Frost & pipe stat energy saving idea

[fourtytwo]

I have a boiler in the garage together with a frost & return pipe stat. The wiring is Y-plan with a Honeywell 42005748 junction box that makes it fiendishly difficult to work out whats going on (connections buried in pcb)!
I found on a few recent cold nights a lot of gas was consumed because the system was running the entire houses radiators for some time just to protect the boiler and a few meters of pipework in the garage. I thought at first there was a fault but discovered according to the wiring instructions in said junction box that is how it is intended to work.
Well of course running all the heating means it takes a considerable time for the boiler return pipe to become warm hence the high gas usage.
I have altered the wiring of my frost stat such that it runs the system in hot water only mode, this means the return pipe heats up much more quickly, the radiators remain cold and the gas consumption is very much lower.
I can post more details if anybody is interested.

 

[fourtytwo]

EDIT : Actually it's much harder than I thought if you are unfortunate enough (like me) to have a 3 way valve (V4073A) as it has a built in "stick in last position" function that means if the last program at night was central heating then when the frost stat kicks in during the night, guess what, whatever you thought you had achieved goes out the window because the wretched valve is still stuck in the central heating position!!

One way of fixing this is to add a short hot water program at the end of every day or alternatively rewire it as a 2 way valve so the stick function is disabled.

 

[Exedon]

Adding a extra hot water program wont necessary work if temperature already satisfied nothing will happen.
What your finding is one of several reasons we never use 3 ports valves.
S plan much better system valves last longer easier to wire no problems with frost control tho you may also need system by pass boiler dependant.

 

[fourtytwo]

Phew finally fixed the 3 way valve problem but I had to add a relay to the junction box to do it (see pic)!
Interrupts the valves grey wire if the CH is not on, coil wired between valve white & blue.
These damm 3 way valves are just unfit.............. (IMOP)

 

[Exedon]

Fair play to you.
I really couldn't have been arsed would just have converted to S plan and moved on
Y plan work of the devil saves very little money on install and can cause loads of problems.
That 3 port valve will fail they all do!

 

[JohnD]

If you put a small, low radiator in the garage, under the boiler and pipes, with a TRV set fairly low, surely it would prevent the frost stat kicking in so much?

I have a low power electric pipe heater in my garage, on a stat set to 5C. The cost is insignificant.

 

[oldbutnotdead]

What temperature is the frost stat set to- dunno where you are but we haven't had anything like a frost yet in t'frozen Co Durham (think lowest has been about 3 Deg c so far)

 

[fourtytwo]

What temperature is the frost stat set to- dunno where you are but we haven't had anything like a frost yet in t'frozen Co Durham (think lowest has been about 3 Deg c so far)

We got one this morning alright, white!
Anyway stat is usual Honywell one and as far as I can measure it wont go below 2C so that's about where it kicks in, better to err on that side I guess and not face a burst heat exchanger (ie new boiler)!
I am in North Lincolnshire, need to update my profile...

 

[fourtytwo]

I can quantify what I have been going on about...... I unfortunately inherited so called smart meters in this house and the indoor display is complete rubbish, however in my case with Octopus I can download the readings from there website.
This has allowed me to find that each time the frost stat operates the boiler burns 0.6Kwh this being enough to heat the hot water circuit & return to the pipe-stat cutoff temperature. At present outdoor temperatures (-3 overnight and <+2 daytime) there are 10 little burn blips per 24 hours totaling 7Kwh. This is in addition to the CH being on twice a day for 2 hours each totaling 50Kwh.

Previously the frost stat turned on the whole heating system, I never found out the consumption (horrendous) precisely as as soon as I found out I stopped it behaving that way, just in time given the weather in the last few days!!