No Heating without Hot Water: Faulty MV or bad wiring? Help!

[FiercelyFuzzy]

Hi All

I'm having a bit of trouble with my central heating system & hope someone can help me!

I live in a 6 year old property which we bought 3 years ago. Since we moved in we have only been able to get CH when the HW is on. I though that this was how our system worked (my old flat was like that). However after reading about balancing the system, I found this website & read the FAQ's & visited the forum, so now I think that our MV is at fault or the wiring to the circulating pump is wrong. Hopefully someone here can help!

Here is my system specs anyway:

Ideal Classic FF 330 Boiler
Grundfos Alpha Circulating Pump
Drayton MA1 Midpoint Motorised Valve
Lifestyle LP522 Electronic Programmer
Drayton RTS1 Room Thermostat
System fed by feeder tank in the loft.

The MV is midpoint 3 way & comparing the diagram on the MV instructions to the wiring centre it has been wired for independent CH. (there is a red wire from the programmer with a grey wire from the MV & a wire from the cylinder thermostat in the same hole on the wiring centre).
I've looked at the programmer & it too has been wired for independent CH. There's nothing glaringly obvious that is wrong on the wiring centre.

When HW is selected on the programmer the MV indicator moves to H & the pump comes on.
When CH+HW is selected the MV indicator moves to M & the pump comes on.
When CH is selected the indicator remains on M & doesn't move to H. The pump doesn't come on.

So I'm wondering, is the MV is stuck, or is the wiring wrong? Has it been wired so the pump won't turn on for CH only? I mean if the MV won't move beyond M to H, wouldn't the pump come on anyway & I'd get CH+HW?

If it's the MV that's great as it's covered under British Gas. If it's the electrics, I'll have to get a Sparky in.

Many Thanks for any help. I'm driving my wife nut's with this as it's become a bit of an obsession!

I should also mention that the water cylinder has a thermostat. This means that as we can only get CH+HW, the heating sometimes cuts out when the tank is fully hot. I've pushed up the thermostat to stop this, but this makes me think even more that we should be able to get CH independently.

 

[D_Hailsham]

If you have not changed the timings, the LP522, as supplied, has the same timings for HW and CH.

Just in case you have not got them, here is a link to the Installation and User Instructions

Have you checked that the link on the back of the LP522 is set to P (pumped) and not G (gravity)?

 

[FiercelyFuzzy]

Thanks for the reply and the link!

The small black lever on the back of the programmer is definitely set to "P".

I've got the "oldstyle" programmer. the instructions for it can be found here:
http://lp522guide.tripod.com/sitebuildercontent/sitebuilderfiles/lp522guide.pdf

The programmer is wired with a red wire going to "1". From the instructions this should be the case for a pumped system. If it was gravity there'd be no wire at "1"

Thnaks again!

 

[D_Hailsham]

Unfortunately, wire colours are not standardised.

First, check that the motorized valve is the correct way round! The three branches are labelled A, B, AB. AB goes to the pump; A to the CH; B to the HW cylinder.

Check that you have a wire from LP522/T1 (HW OFF) connected to the GREY wire of the motorized valve.

Check that you have THREE wires connected to the thermostat on the side of the HW cylinder. "Common" should connect to the LP522/T3 (HW ON); "Call" or 1 should connect to the same terminal as the Orange from the valve; "Sat" or 2 should connect to the same terminal as the Grey wire from the valve.

 

[FiercelyFuzzy]

Thanks for taking the time to reply. I've just had a look & all seems to be present & correct.

First, check that the motorized valve is the correct way round! The three branches are labelled A, B, AB. AB goes to the pump; A to the CH; B to the HW cylinder.

Yup, all the branches go to the correct places.

Check that you have a wire from LP522/T1 (HW OFF) connected to the GREY wire of the motorized valve.

It does, along with a blue wire from the cylinder thermostat.

Check that you have THREE wires connected to the thermostat on the side of the HW cylinder. "Common" should connect to the LP522/T3 (HW ON); "Call" or 1 should connect to the same terminal as the Orange from the valve; "Sat" or 2 should connect to the same terminal as the Grey wire from the valve.

Three wires come off the cylinder stat.
The Green+Yellow connects to the LP522/T3.
The Brown connects with Valve Orange (along with brown from the Pump & a Yellow from I think the boiler)
The Blue connects with the Grey from the Valve & the LP522/T1

Cheerio
FF

 

[phoenix79]

Hi i am having the exact same problem and i do not have a clue if you do find out please let me know. Likewise if i find out i will post you.

 

[D_Hailsham]

Three wires come off the cylinder stat.
The Green+Yellow connects to the LP522/T3.

That means the Green/Yellow wire is being used carry 230 volts. A green and yellow wire is supposed to be used as an earth wire and nothing else. Unfortunately many heating engineers get lazy and can't be bothered to use the correct cable. If you can get hold of some red sleeving, or red insulating tape, you should use it to cover both Green/Yellow ends of this wire. Doesn't solve your problem but may prevent someone getting a nasty shock.

Your wiring seems OK so there must be a fault in the valve or actuator.

Here are some checks to do:

1. Turn of the main power to heating system - this resets the MV
2. Turn off CH and HW at programmer and set HW and CH stats to min
3. Turn on power to boiler; set programmer to HW ON; turn HW stat up to max. The boiler should light and the branch to HW should be hot (the valve does nothing in this situation)
4. Leaving HW as it is, turn CH ON; turn CH stat up to max. The boiler should continue to run and valve move to mid position. Both branches should be hot.
5. Turn the HW stat down to min. The valve should move over so only CH branch is hot and boiler continue to run.
6. Turn HW stat up to max (valve goes back to mid pos) the turn HW OFF at programmer. The valve should move over, so only CH branch is hot and boiler continues to run.

 

[MANDATE]

It's most likely a valve problem, You have to establish if the quadrant/valve moves to the CH only position. Best way, if you can, is to remove actuator head off the valve spindle and observe the underside while testing. If the quadrant/valve does move to the correct position, then that would suggest the microswitch within the actuator head is faulty and failing to make the orange wire live, which is required in order to light boiler.
If the quadrant/valve does not move to the correct position, then that would suggest the motor is faulty or the spindle is too stiff. You should be able to turn spindle easily between finger and thumb.

 

[FiercelyFuzzy]

I've not had time to do D_Hailsham's check list but I've been able to remove the actuator head and have a look what happens when combinations of CH & HW are selected.

The plastic part which fits over the spindle moves when HW or CH+HW is selected, but not when CH alone is chosen. So I guess that means the motor is faulty.

Good news, as it means I'm covered by British Gas, & I've also managed to learn more about how my heating system works in the process.

I did notice that the spindle was very stiff though. I couldn't move it easily using my fingers, but managed to wiggle it using some pliers. Even then it didn't move much. Maybe a quarter of a turn? Perhaps this contributed to the motor failing. I'll search on the forum for info on spindle loosening...

Thanks for all your help!
FF

 

[FiercelyFuzzy]

Hi All

Just to say that BG engineer came this morning (on a Saturday, after I phoned them on Friday!) and swapped the actuator for a new one. All works fine now!
Thanks a lot for all the help. And I must say I'm very impressed with the service from BG. They get a bad press but I am a happy customer.

Cheerio
FF