Heating problem in modern: boiler runs then instantly stops

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First, apologies: I'm cross-posting. I read your rule, but I'd posted this in DIY-forum.net hoping to reach Dave Osborne (or DaveyOz), but maybe he's away.
So I'm cross posting here. PLEASE don't be too unkind.

Hi,
I'm having a problem with a CH system in a newish house (~2 years old). In the first place I can't out what kind of system, seems to be a modified Y-plan. I'd like to know what drawing tools DaveyOz (Dave Osborne?) used for his superb Sundial etc diagrams. Are you there Dave? So in principle I can draw what I understand of the system.

The problem is that on switching on, after the normal delay of ~11 secs, the boiler switches on - pump or fan running, but then instantly switches off after less than a half second.

The system consists of:
- Glow-worm 18sxi,
- Drayton LP522 programmer,
- Drayton RTS2 (maybe RTS1) roomstat,
- OSO 20 RI cylinder
- Honeywell V4043H (which I suspect is there for safety)
- Drayton MA1 3port mid pos,
- and a puzzling Lifestyle 16(!) terminal wiring centre.

A Glow-worm specialist came, jumpered across the sxi connection cartridge and proved that the boiler would run fine, so pointed the finger at the installer and left. Turns out the installer co is just a shell, which makes contracts with builders then temporarily hires in guys, well not quite off the street, I guess anyone with a Gas Safety Reg cert.

After a couple of weeks living with electric fan heaters while pulling everything apart to understand it, I eventually was able to repeat the Glow-worm guy's trick- thank God I could hear the boiler running sweetly. I at last tried pulling the LP522 off the wall and jumpering across from Live to terminals 1 & 3. Whoopee! It worked.

So I tried disconnecting the LP522 terminal 1, and that did it, I could exactly duplicate the symptoms: ~11secs pause, on, then almost instantly off. So it might be a fault on the V4043H (yes I know they're pretty reliable), or it might be something else.

H-e-l-p !!!

dw32
 
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hi
is this a problem on just central heating?
does hot water work ok?
if so then yes its most likely the valve
Matt
 
First, apologies: I'm cross-posting.
That rule here applies to posting the same thing in multiple fora here, not to other completely separate websites.


I'd posted this in DIY-forum.net
My - that looks like a useful site..... ;)

t246511.jpg
 
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Clearly there is at least one fault with the wiring. Given the mess that these systems get into when incompetent fools have a go at changing bits of them, your quickest route to a properly working system is:

1. Remove the wiring centre and disconnect all of the valves, thermostats, pump, boiler and everything else.
2. Rewire the system properly following the appropriate diagram.

In virtually all cases like this, trying to work out what has been done before and making alterations here and there will take 10 times longer than rewiring the complete system.
 
Clearly there is at least one fault with the wiring. Given the mess that these systems get into when incompetent fools have a go at changing bits of them, your quickest route to a properly working system is:

1. Remove the wiring centre and disconnect all of the valves, thermostats, pump, boiler and everything else.
2. Rewire the system properly following the appropriate diagram.

In virtually all cases like this, trying to work out what has been done before and making alterations here and there will take 10 times longer than rewiring the complete system.

I have lost count of the number of times I wished I had done just that.

And

I have lost count of the number of times I have done just that.
 
Thanks matt1e, Taylortwocities and ban-all-sheds.

I'm heating the water using the immersion at present. I guess I'll have to try switching it off for a while then verifying that NOT DHW is voltage-free.

I'm not sure about posting in a plumbing forum. It's an electrical rather than hydraulic problem. But maybe nowadays plumbers have get certs on wiring combi systems, so I'll have a look. Could you kindly tell me the best forum to use?

(Good to hear it's not double-posting if it's another website. I wasn't sure they're not linked.)

dw32
 
Hi,
I tried to post thank-you's to 3 guys who responded to:
"Heating problem in modern: boiler runs then instantly stops"
but for some strange reason it seemed to goto some other thread or something, which I can't find now.
Could you please move it to Heating problem in modern: boiler runs then instantly stops

Hope you're able to do this.

TIA

dw32
 
Clearly there is at least one fault with the wiring. Given the mess that these systems get into when incompetent fools have a go at changing bits of them, your quickest route to a properly working system is:

1. Remove the wiring centre and disconnect all of the valves, thermostats, pump, boiler and everything else.
2. Rewire the system properly following the appropriate diagram.

In virtually all cases like this, trying to work out what has been done before and making alterations here and there will take 10 times longer than rewiring the complete system.

Hi flameport. In your flame, you seem to have missed the point that there IS no wiring diagram, which is why I'm asking DaveyOz about software.

dw32
 
Hi flameport. In your flame, you seem to have missed the point that there IS no wiring diagram, which is why I'm asking DaveyOz about software.

dw32

I think what flameport was getting at is that what you have doesn't sound anything special. To me, it appears to be standard Y-plan with the addition of a 2-port valve on the cylinder coil on account of this being a requirement for an unvented cylinder.

You should be able to follow the standard Y-plan diagram and modify as necessary to incorporate the extra 2-port valve, although the schematic on page 23 of this document may be exactly what you need.
 
Thank you kindly electronicsuk, fig 3.19 on p23 seems to cover my case. Of course no figure that I've seen includes a 16-terminal wiring centre, but I should be able to map across to my sketch diagram of the connections I could follow, and hopefully it will all fall into place. Thanks again.

dw32
 

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