Drain down or not for the Winter? Scope of frost stat.

[TryingHard24]

Evenin' all.

I have a Pottertons Combi 80 (Combi 80 G.C. No. 47-393-03) in a single level flat. 4 rads with trvs. No room stat.

I am going away for the winter and am trying to decide how to avoid it all freezing while I'm away (without paying a fortune on gas). Specifically, whether to drain it down or not.

As far as I know, there isn't a drain valve. If there is, it's likely under floorboards and laminate flooring, which I'd rather not rip up on-spec. So if I can avoid draining it all down, that will save a lot of time and mess.


I notice in the Installation and Servicing instructions

A frost thermostat is fitted which will bring the appliance on when the local temperature around the applicance falls below 5degC. The applicance will shut down when the temperature of the system water has been raised by approximately 10degC.

The frost thermostat will operate with the central heating switch in any position therefore when leaving the property in cold weather for extended periods, the boiler will be protected even when the switch is set to Off (Mid position).

OK - so it sounds like the boiler itself will be protected. But will the water in the radiators (and the pipes leading to them) be similarly protected. i.e. when the frost stat protection kicks in, does it pump heated water around the CH circuit, or is the frost protection somehow restricted to just the boiler itself ?

Much appreciated

 

[cross thread]

i wou;d drain down,only hours work for a person who knows what they are doing,then same again when refilling,

 

[kevplumb]

fit a frost / pipe stat

frost stat you are referring to is to protect the boiler not the system

 

[Whitespirit66]

The frostat will start the boiler, and heat the radiators to raise the temp above freezing. It will keep firing up and switching off as long as the ambient temp remains below freezing.

This will not only protect the radiator pipes from freezing. It will protect hot and cold pipes in your flat, as well as preventing condensation.

Are you sure that there isn't a drain cock under the boiler, or on the pipes, probably near one of the rads?

If you want to turn the system off whilst away, and there is no drain off cock, you could fit one, or arrange for one to be fitted. If you drain the heating, make sure you also drain the hot and cold pipes, and turn off the main stop cock.

 

[DaveHerns]

How does the system work without a room stat ? The boiler must be firing up constantly and cutting out if there's no circulation possible

 

[TryingHard24]

Thanks for the replies (although I'm still a little confused, since 3 & 4 do seem to be at odds with each other!)

How does the system work without a room stat ? The boiler must be firing up constantly and cutting out if there's no circulation possible

There's a timer on it so you can have it either on or off for each 15 minute block of the day. Or there's an option to leave it on 'constantly'. Room temperature is controlled either with the TRVs or by tuning how often it is on vs off on the timer. I presume that there's also an internal thermostat that tells the flame not to light if it's On and if the return water is above a certain temperature. If there is, then there's nowhere obvious where you can set that temperature.

Not sure when there would be no circulation possible (under normal operating circumstances). I've certainly left the CH 'on' (with only the TRVs controlling the room temp) for long periods without any problem.

 

[kevplumb]

you can get anti freeze to add to the system water

 

[TryingHard24]

Well, D-Day is imminent and I had convinced myself just to rely on the frost stat, when a final read over the manual revealed:

The applicance is fitted with an internal frost thermostat, however the device is purely for the protection of the appliance. If any other part of the central heating system requires frost protection, an external frost thermostat should be fitted

B*gger ! So now I think I will have to drain it after all

The "no drain cock" problem persists.

Down at my local boiler shop, they directed me towards a self tapping drain cock. Are these bad? Is that why nobody mentioned them?

I drained each rad down individually before attempting to fit the new device (yes, I know that sort of defeats the point of it, but I'm a scaredy cat and at least that way I know that the system's almost empty if I screw-up fitting the drain cock!).



So right now, I have all the rads drained (at the points where the pipes join them, about 10cm above floor level. I have a floor board up all ready to add in my new drain valve. But I'm wondering whether it's really worthwhile putting it in at all? There isn't really a "lowest point" in the system. And I can't see how putting it in at point "a" is going to get the water out at points b and c. I'm not fitting 3 of the things!

Right now, the system is (mostly) drained and open at all points marked "o". I reckon any water left in the pipes below the floorboards will probably evaporate before it freezes. Or am I missing something ?


[code:1] ___________
| |
| |
| |
| boiler |
| |
| |
| |
-----------
o| |
| |
| |
| |
| |
| | ______________________o ___________________o ______________o
| | | | | | | |
| | | | | | | |
| | | rad 1 | | rad 2 | | rad 3 |
| | | | | | | |
| | o|______________________ o|__________________| o|_____________|
| | | | | | | |
| | | | | | | |
---------------------------------------------------------------------------------------------------Floor
| | a | | b | | c | |
| |______| |________| |_______| |
*|______________________________________________________________________________________|

[/code:1] (I'm assuming it's plumbed "in-series" like this, but if it isn't, the point still applies). * all the pipes below the floor board are about the same height-above-sea-level.



cheers

ps also, I intend draining all the direct hot and cold water (non CH) pipes