Frost stat question

[am_diy]

Hi, hoping someone can help me me make sense of this:
We have the Honeywell frost protection kit connected to our boiler in the garage. I noticed that when the frost stat kicked in, the boiler was just staying on. Went out to look, frost stat was set to 5 and the pipe state set to 10, when I adjusted the pipe stat up to 25 it turned the boiler off - which made no sense to me?
But the same thing has happened again now, frost stat has kicked in, boiler has now been on for over an hour. What could be the issue?

 

[Deleted member 267285]

If the boiler is new, then the 24v link might have been left in.

 

[Johntheo5]

Hi, hoping someone can help me me make sense of this:
We have the Honeywell frost protection kit connected to our boiler in the garage. I noticed that when the frost stat kicked in, the boiler was just staying on. Went out to look, frost stat was set to 5 and the pipe state set to 10, when I adjusted the pipe stat up to 25 it turned the boiler off - which made no sense to me?
But the same thing has happened again now, frost stat has kicked in, boiler has now been on for over an hour. What could be the issue?

Did you leave the pipestat setting at 25C?
Also, if you move the setting up and down around the pipestat measured temperature is it switching/clicking on/off at itts hysteresis of say 5 to 8C?.

 

[am_diy]

Did you leave the pipestat setting at 25C?
Also, if you move the setting up and down around the pipestat measured temperature is it switching/clicking on/off at itts hysteresis of say 5 to 8C?.

When I went out earlier, I moved that pipestat from 10 to 25, it clicked and boiler went off. Later on noticed boiler was running for ages again, this time moved pipestat from 25 to 30 and again it clicked and turned the boiler off.

 

[ianmcd]

Sounds like the pipe stat is wired back to front, can you post a pic of the wireing in it, remember and isolate the power before removing the pipe stat cover

 

[Johntheo5]

Strange one, maybe as CBW suggested, the 24V link may have been left in, kin hich case the boiler would just cut in/out on its own boiler stat but why would the pipestat override this then.
Does the pipestat have a adjustable hysteresis, maybe post the make/model, but still doesnt make much sense to me, maybe wired wrongly?

 

[am_diy]

That’s the model, haven’t got a picture of the wiring at the moment, but back to front wiring could make sense as it’s working in reverse to what it should

 

[Johntheo5]

This is the wiring diagram, easy enough to check out?

 

[ericmark]

The diagram shown

seems wrong but not what one first thinks. On reading the instructions it seems the pipe stat is not to switch boiler on, but in fact it is to turn boiler off.

The idea is boiler only heats the pipes just enough in cold weather, once pipes are warm they are not going to freeze, so boiler turns off what ever the room temperature is.

If I have miss under stood likely others could also get it wrong, so wall thermostat turns it on, pipe thermostat turns it off.

 

[stem]

@ericmark is correct.

The froststat should be located in the area where pipes are judged to be at risk of freezing and set to around 5 degrees C. The froststat turns the heating on when the ambient temperature falls to 5 degrees C in the at risk area.

The pipestat is on the return pipe to the boiler and usually set to around 15 to 20 degrees C. When the return water going back to the boiler reaches this, the boiler is turned off. This prevents the radiators getting too hot as it's designed for frost protection only.

When the heating is in operation, the return pipe will be over 15 to 20C so the pipestat will be switched off allowing the normal heating controls to operate the system.

I suspect from your description of the pipestat operating in reverse that the use of terminals 1 and 2 are transposed.

 

[am_diy]

@ericmark is correct.

The froststat should be located in the area where pipes are judged to be at risk of freezing and set to around 5 degrees C. The froststat turns the heating on when the ambient temperature falls to 5 degrees C in the at risk area.

The pipestat is on the return pipe to the boiler and usually set to around 15 to 20 degrees C. When the return water going back to the boiler reaches this, the boiler is turned off. This prevents the radiators getting too hot as it's designed for frost protection only.

When the heating is in operation, the return pipe will be over 15 to 20C so the pipestat will be switched off allowing the normal heating controls to operate the system.

I suspect from your description of the pipestat operating in reverse that the use of terminals 1 and 2 are transposed.

Thanks that sounds right from my limited knowledge, what is the easiest fix for this?
Is it something I could DIY or safer to get someone out?

 

[Johntheo5]

I take it that the Honeywell wiring diagram is correct??

At night when both CH & Hw systems are normally programmed off; how does the water circulate if no zone valve opens?.

 

[Johntheo5]

Thanks that sounds right from my limited knowledge, what is the easiest fix for this?
Is it something I could DIY or safer to get someone out?

For a start, just check that wires are connected in to C & 1 above in the pipestat, post #8.

 

[stem]

@am_diy The Honeywell diagram looks correct. So, if there is a wire in terminal 2 move it to terminal 1. Only you can determine if you can do it safely.

When the pipestat is above its set temperature, it is in the position shown and the circuit is open
When the pipestat is below its set temperature it moves so that C and 1 are electrically connected and the circuit is complete. [Assuming that the froststat is also 'on']

@Johntheo5 The frost stat should be wired to the heating zone valve so that it does open. The valve in turn starts the boiler. In a domestic setting it's not usual to link the frost stat to the hot water system as they are not normally at risk of freezing, unless the hot water cylinder is installed in a unheated loft or garage.

On larger systems with multiple zones, I have fitted a relay so that the frost system will open the motorised valves of all the zones.

 

[am_diy]

@am_diy The Honeywell diagram looks correct. So, if there is a wire in terminal 2 move it to terminal 1. Only you can determine if you can do it safely.

View attachment 288719

View attachment 288720

When the pipestat is above its set temperature, it is in the position shown and the circuit is open
When the pipestat is below its set temperature it moves so that C and 1 are electrically connected and the circuit is complete. [Assuming that the froststat is also 'on']

@Johntheo5 The frost stat should be wired to the heating zone valve so that it does open. The valve in turn starts the boiler. In a domestic setting it's not usual to link the frost stat to the hot water system as they are not normally at risk of freezing, unless the hot water cylinder is installed in a unheated loft or garage.

On larger systems with multiple zones, I have fitted a relay so that the frost system will open the motorised valves of all the zones.

Thanks I will check.
When the frost protection kicks in, only the towel heaters heat up (this is the same if only the hot water system is running). None of the radiators come on with the frost protection. We have a two zone system, plus a separate control for the hot water.