hi, just brought a digital stat to replace an old honeywell, fitted it wired all up etc heating comes on but i can't turn it off!!, stays on constant, the wires into the stat are; RED, BLUE, YELLOW, EARTH and the terminals on the stat are N L 1 2 3 4 , with 1 & 3 being redundant, number 2 says COMM, and number 4 says ON, there is also an open switch diagram going from COMM (2) to ON (4), also between L & COMM (2) says a link required for mains voltage applications, when link is in the heating works, when its not in it dosen't also the stat dosen't work if the Neutral is not in place, its not a combi boiler, and ive reset all the times etc and even restored factory settings, bit of a head scratcher for me chaps, hope someone can help me out, thanx
horstmann PRT1 room stat won't turn heating off!!
- Thread starter bigdeano
- Start date
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So what wires have you put where ?
BLUE = NEUTRAL
RED = LIVE
YELLOW = 4 (ON)
LINK WIRE BETWEEN L & 2 (comm)
ive tried switching the yellow and red over in case the colours don't correspond with whats coming out of the boiler, but everythings right, link wire between L & 2 (comm) make the boiler fire up but when its removed it won't fire up, it also fires up when the YELLOW is in 2 (comm) as well as 4 (on),!!
RED = LIVE
YELLOW = 4 (ON)
LINK WIRE BETWEEN L & 2 (comm)
ive tried switching the yellow and red over in case the colours don't correspond with whats coming out of the boiler, but everythings right, link wire between L & 2 (comm) make the boiler fire up but when its removed it won't fire up, it also fires up when the YELLOW is in 2 (comm) as well as 4 (on),!!
So you definitely need the link.
Is this with the link from L to 2 in place? If so, you are bypassing the thermostat switch meaning the boiler will fire all the time.
The PRT1 is a programmable thermostat. Which profile are you using? What are the Warm and Cool temperatures?
Do you still have another timer/programmer in circuit? If so, what is it set to do?
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yes link needed by all accounts to fire up the boiler, and link is in place when YELLOW WIRE is in 2 or 4, i have retored factory settings on the stat but the preset programmes are still there, been through them all and reset time date and year but still can't turn off the heating!!, its a simple enough stat to use but somehow won't switch off, and when its on its on full blast piping hot!, no other stat in the circuit,
Which boiler do you have?
Did the old Honeywell stat work properly?
Can you remember how the wires were connected on the old Honeywell stat?
Do you have a multimeter?
Did the old Honeywell stat work properly?
Can you remember how the wires were connected on the old Honeywell stat?
Do you have a multimeter?
its a myson apollo (really old), old honeywell worked, i can't remember the wiring when i took the old stat off, thought it would be a stright swap really, haven't got a multimeter but can get hold of one, do you think its not compatible?
Got one myself.
With that type of boiler you must have one (left pic) or two (right) motorized valves? The fault may be in the valve(s).
View media item 5946 View media item 11762
Would make fault finding much easier.
It's compatible.
You haven't answered my question about an old programmer/timer.
do you think it being a programmable stat with preset programs that it will not work properly ie, to just turn the thing on/off any time of the day and upset the settings??
no other timer in the circuit
You should always be able to override the settings. This type of thermostat does not have a true "off" setting. It just has different temperature settings for different time periods - warm and cool in Horstmanns lingo. The cool temperature being the equivalent of turning the system off. But you can always turn the temperature up/down and it will stay at that temperature until the next programmed time/temperature setting.
And motorized valves? (Probably near the HW cylinder.)
has a motorized valve but no make on it
Forget the make, which type is it - look at the pics I posted?
looks like the left one to me
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