Outdoor thermostats again

[Roger Mills]

I think that most people's response to yesterday's thread about an external stat to control a pond heater was "I wouldn't start from here!"

- and no-one identified any suitable stats.

I have another application for one - but Google hasn't come up with anything sensible.

The insurers for my holiday flat are tightening up the cover for damage due to water escape - and require either that all water is drained when the flat is unoccupied between November and March, or that the heating is left on all the time in order to maintain a temperature of at least

13 degrees. We use the flat for about one week in four - even in the winter - and it would be totally impractical to drain the sealed CH system and unvented HW cylinder after each period of occupancy. The heating is controlled by a wireless room stat with a frost setting which I *could* set to 13 degrees - but that would cost a fortune in gas. [Our practice so far has been to turn off the water and gas, and to rely on the fact that the flats below and above are permanently occupied and heated - thus reducing the risk of out flat getting cold enough for the pipes to freeze and burst].

If I go down the road of leaving the heating on, I can't see any point in running it unless it is freezing outside. It seems to me that what I need is an external thermostat - switching on at (say) 1 degC - wired in series with the roomstat. It would, of course, need a by-pass switch for when the flat is occupied - but this could be separate and not part of the stat itself.

I think that what I actually want is a manual stat with an operating range of a few degrees either side of zero, and with an external sensor. [The stat itself doesn't need to be weather-proof as long as the remote sensor is.]

Any idea where I might find such a beast?

TIA.

[NT]

If you can count on some heat from at least one of the enighbouring flats, you can presumably set your trip point to below 0C exterior temp. The usual temp setting for frost protection is 5C. Another option is heating tape on all pipework, far cheaper to run, and again can be on a frost stat.

NT

[Fredxx]

1 Has the flat got any water storage? If the water to the flat is turned off after you leave the flat, what's the most damage that could be done? 2 I presume the boiler has a latching over-temp cut-out and is a sealed system, such that if there was any water loss, the boiler wouldn't fire up from reduced pressure? So inherently a safe system, or as safe as can be.

For one year I might be tempted to leave the stat at 13degsC just to see how much gas is actually used, and keep a log. Another alternative is to find another insurer, but the cost of water damage to your flat, and to ones below would be not inconsiderable, so I don't blame them for making such stipulations.

Personally I leave my stat at 10degsC.

[ARWadsworth]

Bloody hell. MM would have a heart attack if he had to heat his house to 13 degrees and he lives in his house:-)

[Roger Mills]

There's no cold water storage. There's an unvented hot cylinder holding maybe 25 gallons of water in the same cupboard as the boiler. If that burst, most of the water would probably seep through the floor into the flat below rather than doing much damage to our flat. [I'm guessing that that would be covered by the Public Liability part of my insurance policy even if water damage to my flat was excluded]

There's also the water in the (sealed) CH system - 8 radiators, I think

- none of them massive.

I think there's a latching over-temp trip - not 100% sure whether it's active [ISTR that it can be bridged when the boiler is used with a gravity HW circuit (which mine isn't)]. I presume that the boiler won't fire if the pressure is too low - but again, I'm not absolutely sure.

I doubt whether changing insurers would help. When we bought the flat two years ago, we looked at insurers and this one had by far the best cover and the least exclusions when the property is unoccupied - it's just a pity that they are catching up with the rest. I would really like to find a way of logging the temperatures for a while to see what happens inside with no heating when it's freezing outside. Leaving the heating on would scupper that - but if I don't, I risk invalidating the insurance.

[YAPH]

Recently bought one from EBay trader ROBLAIGHT.

[Roger Mills]

Thanks - but I can't find him/her! Do you have an item number?

[Andrew Gabriel]

Had a similar situation with a relative's empty home. Insurance required min of 16C or drain down and shut off water. Otherwise, wouldn't pay for frozen pipe damage/repair.

I decided to go for 10C (IIRC), and shut off water, and remote monitoring. With a sealed heating system, even if it does burst, the amount of water damage is going to be limited, and I'd probably end up fixing it anyway rather than claiming.

Can't help thinking that a H/W storage cylinder is perhaps not a good choice for occasional occupancy.

[NT]

Maybe its time to assess the no insurance option?

NT

[Jonathan Ward]

Are you suggesting it is cheaper to run your heating all day rather than just in the mornings and evenings?

Jonathan

[Roger Mills]

How did you implement that?

With a sealed heating system, even if it does burst,

Ditto. It could damage the carpets, though.

It was installed by the previous owner who lived in the flat full time during in the winter and went to France for the summer. It's an unvented cylinder, and very heavily insulated - so would need a long period of very low temperatures before it froze.

[Roger Mills]

Interesting thought! The insurance is not *that* expensive - about £120, which provides more than enough contents cover (£13k) in case of a break-in, plus £5M Public Liability cover. It's probably worth it even if the water leakage cover is restricted.

[The Natural Philosopher]

It can be.

Especially if your boilers is vastly more efficient just keeping things warm that heating from icy cold. And your insulation level is high.

[Doctor Drivel]

If you have proper frost protection stat system that prevents freezing, that is all an insurance company is after, unless they are insuring certain types of contents they will not insist on a min' of 13C in the flat. Get back to them.

[Andrew Gabriel]

It was very Heath Robinson. Used a PC and a modem (long before ADSL existed), and a serial thermometer. Modem picked up my caller-id on an incoming call which wasn't answered, waited a bit, and then connected to Demon. I could then retrieve the values over the Internet.

[Steve Walker]

Yes. Can you extract any power from that mill stream?

SteveW

[Martin]

I'd look for another source of insurance. 14C is much too high. My combi boiler thermostat turns on the central heating at 7C whatever the settings.

[Martin Bonner]

That's alright. If he's there, he'll notice the leak and turn the water off. (The thing that scares insurers is the water running for three or four days.)

[John Stumbles]

Beg pardon - seller's ebay name was

"HIGH QUALITY AIR CAPILLARY WEATHERPROOF THERMOSTAT" £38

[Onetap]

A lot of modern boilers have optional extras, like weather compensation, which have frost protection programmes, night-setback etc., built in to the elctronics. If it's fairly recent and not a cheapo DIY shed job, the manufacturer's controls may have something with frost protection.