Central heating chaos

[Johntheo5]

Santa did not bring heating today
One radiator that has been working the last few days downstairs with all the others has decided to stay cold. I’ve not changed or done anything …. It’s like my radiators pick and choose what ones to go to. I don’t get it.

Happy Christmas to all and have a look at the attached.

 

[Harry Bloomfield]

Santa did not bring heating today
One radiator that has been working the last few days downstairs with all the others has decided to stay cold. I’ve not changed or done anything …. It’s like my radiators pick and choose what ones to go to. I don’t get it.

Do the radiators, fed on 15mm pipes (upstairs?), have TRV's fitted? If so, when the TRV's are open, perhaps those radiators are hogging the supply of hot water from the boiler.

You earlier mentioned lots of air collecting in one radiator. That to my mind suggests you might have air-locks in pipework. The best way to fix that', is by turning all the radiators to off, then turn only one on at a time, to force the air out, and into the radiators. With, of course, the heating running

 

[Jurassicspark]

Do the radiators, fed on 15mm pipes (upstairs?), have TRV's fitted? If so, when the TRV's are open, perhaps those radiators are hogging the supply of hot water from the boiler.

Hence why I asked,

Have you got TRV's fitted? If so, which ones are fitted?

Drayton's self balancing TRV's are quite good.

 

[CMJB]

No. I just have a knob to turn one side and the other one with a spanner. Does not have specific numbers on.

 

[CMJB]

Here

 

[CMJB]

I’m scared if I turn them all off they will go back to none working downstairs as I’ve had to spend ages trying to balance.

 

[Harry Bloomfield]

I’m scared if I turn them all off they will go back to none working downstairs as I’ve had to spend ages trying to balance.

Mark the settings, before you start, then you can return to them after.

 

[omph]

Did you have the same problem with the old radiators ?

Radiators distribute the heat, the room utilises and dissipates that heat. The higher the heat loss in the room the quicker the room will utilise that heat.

Pipework has a limit for the maximum amount of kWs it can carry. An 8mm pipe with a flow rate of 0.9 metres per second can carry approx 2250watts (or 2.25kW). Compare that to a 15mm pipe which at the same flow rate can carry up to 8.25kW or a 22mm pipe that can carry 18kW. What you have done is upgraded the radiators, but they still distribute the same amount of heat but it is dissipated amongst more panels. Whereas before you had 2.25kW distributed amongst say 4 panels, now you have 2,25kW distributed amongst 8 panels (assuming you upsized 4 single panel rads to double panel). Not only will the radiators heat more slowly, they will dissipate a lot less heat.

Bigger radiators have a larger surface area and with the same heat input will naturally run at a "lower temp" but they are still dissipating the same amount of heat. More radiators also increase the pressure (i.e. resistance) in the system so the pump must work harder to compensate.

Increasing the pump speed will help but it will only take you so far. The faster the pump runs the more corrosion it causes within the system due to friction against the pipework.

The heating engineer should have done a heat loss calculation to identify how much heat you are losing in the property, the heat output of all the radiators, and then calculate whether the current pipework would be able to carry sufficient kWs to supply the rads, and if not, then appropriately up size the pipe where necessary.

If increasing pipesize is too much you can always increase insulation thereby reducing your heating needs.

 

[Johntheo5]

The boiler flow&return temps would be useful, also, since information is 1/2 the battle then knowing the flowrate is vital but Grundfos choose not to even display the pump power on the UPS 3 from which the flowrate can be easily read off from the pump curves.
I would buy one of those £15/£20 plug in energy monitors and install it on the pump cable for a start.

 

[CMJB]

Thanks. How do I get those and where from? Sorry im not very technical and learning as I go along. All these replies are really helpful. Honestly. Can’t appreciate them enough.

 

[Harry Bloomfield]

Thanks. How do I get those and where from? Sorry im not very technical and learning as I go along. All these replies are really helpful. Honestly. Can’t appreciate them enough.

A couple of digital meat temperature displays would do it, or even one, at a pinch.

Turned on, with the probe tip tight against the copper of the pipe, with some sort of insulation placed over the top - a bit of pipe insulation works well for that. The flow and return pipes at the boiler, are the very hot one, flow, and the less hot one, return. The temperatures need to be reported, after the boiler has been running/burning for a while, serving just the central heating. Really, as long as possible, after the boiler's 'burn' began, 10/ 20 minutes.

 

[CMJB]

Ok I’ll see if I can find some bits to check.

 

[Johntheo5]

Thanks. How do I get those and where from? Sorry im not very technical and learning as I go along. All these replies are really helpful. Honestly. Can’t appreciate them enough.

You will have to disconnect (or get disconnected) the pump cable from its wiring centre after carefully noting the terminal block numbers, then connect a bit of cable back into the terminal block with a socket on the other end, connect a 3 pin plug to the end of the pump cable, plug the (3 pin) energy monitor into the socket and plug the pump cable (plug) into the energy monitor and away you go, these monitors are very accurate and even a 1.0LPM change in flowrate will result in ~ 2W change in pump power, very useful even if just balancing rads.