Connecting pump overrun on Glowworm 18HX

[DavidSWP]

Hi,

This is a follow on from my thread earlier this year: //www.diynot.com/diy/threads/am-i-being-harsh-on-this-plumber.428970/

This is where a plumber installed this boiler but said there was no wiring for a permanent live connection or pump overrun. He only connected 3 wires/cores to the boiler (neutral, switch live and earth) and bridged the switch live wire to the permanent live connection point on the boiler. Anyway after much drama I finally managed to run a 5 core electrical cable from the boiler to the pump and wired them together. I got rid of the bridge between the switched live and the fake permanent live, connected a proper permanent live from the junction box, and connected the boiler L,N,E pump connection points to L,N,E connections in the junction box which I could see were going to the pump.

When I first switched it on it fired up immediately and the burner was running even though the CH and HW were both off at the programmer, so I switched it off, after which it made a few funny noises I'd never noticed it make before so I got a bit freaked out. I thought I must have wired up a permanent live wire to the switch live at the boiler but I could swear I didn't so I decided to see what would happen if I just disconnected the pump wiring I had just added. After that it all seemed to work as normal, except that the boiler display was permanently on (as it should be) due to a proper perm. live and it only fires up now when there is a call for heat.

So I am just wondering if there is some reason the pump wiring I connected could have caused the boiler to run the burner when it shouldn't be? I think the pump is actually controlled by the motorised valves as well. Should I maybe disconnect the pump from everything apart from the new boiler connections? Some S-Plan wiring diagrams I looked at seemed to show this.

 

[dreadnoughtheating]

In the Manufacturers Installation instructions (which were of course left with the boiler when the 'Installer' had finished ?) are a series of wiring diagrams.

If you feel competent, read these in conjunction with the ones that relate to the controls package that you have (clock/stats/motorised valves etc). this should point you in the correct direction. Or, find a spark who specialises in heating controls - they do exist, mine is brilliant.
DH

 

[DavidSWP]

Hi, yes I have the installation manual which shows the boiler side of the wiring which is simple. I'm just wondering if on an s-plan system normally the only wires going to the pump would be from the boiler side L,N,E or if it's normal to have L, N,E from other places sharing the same connection at the pump side.

You're right I should get someone to look at it but don't really trust the trades. The only things I've ever got a 'professional' to do I've had to fix myself afterwards. I'd also contacted every glowworm approved installer within 20 miles and none of them wanted anything to do with another plumbers botched job.

 

[bernardgreen]

Hi, yes I have the installation manual which shows the boiler side of the wiring which is simple. I'm just wondering if on an s-plan system normally the only wires going to the pump would be from the boiler side L,N,E or if it's normal to have L, N,E from other places sharing the same connection at the pump side.

In a modern boiler the pump is controlled by the pump. Various reasons for this, one is for pump over run to circulate water after the boiler has stopped burning gas to cool the heat exchangers down. Hence the pump should ( in most situations ) be supply with mains ONLY from the boiler.

This is where a plumber installed this boiler but said there was no wiring for a permanent live connection or pump overrun.

Then he should have done what you done.......installed the extra cable as necessary.

 

[DavidSWP]

]

Hence the pump should ( in most situations ) be supply with mains ONLY from the boiler.

Thanks Bernard, that was just what I was looking for - some confirmation that I am thinking in the right direction. Maybe I just need to separate out the pump from the other feeds and connect only to the dedicated boiler feeds. I'll study the thing a bit more first.

Then he should have done what you done.......installed the extra cable as necessary.

While I was fixing it all yesterday I also found this nice section on the original cable to the boiler he wired in originally! Looks like he melted it while soldering because it was resting up against a joint he did on a copper pipe. It actually had 2 spare cores in it but probably not usable after being incinerated. So maybe he made up the entire story about the wiring not being available.

 

[Agile]

In a modern boiler the pump is controlled by the pump.

How can a "pump" be controlled by a "pump" ?


Makes me think of the blind leading the blind!

 

[Agile]

David, I think that you must have connected the boiler pump output onto the pump WITHOUT isolating it from other wiring.

The boiler pump output should go directly to the pump with NOTHING else involved.

Tony

 

[bernardgreen]

In a modern boiler the pump is controlled by the pump.

How can a "pump" be controlled by a "pump" ?
Makes me think of the blind leading the blind!

Maybe I had intended to write by a pump output from the boiler. Or something similar to that......

 

[DavidSWP]

In a modern boiler the pump is controlled by the pump.

How can a "pump" be controlled by a "pump" ?


Makes me think of the blind leading the blind!

I assumed that was a typo - pretty sure he just wrote pump twice by accident.

 

[DavidSWP]

David, I think that you must have connected the boiler pump output onto the pump WITHOUT isolating it from other wiring.

The boiler pump output should go directly to the pump with NOTHING else involved.

Tony

Hi Agile, yes that's what we are talking about. Thanks for the further confirmation