On Sun, 1 Feb 2009 18:44:29 +0000, Kennet Boater <[email protected]> wrote:
>Hi Brian and Richard >I have fitted an overide switch so the pump can be switched from thermostat to >constant to prevent the 'boil up' as the fire initially gains heat. (The >boiler fittings are small and don't allow the heat to travel the pipe and >start the therostat before boil up) > >Once the system is hot I switch back to theromstat (set low to avoid boil up) >and all is fine. >We burn wood rather than coal so when the fire dies down (if we are slack at >'log chucking', go out or go to bed) the pipe seems to get very cool before >the thermostat cuts out. >Im not bothered by the rads getting a spell of cool water but the calorifier >looses a fair bit of heat. > >What how does the thermostat on a older type car work? Would that stop/allow >water along a pipe. > >The system is on my refit boat so the pipe thermostat is less than a year old >and has only been used on and off (ha ha!) this winter. > >Currently fiddling with the pipe stat settings but its as long job as envolves > a full cycle of cold/hot/cold. Would like to have the calorifier only receive >the hottest water, without me having to go wardrobe potholing each day! ho hum! > >Thanks for your suggestions >Lee IMHO you have a basically crap control system! My initial reaction to your original post was "Just get a Thermostat with a smaller switching differential". However this subsequent post has indicated that is not enough. Your comment that "I have fitted an overide switch so the pump can be switched from thermostat to constant to prevent the 'boil up' as the fire initially gains heat." is the killer. No external system whether mechanical as Bru has suggested or electrical will handle the problem as described. IMHO you need to get a low differential thermostat that monitors the Boiler water temperature, only then will you have a safe workable system. If you cannot monitor boiler temperature directly then you need to change your "Hot" outlet configuration so that you get some rise from the boiler before circulating. Given a vertical pipe the hot water will rise to that area with or without the pump. The stat should be fitted to that vertical pipe. You do need a reasonable diameter pipe to ensure gravity circulation in that area. Ensure that your header is higher than this vertical, fit a vent at the top. Sorry but I have seen this problem before and the above bis how I sorted it. Problem is it is difficult to make it look "pretty" <G> -- Richard
