Adding a pump overrun

On 20/09/2017 20:14, swoopdave wrote:

Electricity?
This must be a record for homeownershub - a question posted 14 years ago
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On 20/09/2017 20:14, swoopdave wrote:

I presume this is reply to a very ancient post since Ed has not posted hear for ages. However you will probably find what you need here:
http://wiki.diyfaq.org.uk/index.php/Central_Heating_Controls_and_Zoning#Adding_Pump_Overrun
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Why does it matter which way it's open during overrunning?
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On 22/09/2017 10:33, Andrew Gabriel wrote:

If its open to the DHW, and that is already satisfied, you won't dump much additional heat from the primary circuit into the cylinder - and will lose more out of the flue than you would expect if overruning through the rads.
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On 22/09/2017 16:53, John Rumm wrote:

And if it dumps it to the CH, and all the rads have TRVs which are closed, it won't have anywhere at all to go.
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On 22/09/2017 22:35, Roger Mills wrote:

Wouldn't that have been happening before the boiler turned off?
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On 23/09/2017 02:03, Fredxxx wrote:

The boiler would probably cycle off on its own stat in the circumstance.
Just one of those cases of not being able to win em all!
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Thought it wasn't recommended to have TRVs on every rad?
I have none in the living room and that's where the main temperature sensor is. Every other rad has a TRV.
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On 23/09/2017 10:01, Dave Plowman (News) wrote:

Its isn't generally - although you do find some systems that have no main stat and have all TRVs.
(Some systems have a bypass to ensure there is always an available path for flow, and some modern boilers include an internal one (as does my Vaillant for example)).

Yup, similar arrangement here - although I have a second zone upstairs where all the rads have TRVs, you get enough heat leakage into the landing (where the zone stat is) from downstairs to satisfy that stat anyway.
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The cheapie BES cyl stat has a pipe fitting option and has changeover contacts: http://www.bes.ltd.uk/products/110.asp item 9777 The coily spring thing in the picture is the pipe fitting spring. 6.73 + vat & post.

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When I fitted an over-run, I had a play with this but discovered it not to be quite so simple - the volts from the thermostat went the 'wrong' way as well and caused problems with my 3 port valve. Can't remember exactly what as it's a long time ago - something to do with wanting it to work after the entire system had shut down as well. The way round would of course have been to add a relay which isolated the valve switching etc. But having concluded that, I simply made an electronic timer using bits I had lying around based on a U6047 car heated rear window timer chip and a relay, as I didn't have any suitable mains coil relays 'in stock' at the time.
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CH Pump overrun pcbs are readily available (maybe not the cheapest option though)
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What's the boiler?
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ARWadsworth wrote:

Before you spend anything (money or time) you could wire the pump to be on permanently, to see if it actually fixes the problem.
Bob
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Nice idea, simple is best . . . .
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fred wrote:

Well I was thinking short term, just to see if it would work, but you could do a permanent job by having the pump switched on by the CH timer.
Incidentally, my dad has his on permanently to stop the sludge building up in the pump during the summer months, because his pump is low in the system.
Bob
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writes

could
system.
If there is sludge in the system something wrong with the system and it should be rectified. Also the sludge should be removed and correct inhibitor used.
He could have saved a ton of money in electricity by using a simple timer to turn the pump one a day for 30 seconds.
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With a *proper* heating/hot water system, the pump will run anyway when heating the water.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Thu, 27 Nov 2003 14:40:53 +0000, Bob Smith wrote:

Which is the bog standard way of doing things for this type of installation.

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