Cannot get HW by itself since motorized valve replacement.

[citizencydonia]

The order of how things have happened:

1) The motorized valve would produce a really loud knocking sound unless both CH and HW were calling (e.g so it had to be in the middle position or else the knocking noise occurred)
2) Plumber identified that the motor was broken in the valve and replaced with a new one, electrician wired it up. Also had boiler serviced at same time.

Ever since:

We never can get HW if only HW is selected on the programmer. Boiler and pump fire up but heat is going nowhere. Only works if CH is also on, when the motorized valve switched over a lot of air is sucked into the system from the pressure release valve on the hot water tanks flow from the t-valve. Results in much air in the system and daily rad bleeding, sometimes the header tank overflows, sometimes the boiler needs resetting.

1) Electrician reinspected his work - looks ok
2) Second electrician inspected the wiring - valve is definitely wired ok, all thermostats are working and the programmer is calling with correct signals.
3) Plumber returns - valve is simply not ever moving over to the HW only position - fitted another motorized valve of the same model - no change.

So what else could it be? We are at a loss. Guessing the air related problems are caused by the valve not opening correctly......

Additional info: pump is on the return to the boilder.

 

[Dan Robinson]

It's not wired properly.

Or the timer is guffed.

 

[MANDATE]

I'm a bit puzzled regarding your motorised valve.
Mid position is mentioned so it must be a 3 port mid position valve.
I understand these valves are 'spring return' to the rest position which is the HW position.
So the motor must be ok if it moves the valve to mid position.
I can understand the valve not moving any further than mid position due to various reasons, but when CH is satisfied or switched off the valve should just drop back to the HW position under the strength of the return spring when the power source is removed. (unless the valve is stuck in mid position)
I think the first action is to remove the actuator head off the valve spindle and see if the spindle is easy to turn or is it stiff.
With the head off the movement of the actuator could be tested according to what is selected and check to see if the actuator moves to all three positions.
You dont state what valve it is. Some valves don't have removable heads.
A new valve has no power to it, so it's already in the HW position when first fitted and it only moves to mid position when power is supplied to it via the room stat and when that power is cut it drops back to the rest position.
Also you have to understand that 'mid position' is only temporary. Both CH and HW are getting a share of the water until one of them is satisfied. This would usually be HW so when this happens the valve would move to CH only, but this means the valve moving beyond mid position which your valve may or may not do.
There are quite a few things that can go wrong such as stiff spindle, quadrant gears stuck, faulty motor, faulty micro switches, in correctly wired, loose terminals. faulty programmer.
Note power to boiler goes through cylinder stat if HW is involved. If only CH is involved power goes through the valve.
I think if your plumber and electrician fully understand how it works it would be easier to pin point the problem. I recall having problem and taking ages to fully understand it.

 

[Agile]

This thread shows the problems which can arise when a plumber is called who cannot wire up or fault find electrical circuits!

Far better to have heating engineer who can do everything himself.

Tony

 

[bazdaman]

As Tony said a plumber that needs a spark to wire n a 3port obviously does not know a great deal of fault finding, he may have just not fully opened the iso valve to the cylinder, are you getting any heat whatsoever at the cyl circs.

 

[citizencydonia]

Thanks for the replies.

Dan_Robinson / Agile - It certainly does still seem to be pointing to the electrical side of things - but as I said 2 separate electricians have confirmed it is ok on that side of things, it is wired correctly and the programmer is working - do it get a third electrician out - a 4th? As you said though - a proper heating engineer who can do both is the next logical step.

MANDATE - The model is a BOSS BMPV222 3 position valve, but as I said, we have tried 2 brand new ones now, the head has been removed and inspected and the valve makes no attempt to move across when only HW is calling. So unlikely to be stiffness or a fault in the valve now unless we are incredibly unlucky.

bazdaman - agreed, but the plumber is decent and has done good work for us in the past, he knows the electrical side of things just does not have the certification required in the uk. We are getting heat at the cyl circs, but only when CH is also on.

So...next step is to get a proper heating engineer out, would they normally quote a fixed price up front? I only ask as I am starting to think this will require a days worth of trial and error to track down the fault.

 

[matt1e]

Id forget the electrical side of things for now and concentrate on the circulation problems first
Is the valve installed correctly for a start? because it doesn't sound like it
Post some pics if you can

Matt

 

[citizencydonia]

Before we had a Drayton TA/M4 actuator. Now we have a BOSS BMPV222, 3 port mid position valve.

Looking at these posts which have the same model - is it possible that the valve is wired the wrong way around, or that what I have now is not compatible?

//www.diynot.com/forums/viewtopic.php?t=150037
//www.diynot.com/forums/viewtopic.php?t=240322

 

[matt1e]

they are different wiring schemes
post some pics of the wiring too

Mtt

 

[MANDATE]

Thanks for the replies.



MANDATE - The model is a BOSS BMPV222 3 position valve, but as I said, we have tried 2 brand new ones now, the head has been removed and inspected and the valve makes no attempt to move across when only HW is calling. So unlikely to be stiffness or a fault in the valve now unless we are incredibly unlucky.

You state the valve makes no attempt to move across when only HW is calling, but move across from where?
In a newly installed valve, it cannot move across because its already in the HW position, so where would it move across from.
If the valve had already moved to CH only position the follow actions would happen depending on settings etc.
(a) If CH became satisfied, the room stat would cut off the power supply to the valves white wire and therefore no power out from valve until room stat restores the power. The valve itself would stay at the CH position.
(b) If the CH was turned off at the programmer, it would be the same as (a)
(c) If CH was turned off and HW was turned on, the power on the grey wire which was keeping the valve at CH position is removed and the motor would simply unwind with the force of the return spring to its rest position which is HW.
If its not returning from CH position or mid position and its not stuck, then the power is not being cut off.
Note With both CH and HW off, there is still a wire from the programmers HW OFF terminal that is 'live'.
So if all power to the boiler is switched off, does the valve then return to HW position.
I suppose confirmation is required first to ensure valve is fitted the correct way round.

 

[citizencydonia]

Again many thanks Mandate and matt1e. I will try and get some photos.

Everything you say mandate makes sense, I have very little electrical skills/knowledge but what you describe is logical. When I say 'move across' I do mean from the mid / CH positions - as these are working fine and you can here the valve 'moving across' inside as the motor winds presumably, and the plumber did state that with the casing off he saw that the valve was not moving back when only HW is calling.

So the valve or the wiring being the wrong way around has to be the favourite. I will do some experiments with combinations on the programmer and all power off (something I had not thought of) and get photos...

 

[MANDATE]

If the valve moves from mid position to CH and happily drops back to mid position but will not go back to HW I can only think of two possible reasons.
Although I doubt it as its all new, the gears could be fouling.
The quadrant will probably have only about 16 teeth and the motor pinion about 8 teeth, so the motor only turns a couple of turns to turn the quadrant over the full range. So any damage on the first few teeth on the quadrant could prevent the motor unwinding fully. As said I doubt if this the case.

Just thought of something else. There is normally a lever which is used to manually wind the motor/quadrant to mid position. this is for use refilling a drained down system. The lever is moved to mid position and latched and unlatched after filling. Could be lever is still in latched position so cant return to HW.

Other than those it sounds as though the power supply to valves 'white' wire which is controlled first by the CH switch on the programmer and secondly by the room stat is permanently on. The power supplied on the white drives the motor to mid position only It is then cut by micro switch and replaced with power supplied on the grey. So if the valve has a permanent supply on the white wire it could drop back from CH to mid position but no further. So verify there is no voltage on white wire when room stat turned down. If voltage present then incorrect wiring or faulty room stat.

 

[swbjackson]

Before we had a Drayton TA/M4 actuator. Now we have a BOSS BMPV222, 3 port mid position valve.

Looking at these posts which have the same model - is it possible that the valve is wired the wrong way around, or that what I have now is not compatible?

//www.diynot.com/forums/viewtopic.php?t=150037
//www.diynot.com/forums/viewtopic.php?t=240322[/QUOTE]

The Drayton TA/M4 valve is used with a special relay box. A standard 3 port valve is not a direct replacement unless the system is rewired to a standard Y plan configuration. If the junction box says RB1 or RB2 on it the chances are the wiring is incorrect.

As Tony (Agile) said, this is the problem with using a heating engineer who doesn't understand control wiring.