Back last autumn I decided to replace my 40 plus year old Satchwell room stat with a Honeywell DT90E I thought all was fine hot water and heating working as before, last week I discovered that heating was still coming on I checked new room stat by switching on & off manually heating still on. Ok so I thought back in the past I have had to replace both of my Sunvic actuators so I went to check them and found that the water valve was in the open position hence the heating staying on. Tested by swapping over the heating ones wiring to the hot water wiring actuator working fine. When I fitted the DT90E I used the red & yellow wires and left the blue one insulated. My boiler is a Potterton MK2 Netaheat 10-16 behind the bottom cover there is a connector strip the red cable is connected to the live (L) terminal the yellow is connected to terminal 5 which on to other side has a white cable the blue cable cable is connected to the neutral (N) Am I missing a neutral somehow to the actuator? Any help much appreciated Iain
A while back I had to do some work on a system with Sunvic valves. They were MoMo (motor on, motor off), and used an extra wire. I think it required a 'satisifed' call from the stat. Sorry, a while ago, and can't remember details, other than it was a PITA and wouldn't work with the new stat. Sound familiar? In which case your blue wire may not be a neutral...
Larger commercial valves are often fully motored, no spring return, and do indeed require signals to open and close. Usually large valves though, not smaller ones.
I'm not familiar with the Sunvic valves, most people use Honeywell or Drayton around here. Is there a flag on it to show when it's open / opening? Does this respond as it should with the controls on both HW and CH? The boiler/pump should only fire once one or both valves have opened. When you say the heating comes on, the rads get hot? Not just the boiler firing? No plumbing changes? No extra rads teed in?
OK just spent an hour looking at all my wiring and have come to conclusion that my original post was right. Found this from Onetap Instructions for a Sunvic SM 5203 (later version, I think Sunvic took over the Minival business from Satchwell, or they were a subsidiary). gn/y earth blue motor neutral supply on white (terminal 2 on TLX)closes valve this is my missing feed not connected at stat stopping valve closing supply on yellow (terminal 1 on TLX) opens valve I think I may need to change some wires at boiler end.
Have the live from the stat turn the relay coil on/off. Changeover contacts in the relay feeding a perm live to either the open or close, depending on which position the relay is in, if that makes sense.
Forums
Facebook
Twitter
You Tube
Instagram
Shop