Switches on my Heatrae Sadia Megaflo tank

[whensman]

We live in a new 4 bed detached house which has a large Heatrae Sadia Mega flo water heater in the cupboard upstairs. It also has a much smaller red tank to the side above it which only seems to have cold pipes going in and out and has a gauge and a valve (when I open the valve the pressure on the gauge goes up). Additionally there is a Grundfos Alpha+ pump.

Heatrae Sadia Mega Flo

• whensman
• 7 Aug 2008
• 2

Heatrae Sadia Mega Flo

We also have a honeywell st6400c control panel downstairs in the utility room and an ideal boiler SE15 FF (with freezestat??) in the garage.

My question is to do with 2 single switches (like light switches) that are on the wall next to the large heatrae Sadia Mega Flo tank. What are they for??? I think one is for the immersion heater (e.g. if the gas supply fails) and this has always been off, what is the other one for (it is on)??

I can program the honeywell control panel for hot water and heating and have been reducing the time it's programmed to be on to try and save money, but it seems to make no difference to the hot water (it's always hot when we want it) - the heating is off permanently as it's summer. Recently I turned off the 2nd (unknown) switch next to the large tank and suddenly we started only getting luke warm water - what's that all about??

Also there is a switch downstairs next to the honeywell control panel that says "water heater" (it had always been off too) what is this for??

Some help would be VERY greatly appreciated

 

[Paul Barker]

Fairly certain (but get someone in as consultant) that you have a sealed heating system made sealed by the redexpansion vessel fillingllop and 3bar pressure relief valve in the airingcupboard which shares the D" drain pipe of the unvented (white) domestic hot water cylinder.

The switch beside the boiler downstairs and one of the ones in the airing cupboard both must be on for the electric heating using immersion heater.

Possibly the other switch shuts the zone valve to the dhw cyl. (there should always be one fitted which fails shut as a safety measure to prevent the unvented cylinder overheating.

 

[Mike2007]

Firstly, two stats should be under the grey/black plastic box on the cylinder. One stat is a HIGH level stat, about 95 degrees cut-out. The other for regulating the water temperature, say normally 65 degrees.
Electrical power must run through all "closed" stats to send power to the motorised valve (box in pipe with flex running to it).
If power gets to this valve "contact" will be made as it opens up, sending a current to the gas boiler, pumps hot water into cylinder.
The immersion which should be one of those switches on the flat surface, also runs current through the safety stats but does not open the valve!
Sounds a bit like the gas water heating is coming on with its cycle BUT the immersion has been on permanently??
I would be more tempted to get a sparky in rather than a plumber....but saying that, there are some very competent plumbers??
Get a tradesman that everyone rates as a top bloke and use him. Less than one days labour.

 

[Rico99]

Hi there,

I also second the advise to get someone in to have a look, but PLEASE PLEASE PLEASE make sure they have their G3 cert for working on un-vented cylinders.

Rico

 

[mickyg]

The red vessel-- thats the expansion vessel for your heating system. Pressure gauge shoule be set 1-1.5

Switches-- The one nearest to the picture is for the immersion, the other one is almost certainly the main isolator for your heating/hw system from the boiler, seeing as its next to a heating wiring centre. If you turn this off you will see that you lose power to your timer, hence when you turned it off you cut power to your boiler, and the cylinder cooled down to luke warm temperature....Although you are reducing your times you have a very large well insulated cylinder, maybe your just not using all the water and therefore its remaining hot.
The other switch is probably the power supply to the immersion switch, just more practical place for immersion control.
No idea why people are telling you to get people out as it appears things are as they should.


[/quote]

 

[Mike2007]

The red vessel-- thats the expansion vessel for your heating system. Pressure gauge shoule be set 1-1.5

Switches-- The one nearest to the picture is for the immersion, the other one is almost certainly the main isolator for your heating/hw system from the boiler, seeing as its next to a heating wiring centre. If you turn this off you will see that you lose power to your timer, hence when you turned it off you cut power to your boiler, and the cylinder cooled down to luke warm temperature....Although you are reducing your times you have a very large well insulated cylinder, maybe your just not using all the water and therefore its remaining hot.
The other switch is probably the power supply to the immersion switch, just more practical place for immersion control.
No idea why people are telling you to get people out as it appears things are as they should.

[/quote]

I have to say the isolators are in a stupid (if not dangerous)position. If the cylinder leaks as they sometimes do, water would penetrate the low IP switches.
If the isolator for the boiler was here as well, its in a silly position! Should be close to programmer in kitchen or wherever. Whole electrical circuit needs a once over by a professional!
Sometimes you have to know your limitations in DIY.