Knackered cylindar ??

[aroundM21]

Fully pumped but not sealed ch system.

Did have problem that scorching water from the bioler was only lukewarm when it reached the cylindar. Fixed that mainly by letting air out (air lock key in the pipe that continues past the input to cylindar).

Now the water is scorching hot when it gets to the cylindar. But not when it comes out (at the top, and from the taps).

Temporary saving grace is that the emersion does give scorching hot water from the cylindar, so something's ok.

Any ideas on how I can 'diagnose' the cylindar problem further would be much appreciated. I assume it has a coil inside, but could be a primatic with air etc inside .... I don't know how to tell from the outside !!

Thanks in advance for any suggestions .... Mike

 

[clf-gas]

IF in a hard water area the coil may be scaled up reducing heat transfer,

Is cyliner stat set at 55-60`

 

[gas4you]

Assuming that any zone valve is working ok I would suspect a blockage in the return where it leaves the hw cylinder.

 

[Softus]

How long did you leave the cylinder to heat up before deciding that it was producing only lukewarm water?

 

[gasandoilman]

Is there a vent on pipe on the primary?

 

[aroundM21]

Thanks for all suggestions - answers to questions below :

> IF in a hard water area the coil may be scaled up reducing heat transfer,
Sure, and not much I could do to prevent. We're in Manchester - I don't believe that's the hardest water. But it happened quite suddenly, so this may be a factor but can't be the only thing.


> Is cyliner stat set at 55-60
Yep (I thought it was for emersion only .... anyway, it's not on low)


> Assuming that any zone valve is working ok I would suspect a blockage in the return where it leaves the hw cylinder.
Hmm .... I have 2 zone valves, 1 has just been replaced (the one from boiler TO the cylindar. My CH room thermostat isn't effective - ie I cannot turn CH off with HW on - but electrician tested the actual thing fine, so we think the other zone valve does need replacing).
I don't THINK that valve effects the Cylindar, but not sure about the return so now you've said this I might replace that valve anyway .....

** How hot would you expect the primary return to be please ??


How long did you leave the cylinder to heat up before deciding that it was producing only lukewarm water?
> Hours. I can't remember exactly, but it was long enough to work fine a month or so ago.


> Is there a vent on pipe on the primary?
Er, the primary input (ie water going into the coil, or the other mechanism if it is primatic) has a vertical pipe with a horizontal offshoot that goes to the cylindar. The vertical then continues and terminates with a bleeding 'screw' (vent ?) (can use same bleed key as Rads). So no overflow to F&E, and not sealed.
The plumbers bled this (with system & pump off obviously) to get the primary supply working - previously was leaving boiler hot and reaching cylindar luke warm.

** Any other suggestions re this 'vent' ?

THANKS TO ALL ....

 

[Softus]

Is cyliner stat set at 55-60

Yep (I thought it was for emersion only .... anyway, it's not on low)

How high up is your cylinder stat?

How long did you leave the cylinder to heat up before deciding that it was producing only lukewarm water?

Hours. I can't remember exactly, but it was long enough to work fine a month or so ago.

Is there a vent on pipe on the primary?

Er, the primary input (ie water going into the coil, or the other mechanism if it is primatic) has a vertical pipe with a horizontal offshoot that goes to the cylindar. The vertical then continues and terminates with a bleeding 'screw' (vent ?) (can use same bleed key as Rads). So no overflow to F&E, and not sealed.

If you have an active F&E, then you should have a vent terminating above that cistern. If you have neither, and have only this manual vent at a height above the top of the coil, then you must have a sealed system.

Are you sure that there isn't a vent leaving the primary circuit at some other point? Just before the pump, for example?

The plumbers bled this (with system & pump off obviously) to get the primary supply working - previously was leaving boiler hot and reaching cylindar luke warm.

** Any other suggestions re this 'vent' ?

It's hard to know what you mean by this, since the vent is unlikely to be related to your problem.

If you have a blockage on the return, then there would be no flow to the coil unless there was a bypass installed.

If the boiler is staying lit for any reasonable length of time, and the pump is running, and one of the MZVs is open, then the heat must be going somewhere. If you're saying that it's going to neither the coil nor the radiators, then which of the above conditions is not true?

 

[aroundM21]

Softus,
thanks for this. In order of most directly meaningful to me (I mean what I know I understand best in detail):

>> If you have a blockage on the return, then there would be no flow to the coil unless there was a bypass installed.

Agreed - and since the primary water (ie from bioler) input to the cylindar really does get hot, I am sure there is a flow into the coil (rememeber I don't KNOW it's a coil .... is there any way to identify for certainty whether it's a primatic with the inner cylindar and air traps etc affair ??)
Whether it's a coil or primatic, heat doesn't just vanish, I do agree.....


>> If the boiler is staying lit for any reasonable length of time, and the pump is running, and one of the MZVs is open, then the heat must be going somewhere. If you're saying that it's going to neither the coil nor the radiators, then which of the above conditions is not true?

Can answer easily : the Rads are working just fine, nice and hot. But see comment above about hot input to the cylindar's primary ....


>> How high up is your cylinder stat?
60-65. Should I put it on the max (80-90) to see what happens ??


>> If you have an active F&E, then you should have a vent terminating above that cistern. If you have neither, and have only this manual vent at a height above the top of the coil, then you must have a sealed system.
Are you sure that there isn't a vent leaving the primary circuit at some other point? Just before the pump, for example?

Not sure this is fixing the problem, but good to get certainty ...
The plumbers agreed the vertical pipe (continuation after primary water input to cylindar) should really go over the F&E as an overflow. They said it was not sealed. That's my only basis for saying it's not sealed.

I thought that F&E was just to keep pressure ? I'm pretty certain the F&E is connected (both flow & return) from 'off-shoot' pipes that leave just before the pump.

Can you give me a clue as to what a vent elsewhere would look like ? (sorry!). The pump is under the living room floor (near the boiler behind the fire) and there really doesn't seem to be space or any "unusual" looking piping, so I don't think so.




Thanks again ..... Mike

 

[WelshMan]

What softus means is its location and not the temperature set m8. I beleive the stat should be located in the bottom third of the tank. Dont put the stat upto the figures you said, this will only increase your hard water problems,as limescale begins to form at 70-75.

 

[gas4you]

What softus means is its location and not the temperature set m8. I beleive the stat should be located in the bottom third of the tank. Dont put the stat upto the figures you said, this will only increase your hard water problems,as limescale begins to form at 70-75.

Try anything over 60C

 

[WelshMan]

Well slap me with a wet fish and call me Barbara !.

 

[gas4you]

Well slap me with a wet fish and call me Barbara !.

Ok Babs

 

[aroundM21]

Sofus, Gas4you,

Just to confirm that my thermometer IS on the bottom third of the cylindar.

I'd previously said I thought it was for the immersion - but looking again it has a wire that dissapears, ie does not connect to the immersion; presumably it goes to one of the zone vents, ie is controlling the boiler / CH system which has problems. So is very relevant. (btw my boiler does go on and off even with CH thermostat righ up, so I think the cylindar thermostat is working).

Having read your appends, I cannot be certain whether the system is sealed or not. The vertical pipe (continues after primary water input) doesn't go to the top of the cylindar - it goes perhaps 18 inches past the input (which is almost half-way up).

Thanks for your comments .... Mike

 

[gas4you]

The vertical pipe (continues after primary water input) doesn't go to the top of the cylindar - it goes perhaps 18 inches past the input (which is almost half-way up).

Sounds like an air bleed point for the hw circuit. This can be on sealed or open vent system.

Have you a small tank in loft set alongside a larger one? This would be the F&E tank for the heating system which would mean you have an open vented system.

 

[aroundM21]

The vertical pipe (continues after primary water input) doesn't go to the top of the cylindar - it goes perhaps 18 inches past the input (which is almost half-way up).

Sounds like an air bleed point for the hw circuit. This can be on sealed or open vent system.

Have you a small tank in loft set alongside a larger one? This would be the F&E tank for the heating system which would mean you have an open vented system.

Guilty as charged - I do have a small F&E tank .... thanks, I now know (and know why) it's open vented.