Worcester Bosch Greenstar Ri Frost protection

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Hi,

I have a Worcester Bosch Greenstar 18Ri regular boiler installed within my garage.

There is also a Honeywell T4360 Frost Thermostat installed just above and to the left of
the boiler.

The problem I was having was that the Frost Thermostat was kicking in in cold weather
and firing up the boiler for very long periods of time which in turn was heating up the house.
After reading up on the internet, I did find out that if a frost stat is used that a pipestat
should be used in conjunction to turn the boiler off once the pipework temperature is high
enough to prevent the pipes from freezing, which one is not currently fitted.

From reading my boilers user manual it states that there is already an inbuilt
frost protection function within the boiler. So for a quick fix we temporarily disconnected
the power from the frost stat, to prevent over heating as it was becoming a major problem.

So wondered if anyone could confirm the following queries.

1.
Does my boiler actually need an additional frost stat and pipe stat?
As the boiler has its own frost protection function, or should it have both frost/pipe stat and
the boilers inbuilt protection active?

2.
If the frost stat is still wired into the boiler, but does not have power going to the frost stat
itself, will this prevent the boilers inbuilt frost prevention function from activating?

3.
As you can see from the snippet from my boilers user manual this is how the inbuilt frost
protection function works:

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 does not rise to 9°C within 30 minutes of the pump operating, the boiler
will fire up to provide heat to bring the temperature up.

If the temperature within the boiler falls below 5°C the boiler will fire, 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.



Last night the outside temperature dropped to -1.6C (about 4.0C in the garage) but I did not hear the central heating pump come on, so I am not sure if the boilers inbuilt frost protection
is working or not.

FYI. the heating in the house was off over night, it turned off at 23:00. So there was no heating demand throughout the night.

So I would have expected that the frost function would have activated as the temperature in the garage was less than 9.0C.

Would the temperature within the boiler have stayed above 9.0C all night if the heating was turned off at 23:00? I was up until 2:30 in the morning (in bed), and never heard the pump come on. Only until 5:00am when the timer was set to turn the Central Heating back on.


Also, when the above mentions that 'the pump will run to circulate water' would this be an 'internal pump' within the boiler, or the pump which is located within my airing-cupboard? Just so I know if I should be listening for the one in the airing-cupboard or not.

Any advice would be appreciated.
 
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H

Hot&Cold

So I would have expected that the frost function would have activated as the temperature in the garage was less than 9.0C.

That is your garage air temperature,

If the temperature within the boiler falls below 8°C the pump will run to circulate water and
prevent the system freezing.

That is within your boiler which monitors internal boiler primary water temperature,the sensor usually sits in a dry pocket and will activate autofrost functions when the boiler Water is approx 8 oC hopefully :!:

Does my boiler actually need an additional frost stat and pipe stat?

Most probably as the boiler autofrost function protects the boiler only,belt & braces approach.It needs onsite inspection to say a definitive yes or no.

when the above mentions that 'the pump will run to circulate water' would this be an 'internal pump' within the boiler, or the pump which is located within my airing-cupboard?

pump in airing cupboard,no pump in boiler.

Your honeywell froststat will cease calling for heat when the air around has heated (could be a while if no radiator in your garage) The setting in the frost stat can be checked ,you can remove the cover and check its set correctly,see honeywell information reference guide.

Personally i would reconnect the honeywell froststat until you can get a pipe thermostat fitted,it's cold again tonight.:idea:
 
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Thanks for your reply.

I will reconnect the 'frost stat' and get a 'pipe stat' fitted to the return pipe,
over the next few days.

In the mean time, just out of interest, can you advise on my earlier mentioned point '2', below.

2.
If the 'frost stat' is still wired into the boiler, but does not have power going to the 'frost stat'
itself, will this prevent the boilers inbuilt frost prevention function from activating?
Just want to make sure that the boiler is still protected.
 
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You wire your pipe stat in series with the frost stat

If the frost stat calls it sends power to the pipe stat which will in turn send power to the boiler to fire ( protecting the boiler) and will continue to until the pipe stat is satisfied ( protecting the pipework )
 
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Hi Terry, Thanks for the explanation.

But what I really would like to know is; with my external 'frost stat' currently disconnected from power, but
still wired into the boiler, will this stop the boilers own frost protection from working?

I am just thinking that could the boiler 'know / sense' that the external 'frost stat' is wired up/connected to it,
and therefore the boiler thinks its protected by the external frost stat, so disables it's own inbuilt protection.
 
H

Hot&Cold

2.
If the 'frost stat' is still wired into the boiler, but does not have power going to the 'frost stat'
itself, will this prevent the boilers inbuilt frost prevention function from activating?
Just want to make sure that the boiler is still protected

The boiler autofrost will activate as long as the boiler has been wired correctly (should be) and the boiler thermostat is not off.
 

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