Pump on hot water circulation does not stop.

khalil · 20 Apr 2010

Hello,,

Please bear with me as I am only an amateur.
I have got a glow worm 40FF boiler with Megaflo unvented hot water tank.

My problem is with the pump circulating the hot water in the boiler and un-vented hot water coil.
The problem is that even when I turn off the room unit, and the bolier is off the pump does not stop working.

The only way to stop the pump is to cut the power from the mains to the pump.

The boiler starts and stops normally to heat up the water temperature and both CH and DH waters get warm when needed.

The circulating pump makes a conitnuous noise.

The 2port motorised valve on the Hot Water Tank for DHW was not working properly and I got some one to replace it.

Is the problem with the PCB in the boiler?

Could please some one help me to understand?

D_Hailsham · 20 Apr 2010

khalil said:
Is the problem with the PCB in the boiler?

Yes

The pump is supposed to run for a few minutes after the heating goes off -it's call overrun. This is controlled by the PCB.

45yearsagasman · 20 Apr 2010

Gloworm 40 FF? Is it the Ultimate or Micron 40FF? because the pump overun on the ultimate is in the main boiler stat and the micron's is pcb controlled

khalil · 20 Apr 2010

The boiler is Glow Worm Micron 40 FF.
The hot water tank is Megaflo and is upstairs, with the pump just beside it on the hot water circulation pipe.
And there is smartfit controller on the hot water tank as well. With the room unit being downstairs.

As far as I understand the pump is connected to the the smartfit controller.

Any possibility that the problem is with the smartfit controller?

picasso · 20 Apr 2010

I wonder how your plumber has managed to connect a megaflo to the smartfit system, I was under the impression that is wasnt possible as the smartfit uses low voltage (24v?) for the cylinder sensor and 2/3 port valves, I could be wrong on this as I have never installed a smartfit system, could be concidence that a 2 port valve was changed and then you had problems with overrun.

khalil · 21 Apr 2010

The hot water tank is similar to the left picture on the first page of the following link:

http://www.partsarena.co.uk/baxi/System/DATA/Dx/DS1/installation/2981/I48-2981/I48-2981.htm

Paragraph 6.4.6 on page 12 of the same link clearly says if I switch off the Room Unit the boiler and the pump and motorised valves should stop working.
Well, after I swich off the Room Unit the boiler stops but the pump and the motorised valves are still running.

I haven't altered any wiring in the system. Could it still be a problem in boiler's PCB?

I am totally confused.

picasso · 21 Apr 2010

my mistake, I thought you had a standard megaflo fitted to your smartfit

, I would hazard a guess that whoever changed the 2 port has altered the wiring in some way, if not then your probably right with the pcb.

khalil · 21 Apr 2010

I have been advised by glowworm that they don't think the issue lies with the boiler, but would think it lies with the megaflo unit and smartfit controller.

I have sent a query to megaflo to get their advice.

I am really really confused.

khalil · 21 Apr 2010

In fact glowworm has just informed that the Micron 40FF has no bearing on the pump.

Homesafe · 21 Apr 2010

picasso said:
my mistake, I thought you had a standard megaflo fitted to your smartfit , I would hazard a guess that whoever changed the 2 port has altered the wiring in some way, if not then your probably right with the pcb.

From what I know about these systems, a fault with the M.valves can cause probs. like these as Picasso has stated. One wire incorrectly fitted can give the same symtoms as you have, It's worth looking at.

picasso · 21 Apr 2010

I should have made it clearer, there is a small pcb in the smartfit control box, this is what I meant when I said pcb.

khalil · 21 Apr 2010

Thanks everyone.

I called honeywell and they said if there is any problem with smartfit pcb there should be a fault on the room unit.
Clearly the room unit is not showing any faults. Even when it is turned off the pump is running.

I guess the electricty is being passed through the control board somehow to the pump and motorised valves. Is there any relay on the board which is not functioning?

How can I open the motorised valve and have a look to wiring etc?

khalil · 21 Apr 2010

I have just noticed that there is a manual lever on the 2 port motorised valve which is "loose".
Could this be related to the continuous running of the pump?

Any help is highly appreciated.

Gasop · 21 Apr 2010

khalil said:
I have just noticed that there is a manual lever on the 2 port motorised valve which is "loose".
Could this be related to the continuous running of the pump?

Any help is highly appreciated.

Switch off all electric power to the two port valve.

If the lever remains "loose" then this will indicate a problem most likely connected to the continuous pump run.

khalil · 21 Apr 2010

When I cut the power off the whole system from the boiler fuse, the lever on the motorised valve is not "loose" any more and becomes firm. It can only be moved manually just to the middle of the available slot.

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Pump on hot water circulation does not stop.

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