How can I tell if my external boiler is wired properly for frost stat operation??

[delberto]

Hi,

As per the title, could anyone please tell me how I can tell if my new grant external boiler has been wired up properly for the frost stat to work?

Is it right that if I turn off the hot water and heating on the programmer that operating the test switch should tell me if the permanent live is in place to operate the frost stat?? Or is there another way without waiting for another sun zero day??

I ask because the plumber who swapped my boiler insisted on getting his own spark in. The spark was still about when I got home and said I should keep the boiler running constantly during a really cold snap to stop anything freezing. When I mentioned the inbuilt frost stat he said they don’t work…. Which worried me hence the question.

Any advice greatly appreciated.

Oh and seasonal efficiencies to all

 

[delberto]

Another thing is that the ‘boiler on light’ on the control panel only comes on when heat is called for.. which I assume means there is no permanent live…

 

[ianmcd]

The boiler requires a permanent live, and the frost stat will only protect the boiler itself not any outside pipework,

 

[delberto]

Hi Ian,

I know it requires a permanent live, what I am trying to work out is (without paying a spark to come and look at it) how can I check if it is wired correctly??

Again, optimum seasonal efficiencies to all

 

[Exedon]

Which model Grant? Combi is wired differently to heat only/system

 

[delberto]

Hi Exedon,

It is a heat only vortex external module (now discontinued due to streamlining range)- vortmod 15-21kw.

Any advice would be welcomed

 

[Exedon]

OK first have they fitted a pipe stat on boiler return?
Is there a system bypass? How many motorised valves?
Finally where is your pump fitted?

 

[delberto]

No pipe stat visible on the return. I know as I opened it up today to see naked bits of pipe and a condensate pipe knked so badly it would probably not let by. That said I believe the vortex frost stat is built in….
3 motorised valves hot water and 2 heating zones up/down.
No idea on system bypass-

Pump is in boiler casing on return.

It’s an old s-plan plus system….

:-/

 

[Exedon]

Yes frost stat built in and should have a permanent live.
Do you want just boiler protected or in you case either of 2 heating zones?
Will then run you through wireing.

 

[delberto]

Just the boiler really, the house is reasonably well insulated and I spent an hour insulating the external pipe work- mostly inside the boiler plus the 30mm between house and casing.

Is what I said above the east way to test that it has or haven’t been wired correctly in the first place??

Obviously the wiring info would be most helpful.

Thanks

 

[Exedon]

Some pictures of instal would be interesting I would say it's difficult to cock up condensate on that boiler there's so much room!
For it to work correctly follow wireing on page 29 of installation manual.
Into boiler you will need a 5 core cable permanently live switched live neutral earth and a feed back to a motorised valve
Grant suggest a feed back to heating valve we often (in discussing with end user) feed hot water valve .
Done this way return gets hot much quicker but can of course raise D H W above set point.
You really should have a pipe thermostat as that will make boiler shut down much faster.
If you had a automatic bypass fitted feed to valve can be omitted but again needs a pipe thermostat.

 

[roguetrader]

In fairness, grant don't specifically ask for the pipe stat and feed back to valve, although it's best practice and the wiring diagram shows the connections.
They want at the very minimum, the permanent live to allow the frost stat to fire the boiler.
The pipe stat/valve connection is more for the pipework.

 

[delberto]

Hi exedon, mine is the 15/21 which is a tightly fitted unit and why I chose it as it was going on a walkway of 900mm and only taking up 400mm all in. I’ll get a look at the wiring tomorrow and if it’s no right I’ll get you it sorted.

But I guess my main question is how can I tell if there is no permanent live to the boiler at present by using what is actually there??

Cheers

 

[Exedon]

In fairness, grant don't specifically ask for the pipe stat and feed back to valve, although it's best practice and the wiring diagram shows the connections.
They want at the very minimum, the permanent live to allow the frost stat to fire the boiler.
The pipe stat/valve connection is more for the pipework.

Agreed but when boiler and pump run and can't circulate anywhere not best idea

 

[roguetrader]

Agreed but when boiler and pump run and can't circulate anywhere not best idea

Quite agree with you Exedon. That's how we always do it.

Grant say frost stat alone it the basic minimum to get some temp into the casing and would suffice for warranty purposes.