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Discuss Boiler Frost Protection in operation? in the Gas Engineers Forum area at PlumbersForums.net

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Jurgenjay

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Hi all,

Our heating set time is 7:30am off. This morning at around 8:35am the pump started to run, water motorised valve opened, and boiler started to operate! This operation ran till 12:15pm (pump stopped, valve closed and boiler stopped), totally around 3hour and 40mins!
====I assume this was boiler Frost Protection in operation? If yes, then Frost Protection needs nearly 4 hours to bring the boiler temperature up to 12°C??

Below is the manual of my boiler regarding Frost Protection:

"If the temperature within the boiler falls below 8°C the pump will run to circulate water and prevent the system freezing. If the temperature within the boiler falls below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C to avoid the possibility of the system freezing. This process will be repeated until such time that the boiler temperature does not drop below 5°C."
 

Timmy D

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You said water motorised valve opened, can you clarify?

I assume you’re talking about the zone valve for the hot water cylinder?

If so, the boiler can’t open this valve.

The sequence of demand/operation goes:

Programmer signals for heating/hot water.
This signal goes to the thermostat (heating or cylinder).
If heat is required, the stat sends a signal to zone valve.
Zone valve opens and sends signal to boiler.
Boiler fires.

Now, if there was no programmer demand for heating or hot water, power would not be sent to the stat and on to the zone valve.
Without this power, the zone valve can’t open.

If the zone valve is open, it will always tell the boiler to come on.
 

Jurgenjay

Messages
166
You said water motorised valve opened, can you clarify?

I assume you’re talking about the zone valve for the hot water cylinder?

If so, the boiler can’t open this valve.

The sequence of demand/operation goes:

Programmer signals for heating/hot water.
This signal goes to the thermostat (heating or cylinder).
If heat is required, the stat sends a signal to zone valve.
Zone valve opens and sends signal to boiler.
Boiler fires.

Now, if there was no programmer demand for heating or hot water, power would not be sent to the stat and on to the zone valve.
Without this power, the zone valve can’t open.

If the zone valve is open, it will always tell the boiler to come on.
Thank you Timmy for your reply!
Yes, you assumption is right, I meant that zone valve for hot water.

And your sequence is correct---when it is normal working condition!

This morning, the programmer was off (set to be 7:30pm off), when it was 8:35am, the pump started, and at the same time zone valve for hot water opened, then boiler started to run.

Why was this? I assume it was because the frost protection was in operation! As quoted from the manual for frost protection:
"If the temperature within the boiler falls below 8°C the pump will run to circulate water and prevent the system freezing."

This morning at 8:35am outside temperature was -6°C, and the garage (where my boiler is locates) temperature was 6.6°C, so I guessed because this garage temperature was below 8°C, so it triggered the boiler to start the frost protection function.

I never saw frost protection in operation, that's why I am asking here if what happened this morning was actually frost protection in operation, I am just not sure it would take nearly 4 hours for the pump&boiler to stop for bringing the boiler temperature back to 12°C?
 

John.g

Messages
2,793
Was the boiler actually firing continuously during this period or just occasionally?.
I would think that in built boiler frost protection only looks the boiler water temperature and circulates or/and fires the boiler as required just as it states, "If the temperature within the boiler falls below 8°C the pump will run to circulate water and prevent the system freezing. If the temperature within the boiler falls below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C to avoid the possibility of the system freezing. This process will be repeated until such time that the boiler temperature does not drop below 5°C."
The key word there is circulates, if, somehow it opens a zone vale(s) then the temp should rise from 5C to 12C in a few minutes. if it doesn't open a zone valve then it has to circulate either through a external ABV or a internal bypass, again only a few minutes firing.

You stated in another thread that you have a external Frost Stat mounted in the garage alongside your boiler, it was suggested that you remove the frost stat's cover and see what its setpoint is??.
 

Jurgenjay

Messages
166
Was the boiler actually firing continuously during this period or just occasionally?.
I would think that in built boiler frost protection only looks the boiler water temperature and circulates or/and fires the boiler as required just as it states, "If the temperature within the boiler falls below 8°C the pump will run to circulate water and prevent the system freezing. If the temperature within the boiler falls below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C to avoid the possibility of the system freezing. This process will be repeated until such time that the boiler temperature does not drop below 5°C."
The key word there is circulates, if, somehow it opens a zone vale(s) then the temp should rise from 5C to 12C in a few minutes. if it doesn't open a zone valve then it has to circulate either through a external ABV or a internal bypass, again only a few minutes firing.

You stated in another thread that you have a external Frost Stat mounted in the garage alongside your boiler, it was suggested that you remove the frost stat's cover and see what its setpoint is??.
Thank you for your input!

The boiler started as the zone valve for hot water opened( pump started to run), so it fired continuously like when working normally ; then when, I think, the hot water in the cylinder is full, it fires like periodically---the Burner indicator (green light) was on for a minute and off for a minute.---I am not sure this is being like the manual states:"If the temperature within the boiler falls below 5°C the boiler will fire periodically".

When I read manual "the pump will start to run to circulate water", I thought it just circulate water but boiler not fire & heat water, but the fact is: when the pump started to run, the zone valve for hot water did open, and the boiler started to fire for hot water (then later boiler burner indicator came off and on periodically).

Actually, the manual states: "If the temperature within the boiler falls below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C to avoid the possibility of the system freezing. This process will be repeated until such time that the boiler temperature does not drop below 5°C.""===but in my case, I checked the thermometer, the garage temperature was 6.6°C---this was below 8°C which means the pump will run to circulate water but as it was not below 5°C so why the boiler has fired like normal? ---Although later it was periodically(hot water in the cylinder was full I guess).

You mentioned the temp should rise from 5°C to 12°C in a few minutes----this is my biggest concern that: why my pump/boiler has been operating from 8:35am till 12:15pm(outside of timer setting time) only then the zone valve closed and boiler stopped?
It was 3hour and 40minutes! My understanding is just to fire boiler temperature from 5°C to 12°C should not take that long! So what happened yesterday morning 3hrs and 40mins pump/boiler all of sudden started to run---was that actually frost protection in operation???

Thank you for reading and connecting the other thread! Yes, I was not sure if the separate frost protection was in operation too, if that was, then will that conflict with the built-in one? Sadly, my gas engineer even could not answer me this, he does not know.....
And I dare not/not sure to open and test...
 

John.g

Messages
2,793
Actually the manual states "Appliance frost protection If you are leaving your property unoccupied during cold weather, please leave your programmer on constant and your room thermostat set to 15°C. ▶ If the temperature within the appliance falls below 8°C the pump will run to circulate water and prevent the system freezing. – If the temperature does not rise to 9°C within 30 minutes of the pump operating, the appliance will fire up. ▶ If the temperature within the appliance falls below 5°C the appliance will fire immediately, bringing the appliance temperature up to 12°C to avoid the possibility of the appliance freezing. ▶ This process will be repeated until such time that the appliance temperature does not drop below 8°C." So the circ pump should run for 30 minutes on its own and if the water temperature doesnt reach 9C in this period then the burner fires up. The boiler does not look at the garage temperature, it monitors its own boiler water temperature. Still doesn't explain though the constant firing as it should get the temp to 12C in a very few minutes.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
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