plastic pipes - central heating

[wig]

Hi,

I saw some plastic pipes in the local diy store.

"John guest speed fit 15mm BPEX" I think it should be easier to us these for my up coming full central heating installation.

The website says they can be used for central heating have a workin temp up to 93 degrees with a MAX temp of 114 degrees for a "short time they didn't say how short. In case of boiler thermostat failure.

Some questions I have.

Would you use these for central heating? access is no problem (I have no floor boards yet) so alternative i

15mm copper.

What is the normal working temp of water output from a combi boiler?

What effect would the anti corrosion additive have on the seals?

How are you expected to know if your thermostat cut off on the boile has failed?

cheers Wi

-- wig

[Andrew Gabriel]

Well, since you asked, I installed central heating about 3 years ago and used copper with soldered joints as I know from past experience it lasts (in this case, probably longer than I will). Maybe plastic would too, but I don't have any past experience to back that up, and saw no point taking the risk.

Central heating max is normally around 85C.

You hear girgling noises, followed by hissing noises, followed by a loud bang. ;-)

More seriously, boilers tend to have overtemp cutouts, and a sealed system will have a fallback of a pressure relief valve.

[John Stumbles]

yes, I've used speedfit (pex) and hep2o (pb) for ch systems and parts of systems with no problems. The first metre of pipework from the boiler is still supposed to be in copper on most boilers.

[John Rumm]

Could well be...

I have done a short section of an extension to the CH in it when I needed to play "dodge the joist" on my loft conversion.

85 for normal, less for a condensing one.

I refer you to one of Andy's former posts:

[Doctor Evil]

The working temp on a condensing boiler is what you want it to be, depending on control system boiler. If you want 82C then there are condensing boilers that will provide this continuously.

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[John Rumm]

I think the thrust of what I was saying is "less than the pipe is rated at - irrespective of boiler type"

[Doctor Evil]

You were. Stop telling porkies. You are squirming like Dracula.

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[John Rumm]

What are you babbling about now?

[Ian_m]

My year 2000 build house has copper pipes from boiler in garage to airing cupboard tank, copper to loft tanks, including expansion overflows but all the pipes for hot water, for showers and from CH pump are all plastic Osma Gold push fit. I queried why so much copper work during snagging and was told its because if there is a boiler fault and it starts boiling the water it can vent safely (???) etc without any pipes melting.....

There are also two thermostats externally on top of the boiler one attached to pipe set at 90C and other set at 6C. I assume overtemp and frost stat.