes to the pipe and
comes on close to freezing - works a treat so far

Andrew



The only problem with that is the Myson itself - it has a myriad pipes
and fins inside and is probably the only or at least the first bit that
would freeze

Have a look, you might be able to fit a drain pont to it depending on how the internal pipes are laid out.


NT

On 20/11/2017 10:50, Tim Watts wrote:

So what I expect is that most of the time, when heating is running, it
will be fine.

If we happen to go away for 1-2 weeks in January/February, a quick local
drain down might be in order.

Would not an extra frost stat sort most of the problems?


--
Cheers,

John.

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On 21/11/17 20:50, John Rumm wrote:
On 20/11/2017 10:50, Tim Watts wrote:

So what I expect is that most of the time, when heating is running, it
will be fine.

If we happen to go away for 1-2 weeks in January/February, a quick local
drain down might be in order.

Would not an extra frost stat sort most of the problems?



I've effectively got that already (the system will power up the boiler
if temperature some limit I choose).

I was considering a more passive solution - but the thing to do this
winter, I think, is to put a min/max temperature probe on the pipes
themselves and leave the room unheated for a few days when it's very
cold outside - and see just where the pipes go (if they are consistently
5C warmer than outside, that's good enough).

Of course, water does not instantaneously freeze at 0C either - it's got
to shed a load more energy (specific latent heat of fusion) which for
water is:

334kJ/kg

equivalent to the heat lost by the same mass of water cooling 80K and
without the advantage of a large temperature differential to help.

Perhaps the pipe would never freeze in practise - some cool
experimentation needed

Especially if combined with a pipestat set to a low temperature on the vulnerable section so the boiler etc only just warmed the pipes. If memory serves me correctly Danfoss ATP was available for just such a duty.

On 23/11/17 13:34, Cynic wrote:
Especially if combined with a pipestat set to a low temperature on the vulnerable section so the boiler etc only just warmed the pipes. If memory serves me correctly Danfoss ATP was available for just such a duty.


I was thinking about just removing the TRV head and letting HW circulate
whenever anything cut in (which would be by design if we left the place
for a week in winter). In fact I think my insurance prefers heating to
be left on an set to 15C if away.