Boiler Pressure Gauge in S-Plan heating

[MaciejZ]

Hi All,

I just moved in to a new house and have a question. Heating and DHW are fed by Worcester bosch CDI30 setup within S-plan (2 motorised valves, indirect cylinder etc) and also expansion tank + feeding tank.

Question is - as this is a non pressurised system - should I be concerned with the pressure gauge reading on the boiler (which is close to 0) - boiler is on the top floor and tanks just above it - not more than 2 meters.

This may sound silly, but just moved in from a house with no tanks and want to make sure that boiler is not going through some pain.

Merry Christmas.

 

[Dan Robinson]

Search the FAQ for filling loops and top the pressure up.

 

[45yearsagasman]

Assuming your boiler is approved for open vented systems ( I haven't checked, but it will say in the Inst instructions ) then forget about your gauge, it has no relevance on an open system.

 

[MaciejZ]

Many thanks for answers.

Just to expand on it - assuming that the expansion tank is 10 meters above boiler - should I expect to see 1 bar pressure on the gauge ?

and also - I can not see any pumps - is it likely that all the pumping is done by the combi boiler ?

thanks again.

 

[45yearsagasman]

You would see a pressure indicated on a gauge with that much head above. Those gauges are not 100%accurate. With a tank 2 metres above a lot of gauges would not register. You now mention a combi? Are you confusing it with what is known in the trade as a system boiler?

 

[MaciejZ]

Many thanks for you reply gents. You were both correct.

After opening the cover of what I thought was expansion tank I noticed that it is bone dry. It was disconnected long time ago and is not being used. This makes it a pressurised system, repacing all leaking lockshields (most of them seized + trvs) and filling to 1 bar and it is now all good - once again - thanks for replies.

Using this ocassion i would like to ask few more questions regarding S plan .

I have horstman c27 programmer and what I noticed is that if heating/HW is called by the boiler - both motorised valves work fine, but if there is no call for heating/hot water - boiler switches off completly (I think it is wired this way ) just like it was switched of from mains power. Is it correct way to operate like this, or should this be on (boiler) and only start heating when called for heat (but power light on).

I have worcester bosch 30cdi.

In the old house Bosch 28i junior ( seems exactly same aparart from more dials for temp control etc) used to have power light on and it would only start heating if there was a demand from either thermostar or hot water (open hot water tap).

many thanks

 

[flameport]

The boiler should have mains power all the time (display on the front should be lit up), and heat water when required by the programmer/thermostats.

If it has no power when no heat is required, it has been installed by a moron who probably just reused old wiring from the previous boiler. The wiring needs to be changed so that it operates properly.

 

[MaciejZ]

So
Should bolier be fed by a fused spur or from the wiring centre ?

 

[MaciejZ]

managed to get it working ( it was all wired incorectly + thermostat on cylinder gone)

a question now is -

If I programm the programmet to have heating and hot water all the time - should I expect both motorized valves to be open (as long as there is demand for heat/hw) or is it the case of hot water always having priority ?

 

[45yearsagasman]

If wired as a standard S plan the valves will stay open so long as there is a call from both the programmer and the relevant thermostat. There is no priority for either. If either stat is satisfied the related valve will close. If the programmer switches off then the valves will close irrespective of the stats.

 

[MaciejZ]

hi, done the checks and still no idea what can be wrong :

programmer : both - ch and dhw setup to work 24/7
both thermostats (room + cylinder) setup higher than actual (so both will demand heat)

and still only 1 motorized valve open at any given time (when heating zone open, I need to switch of at the programmer and then that zone closes and hot water valve opens)

any ideas what can be causing that ?

 

[Echo the husky]

If you are sure it is a normal S Plan then the components are wired wrong. You can configure heating components to work in all sorts of ways. S Plan is one of the most simple setups and is basically the same wiring done twice, once for heating, once for hot water. Post a clear photo of your wiring centre.