Cold Showers again

Channel Hopper

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#1
Got a boiler (Saunier Duval 620) that is refusing to produce hot water, for the past two days. When I run the hot tap the vent opens, but there is no gas sent to the butner

It provides heat for the central heating fine (so the gas must be running OK - not that I would touch it ) and on winter setting, if I turn the room thermostat right up, warm water will come out of the tap, but this is probably due to the conduction of heat inside the boiler.

I have a spare boiler in the shed but do not know what part inside the fitted one has failed, or what it would look like

Is it likely to be a pressure sensor (the drop of water pressure caused by an open tap turns the gas on ), or an electrical (flow) sensor

What am I to replace without calling in someone who will have to order a part and wait three weeks for delivery, even though Ive got all the parts needed ?

Help appreciated as the wifes not happy.
 

bigrandydavid

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#2
theres a decent `diy` section at `all-forums.com`.
i`m sure somebody will be able to help on there
 
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#3
Channel Hopper,
I've had similar probs in a couple of houses. Both time caused by the motorised changeover valve. This valve directs the water flow to either hot water only of hat water and heating. Sometimes it jams mid position. All you do in this case is take the motorised bit off the top (220V so be carefull) and use an adjustable spanner to free it up.
Hope it helps
Soapy
 

drag0nfly_69uk

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#4
mine doing something else altogether! sometimes when i turn on hot water tap, the boiler demand light lit up, but cant or wont ignite, i give it a tap on the control panel, then it starts ok. when i use hot water, all the radiators warm up as well :(
 

Channel Hopper

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#5
Dear Soapysoap

Thanks (and the rest of you ) for the replies

What does this part I need to take off look like, and what size spanner

If you know the SD boilers where would it be (left, right, near the pump or part of the pump ?)

I can remove the power to the system so shocks are not an issue
 

rolfw

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#6
Very often the solenoid valve can stick, a sharp tap with a hammer will often cure the problem, not on plastic bits though. :)
 

drag0nfly_69uk

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#7
anyway, we have threads just about any subject under the sun, we might as well have a thread on DIY emergency? :D
 

Channel Hopper

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#8
Sorry Rolf

Im looking at it with the same confusion as I would if I was presented with fixing an alien spacecraft (hmmm no spark plugs)

I can see a large relay operating box near the on / off / ignite switch, but this appears to be functioning correctly. I would not wish to start thumping everything in site with a hammer (actually I would but its not really productive)
 

dishdoctor

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#9
If you can find where the hot water leaves the heat exchanger in the boiler,follow that one pipe untill it reaches a junction where it splits into two feeds,the changeover valve should be there,a three way joint with a electro-mechanical valve conected to a electric feed and return cable,saunier-duval or something similar......best of luck....brian
 

rolfw

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#10
LOL, CH, I did mean a sharp tap, not smashing seven bells out of it. :D If you tap it on the brass joint and not the housing it will very often solve the problem
 

Channel Hopper

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#11
Well thumping it didnt do much good.

No damage (apart from paint removal a couple of missed glancing blows anyway)

I cannot find a point where the pipe splits into two parts with a valve in between


As mentioned before the only way to get hot water is to run the central heating on full for about 30 minutes and then run the hot tap very lightly, but I believe its only because of conduction within the heat exchanger

Any other ideas - I am dreading trying trial by substitution with the other unit, as I know how tight the boiler is the the wall and the condition of the seals that connect the pipes to the important parts, I can see I am going to get rather wet
 
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#12
Channel Hopper,
Have you tried looking in the area around your hot water tank. The part you are looking for looks like a 600mm square plastic box sitting on a tee piece. You don't needa spanner to remove the plstic bit (prob' two screws) but use an adjustable to turn the brass actuator when the plastic is taken off. Hope this helps.
Soapy
 

Channel Hopper

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#13
Hot water tank

The boiler is the only thing in between the incoming mains water, and the rest of the system

The house has no tank to speak of, its all running at mains pressure, not even a header tank
 

Razor

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#14
No tank up in the roof space and no header tank for over flow.
Very strange, hope you don't have rads and I hope they don't over heat.

They say that when the pluming starts to go so should you......

One big, well placed For Sale sign.
 

Channel Hopper

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#15
The reason for no header tanks is ...... There is no roof

Its a flat roof two storey building, I would not like to obscure the satellite look angles by putting a tank up there (or put pipes through the roof)
 

haga

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#16
Hi mate, sorry to butt in, you have whats known as a pressurised system, as has been said the valve that controls the water and rads has either stuck or packed up, they aren't dear to buy but there are many on the market and getting the right one is a job for a plumber, as is fitting it.
Job shouldn't take more than half an hour so doubt your looking at a huge bill.
hope this helps
haga
 

Channel Hopper

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#17
Dear Haga

As said before all I need to know is what it looks like

I have a complete boiler for the parts, and have drained the system before.

I am thinking of changing the switch part in the boiler for the replacement one, as on another site someone said a diaphragm may have gone. Just want to be sure

As for your last comment, plumbers round here arent cheap, £70 callout is the norm, before parts (they tried to charge £320 when the fan motor packed up two years ago - something to do with cement fragments they left in the flue whern they installed it five months earlier ? - and wouldnt use the one off the other boiler)

Thats why Im playing safe
 

haga

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#18
Sod that, I see your point with the plumber, bloody cowboy!
What you are looking for, which should be somewhere near boiler/pump is a unit with an electrical wire attatched, has a lever at the top and is attatched to a vertical pipe with another pipe coming out horizontally at the rear. You can manually move the lever from right to left, when boiler is on it has three positions, one for hot water only, one for heating only and the middle position for both heating and hot water, it is uncommon for these to go but, not unheard of.
It may be the programmer that is not sending out a pulse to alter the unit, if you have a spare programmer it may be easier to change that first to eliminate that.
If I can be any more help, let me know.
haga
 

G55

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#19
Originally posted by drag0nfly_69uk
mine doing something else altogether! sometimes when i turn on hot water tap, the boiler demand light lit up, but cant or wont ignite, i give it a tap on the control panel, then it starts ok. when i use hot water, all the radiators warm up as well :(
Hi drag0nfly_69uk

To get the pilot to light replace the pilot Jet, then check your three port valve it could be stuck in the centre position.
 

Channel Hopper

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#20
Dear Haga

Thanks for sticking with this

The switch is the thing I intend on ripping out over the weekend, so the wife will be bathing with the tadpoles in the garden methinks.

I have a spare, the SD unit has a two position switch for summer/winter and some electrical connections. Just my luck its right in the centre of the plumbing in the boiler.

I dont use a programmer, when Im in I turn the thing on, when Im out its switched off - the miser in me dont you know
 
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