Megaflo CL170 usage

I have just moved into a new house with a Megaflo CL170 & Potterton Promax He controlled by a Potterton EP2002 - the problem is there's no user manuals and I'm only used to night storage heaters and combi boilers.
So what is the best way to use this ?? I've switched the heating on the EP2002 to ON and the hot water to OFF but the Megaflo still whirs away. Conversely if the hot water is ON but the heater is OFF the Megaflo is totally silent. Does this sound right ??
Aside from that, what is the best way to use the Megaflo - does it switch itself off when the tank is full or if I left it ON all day would I have a big bill (like an immersion heater would give if left on permanently) ? What does the ONCE switch on the EP2002 do in relation to hot water ? (I know what it does for the boiler).
Many thanks !!
Richard.
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It is well insulated. I'd leave it on all day, or time it so it goes off during the night. The same with an immersion heater. If your tank is well insulated, an immersion won't waste much electricity compared to turning it on for a few hours a day.
Christian.
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On Mon, 22 Dec 2003 09:22:33 +0000, Christian McArdle wrote:

2nded. The megaflow and its ilk are well insulated.
There does seem to be a problem with the operation of the controls. The boiler should fire when either the heating or the HW is needed. There should be a thermostat on the Megaflow to prevent the boiler firing needlessly for to heat the HW.
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Ed Sirett - Property maintainer and registered gas fitter.
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