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Replacing an Indirect Hot Water Cylinder



 
 
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  #1  
Old January 15th 06, 12:50 PM posted to uk.d-i-y
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Default Replacing an Indirect Hot Water Cylinder

Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.

The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).

With respect to replacement. There is a shut off cock for the cold
water in and a gate valve on the CH boiler hot inlet to the coil
(think it is the inlet). There is no isolation on the other side of
the coil (outlet).

My question is do I need to drain down the CH system to replace? What
crossed my mind is I could put a cork into the outlet from the CH
header tank in the loft that should stop drainage from the outlet side
of the coil when I disconnected, at least in theory. Any thoughts on
this?

With respect to the immersion heater. Do you think I will be able to
get it out of the old cylinder bearing in mind it has been there 15
years or so? I know I will need to buy/rent a spanner but are these
things in to stay once they are this old? Further, do you think it
sensible to replace the immersion heater anyway as I guess they don't
last forever?

All guidance will be much appreciated.
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  #2  
Old January 15th 06, 01:08 PM posted to uk.d-i-y
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Default Replacing an Indirect Hot Water Cylinder

Edward W. Thompson wrote:
Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.

The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).

snip
All guidance will be much appreciated.


I'd certainly first try to see where it's leaking from - and if it's a
place where pipes go through, to give the relevant nut another 1/6 turn
or so.
If that diddn't cure it, back the nut off, put in some PTFE, clean the
surface a bit, and tighten it back up.
They rarely - though not never - leak through the wall of the cylinder.
  #3  
Old January 15th 06, 01:28 PM posted to uk.d-i-y
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Posts: n/a
Default Replacing an Indirect Hot Water Cylinder


"Edward W. Thompson" wrote in message
...
Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.

The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).

With respect to replacement. There is a shut off cock for the cold
water in and a gate valve on the CH boiler hot inlet to the coil
(think it is the inlet). There is no isolation on the other side of
the coil (outlet).

My question is do I need to drain down the CH system to replace? What
crossed my mind is I could put a cork into the outlet from the CH
header tank in the loft that should stop drainage from the outlet side
of the coil when I disconnected, at least in theory. Any thoughts on
this?

With respect to the immersion heater. Do you think I will be able to
get it out of the old cylinder bearing in mind it has been there 15
years or so? I know I will need to buy/rent a spanner but are these
things in to stay once they are this old? Further, do you think it
sensible to replace the immersion heater anyway as I guess they don't
last forever?

All guidance will be much appreciated.


When replacing a cylinder go for a quick recovery m,model. Part L is 'not'
quick recovery. They go by names of Super Duty Ultra Cal and the likes.

Quick recovery takes all the boilers output heat up very fast and are
cheaper to run. You existing boiler may not take full advantage of the coil
as the coil may be capable of taking a boiler much larger, but when you
change the boiler, in time, it certainly will show even more dividends.

  #4  
Old January 15th 06, 01:50 PM posted to uk.d-i-y
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Default Replacing an Indirect Hot Water Cylinder

On Sun, 15 Jan 2006 11:50:32 +0000 (UTC), Edward W. Thompson
wrote:

Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.


Notwithstanding Ian's comments, which do make sense, I've put a few
comments below if you do need to or decide to replace......



The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).


Well yes, but will always take longer than you think. Nowadays, they
are better insulated so do check external dimensions if the cylinder
is a tight fit in the airing cupboard.



With respect to replacement. There is a shut off cock for the cold
water in and a gate valve on the CH boiler hot inlet to the coil
(think it is the inlet). There is no isolation on the other side of
the coil (outlet).

My question is do I need to drain down the CH system to replace? What
crossed my mind is I could put a cork into the outlet from the CH
header tank in the loft that should stop drainage from the outlet side
of the coil when I disconnected, at least in theory. Any thoughts on
this?


There is a technique where you can put bungs in the vent pipe and the
feed pipe from the roof tank. Normally this is for radiators swaps
etc. I am sceptical that you would get away with it for this because
the pipe is 22mm normally and you are likely to get water running out
more easily. You might be able to remove the pipe quickly at the
cylinder and bung that end as well, but I'd suggest draining down and
not having the hassle



With respect to the immersion heater. Do you think I will be able to
get it out of the old cylinder bearing in mind it has been there 15
years or so? I know I will need to buy/rent a spanner but are these
things in to stay once they are this old? Further, do you think it
sensible to replace the immersion heater anyway as I guess they don't
last forever?


If it's the original, then I would dump it along with the cylinder.
New ones are also safer since they have an extra safety cutout to
reduce the risk of boiling if the thermostat fails.


--

..andy

  #5  
Old January 15th 06, 01:56 PM posted to uk.d-i-y
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Posts: n/a
Default Replacing an Indirect Hot Water Cylinder

In article ews.net,
"Doctor Drivel" writes:

When replacing a cylinder go for a quick recovery m,model. Part L is 'not'
quick recovery. They go by names of Super Duty Ultra Cal and the likes.


Don't do this unless you have a condensing boiler,
as it will force a non-condensing boiler into condensing
mode, and rapidly destroy it.

Also probably not a smart move if you have a mid-position
valve, as you might find the cylinder steals too much of
the boiler output for the heating to continue working,
unless your boiler has an output power well in excess of
the house heating alone (which is unlikely as the system
was designed to heat a hot water cylinder).

Quick recovery takes all the boilers output heat up very fast and are
cheaper to run. You existing boiler may not take full advantage of the coil
as the coil may be capable of taking a boiler much larger, but when you
change the boiler, in time, it certainly will show even more dividends.


Quick recovery cylinder is one part of a complete heating
system design. You can't drop one in without knowing the
rest of the system was designed to support it.

--
Andrew Gabriel
  #6  
Old January 15th 06, 02:22 PM posted to uk.d-i-y
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Posts: n/a
Default Replacing an Indirect Hot Water Cylinder


"Andrew Gabriel" wrote in message
.. .
In article ews.net,
"Doctor Drivel" writes:

When replacing a cylinder go for a quick recovery m,model. Part L is
'not'
quick recovery. They go by names of Super Duty Ultra Cal and the likes.


Don't do this unless you have a condensing boiler,
as it will force a non-condensing boiler into condensing
mode, and rapidly destroy it.


Nope. You put in a gate valve in the coil return to the boiler and balance
the coil to suit the boiler. When a boiler change you open up the gate.

Quick recovery cylinder is one part of a complete heating
system design. You can't drop one in without knowing the
rest of the system was designed to support it.


Hence the gate valve in the return pipe. Must cost all of 2-3.

You could insert a quick acting Reliance UFH blending valve (TMV) on the
coil flow and return. This ensures the boiler only pumps 80C heat into the
cylinder coil and keeps the return temp above the dew-point, and heats up
very quickly. Recommended for quick recovery coils and heating direct
thermal stores/heat banks.


  #7  
Old January 16th 06, 07:20 AM posted to uk.d-i-y
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Posts: n/a
Default Replacing an Indirect Hot Water Cylinder

On 15 Jan 2006 12:08:11 GMT, Ian Stirling
wrote:

Edward W. Thompson wrote:
Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.

The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).

snip
All guidance will be much appreciated.


I'd certainly first try to see where it's leaking from - and if it's a
place where pipes go through, to give the relevant nut another 1/6 turn
or so.
If that diddn't cure it, back the nut off, put in some PTFE, clean the
surface a bit, and tighten it back up.
They rarely - though not never - leak through the wall of the cylinder.


Thanks for the suggestion but the 'drip' is appearing at the front of
the cylinder almost exactly 90 displaced from all pipe connections.
While the leakage could migrate under the insulation I doubt whether
it would migrate 90. Further, having been 'tight' for 15 years it
seems improbable that a pipe connection should begin to leak at this
stage. Regrettably I think the cylinder itself must be leaking for one
reason or another.

The complication of fitting a 'quick recovery' cylinder is simply not
viable or economical for me. There are only two of us in a small
cottage and our heating bills are hardly a major expenditure.
Further, being in the geriatric category I simply can't be bothered to
modify the pipe work, as will likely be required. Thanks for the
suggestion.

The cold water supply to the cylinder is 22mm but the CH connections
are smaller (18mm?). I can isolate the cold water but not both sides
of the CH boiler connection to the heating coil. I know it makes most
sense to drain down especially as I need to replace a few of the
radiator thermostatic control valves. I suppose I better 'bite the
bullet ad do the job properly.

Thanks for the advice re immersion heater. I suppose I can buy a
cylinder complete with immersion heater and thermostat fitted. The
present cylinder looks as though it was a fully assembled unit judging
from how it is insulated.

Off to B&Q, Wickes and Plumbase this morning!
  #8  
Old January 16th 06, 10:32 AM posted to uk.d-i-y
external usenet poster
 
Posts: n/a
Default Replacing an Indirect Hot Water Cylinder

Edward W. Thompson wrote:
On 15 Jan 2006 12:08:11 GMT, Ian Stirling
wrote:

Edward W. Thompson wrote:
Have just found a drip from the bottom of my hot water cylinder so I
guess its time to replace it! I need some advice.

The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).

snip
All guidance will be much appreciated.


I'd certainly first try to see where it's leaking from - and if it's a
place where pipes go through, to give the relevant nut another 1/6 turn
or so.
If that diddn't cure it, back the nut off, put in some PTFE, clean the
surface a bit, and tighten it back up.
They rarely - though not never - leak through the wall of the cylinder.


Thanks for the suggestion but the 'drip' is appearing at the front of
the cylinder almost exactly 90? displaced from all pipe connections.
While the leakage could migrate under the insulation I doubt whether
it would migrate 90?. Further, having been 'tight' for 15 years it
seems improbable that a pipe connection should begin to leak at this
stage. Regrettably I think the cylinder itself must be leaking for one
reason or another.


It's not impossible.
Some sorts of insulation are slightly water permeable, and drips onto
one bit can come out elsewhere.
First thing I'd do is to give all the connections a little more turn.
If it works, it's free.

Other approach is to simply dig out the insulation using a bit of wood,
and get down to the bare cylinder.
This'll take all of a minute, and will let you see directly if there is
a pinhole leak.
  #9  
Old January 17th 06, 02:11 PM posted to uk.d-i-y
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Posts: n/a
Default Replacing an Indirect Hot Water Cylinder

Andy Hall wrote:
The cylinder is probably 15 years old and is lagged with expanded
polystyrene, I guess. It is an indirect cylinder with an immersion
heater. Looking at the catalogues it appears an identical cylinder is
available with the correct configuration of inlets and outlets. So
far straight forward to replace ;-).



Well yes, but will always take longer than you think. Nowadays, they
are better insulated so do check external dimensions if the cylinder
is a tight fit in the airing cupboard.


Agreed - my "it'll only take a few hours" cylinder swap a few months ago
tunrned into a whole weekend - including the usual mad dash to B&Q on
Sunday afternoon before it shuts for extra parts!

One other thing - are you absolutely sure that all the inlets and
outlets are in identical places? We though they were, but when we got
home it seemed that the top inlet for the coil was higher than on the
old one - presumably because the coil was larger to comply with Part-L
regs.

With respect to replacement. There is a shut off cock for the cold
water in and a gate valve on the CH boiler hot inlet to the coil
(think it is the inlet). There is no isolation on the other side of
the coil (outlet).

My question is do I need to drain down the CH system to replace? What
crossed my mind is I could put a cork into the outlet from the CH
header tank in the loft that should stop drainage from the outlet side
of the coil when I disconnected, at least in theory. Any thoughts on
this?



There is a technique where you can put bungs in the vent pipe and the
feed pipe from the roof tank. Normally this is for radiators swaps
etc. I am sceptical that you would get away with it for this because
the pipe is 22mm normally and you are likely to get water running out
more easily. You might be able to remove the pipe quickly at the
cylinder and bung that end as well, but I'd suggest draining down and
not having the hassle


I agree - remember, you probably won't have to drain the whole system,
just to the point below the cylinder.

With respect to the immersion heater. Do you think I will be able to
get it out of the old cylinder bearing in mind it has been there 15
years or so? I know I will need to buy/rent a spanner but are these
things in to stay once they are this old? Further, do you think it
sensible to replace the immersion heater anyway as I guess they don't
last forever?



If it's the original, then I would dump it along with the cylinder.
New ones are also safer since they have an extra safety cutout to
reduce the risk of boiling if the thermostat fails.


Definately scrap it - I can't imagine it would be easy to get it out of
the old cylinder anyway. We got a new one for less than 15 so hardly
broke the bank!
 




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