Albion Superduty CF45 cylinder stat setting?

30 May 2004
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United Kingdom
Have just installed an Albion Superduty CF45 hot water cylinder, complete with a Danfoss ITC100 immersion stat.

The manufacturers recommended that particular probe stat & that it be set to 35 degrees C. Water is reaching hand hot temperature & improved when I reset at 45 degrees C.

Grundfos 15/50 pump set at mid-speed & Potterton Suprima 50 at max.

Any recommendations on the setting or do I just keep increasing until I get a tank full of hot water?
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Is the thermostat calling for heat all the time? At intervals but before the water in the cylinder heats up? Whereabout on the cylinder is the stat fitted? Is the boiler 'hunting' (ie. cycling on and off rapidly) or burning for reasonably long periods (more than 5 minutes at a time)?

If the thermostats (on cylinder and boiler) are correctly fitted and wired, and working correctly, all that's left is the possibility of a partial airlock in the heating coil left over from when you fitted the cylinder. If hot water is flowing from the boiler and through the coil, the water in the cylinder HAS to get hot!

Don't quite understand the 35 degree recommended setting on the thermostat - that's only body temperature.
The stat is fitted into the cylinder at the base. I was advised that it is cooler here than at the top of the tank, hence 35 degrees C.

Pump running so I assume the stat is calling for heat (HW only, set on timer), unless this is to do with overrun through the bypass as the pump is wired to the boiler.

The new Honeywell 2 port zone valve closes & the feed into the tank cools BEFORE tank has reached a decent temp.

Boiler is not 'hunting'. Return is cool when feed pipe into tank is hot, though I'm told this should be the case in an efficient cylinder. Bypass is hot.

New stat was wired in exactly the same as the external cylinder stat it replaced.

Would it cause any harm to turn it up to 50 - 60 degrees C?
Would speeding up the pump help or does that just create airbubbles (I do get air in my rads)?

CH has not yet been reconnected to the system (ie. all rads locked off both ends).
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The stat in my tank is located in the centre and is set to 60 deg. I get hot water!

There's no harm in increasing the stat setting until you get a satisfactory water temperature, after all that's what it's for!

I don't understand the 35 deg setting either, unless you had un ultra efficient heat exchanger the water temp will tend to warm up overall anyway (but always hottest at top) and it would reach 35 deg pretty quickly.

Changing the pump speed won't affect the temperature of the water it will only change the rate at which it heats up.
I think they are usually set to 50-55 degrees. I believe 60 is the max before scale starts to form.
There's no way with 'adequate' rate of flow through the heating coil in the cylinder that the return pipe could stay 'cool' with the flow pipe hot. OK - Albion claim that the high performance coil in this cylinder allows a low return temperature well-suited to condensing boilers (which your Suprima is not!).

It's very bad for your boiler to have excessive difference between flow and return temperatures. I seem to remember there should not be more than 11 or 12 degrees C difference.

Somewhere, something is restricting the flow.
Reset the stat to 50 degrees C & now both the flow & return at the cylinder are hot. Seems to have done the trick. Sorry to have been so cautious.

My only concern now is that I have reconnected the CH. This runs fine till shut down then, for some reason the pump does not overrun (like it does for HW only) & the boiler starts banging.

As the HW is working fine now, the valve is closed after reaching the required temp. Is it this valve that determines the overrun or a stat in the boiler?

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