# Vaillant boiler question



## Tab373 (Feb 4, 2018)

Hi just moved into a property fitted with a Vaillant eco tec plus 937 boiler. The boiler is constantly clicking on and off runs for 5 mins switches of then back on for 5 then off.only off for approx a min. Any ideas. As have no manual heating comes on fine but it seems to me that the boiler is firing on and off too regularly and will cost me a fortune. Iâ€™m with British Gas shall I just call them to arrange for a service and advise me. Please help


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## Stuart_C (Feb 4, 2018)

Tab373 said:



			Hi just moved into a property fitted with a Vaillant eco tec plus 937 boiler. The boiler is constantly clicking on and off runs for 5 mins switches of then back on for 5 then off.only off for approx a min. Any ideas. As have no manual heating comes on fine but it seems to me that the boiler is firing on and off too regularly and will cost me a fortune. Iâ€™m with British Gas shall I just call them to arrange for a service and advise me. Please help
		
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it sounds like you have  got the water on preheat mode, so your hot water is always hot.


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## jim8flog (Feb 4, 2018)

I know my Vailant eco TEC boiler has self test modes but not that frequently.

Vaillant offer an online questions service at vaillant.co.uk and you can download the manual (literature and search on boiler number)


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## jim8flog (Feb 4, 2018)

and yes I agree with Stuart if it is a combi with a preheat mode.

Does the display have a 'C' in the window. If yes turn the hot water temperature control fully anti clockwise to turn it off (the 'c' should no longer show).


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## Stuart_C (Feb 4, 2018)

Iâ€™ve just checked it is a storage combi youâ€™ve definitely got the preheat mode on, give us a pm if youâ€™re stuck


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## jim8flog (Feb 4, 2018)

Just realised that the instruction I gave you was unfinished.

After turning the water temperature dial full anti clockwise to turn off preheat function turn it back to the desired hot water temp I run mine at 50 degrees which is good enough for washing without the risk of burning. To turn the preheat function back on turn, the dial fully clockwise until the 'C' shows then turn the dial back to the desired temperature setting.


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## Tab373 (Feb 4, 2018)

Hi thank for the feedback I havenâ€™t a clue how to turn preheat off havenâ€™t got any knobs to turn just a display and 4 buttons.


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## jim8flog (Feb 5, 2018)

As said you can download the manual on the Vaillant website.

Your reply is somewhat odd because the manual shows you to have the same control set as mine

Operating manual
ecoTEC plus 937


 
 
The storage tank charging of the layer charging storage
tank is only active if the warmstart function is switched on.
This is shown by the symbol in the display (see Section
4.4.2).
If the storage tank charging function is switched on you
can use the knob for the hot water draw-off temperature
to set the following temperatures:
 
*â€“ Knob setting "bâ€œ 50 Â°C
â€“ Knob setting "aâ€œ 65 Â°C
 
 
*If the storage tank charging function is switched off you
can use the knob for the hot water draw-off temperature
to set the following temperatures:
 
*â€“ Knob setting "câ€œ 35 Â°C
â€“ Knob setting "aâ€œ 65 Â°C
 
 
*a
a
b
c
c
1
1
1
 
*Fig. 4.8 Setting range for the storage tank temperature
 
 
*If the storage tank charging function is switched off, the
tank is not held at temperature. The unit only switches
on in this case if the water is drawn off and only operates
in the through-flow mode.


Sorry it appears that the diagrams will not cut and paste


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## Tab373 (Feb 6, 2018)

sorry but canâ€™t see any knob on my boiler


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## jim8flog (Feb 6, 2018)

Wow! this is the control shown in the manual for that boiler number and on mine.




On their website there is a helpline number and maybe they can point out or send you the correct manual.


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## jim8flog (Feb 6, 2018)

PS have you checked behind the drop down flap next to the display or at the bottom of the boiler


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## Tab373 (Feb 6, 2018)

hi the drop down flap next to the display doesnt drop down. But will try i again tomoz as working nights at mo. i actually think its the heating that the boiler is switching on and off for as the radiator pic is in the display when it fires up. but only have rads in bedrooms as underfloor heating in all other rooms and that i think is a seperate system which is under the stairs with various pipes and valves. Have a mate whos a heating engineer coming on Friday to have a look. the previous owner hadnt a clue how it all worked when i asked him when i put in the offer but sure i will get it sorted. thx for the advise


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## Stuart_C (Feb 6, 2018)

Tab373 said:



			hi the drop down flap next to the display doesnt drop down. But will try i again tomoz as working nights at mo. i actually think its the heating that the boiler is switching on and off for as the radiator pic is in the display when it fires up. but only have rads in bedrooms as underfloor heating in all other rooms and that i think is a seperate system which is under the stairs with various pipes and valves. Have a mate whos a heating engineer coming on Friday to have a look. the previous owner hadnt a clue how it all worked when i asked him when i put in the offer but sure i will get it sorted. thx for the advise
		
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ahh UFH?? you never told me that. where is your boiler fitted and the manifold for the UFH pipes?


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## Tab373 (Feb 7, 2018)

Boiler is fitted in down stairs toilet and ufh manifold is under the stairs. Have separate controls in every room of house for the ufh.ive set the temp and timer for under floor heating to come on twice a day early morning and early evening as it stays warm for ages even after going off.


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## Stuart_C (Feb 7, 2018)

Tab373 said:



			Boiler is fitted in down stairs toilet and ufh manifold is under the stairs. Have separate controls in every room of house for the ufh.ive set the temp and timer for under floor heating to come on twice a day early morning and early evening as it stays warm for ages even after going off.
		
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ah right, there's usually only 2 reasons why it would come on for short periods as you said previous, preheat mode on the hot water and a frost stat kicking it but they're usually fitted in cold areas like Garages and lofts. 

I'm intrigued now...


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## jim8flog (Feb 7, 2018)

Stuart_C said:



			ah right, there's usually only 2 reasons why it would come on for short periods as you said previous, preheat mode on the hot water and a frost stat kicking it but they're usually fitted in cold areas like Garages and lofts. 

I'm intrigued now...
		
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That reminds me of my neighbour who had his fitted in the garage. The boiler was working 24 hours a day with nobody actually living in the house whilst it was being renovated.

What a lot of people and clearly plumbers do not realise is that the 'frost' stat actually kicks in at 8 degrees.


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## Stuart_C (Feb 7, 2018)

jim8flog said:



			That reminds me of my neighbour who had his fitted in the garage. The boiler was working 24 hours a day with nobody actually living in the house whilst it was being renovated.

What a lot of people and clearly plumbers do not realise is that the 'frost' stat actually kicks in at 8 degrees.
		
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I know loads of plumbers  who wouldn't know that.  Heating engineers on the other hand


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## Tab373 (Feb 7, 2018)

the down stairs toilet is a constant 28 but ideal for drying the odd clothes on a rainy day. i will keep you posted when i find out


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## jim8flog (Feb 7, 2018)

I know I did not think much of the guy who installed my neighbours. The exhaust vent was pointing straight at my bedroom air vent just 5 feet away and I could smell the smoke in my bedroom.


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## Tab373 (Feb 9, 2018)

Right the engineer came and after listening me talk about whatâ€™s happening happening he openend up the boiler and removed a link. White plastic plug with a wire looped into it. Said he saw another a few weeks ago with same issue. Boiler now off and only comes on when the timer says. Happy days


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