Frost / Freezing protection for Combination boiler in garage

[Delta925]

I did have a traditional heating and hot water system with a simple gas boiler, loft tanks, a hot water cylinder and Y-plan valve. The boiler is on the rear wall of the garage, presumably from original build. The garage wall is single brick and the roof is flat, wooden planks then rubberbond EPDM rather than felt.

Near to the boiler was a thermostat set to 5C. Regardless of the timer so long as gas and electricity on when this switched over the boiler ran and the Y-plan valve was set to heating position. Hence hot water flowing in the pipes so no risk of freezing. Once from radiated heat from the boiler the local air temperature rose the thermostat switched over again.

This year I have had a combination boiler fitted, a Vaillant Ecotec Plus 832. This is set in comfort mode for hot water so cutting in at 35C and out at the set hot water temperature of 50C. The single electricity feed that previously was switched when any boiler / hot water demand was made permanent and a radio thermostat / timer fitted for heating control.

The existing pipes are now heating only with new pipes installed for the cold water feed and tap hot water delivery. From the house across the beams, so just below the flat roof, then down the single brick wall along the sides of the boiler to the connection points each is around 4.5m. All have standard basic grey foam lagging. The single electricity feed was made permanent and a radio thermostat / timer fitted for heating control.

The boiler states that it has internal frost protection at 12 degC. Beyond ensuring that the internal water temperature does not fall below 12C it is not clear what if any protection there is. Further given the hot water comfort mode keeps the water temperature above 35C will the 12C frost protection ever be triggered?

My concern is both pairs of pipes. For the heating pipes I could re-instate the garage thermostat set at 5C in parallel with the radio thermostat / timer receiver to circulate water in the heating circuit. However this does not help at all with the cold water feed and tap hot water delivery pipes. I have read where both sets have been boxed together but the pairs are separated as along a different beam.

One option is pipe trace heating wire with a 5C thermostat. To cover both pairs a 20m length required. If 10W/metre then 200W load which is one unit per 5 hours.

The starting question is if I am correct to be concerned or worrying about a problem that very unlikely to occur.

 

[cross thread]

As it runs close to the roof I would say yes to either of your ideas,the boiler is protected by its own stat but it’s no idea of the external pipes.

 

[Harry Bloomfield]

One option is pipe trace heating wire with a 5C thermostat. To cover both pairs a 20m length required. If 10W/metre then 200W load which is one unit per 5 hours.

I assume you mean the 5C, measured external to the pipes?

You can get trace heating, with built-in temperature sensing, so if the trace is overall insulated, it would not be on for those entire 5 hours, much less in fact.

 

[Delta925]

I assume you mean the 5C, measured external to the pipes?

You can get trace heating, with built-in temperature sensing, so if the trace is overall insulated, it would not be on for those entire 5 hours, much less in fact.

The systems I have looked at mostly have a nominal 5C thermostat built in, a simple preset bi-metallic switch. In an ideal world this would be in good thermal contact with the ( copper ) pipe but if not it would be inside the grey foam insulation so it ought to be close to the pipe temperature. Given I have to run along 4 sections I need the thermostat nominally mid-way along one section logically the cold water feed.
10W/m presumably is enough to keep 15mm and 22mm pipe above 0C even with the air temperature well below zero. Following on plus thinking about what you have posted when only around 0C the temperature ought to rise rather than being just maintained so the thermostat will cycle.

 

[Harry Bloomfield]

10W/m presumably is enough to keep 15mm and 22mm pipe above 0C even with the air temperature well below zero. Following on plus thinking about what you have posted when only around 0C the temperature ought to rise rather than being just maintained so the thermostat will cycle.

Yes, it will only switch on for quite short periods, using the 15 x10w 150w, always depending upon how good the insulation you fit is. The better it is, the cheaper it will be to run.