compatible cylinder???

[sadowska]

Hope someone can confirm or refute some advice we've had please...

We had an old Potterton Regular boiler replaced with a Worcester 30Cdi System boiler (open vented) last year. The fitter was Gas Safe registered and was recommended to us but we've had some 'issues' with his work. The latest issue came when another plumber working on our house last week raised the alarm about the cylinder. He says it should have been replaced when we converted to a system boiler because it's not compatible.

The plumber wasn't 100% clear but I think the point was that without an expansion vessel in the loft, there will be too much pressure in the cylinder which will cause erosion to the heating elements. This could result in our hot water being contaminated. He also suggested this could be the cause of the pressure dropping constantly (we have to top it up every few days). He said we need a new cylinder with an expansion vessel within it.

Not sure if this makes sense. Which could be because I'm misunderstanding the plumber - will update if he sets it out more clearly.

The boiler itself contains an expansion vessel so surely this is to do the job of the old expansion tank?

I can't see anything on the cylinder which identifies exactly what make/model it is; other than that I don't know what information to look for (there are some labels).

While googling (which has only confused me more) I was very alarmed to find this statement:
"Warning: If you attempt to heat mains pressure water using a cylinder designed for a low pressure system the risk of explosion exists."
http://www.gasapplianceguide.co.uk/Mains_Pressure_Hot_Water_Systems.htm

Any thoughts on that would be appreciated...

I also see some people saying a pumped shower isn't compatible with a system boiler; although this isn't stated consistently. Can anyone advise why that is please? We have 2 pumped showers! Please bear in mind, we have a vented system, not an unvented high pressure system. The pressure in the tank is supposed to be 1.5bar, though as I say it keeps dropping.

thanks for your help

 

[bengasman]

... He says it should have been replaced when we converted to a system boiler because it's not compatible.

Bit hard to say for sure as you don't mention the spec of existing cylinder, nor the recommended replacement, but it sounds like bullsh to me.

The plumber wasn't 100% clear but I think the point was that without an expansion vessel in the loft, ...

You don't need an ev on an open vent

there will be too much pressure in the cylinder which will cause erosion to the heating elements.

Definitely bullshit

This could result in our hot water being contaminated. He also suggested this could be the cause of the pressure dropping constantly

More bullshit

 

[fazedup71]

Smells like.............? can we have a picture of this cylinder please?

 

[namsag]

Without being cheeki or condescending it sounds like you dont really know what your talking about in regards what you already have and the guy speaking to you is taking advantage of that to get you to part with your hard earned cash .
Ask someone else

 

[gasservice85]

the loss of pressure could be caused by a leak on the coil of the cylinder.

any cylinder is compatable with a system boiler aslong as the domestic water side of things remains open vented (you have a large tank in the loft feeding it and a vent pipe over the top) your small tank should be gone.

i would replace a cylinder as part of fitting a sytem boiler because leaks on the coil are quite common and this will cause your heating water to mix with your domestic hot water.

top up the pressure in your system. dont use any low pressure hot or cold water and see if the level rises in your loft tank if it does you have a leak on the coil of your cylinder. (this will take a while to be noticably higher)

if you are losing the much pressure and there are no signs of any leaks then i would say that the cylinder coil is most likely place

the guy who fitted your boiler is not in the wrong unless your cylinder doesnt comply with part L of building regs then it should have been changed along with the boiler. however it is common for this to be "missed" to make the job cheaper

 

[sadowska]

thanks for responses. Here's a photo if it helps.
I appreciate you're not being condescending - of course I don't know what I'm talking about, I'm not especially thick but neither of my degrees had to do with heating engineering! That's why it's helpful to get other points of view through the forum, so I don't get sold the wrong thing.
I actually spoke to the guy from IFS (the website link in my first post) - he got in touch even though it's a Sunday as he didn't want me to be concerned about the suggestion that the cylinder might explode... He clarified that with a vented system our radiator system is sealed and under pressure, but our hot water system is gravity fed and not pressurised; the pressure dial showing 1.5 bar indicates the pressure of the heating rather than the pressure within the cylinder. He said it's possible for the heat exchanger to erode but not especially likely, and we would know about it because the system would abruptly lose all pressure. So in short he advised there was nothing much to worry about.
It made sense as he explained it - but of course if anyone thinks this is also bs I'm sure you won't hesitate to say, for which thanks!

 

[PlumbGas]

the loss of pressure could be caused by a leak on the coil of the cylinder.

top up the pressure in your system. dont use any low pressure hot or cold water and see if the level rises in your loft tank if it does you have a leak on the coil of your cylinder. (this will take a while to be noticably higher)

turn off the cold feed to the cylinder the water will have to go up the Vent pipe and you'll hear or see it quicker if there is a hole in the HW cylinder coil.

 

[Whitespirit66]

Let me help you with your photo.

Untitled

• sadowska
• 10 Apr 2011
• 1

Yes, perfectly standard indirect (ie. hot water to taps seperated from water pumped into cylinder from boiler) gravity cylinder.

As already said, you can safely ignore most of what your plumber says. Your only concern is finding the pressure drop. Try gasservice85's suggestion re. checking rising level in cold water tank. Also, check the copper pressure relief pipe that vents to the outside for signs of water passing. Other than that, it's a case of checking the system pipework for leaks. Problem is, its unlikely that all of it will be visible.

 

[gasservice85]

the loss of pressure could be caused by a leak on the coil of the cylinder.

top up the pressure in your system. dont use any low pressure hot or cold water and see if the level rises in your loft tank if it does you have a leak on the coil of your cylinder. (this will take a while to be noticably higher)

turn off the cold feed to the cylinder the water will have to go up the Vent pipe and you'll hear or see it quicker if there is a hole in the HW cylinder coil.

that is defo a quicker way didnt think of that