Myson Apollo pump running all the time

[Notebook]

Myson apollo
long story but here goes
direction - zone -valve above pump was not switching corectly - rads getting warm.
Changed the valve, but water got on the terminal block (under the valve!!!) and the pump and there was a smell of burning windings / tripping electric when switched on. changed pump. electric ok.
This was a while back - a few months. Only using hot water.

Cold weather arrived
Turned on heating and selected high button - all ok
However if I turn on Low button then the rads warm p etc as with high but noticed the pump running all the tiime. Checked wiring with my neighbours and all looks the same.
Someone suggested change overrun stat on boiler incase that was it. No difference.
On high heat all works fine.
On low heat on boiler, the pump runs all the time.
On high and low, room stat works fine and room temp is controlled ok.
with the cold weather I have had it on high heat, but now want the boiler on low.
just went to the cylinder stat and it is set on 60.
If i turn this down the (stat on low) pump stops (say 50) and if I turn it up to 65 the pump kicks back in.
Hope this helps
Also pic of isolation vaves around pump etc.
Should all these be turned on? they are, but possibly I altered them when working on the system.

Nick

 

[HTB]

I had some very similar problems on my Apollo, was on going for long time, in the end got fed up and I changed controller, 3 way valve and stats. All Fine now.

In retrospect I might have gone for disposing of 3 way valve and modified y/plan to s/plan and fitted 2 simple zone valves which I think would have been better as I subsequently installed a Hepworth underfloor expansion pack in my conservatory and zoning for more eficient control of this would then have been easier.

BTW looks like you might have opened your balance valve all the way and you might want to tweak that back in a bit. It's the highest one on your picture,,,on 15mm tube with no wheel head on it. Don't close it all the way, count the number of full turns from closed to open and try setting it on half see if that helps. Consider replacing it it auto by pass valve.

 

[Notebook]

I had some very similar problems on my Apollo, was on going for long time, in the end got fed up and I changed controller, 3 way valve and stats. All Fine now.

In retrospect I might have gone for disposing of 3 way valve and modified y/plan to s/plan and fitted 2 simple zone valves which I think would have been better as I subsequently installed a Hepworth underfloor expansion pack in my conservatory and zoning for more eficient control of this would then have been easier.

BTW looks like you might have opened your balance valve all the way and you might want to tweak that back in a bit. It's the highest one on your picture,,,on 15mm tube with no wheel head on it. Don't close it all the way, count the number of full turns from closed to open and try setting it on half see if that helps. Consider replacing it it auto by pass valve.

Hi
Thanks for your reply - A few questions.
The balance valve - what does that do? How does it work? Looks like with this open, the water can just circulate into the tank?
Will open it half way and give it a try - what then? what happens if I go a turn more open / closed etc?

Stats
Is there a low and a high stat on the side of the boiler? If so might be worth me changing the low?

Really appreciate all your help - nice to have an answer rather than someone teling you to google etc.
Again thanks
Nick

 

[doitmyself]

On low heat on boiler, the pump runs all the time.

Is it just the pump which runs all the time or is the boiler also staying alight all the time?

Just went to the cylinder stat and it is set on 60.
If i turn this down the (stat on low) pump stops (say 50) and if I turn it up to 65 the pump kicks back in.

If you have a mid-position valve, the boiler is either controlled by the cylinder thermostat or the valve. If heating is OFF and hot water ON, the boiler is controlled by the cylinder stat. If both heating and hot water are on,the boiler is still controlled by the cylinder thermostat. If the HW goes off (at HW thermostat or the timer) the boiler is now controlled by the valve.

Therefore, as the pump stopped when you turned the cylinder stat down the system must have been in either HW only or HW & CH. You say you want to run the boiler switch to Low. The problem with this is that it the water temperature leaving the boiler is only about 65C. This is fine if you are just heating the HW cylinder, but not really enough for central heating. I assume you have a room thermostat. If you do there is no benefit in having the boiler stat on low when heating is on.

Also pic of isolation vaves around pump etc.
Should all these be turned on?

The valves immediately either side of the pump must, obviously, be full on.
The one without a handle, on the T above the pump is a bypass valve. It allows some of the hot water to be fed back into the return to the boiler. This should be about one turn open.

The other two valves are isolation valves for CH and HW circuits. The CH one can be fully open but the HW should be about half open - if it is open too much the cylinder will takie more than its fair share of the flow when both CH and HW are ON.

 

[Plouasne]

Cab I offer just one word of advice, never ever, open any valve full on, always back it off at least half a turn, if not a full turn, this way you can possibly open the valve a bit more, to loosen any muck that is stopping it from closing, then close the valve

 

[doitmyself]

Cab I offer just one word of advice, never ever, open any valve full on, always back it off at least half a turn, if not a full turn, this way you can possibly open the valve a bit more, to loosen any muck that is stopping it from closing, then close the valve

Excellent advice. I always do this myself.

 

[Notebook]

A. only the pump runs all the time - the boiler kicks in and out as normal. On high it appears to work fine.

B. It was on HW and CH
I have used it on low for years - on high its a bit noisy as its a small house and in the kitchen off the living room, but I see what you mean as it indeed has a room stat, so noise really, but as that valve was fully open I will try it tonight with it partially closed.


C.
The CH one can be fully open but the HW should be about half open - if it is open too much the cylinder will takie more than its fair share of the flow when both CH and HW are ON - have changed the phot so that it is easier to say which is which.
Therefore, which is the ch and which is the hw.
Again thanks all

 

[doitmyself]

Only the pump runs all the time - the boiler kicks in and out as normal. On high it appears to work fine.

Very Odd! The only thing that can keep the pump going is the overrun thermostat. This will happen until the water temperature has dropped to a preset temperature. There can only be two causes for the pump running continuously: a faulty oveheat thermostat or a mis-wired pump. Can you say how the pump has been wired?

Therefore, which is the ch and which is the hw?l

A = HW - half open
B = CH - full open then close half a turn
C = Bypass - one turn open
D = Pump valve - full open then close half a turn
E = Pump valve - full open then close half a turn

 

[Notebook]

Hi
Forgot to say, changed the overun stat - guess I wired it correctly?

The pump wireing - its in the terminal box - can you work it out from wire colours if I supplied them?
However it all works ok on high?

I will adjust the valves as you said and turn it on for an hour with the room stat just high enough for it to kick in.

Again thanks

 

[doitmyself]

Forgot to say, changed the overun stat - guess I wired it correctly?

If you had wired it wrongly, I think you would have the fault on both High and Low.

Which model Apollo do you have? It's on the inside of the front cover together with the GC number.

The pump wireing - its in the terminal box - can you work it out from wire colours if I supplied them?

Wire colours mean nothing as installers have their own way of wiring and do thing such as using the earth and neutral wires as live feeds - saves buying a cable with different coloured wires. The only colour which seems to be sacrosanct is brown.

Although the pump is connected to the terminal box, there should be a wire from there to the pump terminal on the boiler. Can you take a pic of the terminal box (lid off!!) and say what each cable connects to?

 

[Notebook]

Hi
apollo 15/30, 30/50, 40 and 50/65?
also 8706 on a rivet

pump brown is connected to a red dissapearing into the wall
blue to blue on 3 way valve
earth to earth
ashes to ashes

getting back to stats - what about the lo stat?

 

[doitmyself]

apollo 15/30, 30/50, 40 and 50/65?

What's the GC Number - starts with 41

also 8706 on a rivet

Guess that's date - June 1987

pump brown is connected to a red dissapearing into the wall
blue to blue on 3 way valve
earth to earth
ashes to ashes

That's OK. The other end of the red should connect to the terminal marked pump live at the boiler

what about the lo stat?

Can't see how that can have anything to do with the problem. The fact that the boiler goes out shows that the low stat is doing its job. Pump running is controlled by the overheat stat.

The overheat terminals should be wired: 1= red, 2 = Yellow, 3 = Brown

When the water is cold, terminals 1 and 3 are closed. When the water is hot, terminals 1 and 2 are closed.

 

[Notebook]

467423 is the only other number on there - on same rivet - different tag.
Silly me - of course it must be working - stat
will check the overheat

overrun wired correctly - checked sticker with theone I originally had on there and the number is the same

 

[doitmyself]

467423 is the only other number on there - on same rivet - different tag.

That sounds like a part number. There should be a metal plate fixed to the back of the boiler front cover with all the boiler data on it. The GC number will be on this plate.

overrun wired correctly - checked sticker with the one I originally had on there and the number is the same

What is the number?

Have you checked continuity of the OH stat, as in my previous email?

Just a thought. The Low/Off/High Switch may be faulty.

If you can understand wiring diagrams, you will find the Apollo info at [DLMURL="http://www.partsarena.com/baxi/"]PartsArena[/DLMURL]. When you first use the site it will ask to install a small app to read the files.

 

[Notebook]

4178953
15/30B - 37500

checked stat in cup of boiling water and acting correctly

why low / high off switch faulty?

will look at drawings

again thanks

any ideas which mine is?