Boiler rad not getting hot

[gary.holt]

After two days away, I have just come back to this problem.

Turned on the heating and water on the poiler both lights on, result boiler power light on and boiler starts okay. But after about 40 mins the power on light goes out and and the heating and water lights are still on but the boiler had turned it self off. Result was hot water but rads cold, therefore emptyed the hot water tank and set the 3 way valve to manual and switch heating and water backon. Result rads getting warm but after 20 mins lockout occured therefore pressed reset on boiler and

switched heating and water on again all okay. But after about 20 mins boiler power on light has gone out and the boiler is quiet ?

Have tryed increasing the temp dial on the outside of the boiler but this does not have any result. The room stat is set to 25 and is only about

2 years old.

Boiler : Worcester Danesmoor 20/25

Have just emptyed the tank again and the boiler has started ? Looks like it it not understanding the room stat ?

Have just emptyed the tank again and the boiler has started. Therefore have turned off the hot water and the boiler has stopped ? But the heating light is set to on ? So turned off the heating and turned on the water, boiler running have left 3 way valve at manual to get some heating on.

[Tim S]

I don't know this boiler but I would guess it may be the boiler thermostat. We had a similar problem with very similar symptoms. As the "high" thermostat (in our case) had failed closed, the boiler was running until the protection thermostat shut the thing down requiring a full reset as in your case.

Easily diagnosed in my case - just set to use the "low" thermostat and all was well. In your case, you could prove this by measuring whether the adjustable thermostat is switching at all (usual caveats about lethal voltages etc etc). For a more basic test, if you turn the thermostat knob back and forth when the boiler is operating but not yet locked out and don't get a "click" then then that would be a fair indication that it's failed if its a basic mechanical stat - which it sounds like you perhaps did?

HTH

Tim

PS I'm tired so I may have misread something...

[gary.holt]

Looks like the heating light is having no effect, if I turn it to on the boiler does not start ? If I turn on the water the boiler starts but will turn it self off when the water reaches its required temperature.

So the water side is fine and if I cheat and put the 3way valve to manual I will get rads on for an hour.

But switching the heating on does not have any luck.

Cheers

Gary

Tim S wrote:

[Roger Mills]

The problem is almost certainly either with the 3-port valve or with the room thermostat. In CH mode, the programmer feeds power to the valve via the room stat. This causes the valve to motor to either the mid or CH-only position (depending on whether there is also a HW demand) - and a switch in the valve actuator then turns on the boiler and pump. So no valve movement, no CH!

I'm assuming that you have a Y-Plan system. If you look at the Y-Plan circuit diagram in

you'll get an idea of how it's *supposed* to work.

If you move the valve to manual (mid position) while the HW is being heated, the hot water from the boiler will go to the tank and radiators at the same time. But chances are that the system will only be driven by the cylinder stat - so as soon as the HW is hot, it will all go off.

I can't quite explain why your boiler locked out. That imples that it over-heated - so you may have more than one problem. But I would sort out the lack of CH first.

You need to trace the wiring from the CH-on output of the programmer, to the room stat, to the white wire of the valve actuator. You will need a mains voltmeter *not* a neon screwdriver. If there is a live feed to the white wire but the valve isn't moving, either the motor in the actuator is duff, or the wet part of the valve is seized. You can check this by removing the actuator from the valve (couple of screws) and see whether the inernals of the actuator *then* move. Check that the spindle of the valve turns fairly free when gripped with finger and thumb.

I presume that it *has* worked properly in the past? One feature of Y-Plan systems is that the programmer *must* have a HW-off output in addition to HW-on, and the cylinder stat *must* have change-over contacts, as shown in the diagram. It's the HW satisfied (or not required) signal which powers the system when only CH is required. If that is missing, you get no CH!

[The Natural Philosopher]

A blocked CH circuit or faulty pump wold do that.

Since the DHW is OK, that would seem tyo imply teh tank circuoit is opemn and pumping, which possible leads to the thought that the CH circuit is blocked with sludge, or - gasp - has gas (air lock) in it..have you tried bleeding the rads?

>

[gary.holt]

Just to add an update, first thing this morning and the boiler had not been turned on all night. I switched on the heating but the heating light came on but the boiler did not ?

As soon as I turned on the hotwater switch the boilers red light came on.

So I presume that the basic boiler is okay and the lockout was just one of those things. But something (either the thermostat inside the boiler or the room stat) is telling the boiler not to start ?

The Natural Philos> > > >

[Roger Mills]

Did you *read* my previous post?

In CH-only mode, the programmer and room stat tell the valve to move to the CH position - and the valve tells the boiler and pump to start.

If the valve doesn't move (other than in HW mode) *nothing* tells the boiler to start - so it doesn't.

You need to sort out why the valve isn't moving, which could be due to:

• Faulty actuator

• Seized mechanical part of valve

• Faulty room stat

• Faulty wiring

It's impossibe to say which without doing some investigations. I gave some clues as to how to go about it in my previous post.

[gary.holt]

Sorry Roger did read your post but just trying to confirm the problem.

As the wir> >

[Roger Mills]

Please read this SLOWLY so that you don't need to ask the *same* questions again . . .and again . .

YES, a faulty valve *will* prevent the boiler coming on for the CH even though it comes on for HW.

The actuator is the electrical box of tricks which sits on top of the 'wet' part of the 3-port valve, and rotates the shaft of the valve to the appropriate position (HW-only, HW+CH, CH-only). There are some switches inside the actuator which open and close when it reaches certain positions. These are *vital* to the operation in the system. In CH-only mode, it is a switch inside the actuator which switches the boiler on. If the actuator is faulty and doesn't move away from the HW position, this vital switch doesn't close and the boiler doesn't get switched on. That appears to describe your symptoms fairly well!

[gary.holt]

Looks like you are spot on, have just tested the room stat and live feed to the 3 way valve. All looks okay but the valve is not working. Then with the boiler with the heating on and water off pulled the leaver towards manual and then hold the leaver just before manual the boiler starts. So how simple is it to replace a 3way valve, can I just replace the electrical parts of honeywell 9122.

Cheers aga> >

[The Natural Philosopher]

Yes, and its relatively trivial. Go online for suppliers.

[Roger Mills]

Make a careful note of the wiring when you disconnect the old one, and wire the new one *exactly* the same.

[gary.holt]

Sorry me again, went to the plumbing centre today to get a replacement but then found out that it may not be a case of just replacing the head?

The valve I have is a V4073A1039 and the plumbing centre advised that I may dot be able to change the head ? Therefore have checked with honeywell and if the valve has 2 screws then you do not need to drain down otherwise 4 screws will result in you having to drain down.

Roger Mills wrote:

[gary.holt]

Forgot to add my question !

Would I still be able change just the motor ?

[e-mail] wrote:

[Roger Mills]

I take that to mean that, since you have a V4073 series valve, you *can* change the actuator without draining the system and that, if you had an older one which required draining, it would have a different number. I could be wrong of course!

I doubt whether you can change the motor without removing the head - whichever sort you've got.

Anyway, how many screws *does* it have?

[gary.holt]

Roger,

Looking at the device looks like 4 screw threads, with out opening it up !

So looks like a drain down and air blocks here we come ! Would have prefered to do this in June.

Cheers

Gary

Roger Mills wrote:

[gary.holt]

Roger,

Just an update,changed the motor inside the 3 way valve yesterday and it has resolved the problem.

Thanks for all the help/advice.

Cheers

Gary

Roger Mills wrote:

[Roger Mills]

Good! I thought it would .