Combi CH system

[pinnerite]

My bungalow has a new (last August) Combi heating system. The Hot Water part works fine but the Central Heating does not.

I have struggled to analyse why.

The boiler is installed in a cupboard roughly just off-centre of the property.

The outside of the cupboard is part of the wall of a short hall. Th thermastat is on that wall.

The hall ends at the front door which is south facing. Actually there are two doors. Our predecessor installed the second one to enclose the porch. Both made from double-glazed uPVC. When the sun shines through them it gets very warm in the hall and can push the thermastat beyond its setting of 22 degrees C and holds that until late.

Could the boiler be heating the thermastat through the stud wall?

The effect of this is that rest of the property remains fairly cold just when I want it warm.

Bleeding the radiators was not expected to improve matters. It didn't. Yet it was not always like this.

But the radiators do heat up in the mornings.

The thermastat can set to different tmerature limits for each of four periods.

I am tempted to raise the thermastat's temperature limit for the third quarter to say 24 or 25 degrees which should have effect of raising the bedroom temeratures to 21 or 22 degrees.

Am I going about this the wrong way?

[Tim+]

I think relocating the stat would be a better place to start. If it?s a wireless one just take it off the wall and try it in different places (not in direct sun) and see how it affects the comfort of the house.

The problem with just ?cranking it up? to compensate is that it will be set too high for cloudy cool days when your hall isn?t being warmed by the sun.

Tim

[John Rumm]

Probably...

Stats generally want to be in the place that will tend to heat up

*last*, to give all the rest of the house to get to the set temperature.

If the stat is in a room with radiators, then they *must* be uncontrolled - i.e. no TRVs, or TRV heads removed, or at least TRVs set to maximum (otherwise you can defeat the stat working as a system interlock (shutting off the heating when the place is warm enough) because the TRV shuts down first and the stat is never satisfied.

You may be better off swapping the stat for a wireless one, so you can tote it about to a more appropriate location (that may not necessarily always be the same place)

[David Wade]

I think so. I assume all the other radiators have thermostatic valves, but the one in the hall doesn't. For a cheap solution put the thermostat in the room you want to be warm and open its TRV. If its wired get a wireless one so you can do this.

If you do have TRV valves on all the other radiators you might want to consider a system like Wiser

or Tado

(I would avoid Hive. Generally they just WiFi the thermostat)

which allows you to replace the heat sensing part of a TRV with a wireless module that has both a valve and temperature sensor. These allow each radiator to be individually controlled so you can turn the bedroom heat off during the day and the living room heating off at night. When any room needs heat, the controller opens the radiator valve and fires up the boiler.

I have Wiser. I love it.

Dave

[Andy Burns]

ZigBee from the roomstat to boiler I think, judging by the one that BG fitted along with my dad's boiler.

There's also an 'gateway' device that can connect to the router via wired ethernet, but it all works without the gateway, you just lose the ability to control it from the phone app.

[ARW]

That sounds similar to my parents holiday apartment setup.

I would say their biggest problem is the radiator in the lounge is undersized but all is well if the stat is at 23 deg.

I will at some point install a wireless stat but keep the existing one as a frost stat/backup.

[Scott]

Could the pump be faulty?

[Brian]

Is it a pressurised system? If it is, have you checked it is up to pressure? Certainly, if you?ve bled it, you probably need to top it up.

Different systems use different methods. Eldest?s uses a ?key? thing which goes into a socket and diverts mains water into the heating circuit. There is a gauge so you can see the correct pressure. Others have a loop of pipe etc.

Is the pump running?

?Balancing? is another possible issue. Each rad has two valves- one is sometimes thermostatic, the other is the balancing valve. As a ROUGH guide the rads low down and further from the boiler have the balancing valves more open that those closest. Some will be hardly open, a fraction of a turn.

Ideally, you set them by measuring the temp between the inlet and outlet pipes - you want 12 degrees . In practice, you can get acceptable results without the thermometer, it just takes longer.

Another possibility - or two related ones- if it is a vented system, is the header tank is empty or the pipe from it to the system ( the one that leaves the bottom of the tank) is blocked. Either of these result in a partially filled system which which won?t run correctly.