UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 42
Default CH: convert from gravity to fully pumped

I plan to install a new twin-coil solar HW cylinder soon, and plan to
convert the CH system from gravity-fed to fully pumped at the same time.
(Solar coil to be utilized at a later date)
Currently the boiler and pump are downstairs with 28mm gravity-feed pipes
and 22mm CH pipes heading upstairs.
There is currently 1 thermostat downstairs, and no cylinder stat. TRV's on
all rads but 1.

I plan to utilise the original pipework where possible but move the CH pump
to upstairs and install a motorized valve to divert flow between CH and HW.
I'll also fit a cylinder stat.

I *could* also use a motorized valve to create upstairs & downstairs zones
if worthwhile.
The programmer supports fully pumped with cylinder stat and (I think) 2
zones - will check.

Any recomendations from the group of which CH plan to go with and whether
it's worth creating upstairs & downstairs zones?

Any suggestions on plumbing config and type of motorized valves to use?

Thanks in advance,

Alan.


  #2   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 2,488
Default convert from gravity to fully pumped

In an earlier contribution to this discussion,
Alan wrote:

I plan to install a new twin-coil solar HW cylinder soon, and plan to
convert the CH system from gravity-fed to fully pumped at the same
time. (Solar coil to be utilized at a later date)
Currently the boiler and pump are downstairs with 28mm gravity-feed
pipes and 22mm CH pipes heading upstairs.
There is currently 1 thermostat downstairs, and no cylinder stat.
TRV's on all rads but 1.

I plan to utilise the original pipework where possible but move the
CH pump to upstairs and install a motorized valve to divert flow
between CH and HW. I'll also fit a cylinder stat.

I *could* also use a motorized valve to create upstairs & downstairs
zones if worthwhile.
The programmer supports fully pumped with cylinder stat and (I think)
2 zones - will check.

Any recomendations from the group of which CH plan to go with and
whether it's worth creating upstairs & downstairs zones?

Any suggestions on plumbing config and type of motorized valves to
use?
Thanks in advance,

Alan.


A lot depends on the layout of the existing pipework. Presumably there are 4
connections to the boiler at present - 2 for the HW and 2 for the CH? If you
go fully pumped with a single pump, you'll only need 2 - although you could
keep separate returns, and have 3, if that was easier.

How is the downstairs CH circulated? Is it below the downstairs floor so
that the CH pipes going upstairs are only for the upstairs rads, or does it
*all* go up and then come down to each individual downstairs rad?

If you have a single pump upstairs, *everything* (including the water for
the downstairs rads) has to go up, and then be distributed using zone
valves - probably in the airing cupboard. The ease with which this can be
achieved depends on the current setup.

If it is difficult to achieve this, an alternative fully pumped strategy is
to keep the existing pipes and simply insert a second pump into the HW
circuit. You would control the pumps with the respective room and cylinder
stats, and you then need a bit of relay logic to turn the boiler on whenever
either pump is running. You would also probably need an anti-gravity valve
in the HW circuit to prevent any flow when the HW pump isn't on.

Assuming that a single pump solution *is* viable, an S-Plan+ system would
give you the most flexibility - and allows you to have as many zones as you
wish. Whether or not it's worthwhile having separate up and down zones
really depends on how you use the rooms. If there are long periods when you
only want to heat upstairs but not downstairs, and vice versa, then it is a
good idea. However, you need to consider whether the bathroom needs to be
warm all the time. Going back to the question how about the CH is
distributed, if you have a single 'between the floors' circuit it will be
very difficult to have up and down zones. On the other hand, if they're
already separate, you'll have to solve the problem of getting the downstairs
radiator water upstairs and back down again.

If you *do* go for zoning, I would recommend using a programmable thermostat
for each heating zone. It doesn't then matter whether the main programmer
supports zoning - you just leave the CH control on that set to 'on', and use
the programmer to time just the HW.

For an S-Plan plus system, you'll need one 2-port valve per zone - so that's
one for the HW and probably two for the CH. They need to have auxilliary
'volt-free' contacts which can be used to switch on the boiler and pump
whenever one or more of the valves are open - as per the standard S-Plan
arrangement. [See http://content.honeywell.com/uk/homes/systems.htm ]

Any reputable make of valve - Danfoss, Drayton, Honeywell, etc. - should be
ok. Even if you use the existing 28mm flow and return pipes from the boiler
to the airing cupboard, I assume that you will use 22mm after the pump - so
the valves only need to be 22mm.

HTH.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!


  #3   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 3,356
Default CH: convert from gravity to fully pumped

On Mon, 26 Mar 2007 11:42:11 GMT someone who may be "Alan"
wrote this:-

I plan to install a new twin-coil solar HW cylinder soon, and plan to
convert the CH system from gravity-fed to fully pumped at the same time.
(Solar coil to be utilized at a later date) [snip]

I plan to utilise the original pipework where possible but move the CH pump
to upstairs and install a motorized valve to divert flow between CH and HW.
I'll also fit a cylinder stat.


It is often simpler to add a pump to the former gravity circuit and
leave the central heating pump where it was. These pumps can then be
controlled by a thermostat and time clock as appropriate.

The only major thing to watch is that the gravity circuit was often
used as an expansion pipe and this must not be interfered with.

I *could* also use a motorized valve to create upstairs & downstairs zones
if worthwhile.


Depending on the arrangement of the building it can be better to
have north/south zones rather than top/bottom. However, this very
much depends on how rooms are arranged in the house.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
  #4   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 42
Default convert from gravity to fully pumped


"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Alan wrote:

I plan to install a new twin-coil solar HW cylinder soon, and plan to
convert the CH system from gravity-fed to fully pumped at the same
time. (Solar coil to be utilized at a later date)
Currently the boiler and pump are downstairs with 28mm gravity-feed
pipes and 22mm CH pipes heading upstairs.
There is currently 1 thermostat downstairs, and no cylinder stat.
TRV's on all rads but 1.

I plan to utilise the original pipework where possible but move the
CH pump to upstairs and install a motorized valve to divert flow
between CH and HW. I'll also fit a cylinder stat.

I *could* also use a motorized valve to create upstairs & downstairs
zones if worthwhile.
The programmer supports fully pumped with cylinder stat and (I think)
2 zones - will check.

Any recomendations from the group of which CH plan to go with and
whether it's worth creating upstairs & downstairs zones?

Any suggestions on plumbing config and type of motorized valves to
use?
Thanks in advance,

Alan.


A lot depends on the layout of the existing pipework. Presumably there are
4 connections to the boiler at present - 2 for the HW and 2 for the CH? If
you go fully pumped with a single pump, you'll only need 2 - although you
could keep separate returns, and have 3, if that was easier.

How is the downstairs CH circulated? Is it below the downstairs floor so
that the CH pipes going upstairs are only for the upstairs rads, or does
it *all* go up and then come down to each individual downstairs rad?

If you have a single pump upstairs, *everything* (including the water for
the downstairs rads) has to go up, and then be distributed using zone
valves - probably in the airing cupboard. The ease with which this can be
achieved depends on the current setup.

If it is difficult to achieve this, an alternative fully pumped strategy
is to keep the existing pipes and simply insert a second pump into the HW
circuit. You would control the pumps with the respective room and cylinder
stats, and you then need a bit of relay logic to turn the boiler on
whenever either pump is running. You would also probably need an
anti-gravity valve in the HW circuit to prevent any flow when the HW pump
isn't on.

Assuming that a single pump solution *is* viable, an S-Plan+ system would
give you the most flexibility - and allows you to have as many zones as
you wish. Whether or not it's worthwhile having separate up and down zones
really depends on how you use the rooms. If there are long periods when
you only want to heat upstairs but not downstairs, and vice versa, then it
is a good idea. However, you need to consider whether the bathroom needs
to be warm all the time. Going back to the question how about the CH is
distributed, if you have a single 'between the floors' circuit it will be
very difficult to have up and down zones. On the other hand, if they're
already separate, you'll have to solve the problem of getting the
downstairs radiator water upstairs and back down again.

If you *do* go for zoning, I would recommend using a programmable
thermostat for each heating zone. It doesn't then matter whether the main
programmer supports zoning - you just leave the CH control on that set to
'on', and use the programmer to time just the HW.

For an S-Plan plus system, you'll need one 2-port valve per zone - so
that's one for the HW and probably two for the CH. They need to have
auxilliary 'volt-free' contacts which can be used to switch on the boiler
and pump whenever one or more of the valves are open - as per the standard
S-Plan arrangement. [See
http://content.honeywell.com/uk/homes/systems.htm ]

Any reputable make of valve - Danfoss, Drayton, Honeywell, etc. - should
be ok. Even if you use the existing 28mm flow and return pipes from the
boiler to the airing cupboard, I assume that you will use 22mm after the
pump - so the valves only need to be 22mm.

HTH.
--
Cheers,
Roger
______


Roger,

Thanks for the informative response.
There are 3 pipes into the boiler - the return from the gravity circuit goes
in via a "Y" piece with the CH return.
I will need to cap off the current gravity output from the boiler and just
use the remaining 2 connections.

The output of the pump is teed and one leg feeds the downstairs CH circuit
and the other goes upstairs on one of the 22mm pipes.
Adding a 2nd pump isn't an option I had previously thought of, however from
what you say I can achieve what I need to with 2 or 3 valves.
The pipework for downstairs is all below floorboard level and starts and
ends by the boiler, so converting to seperate zones would be reasonably
easy, but as every room is used daily there may not be much point.

I will look at the S-Plan+ details, sounds like it's what I need.

Many thanks,

Alan.


  #5   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 42
Default CH: convert from gravity to fully pumped


It is often simpler to add a pump to the former gravity circuit and
leave the central heating pump where it was. These pumps can then be
controlled by a thermostat and time clock as appropriate.


OK, this may be an option. The S-Plan+ suggested by Roger is another
solution.

The only major thing to watch is that the gravity circuit was often
used as an expansion pipe and this must not be interfered with.


You're right, it is. I'll have to design this into the new system.

Depending on the arrangement of the building it can be better to
have north/south zones rather than top/bottom. However, this very
much depends on how rooms are arranged in the house.


Existing pipework is upstairs/downstairs, so will keep it that way.

Many thanks,

Alan.




  #6   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 3,356
Default CH: convert from gravity to fully pumped

On Mon, 26 Mar 2007 14:26:43 GMT someone who may be "Alan"
wrote this:-

The only major thing to watch is that the gravity circuit was often
used as an expansion pipe and this must not be interfered with.


You're right, it is. I'll have to design this into the new system.


Pumping the return usually deals with this. Beware of difficulties
with connections though.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
  #7   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 2,488
Default convert from gravity to fully pumped

In an earlier contribution to this discussion,
Alan wrote:


The output of the pump is teed and one leg feeds the downstairs CH
circuit and the other goes upstairs on one of the 22mm pipes.
Adding a 2nd pump isn't an option I had previously thought of,
however from what you say I can achieve what I need to with 2 or 3
valves. The pipework for downstairs is all below floorboard level and
starts
and ends by the boiler, so converting to seperate zones would be
reasonably easy, but as every room is used daily there may not be
much point.

Ok, this needs a bit more thought! Is the pump in the flow or the return?

For a zoned system, the pump needs to be in the flow pipe, and needs to be
*before* any zone valves. You're going to have to leave it where it is
rather than moving it upstairs - otherwise the downstairs heating circuit
will tee in in the wrong place.

You could put one valve in that circuit, just after the tee, and two more
valves upstairs. At the top of the upstairs heating feed, split it into
two - with a valve in each leg - connecting one leg to the existing upstairs
heating circuit and the other to the coil in the HW cylinder.

With regards to the existing HW gravity feed, leave that comnnected to the
boiler as a vent pipe (the top probably already goes up and over the F&E
tank?) but blank off the connection to the cylinder, using the pumped feed
instead.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!


  #8   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 42
Default convert from gravity to fully pumped

Ok, this needs a bit more thought! Is the pump in the flow or the return?

Flow

For a zoned system, the pump needs to be in the flow pipe, and needs to be
*before* any zone valves. You're going to have to leave it where it is
rather than moving it upstairs - otherwise the downstairs heating circuit
will tee in in the wrong place.

You could put one valve in that circuit, just after the tee, and two more
valves upstairs. At the top of the upstairs heating feed, split it into
two - with a valve in each leg - connecting one leg to the existing
upstairs heating circuit and the other to the coil in the HW cylinder.


Ahh, OK, so three paths for pump output, depending which valve(s) are open.

With regards to the existing HW gravity feed, leave that comnnected to the
boiler as a vent pipe (the top probably already goes up and over the F&E
tank?) but blank off the connection to the cylinder, using the pumped feed
instead.


Yes, one gravity pipe goes to the F&E vent, the other is the tank's output
into the CH system (to fill it etc).
Both currently have unequal (28x18x15) tees at the cylinder connections. I
could replace the tees or blank off the existing cylinder connections and
use the new valve output instead then.

So 3 valves, a cylinder thermostat, and maybe 2x programmable room
thermostats is probably what I'll need then.

Alan.


  #9   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 2,488
Default convert from gravity to fully pumped

In an earlier contribution to this discussion,
Alan wrote:


So 3 valves, a cylinder thermostat, and maybe 2x programmable room
thermostats is probably what I'll need then.

Alan.


Yes. You'll still need a valve on the downstairs circuit even if you
parallel it with the upstairs one and use a single room stat for the whole
house - otherwise you won't be able to have HW without downstairs heating.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!


  #10   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 42
Default convert from gravity to fully pumped


Yes. You'll still need a valve on the downstairs circuit even if you
parallel it with the upstairs one and use a single room stat for the whole
house - otherwise you won't be able to have HW without downstairs heating.


Agreed - looking at various bits on screwfix's site now.
The programmer Honeywell recommend is the ST6400C - which is the one I
already have.
The existing room thermostat is a digital one. I could re-use this and just
add another room stat upstairs?
(This option would give independant HW/CH operation controlled by the
programmer and upstairs/downstairs temperature control (when CH is on) via
each stat)).

Many thanks for your help. Guess what I'm doing over easter.....

Alan.




  #11   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 1,283
Default CH: convert from gravity to fully pumped


"David Hansen" wrote

Pumping the return usually deals with this. Beware of difficulties
with connections though.

Make sure you know the score if you consider pumped return arrangement.
I inherited a system with pumped return and could not get it to perform.
With pump speed sufficient to heat the house in a reasonable time, there was
a serious issue with pump over into the header tank.
If you are intending to stick with a vented system rather than going sealed,
would recommend you opt for pump in the flow with make up water connection
close to vent.

Phil


  #12   Report Post  
Posted to uk.d-i-y
external usenet poster
 
Posts: 529
Default CH: convert from gravity to fully pumped

"Alan" wrote in message
news

It is often simpler to add a pump to the former gravity circuit and
leave the central heating pump where it was. These pumps can then be
controlled by a thermostat and time clock as appropriate.


OK, this may be an option. The S-Plan+ suggested by Roger is another
solution.

The only major thing to watch is that the gravity circuit was often
used as an expansion pipe and this must not be interfered with.


You're right, it is. I'll have to design this into the new system.


Last autumn I converted my house. It is 2 storeys and has a solid ground
floor. The C/H distribution is between the two floors. Installing separate
distribution for each floor would have been very difficult, so I just have
one zone. The system is controlled by the same programmable thermostat
(Danfoss TP9). The sensor is in the sitting room. I find that I can
achieve a sensible heat distribution throught the house by a one time
setting of the radiator valves.

My pump is on the return just before the boiler where it always was. The new
valves are just before that.

The expansion is unimpeeded via the old gravity H/W flow pipe.

I installed a new feed from the header tank which connects between the pump
and boiler - so there should always be water in the boiler.

(The original feed was via the old gravity H/W return pipe. )


--
Michael Chare

Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Suitable for Fully Pumped or Gravity Programmer - For Combi?? Richard Faulkner UK diy 3 March 21st 05 06:02 PM
Converting from gravity hw to fully pumped don UK diy 8 November 3rd 04 02:25 PM
Central Heating Gravity system (again) -how to get to zone valve or fully pumped Clive M UK diy 8 July 15th 04 01:20 PM
BAXI boiler - semi gravity to fully pumped Ian C UK diy 0 August 27th 03 05:17 PM
Gravity to fully pumped and oil to gas ! Andy Hall UK diy 5 July 13th 03 05:26 PM


All times are GMT +1. The time now is 12:11 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"