Heatrae Sadia 900 (no heating or hot water)

10 Dec 2023
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United Kingdom
I live in an apartment, I have the following items as part of what I feel is a complex system.

- Heatrae Sadia 900
- PrimaFlow CP5
- Two yellow boxes (pump valves, assuming on and off peak?)
- two switches one for off peak and one for boiler
- Albion Ultrasteel boiler
- Zilmet 10 bar 110-Ultra Pro (no idea what it is)
- Red tank, looks similar to Zilmet above but smaller and with a valve on it with bars, immersion heater?

That's the setup, in terms of thermostats I have one for the hot water which SHOULD turn on between 2am and 5am but doesn't and then an old online system called Owl Intuition which does the heating and of course all electric, no gas.

Now, for ages now, the PrimaFlow CP5 has been very loud, when its heating water or whatever it does, the other day the heating didn't turn on so I bled the CP5 and then the heating turned on... I am not sure if since then I triggered a switch or something, because nothing has worked after the heating turned off.

The valve on the red tank, looked low, so today I opened up the water valves to add pressure, thinking that would help, it didn't.

Now, I am pretty much at the point I don't know where else to go... I am going to be calling an engineer tomorrow, but since I don't know any engineers, thought I'd come and ask you fine experts first.

NOTE: The Heatrae Sadia system call light goes green and heat light goes orange/amber for a minute or so then stops when I try and manually get the hot water or heating turned on, so it seems for whatever reason the heatrae sadia 900 doesn't want to fire up.


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I think your 2 yellow boxes will be an s plan, so one for heating and one for hot water. Bleeding the pump might have released air, which might be why the pressure was low. The motorised valves (yellow boxes) should send a live to the pump and boiler (at least that’s how the gas boilers operate), if this is the case, then I’d say the motorised valves are at fault.
Thanks for the quick reply. The yellow boxes, motorised valves do switch on when I try and manually turn on the hot water or heating, and they do sound like they are working. However, the heatrae sadia system call light flashes green but the heat goes amber for a minute or so then stops and it just shows the green call light, so its like the sadia system isn't firing up.
1. The Heatrae Sadia (Amptec) is your boiler.
2. The Albion Ultrasteel is an unvented hot water cylinder (HWC). It should be serviced annually.
3. The Primaflow CP 5 is a circulating pump. It sends hot water heated by the boiler to the central heating, and / or to a heating coil (non-electrical) inside the HWC.
4.. The yellow boxes are motorised valves, one for the central heating, one for the hot water.
5. The two switches:
5.1 One will likely be an off-peak switch. Power will only come into it during off-peak hours and is normally used to power the lower of two immersion heaters in your HWC. It should always be on.
5.2 The other will be a normal rate switch to power the boiler. It may also be connectable to the upper immersion heater in your HWC to allow you to "top up" hot water if your run out. It should always be on.
6. The red vessel is an expansion vessel to accommodate the increase in volume of boiler water as it heats.
7. The white vessel is an expansion vessel to accommodate the increase in volume of hot water cylinder water as it heats.
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Thanks, that makes a lot of sense.

Weirdly, the off-peak switch seemed to have turned itself off, I just tried to switch it back on and it sparked, so that isn't a good sign, think I'll leave it all alone now.

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