Now that my hot water cylinder has corroded to the point that it leaks, I need to replace it (Cue for Rant: it was previously replaced in 1996 - I thought these should last as long as the house! what's the matter with modern cylinders ?). It's a standard copper, indirect, vented one with 28mm pipework for the gravity-fed heating coil. The return from the heating coil has a Drayton cyltrol mechanical valve, now well seized up, as they all apparently do, and no longer working. So while I'm changing the cylinder I'm thinking of adding a cylinder thermostat and a 2-port zone valve (to replace the cyltrol) e.g Honeywell L641 and V4043H. Hopefully it's a simple job to connect these to the programmer and won't affect the rest of the heating system (unlike converting the whole system to fully pumped).

Various potential snags come to mind. The pipe connections to the cylinder are 1inch parallel BSP, so will need some jointing compound. The old ones seem to use some sort of translucent silicone compound. I suspect PTFE tape won't be up to it. Any recommendations ?

When I fit a new (backup) immersion heater I'm a little nervous of using too much or too litte force (I suspect the old cylinder is now leaking due to the stresses caused by fitting the old i/h). Also, the immersion heater instructions say not to use any jointing compound, although plumbers always seem to use loads of putty for this job. What should I use, and how much tightening ?

When I fit the zone valve and thermostat I want to connect to the existing Potterton EP3000 controller (user guide long gone). I assume this should do the job if I can figure out the wiring. Any help available? Actually, the first problem will be getting the EP3000 off its backplate and getting at the connections - any advice ?

Reconnecting the heating coil will need some adjustment to the existing 28mm pipework, because the spacing between the connections is different on the new cylinder. Although I've done a bit of soldering of 15mm capillary joints in the past, I'm a little nervous of tackling 28mm. Would there be any problem if I dodge the issue and use multiple compression joints instead?

Are there any other potential pitfalls ?

1tim23 wrote:


Now that my hot water cylinder has corroded to the point that it leaks,
I need to replace it (Cue for Rant: it was previously replaced in 1996
- I thought these should last as long as the house! what's the matter
with modern cylinders ?). It's a standard copper, indirect, vented one
with 28mm pipework for the gravity-fed heating coil. The return from
the heating coil has a Drayton cyltrol mechanical valve, now well
seized up, as they all apparently do, and no longer working. So while
I'm changing the cylinder I'm thinking of adding a cylinder thermostat
and a 2-port zone valve (to replace the cyltrol) e.g Honeywell L641 and
V4043H. Hopefully it's a simple job to connect these to the programmer
and won't affect the rest of the heating system (unlike converting the
whole system to fully pumped).

Is ther a 2-port valve on the heating side? If not you'll need to fit one,
and probably a bypass loop as well. If it's convenient to arrange the
pipework to use a 3-way valve and do a Y-plan system it'll be simpler.

Various potential snags come to mind. The pipe connections to the
cylinder are 1inch parallel BSP, so will need some jointing compound.
The old ones seem to use some sort of translucent silicone compound. I
suspect PTFE tape won't be up to it. Any recommendations ?

Boss white and hemp: that way if you susequently disturb the connection it
won't start to leak (inevitably at the bottom connection, requiring you to
drain down the cylinder again. Been there, done that :-(

Hint: use straight connectors, not elbows: you'll never get elbows to seal
and point in the right direction at the same time! You'll probably need 2
with female and 2 with male 1" BSP threads for the cylinder, and I'd use
22mm compression to the system.


When I fit a new (backup) immersion heater I'm a little nervous of
using too much or too litte force (I suspect the old cylinder is now
leaking due to the stresses caused by fitting the old i/h).

Why, is it leaking at the immersion heater boss?

Also, the
immersion heater instructions say not to use any jointing compound,
although plumbers always seem to use loads of putty for this job. What
should I use, and how much tightening ?

I use boss green, a ptfe-based compound, squished over the immersion heater
thread and fibre washer. Shouldn't need it but too many do :-(
For tightening (as for loosening) I think tapping the spanner rather than
exerting continuous force on it is more cylinder-boss-friendly.

When I fit the zone valve and thermostat I want to connect to the
existing Potterton EP3000 controller (user guide long gone). I assume
this should do the job if I can figure out the wiring. Any help
available? Actually, the first problem will be getting the EP3000 off
its backplate and getting at the connections - any advice ?

If you don't have a 'proper' wiring centre connecting it all together then a
12-way chock block in a 2-gang electrical surface wiring box with a blank
plate cover is a good place to bring all the system wiring together. Check
out Honeywell's wiring diagrams for S-plan (on the www) to see how it
should all go together.

Reconnecting the heating coil will need some adjustment to the existing
28mm pipework, because the spacing between the connections is different
on the new cylinder. Although I've done a bit of soldering of 15mm
capillary joints in the past, I'm a little nervous of tackling 28mm.
Would there be any problem if I dodge the issue and use multiple
compression joints instead?

22mm should be enough if it's pumped - and easier to do. I'd arrange at
least one compression joint in each leg (ditto for cold water in and HW
out) which you can disconnect later if you need to, without disturbing the
joints on the cylinder itself.

1tim23 wrote:
Now that my hot water cylinder has corroded to the point that it leaks,

Ha ha! diybanter censors the word "****"!!!


I need to replace it (Cue for Rant:

Careful....


it was previously replaced in 1996
- I thought these should last as long as the house! what's the matter
with modern cylinders ?). It's a standard copper, indirect, vented one
with 28mm pipework for the gravity-fed heating coil. The return from
the heating coil has a Drayton cyltrol mechanical valve, now well
seized up, as they all apparently do, and no longer working. So while
I'm changing the cylinder I'm thinking of adding a cylinder thermostat
and a 2-port zone valve (to replace the cyltrol) e.g Honeywell L641 and
V4043H. Hopefully it's a simple job to connect these to the programmer
and won't affect the rest of the heating system (unlike converting the
whole system to fully pumped).

Various potential snags come to mind. The pipe connections to the
cylinder are 1inch parallel BSP, so will need some jointing compound.
The old ones seem to use some sort of translucent silicone compound. I
suspect PTFE tape won't be up to it. Any recommendations ?

Do it the old-fashioned way.... see Mr. Rhum's post.


When I fit a new (backup) immersion heater I'm a little nervous of
using too much or too litte force (I suspect the old cylinder is now
leaking due to the stresses caused by fitting the old i/h). Also, the
immersion heater instructions say not to use any jointing compound,
although plumbers always seem to use loads of putty for this job. What
should I use, and how much tightening ?

Just damp it a bit & do it up straight away. Don't swing on the
thing - you can't make a watertight joint *more* water tight!


When I fit the zone valve and thermostat I want to connect to the
existing Potterton EP3000 controller (user guide long gone). I assume
this should do the job if I can figure out the wiring. Any help
available? Actually, the first problem will be getting the EP3000 off
its backplate and getting at the connections - any advice ?

Reconnecting the heating coil will need some adjustment to the existing
28mm pipework, because the spacing between the connections is different
on the new cylinder. Although I've done a bit of soldering of 15mm
capillary joints in the past, I'm a little nervous of tackling 28mm.
Would there be any problem if I dodge the issue and use multiple
compression joints instead?

Just clean the fittings and pipe, use Laco flux, and you won't
have a problem. Don't overheat the joint.


Are there any other potential pitfalls ?

I think the pen-pushers like to get involved, 'though I
can't see how they'd know...

In an earlier contribution to this discussion,
1tim23 wrote:

It's a standard copper,
indirect, vented one with 28mm pipework for the gravity-fed heating
coil. The return from the heating coil has a Drayton cyltrol
mechanical valve, now well seized up, as they all apparently do, and
no longer working. So while I'm changing the cylinder I'm thinking
of adding a cylinder thermostat and a 2-port zone valve (to replace
the cyltrol) e.g Honeywell L641 and V4043H. Hopefully it's a simple
job to connect these to the programmer and won't affect the rest of
the heating system (unlike converting the whole system to fully
pumped).

When I fit the zone valve and thermostat I want to connect to the
existing Potterton EP3000 controller (user guide long gone). I assume
this should do the job if I can figure out the wiring. Any help
available? Actually, the first problem will be getting the EP3000 off
its backplate and getting at the connections - any advice ?


I think others have already commented sufficiently on the basic plumbing
bits, so I'll just comment on the control system aspects.

If you fit a zone valve in a gravity HW system, you'll end up with a C-Plan
system (not S-Plan suggested in another post). A schematic and wiring
diagram for this is shown in
http://content.honeywell.com/uk/homes/systems.htm

This is quite cunning in the way in which the volt-free change-over switch
in the zone valve is used to connect the boiler to the programmer when HW is
required and to the pump (and CH circuit) when HW is satisfied. It is vital
that you get the wiring of this correct.

The zone valve must be in a position where it doesn't block the vent path
from the boiler to the F&E tank. The same would apply to the existing
Cyltrol valve - so if you put the zone valve in the same place as that, you
should be ok.

I'm not familiar with the EP3000 controller - but I suspect that it
automatically runs the HW (and hence the boiler) when CH is selected. You
need to stop it doing that, so as to have completely independent control
over HW and CH. There may be a link which you have to remove to achieve
this. If it *can't* be done, you'll need a new programmer.

Once you have independent control of CH and HW, it's well worth having
independent timing as well. You can do this by using a programmable room
stat, and using *that* to time the CH (with CH set to Constant on the
EP3000). Set HW to Timed on the EP3000, and that will then just control the
timing of ther HW.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

It suddenly started leaking near the IH boss for no apparent reason, after not being touched for 9 years. A plumber took a look at it, swapped the IH for a new one, found the leak was still there, then pronounced that a new cylinder was required. The same thing happened last time the cylinder had to be replaced, 9 years ago (but a different plumber !). The story that plumber spun me was that if the cylinder gets dented or stretched by over-tightening the IH, it forms a thin point in the copper wall that is vulnerable to pin-hole corrosion. The latest cylinder did indeed have a dent near the boss, as if the IH spanner had pressed against it during tightening.

Don't know if any of this makes sense, but I want to avoid the same fate for cylinder number 3.

Thanks for all the other advice.

"1tim23" wrote in message
...

Wrote:
1tim23 wrote:


When I fit a new (backup) immersion heater I'm a little nervous of
using too much or too litte force (I suspect the old cylinder is now
leaking due to the stresses caused by fitting the old i/h).

Why, is it leaking at the immersion heater boss?


It suddenly started leaking near the IH boss for no apparent reason,
after not being touched for 9 years. A plumber took a look at it,
swapped the IH for a new one, found the leak was still there, then
pronounced that a new cylinder was required. The same thing happened
last time the cylinder had to be replaced, 9 years ago (but a different
plumber !). The story that plumber spun me was that if the cylinder
gets dented or stretched by over-tightening the IH, it forms a thin
point in the copper wall that is vulnerable to pin-hole corrosion. The
latest cylinder did indeed have a dent near the boss, as if the IH
spanner had pressed against it during tightening.

Don't know if any of this makes sense, but I want to avoid the same
fate for cylinder number 3.

Get your self a high flow combi and be done with. No more space consuming
cylinders to rot.

1tim23 wrote:
Wrote:

It suddenly started leaking near the IH boss for no apparent reason,
after not being touched for 9 years. A plumber took a look at it,
swapped the IH for a new one, found the leak was still there, then
pronounced that a new cylinder was required. The same thing happened
last time the cylinder had to be replaced, 9 years ago (but a different
plumber !). The story that plumber spun me was that if the cylinder
gets dented or stretched by over-tightening the IH, it forms a thin
point in the copper wall that is vulnerable to pin-hole corrosion. The
latest cylinder did indeed have a dent near the boss, as if the IH
spanner had pressed against it during tightening.

Don't know if any of this makes sense, but I want to avoid the same
fate for cylinder number 3.

Thanks for all the other advice.

I dont understand why youre going to the great trouble of replacing the
cylinder when all it needs is soldering or gluing. They key in both
cases is to get the hole spotlessly clean. Then either solder it, or
use high temp epoxy available at car accessory places. With epoxy, use
a good overlap for grip strength.


NT

I tried polishing the dented area with wire wool and cleaning it, revealing what looked like a pin hole, then soldering all over it (Oh how we laughed as the cylinder foam insulation caught fire, set off the smoke alarm etc etc). But there was still a leak coming from somewhere, so I decided the best long term fix was to change the cylinder. It's quite hard to find every pin-hole when the whole cylinder is encased in foam. In a similar situation I might try your idea of epoxy. Though, as you say, the key is to get everything really clean, which isn't always as easy as it sounds.