Reducing times boiler fires up due to pipe stat

[fadewelsh]

My boiler (Valiant Ecotec Plus 630) fires up at night despite the timer being off. The boiler only heats for around 30 seconds, then displays S07 (pump overrun) for 5 minutes before shutting down. 45mins or so later it’ll fire up again and the process repeats. This only happens during cold weather.

Although the boiler is within an inside cupboard, my hot water pipes run through an unheated garage and I am 99% sure a pipe stat (Honeywell L641B1004) attached to these pipes is responsible for the call for heat. The pipe stat is set to 5c. There’s no frost stat, only the pipe stat, although the boiler does have built in frost protection.

The boiler firing up annoys me as I can hear it from my bedroom, especially the vibration of the pump running for 5 minutes just as I’m drifting off to sleep!

I’m guessing that what’s happening is the pipe stat calls for heat, the boiler heats and circulates water, the hot (/warm) water quickly reaches the pipe stat and as the stat is set to 5c it equally quickly terminates the call for heat. The pump then runs for 5 minutes as per the default setting for my boiler. Does that sound right?

Any thoughts on what can be done to stop the boiler from firing up in this way, or is this just normal operation that we need to get used to?

 

[stem]

Sounds entirely plausible. One option would be to disconnect the pipe thermostat and risk the pipes freezing. 5C isn't much above 0C so it must get pretty cold in your garage, therefore I would imagine that could be a distinct possibility without it.

I don't know where you are in the UK, but most of the country will be above 5C even overnight this week, so you should get a good nights sleep for the next few days at least.

An alternative would be to electrically trace heat the pipes where they are at risk and then remove the pipestat.

 

[MNW67]

I don't think pipe stats are particularly accurate. I would put a thermometer you trust in the garage to see how cold it gets. Mine never seems to get below about 7C. Is this the pipe stat and does it have those same settings?

 

[Harry Bloomfield]

Although the boiler is within an inside cupboard, my hot water pipes run through an unheated garage and I am 99% sure a pipe stat (Honeywell L641B1004) attached to these pipes is responsible for the call for heat. The pipe stat is set to 5c. There’s no frost stat, only the pipe stat, although the boiler does have built in frost protection.

I would disconnect the pipe stat and add as much insulation as you possibly can, to the pipes in the garage.

Your boiler's built-in frost protection, should be enough, with those pipes insulated. It may not entirely prevent your boiler firing up, but may reduce the incidence.

 

[oldbuffer]

1. A pipe thermostat should be wired so that it turns the boiler off when the temperature rises ABOVE the set value.
2. The set up is supposed to work like this:
2.1 The frost thermostat (integral to the boiler or separate) determines when the temperature drops below a set temperature, say 3 degrees, and fires the boiler.
2.2 Heated water circulates through the system.
2.3 When the pipe thermostat, installed on the return pipe, confirms that the water has reached a different set temperature, say 5 degrees, it turns the boiler off.
3. Without the frost thermostat / pipe thermostat combination:
3.1 The pipework may never get warm and runs the risk of freezing.
3.2 The boiler may run longer than necessary.

 

[stem]

Your boiler's built-in frost protection, should be enough, with those pipes insulated. It may not entirely prevent your boiler firing up, but may reduce the incidence.

The OP said the boiler was indoors and inside a cupboard, so I would think unlikely to operate its internal frost protection, it's only the pipes that pass through the unheated garage.

 

[Londoner2]

You are correct, the pipestat outside the unheated garage are calling for heat, its doing its job. Whoever installed it may have it correctly but with todays gas prices its gonna add up the costs during cold snaps. The same setup i had on an old boiler in an outback building, heating used to come on many times at night, i used to turn the trvs lower before i went to bed to ensure we werent wasting heat byheating up the rooms too much. With hindsight the cost on gas bills was negligible at that time.

You can have it disconnected, if you do this make sure the pipes are properly insulated, i reckon they wont freeze but you never know an event could happen that could cause it to freeze, only you could determine as you can chek the garage temp over night during a severe cold snap. Also you can lower the setting on the pipe stat to a lower temp to make sure it comes on and switch off at a lower setting.

 

[fixitflav]

I would disconnect the pipe stat and add as much insulation as you possibly can, to the pipes in the garage.

Why not just add as much insulation as you possibly can, and leave the pipe stat in place?

 

[fadewelsh]

Thanks all for the replies. It does indeed look exactly like the device in your picture @MNW67.

Calling the room a garage was a bit generous tbh as it's entirely uninsulated and not fully sealed from the elements. So I imagine things do get pretty cold out there! I'm nervous about turning the stat down due to the risk of freezing, so I like the idea of using a thermometer to compare the pipe stat against the real air temp. If there's a big difference would it make sense to get a frost stat installed? My understanding is there's only a call for heat if both the frost stat and pipe stat trigger?

Will also look to improve the insulation, there's definitely scope to cover the pipes better and to tape the joins between the sections of lagging.

Thanks once again