No central heating. Honeywell 4043

[Pilchard]

Hi,

Ive read through a few posts on here that kind of have the information im looking for, but im struggleing to fully understand.

My situation is that ive recently had solar panels fitted which had electricians all over the place rewiring things and I was wondering is they'd accidentally unwired it. But maybe my lack of central heating is just coincidental.

Basically, the boiler works and we have hot water, but the central heating does not (both independantly controlled). When clicking the CH on, nothing fires up. Ive worked out that the manual lever on the bottom of the honeywell unit will fire the pump and heat the radiators if you sit there holding it, so does that mean it has power going to it and the microswitch works and its the motor thats gone? When moving the lever, its very stiff.

What seems the most likely thing to fix it.

Thanks in advance,
Lee.

 

[JohnKay]

Hi

The manual lever will lock in the open position, take a look at the slot with a mirror.
Although the lever will open the valve (and they are stiff) the travel is not enough to close the microswitch, so will not power the boiler.
I suspect the syncron motor has failed, and can be replaced. It is a universal part, and easily obtained.
Have a good look at the whole valve first though, any signs of water leakage, or if the valve is quite old, it may be better to replace the complete valve.

 

[Pilchard]

If I slide the lever across and slot into the cutout holding it open, nothing happens. But pulling it a little further and holding it as far as it will go, it does turn the pump on. But the slightest movement back and it shuts off. Is that the microswitch doing that so it is recieving power? Therefore would it also be triggering the boiler (its downstairs and I dont know if it starts whilst doing this) or were the radiators just getting warm because there was already hot water in the tank?

Will it do any harm just temporarily wedging the lever open? as the CH clicked on and off with the timer as usual.

I dont really know anything about how the whole system works and i am trying to get a rough understanding so I know what needs doing.

I suspect that it is the motor thats gone but is there any simple tests to determine for sure?

Cheers.

 

[JohnKay]

Thanks for getting back
From what you say, it does look like it's just the little syncron motor that's faulty.
Yes, if the pump starts, the boiler will also.
I would not recomend jamming the valve open any further than it's designed to be in the manual position.

It may be easier for a temp. solution, just to get some warmth - leave the valve manually open, turn down the boiler a bit, and turn up the cylinder thermostat. The hot water will be too hot, but you should get some heating.

The syncrom motor is reasonably easy to replace, but a bit fiddly, not bad if you have good access to the valve.

 

[Pilchard]

Thanks for your advice.

do you need all round access to the whole unit in order to easily swap out the motor?

Access is a bit tight and its pretty much against a wall, facing away from me but i could fairly easily get in there and take the cover off. didnt look in to great a detail at the insides at the time though.

Will give it a go if its possible.

 

[JohnKay]

As you have had the cover off, you will see a round silver coloured component with two wires wrapped round it - That's the motor. It is fixed with either 2 little screws, or 1 screw and a slide in fixing.
Have another look, and locate the fixings. I hope you can get access.

 

[Pilchard]

I can remember seeing the motor side on quite well, I shall have another look later to see if I will be able to replace.

So (hopefully), one last question for my general understanding of the system:

Ill try and explain this as best I can from what I think I understand.

The valve has 3 pipes, "A" at the bottom, "B" at the top, and "AB" from the side. Google tells me this is actually a V4073A 3 port, where AB is the inlet from the boiler, A goes to the radiators, and B goes to the water tank. Does this mean that the valve has 3 positions: 1 for Hot water only, 1 for Central heating only, and 1 for both?

So in a working system:

Central Heating = Pump on, Boiler on, Valve position A.

Hot water = Pump on, Boiler on, Valve position B.

Both = Pump on, Boiler on, Valve position A&B.

Am I right in thinking the switches on the control panel are what triggers the valve motor to move to the corresponding position?

Is the default valve position Hot Water only (Position B) or maybe its just failed in that position? Which is why when both systems are on we only get Hot water as the motor hasn't moved.

I take it the Microswitch triggers the pump and boiler, and it is activated once the motor has engaged any of the valve positions after either the hot water or central heating switches have been turned on, which is why the pump starts when the hot water is switched on now as its already in place, stuck, with the microswitch engaged. However there must be something more to it as it wont power the pump with the central heating switch as it must know its not in the right position.

But with it in the manually open position it still only triggers with the hot water switch but the radiators will heat up.

So, as the timer on my control panel turns both hot water and central heating on and off at the same set times, the valve should move to position A&B? Is that the same position as having it manually opened?

Therefore, can I leave it in the manually open slot (not forcing to trigger the switch as before) and when the hot water clicks on, the pump circulates around the central heating also, as normal, effectively controlling it all using only the hot water switch.

Is there any risk in leaving it open? as the manual for the valve states that it is for draining and filling purposes only.

The only downside to this is if I ever only want Hot water, I have to manually shut the valve, and I have no option for Central heating only (until I get it fixed).

　

Is this how it works? or is it more sophisticated than that? Or am I just Wrong?
　

Cheers,

Lee.

 

[JohnKay]

Hi again.
I've been answering you on the V4043A as in your original post.

The V4073A is more sophisticated, having two microswitches. When in hot water position the power for the boiler/pump is supplied through the cylinder thermostat. The valve is held in the mid position by a diode that applies a DC current to the AC motor. I'ts avery clever bit of design that relies on the correct system wiring.

All your other points are corect. It's OK to run in the manual position, same as mid position.

Although no doubt the fault is still the motor, I would be doing a few tests first, just to make sure. As I'm not going to recomend you carry out any live testing (for safety reasons) I think the best way forward would be to replace that motor.

 

[Pilchard]

Brilliant.

Thanks for all you assistance.