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Clive M
 
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Default simple explanation - wiring two pumps into boiler

Having done a google, I have come across a technique to wire two pumps into
a gravity system to produce a fully pumped system
as per
http://groups.google.com/groups?hl=e...pex.net&rnum=8
http://groups.google.com/groups?hl=e... ws.pipex.net

I am confused of how I can acheive this with my setup.

I have got a danfoss RX2 that provides the inputs for both heating and room
stats (there is no programmer as the room stat is programable)

The connection box RX2 has a zone (zone 2) output that switched live, there
is then two other outputs that is switched live (zone 1 on) or (zone 1 off)

The boiler has a live imput that fires the boiler and pump. There is then
another input (mains Swl) that is the switched live from the external
gravity hot water circuit.

If the boiler is run as fully pumped, it will need to have pump overrun
selected - this will need to overrun the heating pump only.

As far as I can make out I need to wire the RX2 outputs from that stat to
the pump, and then wire two relays across the pumps (1 per pump) so that
when the stat fires the pump, the relay is activated and the "main L" input
to the boiler fires". As they are connected via relays the boiler input
going live will not fire the other pump.

The problem is the boiler overrun - I cant just wire the hot water pump to
the boiler, and ever time the boiler fires the HW pump would run. How can
pump overrun be implimented?


  #2   Report Post  
Pete C
 
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Default

On Sun, 22 Aug 2004 20:09:43 GMT, "Clive M"
wrote:

The problem is the boiler overrun - I cant just wire the hot water pump to
the boiler, and ever time the boiler fires the HW pump would run. How can
pump overrun be implimented?


Hi,

Scuse the dummy question, but why do you need overrun?

cheers,
Pete.
  #3   Report Post  
raden
 
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Default

In message , Pete C
writes
On Sun, 22 Aug 2004 20:09:43 GMT, "Clive M"
wrote:

The problem is the boiler overrun - I cant just wire the hot water pump to
the boiler, and ever time the boiler fires the HW pump would run. How can
pump overrun be implimented?


Hi,

Scuse the dummy question, but why do you need overrun?

To disperse the heat from the heat exchanger into the system

--
geoff
  #4   Report Post  
Pete C
 
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Default

On Mon, 23 Aug 2004 23:00:35 GMT, raden wrote:

In message , Pete C
writes
On Sun, 22 Aug 2004 20:09:43 GMT, "Clive M"
wrote:

The problem is the boiler overrun - I cant just wire the hot water pump to
the boiler, and ever time the boiler fires the HW pump would run. How can
pump overrun be implimented?


Hi,

Scuse the dummy question, but why do you need overrun?

To disperse the heat from the heat exchanger into the system


I see. If it's to prevent kettling then a 'delay off' relay would do,
some cheap ones available he

http://www.engsurplus.btinternet.co.uk/control.automation.htm

More information available from:

www.rswww.com

cheers,
Pete.


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Tony Bryer
 
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Default

In article , Pete C
wrote:
I see. If it's to prevent kettling then a 'delay off' relay
would do, some cheap ones available he

http://www.engsurplus.btinternet.co.uk/control.automation.htm


Just wire the pump through a pipe stat - cold side of stat to
boiler call, hot side to permanent live, common to pump

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser
http://www.sda.co.uk/qsedbuk.htm




  #6   Report Post  
Pete C
 
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On Tue, 24 Aug 2004 11:10:03 GMT, Tony Bryer
wrote:

In article , Pete C
wrote:
I see. If it's to prevent kettling then a 'delay off' relay
would do, some cheap ones available he

http://www.engsurplus.btinternet.co.uk/control.automation.htm


Just wire the pump through a pipe stat - cold side of stat to
boiler call, hot side to permanent live, common to pump


Hi,

Sounds good, I wasn't aware they were available with a changeover
contact.

cheers,
Pete.
  #7   Report Post  
Tony Bryer
 
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Default

In article , Pete C
wrote:
Sounds good, I wasn't aware they were available with a
changeover contact.


All the ones I have installed have had this. IIRC the older MV's
needed DHW on and DHW off feeds

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser
http://www.sda.co.uk/qsedbuk.htm


  #8   Report Post  
Set Square
 
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Default

In an earlier contribution to this discussion,
Tony Bryer wrote:

In article , Pete C
wrote:
Sounds good, I wasn't aware they were available with a
changeover contact.


All the ones I have installed have had this. IIRC the older MV's
needed DHW on and DHW off feeds



Most 3-port mid-position valves still do!
--
Cheers,
Set Square
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  #9   Report Post  
Set Square
 
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In an earlier contribution to this discussion,
Tony Bryer wrote:

In article , Set Square wrote:
All the ones I have installed have had this. IIRC the older MV's
needed DHW on and DHW off feeds



Most 3-port mid-position valves still do!


I've always avoided them like the plague - reading the FAQ
explanation of how they work just makes my brain hurt. With 2 x
2-port valves it's always obvious what's happening.


I agree with you and - given a clean sheet - would do the same, since they
*are* a little complex and they *do* represent a significant single point of
failure in heating systems. However, I inherited a Y-plan system when I
bought this house and it works well enough for me not to want the hassle of
re-jigging everything. I've had to replace the actuator a couple of times,
but I've got quite good at recognising the symptoms when it goes wrong - and
(hopefully) at advising others about the delightful things when they enquire
in this NG.
--
Cheers,
Set Square
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  #10   Report Post  
Tony Bryer
 
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Default

In article , Set Square wrote:
All the ones I have installed have had this. IIRC the older MV's
needed DHW on and DHW off feeds



Most 3-port mid-position valves still do!


I've always avoided them like the plague - reading the FAQ
explanation of how they work just makes my brain hurt. With 2 x
2-port valves it's always obvious what's happening.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm


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