Adding a pump overrun

Is it possible to add a pump overrun to a boiler that does not have this facility built in. I was hoping that there was some sort of control box for this but I have been unable to find one. The reason I ask is that the plumber thinks the heat left standing in the pipes is causing the boiler's thermostat to stop the boiler re firing after it has stood for a while after being used. The boiler is about 15 metres from the pump, rads and HW tank and placed in an outhouse. Any ideas or help please?
-- Adam
snipped-for-privacy@blueyonder.co.uk
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You need a circuit which provides a delayed switchoff, like the overrun timer for a bathroom fan, which are available separately. You would probably need it operating the pump via a relay, as they only contain a small non-heatsinked triac for handling a 20W fan. It may be that dedicated boiler pump versions are available too. The circuit simply by virtue of additional complexity obviously introduces additional risk of failure to operate pump, and unless the boiler has a water flow detector, I would worry about that -- personally I wouldn't want to rely on over temp detector only.
--
Andrew Gabriel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Using a bit of parallel thinking, how about using a pipe stat to keep the pump running until the flow temp drops below a certain value, say 50degrees? Normal pump demand and normally open contact of pipe stat connected in parallel. Certainly a cheap option, 6-10quid.
--
fred

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

this
for
boiler's
after
tank
That is usually the accepted method. Set the pipe stat on the flow near the boiler and set it slight less than the boiler stat.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.542 / Virus Database: 336 - Release Date: 18/11/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to IMM, john coen wrote: have to be careful sending an unprogrammed live feed back through to other stat, Stats are tempermental
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29/09/2017 21:14, john coen wrote:

Did they have pump overruns in 2003?
Given the OP (ARW) is an electrician you might think he knows this and a lot more besides.
This might assist you with posting to a newsgroup, albeit through a website: https://tools.ietf.org/html/rfc1855
- If you are sending a reply to a message or a posting be sure you summarize the original at the top of the message, or include just enough text of the original to give a context.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29/09/2017 21:23, Fredxxx wrote:

Yes - long before that. My c1990 Baxi Solo (still going strong!) has one. They came in with the physically smaller boilers with aluminium heat exchangers - designed for fully pumped systems - whose residual heat could cause them to overheat if the flow stopped immediately when the flame was cut.
Having said that, the over-run logic on my boiler is somewhat flawed - and there are some circumstances which can still result in an overheat trip - so I have added a timer as well.
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29/09/2017 22:37, Roger Mills wrote:

I did add the comment with tongue firmly in cheek!
I recall fitting a boiler 20 years ago which in my opinion had the overrun timer set for far too long.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29/09/2017 22:37, Roger Mills wrote:

On my 25 year old boiler the overrun is controlled by a micro-switch which in turn is switched on/off mechanically by a (bi??) metal arm attached to the water temperature sensor. After around 15 years the overrun started cutting out too early, just after the boiler stopped heating. Easily fixed by adjusting the screw on the metal arm so that the micro-switch again operated when the water was still hot.
--
mailto: news admac {dot] myzen co uk

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Roger Mills wrote:

My (I guess) 1986 (still going strong, but probably not very efficient) Thorn Apollo has one, but I don't know if it's still contributing to the overall heating effort. Perhaps I'll notice if/when it breaks?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I built one for my BE boiler in the '70s. To get the heat out of its cast iron heat exchanger to where it was most needed.
--
*Ham and Eggs: Just a day's work for a chicken, but a lifetime commitment

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29/09/17 21:14, john coen wrote:

Most stats are dry no-volt contact types (including electronic ones which typically have an output relay which you can hear as it goes "click").
Heating systems quite often end up with control elements wired in parallel, eg frost stats so it's not uncommon.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The right one would need to be chosen. Generally pipe thermostats are for preventing freezing.
However, Honeywell make one (L641B-1012) which is adjustable from 50 to 95 degrees and has a changeover contact. Discounted Heating have them as I am sure others do, but price is in the 23 area.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Hall wrote:

How about a capillary stat, e.g. BES 9780, with the bulb strapped to the pipe?
--
Grunff


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Could do. However, the catalogue doesn't say what contact arrangements there are. For this application it needs to have a pair of contacts which are closed above the set point rather than open as is normally the case. Changeover would be OK of course.
The other thing would be making certain that there is good contact between the phial and the pipe. Normally these things go into a pocket in the heated item. Otherwise, the thermostat is likely to be a bit inaccurate, although that probably doesn't matter.
Something like a short piece of appropriate size microbore pipe, soldered to the water pipe being monitored would probably be a reasonable solution. The phial would slide into the piece of tube.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 26 Nov 2003 20:36:52 +0000, Andy Hall wrote:

A way to do this as I understand it: Connect the pump to the common pole of the changeover switch, connect the boiler demand to the pole which is closed when the pipes are cool, connect a permanent live feed to the pole which is closed when the switch is hot.
However none of this adds up as far as the OP is concerned when the boiler is demanded the existing arangements should start the pump and very soon cooler return water will bring the boiler temp down and make it fire.
Perhaps the existing boiler has an overrun thermostat and there is a wiring failure somewhere and/or the overrun thermostat has gone out of spec?
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The impression I am getting is that the boiler is firing, heating for a while, then boiler stat clicks off as expected, but residual temp in the boiler is causing it remain off for longer than is desired. Nice that it is not short cycling ;-), but not what is desired. The pump run on will hopefully sort that out, but hopefully not result in short cycling before the room stat is satisfied.
Makes me glad mine is modulating . . .

True
--
fred

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

while,
is
short
that
That would seem to be precicely the problem. I have not seen the boiler and I have only spoken to my friend and his plumber who cannot fix this on the phone. It is the plumber who thinks an overrun will cure the problem.

I will get the make and no of the boiler tommorow. But I am told that it is old so I do not expect an overrun to be part of it's design
-- Adam
snipped-for-privacy@blueyonder.co.uk
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 27 Nov 2003 10:18:55 +0000, fred wrote:

The root problem here is nothing to do with needing an _overrun_ on the pump we need the pump to _run_ when the boiler is on, that is how older low-tech boilers work.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to Ed Sirett, swoopdave wrote: What keeps the 3 way valve open to the rads while its over running?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.