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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. |
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Hot-water cylinder replacement & control upgrade -advice please
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 ? Last edited by 1tim23 : October 27th 05 at 09:28 AM Reason: title is mangled |
#2
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Ho****er cylinder replacement & control upgrade - advice please
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. |
#3
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Ho****er cylinder replacement & control upgrade - advice please
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... |
#4
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Ho****er cylinder replacement & control upgrade - advice please
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. |
#5
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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. |
#7
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Ho****er cylinder replacement & control upgrade - advice please
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 |
#8
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