Blooming boiler systems!

[BMelectrics]

hello all,

came across a strange one today.

I was told that a motorised valve would not close so was asked to check it out.

When I was checking how it was wired, it is the type that requires a common, open and close.

When I checked the stats wiring that was controlling this valve, the connections were: live, nuetral and call.

What I noticed was that the thermostat was being used like a 2 way switch! The live was used as the common, the NEUTRAL was used as the 'close' for the valve, and the Call was used for the 'open' of the valve.

I slapped my meter on the connections at the valve only to find that when the valve was 'opening' i was only getting 190v between the 'open' connection and neutral.

The person that wired this before done it so that when the stat is calling for heat, the valve will open slowly, but when it is not calling for heat, the valve struggles to close!

The stat has a relay in it and requires a neutral, so im wondering if this is messing the whole thing up??

thoughts please???

This is killing me!

 

[ashrow]

I have not come across anything like you stated above
Generally on relay stats you would have a a timed live from clock and neutral , the live is link across to common if switching mains voltage then the N/C would be used to supply the live to the valve (some valves require a supply via the N/O to close but most demostic ones are spring shut)
You could bypass the relay and connect the live to the N/C to see if that opens the valve and once the power is removed the valve should close

Let me know what motorized valve and stat you are using and i may help further

 

[BMelectrics]

hi ashrow, thanks for your quick response,

The stat in question is a drayton basic stat, with connecions, LIVE, NEUTRAL and CALL.

this was being used like a 2 way switch, the NEUTRAL of the stat controlling the 'close' connection in the valve.

The CALL of the stat was controlling the 'open' connection of the valve.

The valve is a COSTER 90 degree rotary actuator.

 

[ashrow]

With the drayton basic stat you have the live feed from your time clock, neutral and then either terminal 3 to open the valve and if it needs mains power to close terminal 2

Can you confirm what terminals were used ?

I need to google the valve as i have never come across one yet

 

[ashrow]

After reading your first post again, it may seem that, there is no neutral at the stat, but actually a close and open feeds out to the valve. did you check for voltages between this 2 cables to earth ie ie when stat turned up(earth and 3) and then when down (earth and 2) ?

 

[BMelectrics]

yeah, the live was used to feed the controller, terminal 3 was used as the call, but for some reason the neutral is being used as the closer of the valve, this is all the available connections in the stat!

here is the instructions http://www.calor.ro/documents/products/13878/Coster%20CVH%20-%20Servomotor.pdf

in the valve: number 1 has a neutral, 2 is connected to the CALL of the stat (open), and 3 is connected to the NEUTRAL of the stat(close), i think they may have used the wrong stat!

 

[BMelectrics]

yeah i checked the voltages to earth, 2 to earth (when opening valve) gave me 190v, and 160v against 3 to earth. it seems that the voltages are being split across the open and close at the same time.

I think that a different type of stat is needed, as this stats connections are LIVE, NEUTRAL AND 3.

I need a stat that has connections Common, open and close. Am I correct in saying this??

 

[ashrow]

do not assume a blue cable is a neutral (if the old red yellow blue cable is used)

The stat may not work correctly with out a neutral, isolate supply and connect the live to that cable coming out of terminal 2 of the stat and that should close the valve

I would advise you to test for mains voltage on the terminals to earth when stat is up and down before !

 

[ashrow]

Seems like the earth is not connected also, i would double check that connection also !!!

Quick edit

From the link you provided the valve does need a switch live to close, so as i said prior that assuming you confirm the blue is not a neutral isolate the supply, put the red and yellow in a connector to open the valve, make sure 9its open and boiler fires, isolate supply again and then connect red to blue, turn on supply and the valve should then close

It does seem so far to be a stat issue but with out doing this tests we will not know for sure

 

[BMelectrics]

Heres another curveball, the valve has limiting buttons in it to stop the rotation of the arm when opening and closing the valve. putting 0v across terminal 2 in the valve

When the valve was fully opened, it hits the limiting button to stop the voltage from keeping the arm opening.

However when it is closing and the arm hits the 'closing' limit button, the voltage cuts out to stop the arm going any further, but it trys to open again breafly and then shuts, hitting the limiting button again, and this continues until the stat calls for heat again.......AAAAAAAAAAAAAAAAAARRRRRRRRRRRRRFFFFFFFFFGGGGGGGGGG

 

[ashrow]

BM
With out being there to help, it is hard write what i see in my head
if the valve closes when the stat reaches temperature then the stat is working and the valve is closing, the valve will continue to hit the close limit switch until the room stat requires it to open again (ie you turn it up or the temperature drops below what the stat is set at)
If you confirm the stat is giving you 230 volts to a true earth or neutral when asking the valve to close then the valve must be faulty
If you can not confirm this then we are left with only a stat or wiring fault

Take your time and triple check, you will get there

 

[oldtimer]

Ok you must always have a neutral at a traditional room thermostat why ? you ask well a lot of sparks see a room stat as a switch and yes it is a thermal switch so they wire a T&E but it needs a 3C&E because of the neutral so why and how does it work

Well behind the bi-metalic switch there is a Anticipator or Accelerator resistor that has a perminant neutral to it and the other side has loop from the call for heat cable or switchwire now when the thermostat call for heat the resistor starts to heat up and this makes the control band for the stat tighter . So what happens if you ditch the neutral easy your fuel bill goes up by about 8%.