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Central heating problem (Read 3067 times)
summer wine
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Re: Central heating problem
Reply #13 - Jan 16th, 2016, 1:02pm
 
Yes, we do have all the wiring diagrams, clear as mud!

What doesn't make sense is that the fuse he changed was in the boiler on-off switch and that had been working fine.  I admit I don't know much about fuses, but you'd have thought that if the fuse had gone, the boiler wouldn't have fired up, which it was doing.  

Either way I'm not going to argue with it.  It's working (for now!)
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mike4369
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Re: Central heating problem
Reply #12 - Jan 16th, 2016, 12:02pm
 
Just seen your post so if I may ask - do you have any wiring diagrams for your system? It is always helpful when looking to see what a fuse (or anything else) actually does in a system. If you google your boiler and programmer there is sure to be some info from the manufacturer with an installation manual - even for some v old systems - so worth a try looking.
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summer wine
Re: Central heating problem
Reply #11 - Jan 16th, 2016, 11:03am
 
We'd thought it might be a bad batch as the first pump was less than a year old, (and the guy had no hesitation in changing it for a new one which made that seem as if he'd had others returned), but the replacement pump was behaving in exactly the same way right from the start.   Two faulty ones from the same batch, a year apart???  Either they don't sell many or didn't return all the bad lot back to Grundfos!!

Still don't quite understand how, if it was just the fuse, it was working one minute then not the next.    

(The other (new unused) programmer still showed no display but hoping that is just because it's completely lost its internal battery back up charge.  It is 5 years old!)

Thanks again for your help and time.  
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Re: Central heating problem
Reply #10 - Jan 15th, 2016, 10:37pm
 
As per Headrush, if you have 230Vac across the L&N then the pump is working or faulty, perhaps a call to Grudfoss to check whether they have a bad batch.

If the problem persists connect the pump to a fly lead and test.
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summer wine
Re: Central heating problem
Reply #9 - Jan 15th, 2016, 10:04pm
 
Sorry for the delay in getting back, dinner got in the way.  

Anyway, thescruff - yes that was what was happening, and Headrush - yes, there was the correct voltage but the pump was not starting up.  

When the problem first happened, two days ago, everything else seemed to be working so we assumed it had to be the pump, (even though it was just under a year old), and got it exchanged for a new one, but as the problem was still there, it seemed it wasn't the pump.

Could it have been something as simple as a fuse?  We had a new programmer which we hadn't bothered to fit as the other one worked fine.  The other half decided to try it just in case but couldn't understand why we were getting no display on it so, figuring that there must be a problem between the boiler and the programmer, he tested the wiring behind the boiler switch but only got a reading out of two of them, so decided to change the fuse.  Bingo!  It started straight away and since then it's been working all evening.  If it was the fuse, it's even more baffling because why was it working at all before, even for short periods, and the programmer always came on as programmed.  

Still holding our breath but so far it seems to be OK.  If this fuse business turns out to be a huge fluke though, I'd like to be able to come back to you if I may for more of your very kind help.  

Thanks
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Re: Central heating problem
Reply #8 - Jan 15th, 2016, 7:37pm
 
Quote:
Headrush - other half has checked all you've said and says all is as should be.  

It seems to be that when the system is cold, i.e. first thing in the morning, or if it is allowed to cool right down, everything works when the boiler fires up.  As soon as it's up to temperature and clicks off, when it's then required to start again, that's when the pump doesn't start, even though the valves are open, (and it's a brand new pump.)      



Are you saying that there IS correct voltage at the pump when there should be but the pump still does not run or light up? If you are then there must be a problem with the pump..
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Re: Central heating problem
Reply #7 - Jan 15th, 2016, 7:08pm
 
Ok just to confirm.

You have two 2 port valves (S Plan) and neither will run the pump after the boiler has reached temperature, until it's cooled right down.

Can you tell us the exact model of the boiler, preferably the GCNo and approximate age.
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summer wine
Re: Central heating problem
Reply #6 - Jan 15th, 2016, 7:01pm
 
thescruff wrote on Jan 15th, 2016, 6:23pm:
Have you tried programming dhw and htg on together.

Does the hot water work at this time.

What happens if you turn the cylinder stat up.

Same question with the cylinder stat.

Does the boiler fire up even though the pump doesn't run.

Is the primary pipes for hot water gravity or do you have a second valve. ?



1.  Yes, makes no difference once the boiler has kicked back out
2.  Not if pump isn't working
3.  Pump still doesn't kick in
4.  ditto
5.  Yes, fires up and runs for a minute or so, then fires off
6.  Second valve
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Re: Central heating problem
Reply #5 - Jan 15th, 2016, 6:23pm
 
Have you tried programming dhw and htg on together.

Does the hot water work at this time.

What happens if you turn the cylinder stat up.

Same question with the cylinder stat.

Does the boiler fire up even though the pump doesn't run.

Is the primary pipes for hot water gravity or do you have a second valve. ?

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« Last Edit: Jan 15th, 2016, 6:29pm by thescruff »  
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summer wine
Re: Central heating problem
Reply #4 - Jan 15th, 2016, 5:44pm
 
Headrush - other half has checked all you've said and says all is as should be.  

It seems to be that when the system is cold, i.e. first thing in the morning, or if it is allowed to cool right down, everything works when the boiler fires up.  As soon as it's up to temperature and clicks off, when it's then required to start again, that's when the pump doesn't start, even though the valves are open, (and it's a brand new pump.)      

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Re: Central heating problem
Reply #3 - Jan 15th, 2016, 11:27am
 
If the boiler is firing up, this suggests the motorised valves are working properly. Check the pump electrical connections at the pump and terminal box, make sure they are tight and check for 230/250V across the live and neutral connections at both ends when the CH is calling for heat.
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Re: Central heating problem
Reply #2 - Jan 15th, 2016, 10:21am
 
Open-vented system.
Potterton Netaheat Electronic 16-22 boiler;  
Potterton FP2000 programmer;
Honeywell Motorized valves, (either V4043B,C,H or V8043B,G according to paperwork but nothing visible on valves to say which.) (They are opening and shutting.)
Honeywell L641A cylinder thermostat;
Grundfos UPS2 pump.

For the last couple of days it has worked fine first thing - the boiler fires up at 7am, the green light on the pump comes on and the rads get hot.   As usual, after a while the boiler goes off but each time it comes back on, there are no lights showing on the pump and the rads are going cold.
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Re: Central heating problem
Reply #1 - Jan 15th, 2016, 8:49am
 
Post more system information please, makes/model type etc of everything.

Have you any motorized valves as they would be the first to look at followed by cylinder stat and programmers.

Don't go changing anything at this time, you can do some tests first
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summer wine
Central heating problem
Jan 14th, 2016, 9:52pm
 
Over the last couple of days we've had a problem with the central heating. The boiler fired up (so thermostat would seem to be OK?) but after it had been running for a while, when the boiler kicked in the pump sometimes wouldn't start and the system would go cold.  Although the pump was only a year old, we thought it must be that which was faulty so got a new pump (Grundfos) but the same thing happens with the new one.  The system was flushed just under a year ago.  Any help much appreciated.
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