Actually, I don't think it helps, it just gets me past first base, but the
following edited list still applies :-
Q1. Does the hot water circuit use pump or just gravity?
Q2. Should switching to HW on my control unit make the motorized valve
shut ( & trip off the pump if answer to item #1 is gravity )?
Q4. Is one of the 22m pipes in the piping arrangement just the vent to
my header tank?
Q5. Why have a -15°-+10 thermostat in the garage? , but none in the
house , and in which parameters does it work.
Q10. I've never attempted to put any corrosion inhibitor into the header
tank and there's no filtration of any kind in the system. Should there be
Q11. I've just bought replacement sychron motor, but I can tell which
position the gear quandrant should be in when I mount the motor in position.
All I can tell is when the motor is hanging loose and I switch W+H, then
motor activates without stopping.
Q12 my zone valve has 5 wires, brown/blue , white/black and green earth.
The black/white is a contact switch which mades contact as the gear quadrant
ges down. What is supposed to happen as a result of the black/white contact
being made ?
Q13 My control/timer unit is a randall 103E . I can unscrew the bottom plate
but how the hell does the face plate come off so I can see the wiring ?
Q14 Throughout all the messing about I've been doing, in every condition the
CH pump appears to be constantly running. Surely something must shut down
the pump ?
Q15 My HW tank has two 15mm pipes which have concentric reducers terminating
at the top of the tank ( I pressume some kind of HW circuit bleed. There are
screwdriver slots in the top of the reducers, but I would like to try and
unscrew them as they made not go back in place. Has anyone ever seen such an
arrangement and I am safe to try and uncrew them ?
You'll have to trace back along the pipes from the coil in your hot water
tank to find out.
It depends on the type of system you have in Q1.
It depends on the type of system you have.
A thermostat fitted externally is more than likely a what is known as a
frost guard. It works by sensing the external temperature and if it falls
below the set level, then your heating kicks in to stop the house freezing.
Inhibitor is a good idea, especially in hard water areas (lots of lime and
things in the water), but is not totally neccesary. Filters would only be
used if the supply water was known to contain large contaminants, but if
fitlering was needed on your system, then it should be documented on the
boiler or a system diagram for cleaning routines.
A synchron motor, as with any standard motor, will continue to turn when
energised until told to stop by some kind of switching system. The small
micro-switch in the motorised valve is such a system.
A motorised valve has two wires which carry the power needed to make it
turn. It also has some wires which connect to the switching in the valve
head and these are used as signalling connections to the timers or
programmers and tell the boiler to fire up or the pump to run or the system
to shut down and switch off completely and it depends on how the system
setup is configured.
Usually the timer/programmer seperates from the back plate by loosening, not
removing, screws from the bottom or top of the unit. When loosened the face
place lifts to 45 degree angle away from the screws and then lifts off
completely when freed from moulded lugs on the back plate.
This switching depends usually on the motorised valves. Motorised valves
contain micro-switches that, when wired to suit the system, tell the boiler
to fire up, tell the pump to run when needed and generally take care of the
flow of heated water arond the system.
These reducers sound very like air bleeder valves. If you slowly undo one
of the bolts, water should rise out. If you are getting air or even just a
hissing sound, then your system has to much air and not enough water.
Heating air and trying to circulate it around your water and radiator
circuits is not the best way to heat the house. You really need all water
in the pipework to do this the most efficiently.
Have a look at the sites I offered and then try to trace the pipes in your
system to where they match and where they differ. Make some drawings or
notes on the things you discover that are different and then get back to us
with a description and we'll try help you through what the differences are.
Thats why I did this sketch. If you look you will see it is in the pumped
line and tee'd off just before the zone valve. But I don't know whether this
NEEDS the pump or whether gravity still works in the pump switched off
Can you check the sketch & confirm what ystem I have. BTW in the sketch, the
line to the kitchen should come off the middle pipe after the zone valve. I
drew it wrong.
Can you check the sketch & confirm .......
Okay, makes sense. I can only tell if that functions in a few moths time..
Okay, no need to worry too much about that then.
Ahh, I had a play with this whilst the motor was turning. It didn't make any
difference. So maybe the microswitch could be cooked. PS did I put my life @
risk because I suspect the microswitch could be 240V.AC ?
On Q11 you just told me that my black/white switch tripped of the motor. Is
the 'signal' a micro amp signal.
The linked sketch showed the wires in the junction box next to the zone
valve. Can you shed any light on it in relation to my questions.
Hmmm. theres only one screw visible which I undid. All that came off as a
result was the bottom coverpiece. I'll take a closer look later
Could/should my 1-off zone valve with its single microswitch do anything
else including switch off the synchron motor?. Please refer to my sketches
This my make you LOL, but I actually work for a pump manufacturer and
tender quotations for multi-megawatt powered pumpsets for oil riggs &
The main thing I'm struggling with is not so much the piping, but the
switching/signalling and whether it is all 240v. On major machinery, the
instrument signals are 4-20mA.
From your sketches the system has a constant hot water circulation through
the pump any time the boiler fires up. This means that there is a
thermostat on the hot water cylinder. Correct ?
The motorised valve is only activated when you call for heat to the
The wiring sketch shows a "?" on a pair of wires and is most likely the
connection to the hot water cylinder thermostat.
The frost guard 'stat will control the system by over riding the hot water
circulation and only allow the heating to be called for by the radiators.
Everything on the wiring will live mains voltage and should run at no more
than 5 amps at total load. It may even be 3 amps depending on the pump size
and switching loads of the 'stat and things.
The motorised valve will only open when the programmer calls for heating to
the radiator circuit. Unless you've seen things in the wrong places and the
valve is actually a three port, two way valve, which is connected to the
flow pipe after the pump and will swing an arm inside it between the hot
water and heating circuits, or can be set by the system to stop in a mid
point between the two circuits to allow heated water to flow through both
A three port valve has three pipes going to in to it. One is the flow from
the boiler, one is the flow to the hot water circuit and one is flow to the
From your sketch the system relize on the pump to circulate the heated water
around the two circuits and is fed from a header tank. It looks to be a
very basic, and very easily maintained, system.
Thanks for picking up on my queries BigW. I am an OK DIY'er, but I've never
payed any attention to CH/HW before. I got recently mugged by a plumber for
£150 ( the wife called them in out of blind panic ) to put a new pump in, so
now I've decided I need to get more genned up on the subject before winter
I suspect you are right about the thermostat in the HW tank ( I'll check
tonight ). However, if my boiler has a stat on it with a 140-180°F setting,
I can't see the purpose of the stat on the HW tank i.e what will it
activate/de-activate. If going from my sketch there is a permanent unvalved
supply to my HW coil, then all that I can see could happen is that when the
HW-tank thinks its hot enough, it stops the boiler GCV, but this would then
stop the hot feed to the radiators wouldn't it when perhaps there was a
demand ? I could understand the concept of a HW stat triggering a HW zone
valve to close if one was installed...
I think there is also a immersion heater in the tank but its knacked with
the wiring ripped out of the wall socket. I think I need to verify what
wiring exists & replace the heater. ( I thought that you didn't need an
immersion heater if you had a boiler, but it now seems obvious that I should
have one there as back-up in case the boiler goes down )
Re the zone valve, I assume 'activated' means opened and when no power is
supplied the the valve it springs shut. Therefore there should only be a
power supply to the valve when the 'water+heat' switch is toggled. Please
confirm I've got my head round that one......
...and how have you concluded the valve is three port ? Although my system
may be better suited to a three port arrangement, I can definately assure
you that the valve on my garage wall is a tower 672B 22m 2port valve with an
earthwire, plus four other wires connected. Do you think I should replace
the current 2 port with a 3-port , or just install a 2nd 2-port valve (
15mm if available )on the HW line.
Re the frost guard stat, you reckon this stat will 'only allow heating the
be called for by the rads', but as I've stated above, the HW circuit has
nothing to isolate it , so I can't visualise how this can happen when I have
no stat in the house other than the rad-stat-valves. I can understand the
concept of the frost stat just being a by-pass( short circuit ) to all the
other controls such that it fires up the boiler ahead of the timer eg if I
set it to zero°C... Does that make sense ?
Finally the pump. Although it is clear that the HW is fed from a tee
junction after the pump discharge, does this mean that it absolutely cannot
be a gravity based HW circuit. If the boiler is in the garage and the HW
tank is 3-4m above on the upstairs landing of the house, does it need the
pump to get it round or will just the heat energy/pressure entered into the
water force it round ?
( A am not 100% sure on how a gravity system should/could work. )
I'm sure if I checked my gas bills with other people I'll find out I've been
wasting lots of cash running my system wrong. When I've got better informed,
I want to mod my system so that the HW just gets hot & isolates itself until
its needed and the CH does the same & perhaps stops the pump. I wan't to
learn whether there should be more control over the pump, for instance when
'HW only' selected, can't the pump be tripped.
Pls continue to help
I have any my zone valve wiring bares no resemblance to the one on your
page. My zone valve has only 5 wires not six with no orange or grey.
Pls see my post below. the microswitch doesn't do anything. the motor
continuously turns as soon as I ask for water+heat regardless of whether the
microswitch wires are separated or joined...
The motor will turn as soon as power goes to it and remains powered through
the duration of the call for heat. The micro-switch activates the boiler
and pump controls.
The motor doesn't stop until it reaches the limit set by the cog wheel, so
if the cog wheel breaks any teeth the motor will continue to turn. It is
the cog wheel that moves the valve arm inside the valve and not the motor
The micro-switch can have as many connections as is needed by the system,
yours only needs two, and can control the pump, the boiler fire up control,
the thermostats, etc. etc. etc.
Now please understand that the motor will turn continuously until the power
is switched off by some other controller.
If the motor doesn't get power then the spring return closes it.
These motors are designed to work in this fashion. They do eventually burn
out, but it can take many years.
This will call for hot water from the boiler, but when timer/programmer is
set to call for heating and hot water, this 'stat will be over riden by the
switched live from the motoried valve. That's according to your wiring
Power is taken from the timer/programmer to the valve motor which begins to
turn the cog wheel in the valve. When the pre-set limit is reached on the
cog wheel a little tag presses the micro-switch and switches a Live supply
to another appliance in the system. So only one of the wires to the
micro-switch will have a constant Live supply which is then switched by the
micro-switch to turn something else in the system on. It can be used to
turn on a relay, a pump, another valve, the gas flow valve in the boiler,
etc. etc. etc.
Okay, I think I've got the jist.
Can I got back to a question that nobody has conclusivley answered.
Should my pump have any other way of tripping off/on other than the timer ?
Like I keep saying, the pump is running all the time the system is switched
on, and in either water-only & heat&water modes. I thought that in summer,
if I selected water-only then the pump need not run.
And finally my question about zone valve quadrant operational movement of
30°. Is that enough ?
Your hot water needs the pump to circulate heated water around the coil in
the cylinder and will run any time you call for heat or hot water or both.
Your system will be very inefficient if you allow it to be differentially
circulated and would probably take about three days to heat a tank full of
YES !!! The activator arm only has to swing about thirty degrees to move
the rubber ball away from the opening of the valve outlet and is also enough
to move the little tag to activate the micro-switch.
According to what BW has said. the motor isn't told to stop by the
microswitch, it stays energised as long as the 'W+H' switch is toggled. The
microswitch doesn't stop the motor, it activates the pump & gas ctrl valve.
Pls check my wiring sketch link from the older posts and if you see ethings
differently then pls advise..
Erm....sorry it was actually a 102E, apologies. The above made absolutely no
sense so I checked and realised my error.
Theres nothing rotary on this unit, just one single screw underneath which
allows removal of a narrow rectangular plastic bottom plate. I can't see any
obvious points to break it open.
On the subject of these zone or diverter valves with spring returns,
I am sure I can remember that when I installed my first system (late
seventies), the 2 port valves that I used were motorised in both
directions - i.e. no spring return.
IIRC, the motor had two windings or some means of effecting reverse
and there was a live to drive it to open and another to drive it to
close. Then the room and cylinder thermostats were change-over
switches to do this. There was an auxilliary switch as now to
provide the demand live to the boiler.
Do you remember those and when and why they changed? This seems like
a better way to do the job than a motor powered against a spring.
To email, substitute .nospam with .gl
Hmmmmm.... this is getting strange, but your theory below might shed some
light on my latest findings :-
I've just been meddling about with the valve in the garage with a
1. The valve does have free movement albeit limited to about 30° max. Does
that seem right or should it be more like 80-90° ?
2. With the control switch set on 'water plus heat' the motor starts
turning, pressumably to open the valve. Looking at the motor direction of
rotation, this should make the quadrant gear move CCW downwards. At this
point I levered the quadrant down manually to trigger the microswitch, but
nothing happened and the motor kept on turning.
3. Thinking that the microswitch was faulty, I turned my attention to that.
It has three terminals but only 2 wires connected. A black wire underneath
and a white wire in the middle and nothing connected to the top terminal. I
removed the microswitch and tried continuity testing it. Between the two
connected terminals it was a broken open circuit until the switch was
depressed, then continuity was made. When I tested across the two end
terminals I just got a widely fluctuating resistance of 10-70 ohms.
4. ...this is where I loose the plot ! Okay here goes..., with the black &
white wires hanging loose but in a safe position, I switched on the system
and the synchron motor starts turning. I'm not sure why, but I decided to
switch off the system again and connect the black & white terminals together
expecting the motor to stop. But when I switched on the system, the motor
started turning again !!!
My house is a late 60's semi which has a Vulcan boiler , tower 672B zone
valve & 102E randall controller. Some of it was fitted in the 70s and maybe
mods were done in the 80s
Can anyone enlighten me on this as I'm lost
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