XPost: uk.d-i-y   
   From: no@spam.com   
      
   On Sun, 24 Nov 2013 07:44:52 -0000, harryagain    
   wrote:   
      
   >   
   > "Gefreiter Krueger"  wrote in message   
   > news:op.w60jrhnjiunomv@red.lan...   
   >> When I moved in 13 years ago, there was a central heating system utilising   
   >> only radiator stats.  I fitted a room thermostat (the basic bi-metallic   
   >> strip variety), which connected live to the motorised valve, which in turn   
   >> switched on the pump and boiler.  For some reason, it would often arc when   
   >> switching off, which heated the bi-metallic strip up a little and it never   
   >> managed to go off.  Problem solved by using an electronic thermostat which   
   >> contained a relay, causing cleaner switching.   
   >>   
   >> Similar problem now, with the heating system extended so it does the   
   >> garage, aswell as the house, with a seperate electronic thermostat.  The   
   >> problem this time though, is because I could only find a motorised valve   
   >> for the garage which did not have contacts inside it (only one which   
   >> fitted my odd diameter of pipe), I had to fit a relay to switch the boiler   
   >> and pump on and off (if I'd connected the output of the garage stat   
   >> straight to the pump, boiler, and valve, then the valve would open every   
   >> time the boiler and pump ran for the house too).  Anyway, it worked fine   
   >> for a year, then the relay started behaving like the old bi-metallic strip   
   >> thermostat - it arced when switched off, and took ages to do so, making an   
   >> alarming noise.  So I replaced the relay with a big industrial contactor   
   >> which is working for the moment.  The relay I replaced says it can take up   
   >> to 2HP motors, way more than my pump.  Any idea what's going on?   
   >   
   >   
   > Arcing is caused by stored emergy in the system (usually coils/electric   
   > motors.)   
   > You will often get a tiny spark when switching motors, this is normal and   
   > not enough to affect a bimetal strip.   
   > Most switches have a "snap action" to minimise this.   
   > Just what do you mean by arcing?   
      
   For the first one, interference on radios and TV.  When I stand in the same   
   room as the thermostat, I can hear the spark continuously inside it.  It warms   
   the strip up and the thermostat never goes off as a result.   
      
   With the second one, the relay is juddering and making a fucking racket.  The   
   digital thermostat in the garage is still making a funny smell after changing   
   the relay inside it and the one in the loft that it switches.  I suspect the   
   electronics are    
   fucked, it is damp out there.  I don't think there was anything wrong with   
   either relay, just buggered electronics through damp.  So the only inductive   
   problem was the first one.  I tried about 5 different makes of stat and they   
   all did the same, I guess    
   my pump's snubber is broken, but realys can handle it as they switch quicker.   
      
   --   
   The microwave was invented after a researcher walked by a radar   
   tube and a chocolate bar melted in his pocket.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)