Unvented/G3 ongoing install sanity check

[NoRulesRules]

As an aside, the Ideal Logic+ System is confusing when it comes to frost protection. The boiler manual says it has built in frost protection for 5c and below. But then in the same manual it also says that if the boiler is installed in a cold place, (ours is in garage), then a frost stat should be added.

Our installs have added an external frost stat, but I'm not sure its even needed. Will call Ideal Monday.

Also, there is no complimentary reheat stat on the CH return pipe, which I assume means if the garage dips below 5c (happens in winter), then the frost stat would kick in and override room-stat, turning the house in to a furnace.

I feel like I need a heating degree to even buy a system like this!

 

[bernardgreen]

The boiler manual says it has built in frost protection

Probable protects the boiler but does not fully protect pipe work and radiators.

 

[NoRulesRules]

Probable protects the boiler but does not fully protect pipe work and radiators.

Hmm. How does the boiler protect itself? Surely by switching on the burner and pump? If yes, then at a minimum that circulates hot water via the bypass valve, which is therefore protecting flow/return pipes inside garage.

2 port valve on CH does not need to open, rads don't need protecting, they are inside the warm house.

 

[bernardgreen]

2 port valve on CH does not need to open, rads don't need protecting, they are inside the warm house.

If the CH is not turned on then the house may not be warm for long when the outside temperature drops below zero.

 

[NoRulesRules]

If the CH is not turned on then the house may not be warm for long when the outside temperature drops below zero.

Our room thermostat - Hive - has a frost setting that kicks in at 7c.

 

[Gasguru]

The frost stat in the garage protects the pipe work...the boiler fires up and the water flows through the bypass as the zone valves are closed. There should be a pipe stat fitted to the return say a meter from the boiler to shut the boiler off when the pipe is say 20 degrees. Frost and pipe stat wired in series.

 

[NoRulesRules]

The frost stat in the garage protects the pipe work...the boiler fires up and the water flows through the bypass as the zone valves are closed. There should be a pipe stat fitted to the return say a meter from the boiler to shut the boiler off when the pipe is say 20 degrees. Frost and pipe stat wired in series.

Understand that, but my question/confusion is around the fact the boiler has frost protection too, also set at 5C. Does that not do the same thing? Circulating the same hot water through the same circuit?

I.e. why does this scenario need an external frost or pipe stat at all?

 

[Gasguru]

The boiler by virtue of it's thermal mass and water content will retain heat longer than the water in a pipe perhaps the other side of the garage...so the pipework needs protection. That's why smaller bore pipework is at higher risk than larger bore.

 

[NoRulesRules]

The boiler by virtue of it's thermal mass and water content will retain heat longer than the water in a pipe perhaps the other side of the garage...so the pipework needs protection. That's why smaller bore pipework is at higher risk than larger bore.

Ok, the penny is starting to drop.

So the boiler protection is checking the boiler water temp. Which has more chance of being over 5C, due to reasons you state. E.g. Boiler could be 10c due to residual heat, but garage air temp (and therefore frost stat) could be reading <5c, and impacting pipe work in garage.

Ok. So long story short, leave the frost stat there, leave boiler frost protection on, but I need to get a pipe stat to stop low temps in the garage over riding our room stat, during periods of cold weather. Or rather, I need to point out to the installers they have forgotten the pipe stat. (along with the rest of the issues)

 

[Gasguru]

Yes the boiler will use the thermistors inside to monitor its own temp but outside of that the frost stat provides protection. The small amount of heat given off by the insulated garage pipe work would take an age or never raise the garage ambient temperature sufficient to raise the frost stat above its setting so the pipe stat on the return will shut the boiler off once a sensible water temp is reached (and that won't take long with the water only circulating round the bypass valve ( hopefully set at a suitable setting for it to actually open).

 

[Gasguru]

You should find an official explanation on Honeywell/Drayton/Danfoss websites somewhere..
Make sure the pipe stat isn't fitted too close to the boiler otherwise residual heat from conduction from the boiler will defeat the frost stat.