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Topic Title: Glow-worm boiler Overrun timer.
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Created On: 19 May 2017 07:51 AM
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 19 May 2017 07:51 AM
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Zoomup

Posts: 3163
Joined: 20 February 2014

Mornin' All,
I don't do many boilers these days, but a customer asked if an over-run timer can be fitted to his system. He has a Glow-worm ENERGY 12r-30r series gas boiler. The programmer and room thermostat are remotely situated from the boiler so any new wiring may be challenging. Please help.

1. Is an over-run timer essential?

2. Is an over-run timer desirable?

3. How is it wired in please?

Thanks,

Z.
 19 May 2017 08:02 AM
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Thripster

Posts: 803
Joined: 22 August 2006

Hi Zoom,

I think I am right in saying that a boiler is manufactured with overrun (keeps the fan running) to keep the heat exchanger cool after the call for heat has switched off. In which case you need to provide a permanent live to the appropriate terminal in the boiler (look at manual). Sorry if I have misunderstood what you are asking.

Regards
 19 May 2017 08:36 AM
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Zoomup

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Hello Thripster,
thanks for the reply. I understand from the owner of the boiler that he is concerned about it sitting and not cooling quickly enough after the room stat is turned off. Is was considered a good thing to reduce lime scale build up in old boilers to have an over-run system to dissipate heat.

Z.
 19 May 2017 09:22 AM
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mapj1

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Also depends how the pump is supplied - if it goes off with the thermostat contacts, or when the boiler has cooled down - some boilers have a 'pump power' output that is gated so that the wall or tank thermostat only tells the boiler to go on or off, but the boiler puts the pump on pretty much when it gets the call for heat, but leaves it on for a few minutes after flame-out to give a steady cool-down.
This is less stressful for the boiler than killing the circulation and flame together, as there is heat stored around the burner assembly in bits of metal at rather more than 100 degrees that once the air and water flow stops, that stored heat carries on flowing into places that are no longer being cooled.

-------------------------
regards Mike
 19 May 2017 11:01 AM
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Zoomup

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I phoned the technical help line of the maker. I got routed through to Vailant. The guy did not help very much and could not tell me if the boiler has an inbuilt run-on feature to cool it after 'stats had been satisfied. He just confirmed the pump wiring terminals to be used. What has happened to courtesy and customer satisfaction these days?

Z.
 19 May 2017 08:15 PM
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Thripster

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Hi Zoom,

If a Vailant (or manufactured by Vailant) then there will be a permanent supply to the boiler (via 3A FCU) and switched contacts from the thermostat into separate terminals on the boiler PCB via the programmer. In all the Vailants that I have fitted they have internal circuitry that keep the internal pump running for a few minutes after the thermostat has removed the call for heat. The situation may be more complicated if you have external pumps/valves. Either way, you should be able to download an installation maual from the web for the boiler in question which will show how it should be wired. Most combi boilers that I know of have overrun requirements. Tell me to bake my own alaska if this is even a tiny bit patronising/matronising.

Regards
 19 May 2017 09:22 PM
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typiod

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The Glowworm Energy series are just rebadged Vailant eco tec boilers, they can either use the pump over run facility or not, (I have a pdf somewhere from Vailants head of design) The switch live links to the permanent live. They do say that if it is wired without pump overrun then the boiler may not last as long, and also everytime the boiler fires up then it will go into its startup cycle. If however you want to use the pump overrun then you will need a 5 core from the boiler(or a 4 core depending on the existing wiring configuation). Where is the spur for the boiler Zoomup? At the least if you only have a 3core at the boiler then you are going to need to get a cable from the wiring centre to the boiler.
Thirpster yes combi boilers have got pump overrun but then they do need a permant live so that you could have hot water, combis are just system boilers with a bit more inside them both have built in pumps, for a start.
 20 May 2017 09:01 AM
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Zoomup

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Thanks Thripster and tipoid, it appears that the supply to the boiler is via a local fused connection unit. The house owner says that the external pump and external programmer are remotely located from the boiler, some distance I believe. The boiler installer said that the installation was "all right", but for some reason the house owner is concerned about the quality of the installation. Perhaps he had a cheap cash job done. You gets wot you pays for. I have not been able to examine the boiler installation in any detail as yet. Do I want to get further involved? I do not know. Floor board lifting and all that at my age. The installation manual does not seem to cover the run on feature of the boiler at all.
 20 May 2017 11:31 AM
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Thripster

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Not sure why anybody would wish to run a combi without the overrun (unless there is a facility to overrun an external pump) since this will lead to shortened jacket life. There are DIP switch settings for internal pump run preferences; may be worth checking to see whether these are set as expected (that is, you can have on with burner, on with heating demand or continuously running) - probably not relevant here.

With regard to your original question, I would just make sure that there is a permanent live at the boiler and that this then tees off to the thermostat/programmer combo. If there is a permanent feed to the boiler then the likelihood is that the overrun facility is working which you can tell by hearing it operating (fan/pump) for a few minutes after the call for heat is removed. The whole boiler installation should be capable of being isolate by that one FCU - wherever it is situated.

Regards
 20 May 2017 12:07 PM
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typiod

Posts: 483
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Thripster the Glow-worm ENERGY 12r boiler is not a combi boiler, its a regular heat only. It is exactly the same as the Vailant eco tec 4 series.
Zoomup yes the installation manual is the best part of useless for electrical connections, at one time there was no instruction to remove the 24v link if you were using the 230v rt terminal to switch the boiler on and off. As I said in an earlier post these boilers do not need pump overrun but may not last as long. The pump connector is the green plug on the bottom left of the pcb.

Edited: 20 May 2017 at 12:31 PM by typiod
 20 May 2017 06:52 PM
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Thripster

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Typoid,

Sorry, you are right - I was confusing it with my own Ecotec 831.

Regards
 20 May 2017 10:21 PM
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Legh

Posts: 4008
Joined: 17 December 2004

Here you go Z

Your weekend reading material

Legh

-------------------------

http://www.leghrichardson.co.uk

de-avatared
 21 May 2017 06:43 AM
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Thripster

Posts: 803
Joined: 22 August 2006

Have a look at diagnostic codes page 25 d.01 and d.18.
Status codes (page 28) S.05 to 07 and S.25 to 27.

Regards
 21 May 2017 10:56 AM
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Zoomup

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Originally posted by: Legh

Here you go Z



Your weekend reading material



Legh


Thanks Legh,
blinkin ek! Wot a lot of diagnostic and programming codes. I hate anything that challenges my brain cell to understand. There are sections referring to the fan and/or pump overrun settings. I will run away from this. I reckon that it is a gas boiler engineer's job not an electrician's. All that stuff just screws my brain cell. I also hate programming security alarm panels. Too many layers of stuff to juggle with.

I am mature, slow, and hate modern electronic systems devised by men in white coats in the lab just designed to cause installers many headaches. Stuff should be designed to be fitted then forgotten I reckon. GGGGGGRRRRRrrrrrrrr!

I do not wish to be an Alan Turing working at Bletchley Park.

Off for a lay down.



Bye and thanks anyway,

Z.
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