No Hot Water/ Help !!!!

[Mark 9002]

Hi
My heating / Hot water is an open vented system with Indirect HWC. The boiler is a Firebird Popular 90 Oil Boiler. There are no Timers programmed for heating or HW. When I put on the heating the Boiler fires and heats the radiators ok. When I put on Hot Water only, the Boiler does not fire up. There are only 2 Motorised V/V's on the system. When the heating is on and I manually open the Motorised V/V for the HWC I can feel the Flow / Return Pipes to the Cylinder heating up, and then with this V/V still open, when I switch of the heating but leave HW on the Boiler stops again.
The HW Light comes on on the Heating / HW control unit when the HW is selected so it indicated water should be heating, but like I say, boiler doesn't fire.
Anybody any Ideas Pls

 

[oldbutnotdead]

What make are the valves? Sounds as if the motor on the hw valve has failed (not uncommon), the manual lever doesn't engage the microswitch that fires the pump/boiler.
You can definitely get replacement motors for Honeywell valves, avoid the really cheap ones.
Some basic tests required to prove this theory, until then if you latch the hw valve open you can get hot water by running the heating (turn most rads off or down).

 

[Dangee]

Open the wiring centre. Switch to hot water only. Check it’s sending voltage. (Neon screwdriver) if so, check if the hot water mot valve brown cable has voltage. If brown is live & valve not opening to liven the orange then the head probably needs changing. (It might be a stiff valve body spindle)
If programmer is sending live out but brown does not become live, check cylinder stat.
If no live from programmer hw switch live, it’s the programmer.

 

[Dangee]

As obnd said, you can leave valve open manually but........ turn the thermostat on the boiler down as the hot water will get dangerously hot.

 

[Mark 9002]

Wow Guys,
Thanks for the really quick reply's. The valve is a honeywell, but cant see any model #, but just having a quick look as its me lunch hour. I'll do these checks when I get a bit more time. Just one question, how does the cover come of the Motor to test wiring / Replace the motor. I know there's a couple of screws that hold the motor to the Valve, but how to get at 'em.
Dangee, could you expand on " If brown is Live & Valve not opening to Liven the Orange "
As for Hot water just now, we still have the Immersion heater on this HWC so I'll just be using that until I get it sorted

 

[oldbutnotdead]

There's a wee screw in the opposite end of the housing from where the override lever is, undo it a couple of turns & the lid should pop off. WARNING Live parts inside, isolate before removing. Good diagnostic from @Dangee , follow that

 

[Mark 9002]

Hello again
So, I took the head off the Mot V/V and checked the spindle. It seems very free, but only swings approx 45 degrees. I didn't want to force it any more. Is this the normal swing on these Honeywell V/Vs ?. The Valve is Honeywell V4043. Next opened up the wiring centre. Bit of a rats nest of wires, but with the HW on at the Programmer, the brown wire from MOT V/V gives reading of 240v. The Orange wire has Zero v.
Is the head Knacked for sure ?? . If so do I replace complete head, or is it possible to replace Synchro Motor only. Probably better just the whole head ??

 

[terryplumb]

Replace the actuator head complete.

 

[oldbutnotdead]

Yes that 45 degrees sounds about right. Whichever you feel confident with doing, whole head is easier, motor only is cheaper but a bit more fiddly

 

[Dangee]

You’ll need some crimps to change the motor, head is better. Don’t buy a cheap copy, it’ll only last a couple of years. If you look side on, when you push the lever, it moves a paddle to a little black plastic micro switch. If you push that little switch in, it’ll liven the boiler. (Orange)
If the wiring is a mess, it might’ve easier to cut the existing black flex & connect the new head with a 5 way connector.
Ignore the white core on the new head & make sure power off.
Grey is the permanent live, brown is just switch live!!

 

[Mark 9002]

Update
Thanks all for the great help. Rxd new Honeywell V/V and head complete yesterday. ( Its a genuine one ). I'll keep the Valve as a spare. Fitted Head last night and all good again.
I promise I'll never release the Hounds on another Plumber ever again