Unvented Gledhill copper cylinder.

[jase158]

Got called to a customers house the other day as cylinder was leaking from overflow,

Turns out that the cylinder is an unvented cylinder but I have never seen one like it before,

It was copper cylinder made by gledhill, there was no expansion vessel or PRV, it said on the cylinder that the above tank was an expansion chamber, the cold inlet was teed into side of cylinder and then into expansion chamber with a float valve on the inside. It also said that the expansion chamber acted as a expansion vessel.

It isn't a tank on the top as there was no outlet to the main cylinder.

my question is how does this work? if the float valve is shut then it is shut, nothing you can do to open it, even if the water is hot? or am i wronge?

also what could be the cause of the dripping from the overflow, I checked float valve, no leaks, replaced the immersion heater thermostats as they were very old and had no resets on them. only thing was, when i read instructions, they said 11" immersion heaters, when I got 7" thermostats to go in, they were smaller then what was in there. so I guess they wont work properly.

any ideas please?

 

[Dannypipe]

This isn't an unvented mate. Its a combination cylinder.

Often called a fortic.

 

[jase158]

This isn't an unvented mate. Its a combination cylinder.

Often called a fortic.View attachment 5269

was definetly unvented, checked it several times. even instructions said so, pipe had writing on it, saying mains water and there was definetly no outlet from top tank to bottom

 

[jase158]

I cant remember what it is if it is immersion heater, neither I guess

 

[Dannypipe]

Wait a minute. This is a thermal bloomin store!!!!

 

[Dannypipe]

Sorry I need to put my brain in gear. What model of thermal store is this please? I can't believe I didn't clock sooner. I repair thermal stores as one of my specialist services!!

 

[jase158]

no, will go back and get one, was pretty late and completely forgot to be honest.
will go back and post on here.

 

[Dannypipe]

Its not an unvented cylinder Jase. It is a thermal store, which delivers mains pressure domestic hot water.

The reason the Skel stats didn't have a reset in them is that thermal stores are designed to get hotter than a standard stat would allow. You would have also probably noted that there was a green sticker on the stat that said 'factory set'.

That said I have had problems with the stats and now fit stats with a high temp cut out.

 

[jase158]

Its not an unvented cylinder Jase. It is a thermal store, which delivers mains pressure domestic hot water.

The reason the Skel stats didn't have a reset in them is that thermal stores are designed to get hotter than a standard stat would allow. You would have also probably noted that there was a green sticker on the stat that said 'factory set'.

That said I have had problems with the stats and now fit stats with a high temp cut out.

learn something new every day, I thought water couldn't get above 65 degrees otherwise legionellas would start appearing

 

[Dannypipe]

Was it like this:

 

[Dannypipe]

Getting above 65 kills the bugs that cause legionellas mate. Other way round.

No but getting above that can scald people. However a thermal store delivers its hot water in a different way to an unvented cylinder.

 

[PlumbBobBob]

learn something new every day, I thought water couldn't get above 65 degrees otherwise legionellas would start appearing

no legionnaires starts to develop below 60 degrees thats why tank stats should be set at 60 degrees

 

[jase158]

yes and no,
It was the same shape, but not as many pipes, basically it had 2 pipes going into the side 1 hot coming out, 1 cold going in, it had a TMV on the hot to control temperature and 1 pipe going into the expansion chamber which was connected to float valve

 

[Dannypipe]

Or this:

 

[Dannypipe]

Ah right, the TMV means it was another model, hang on I'll find a pic. Those two I posted are mine, don't know if I have one of the model in question.

 

[Dannypipe]

Only got the latest model to have a TMV on it (I fitted this, a BP model) very unlikely to be the model you looked at if you say the immersions are old?

 

[Dannypipe]

Let me know model and I'll help you all I can.

You should have installed the correct length immersion heaters though mate. Too late now.

 

[Dannypipe]

 

[Dannypipe]

Just thought I'd post the rest of the photo's as its quite interesting.

I changed three of these units in the same block.

All leaking at the drain valve behind the galvanised panel. (terminal leak according to manufacturers).

Heres why. When stripped back (for the copper and out of interest) you can see the thing was leaking everywhere!!

The copper is waffer thin. So not worth much in scrap and the insulation is something else!! So thick.

The new BP models seem pretty good, though I can't see inside!!

Taken at my old house a couple of years ago. I got the lad to strip one of the others down, and the last one was nicked when I left it outside the job (which was in London) when I popped back in to pack up. I wasn't sorry to see it go, as it almost did me a favour.

 

[Gray0689]

Not a great pic sorry

 

[Gray0689]

Bit better but not a combination one don't think I have any pics of one

 

[Gray0689]

That's a combination thermal store jase

 

[WaterTight]

Don't think I've come across any of the ones pictured. Are they quite rare? Also how does it deliver mains hot if it's fed from a combination tank?

 

[Nostrum]

It works backwards to an indirect cylinder. Heat source heats the volume of water in the tank, and the DHW gets heated indirectly through a coil/heat exchanger. Idea is that you can have multiple heat sources to heat the volume of water (solar, boiler etc) then draw it off to heat rad's etc, but also means you can pass a mains cold through it and get mains pressure hot water. Good idea in principle but not sure why their aren't more of them about, cost I guess?

 

[Howsie]

Thermal stores can't ship the same volume of hot as an unvented. I think that's why they're suited to flats etc.

 

[WaterTight]

Ah! At last I think I understand what my first boss was talking about on one of our first ever jobs. We were working an enormous country house in it's boiler room with this enormous cylinder. He kept telling me that the coil supplied the DHW. I didn't understand what he was talking about. It must have been a thermal store. He wasn't exactly a talker so I gave up trying to understand.

 

[pobsdad]

Pulsacoil?Stats should be 73 degree.

 

[Megaflo-Experts]

Was it like this:View attachment 5270

[FONT=Tahoma, Calibri, Verdana, Geneva, sans-serif]Just took one out today (gledhill Pulsacoil) and put in a Megaflo.


[/FONT]

 

[Dannypipe]

I'd personally prefer a Megaflo over Pulsacoil any day of the week!!

 

[Megaflo-Experts]

Me too, and another happy customer.

 

[kimbo]

Gledhill used to supply thermal stores with an integrated header/expansion tank as it was cheaper than buying a copper header tank and fitting it above the store. There are fors and against fitting thermal stores, one of which you do not have to have an unvented ticket to fit it.