Nest 3rd Gen and Worcester Bosch 8000 Problem

Newuser0

Hi guys,

I seem to have a somewhat weird problem.

I’ve recently had a new radiator system along with a new boiler and Nest thermostat installed.

The problem is quite a weird one so I’ll explain the best I can.

The thermostat is in my hallway and my house is 2 floors. Lets assume the ambient temp is 17°, I then crank up my thermostat to 30° which then fires up the boiler and rads start getting hot.

My problem starts here, let’s say the thermostat goes from 17 to 19 at that point the radiators starts cooling down, which it shouldn’t as it’s nowhere near the 30° (which I know it won’t ever reach). I don’t think the TRV is switching the rads off as the rooms/hallways are not overly hot. 

However, on rads cooling down if I mess around with the thermostat I.e in this example I change it from 30 to 28 the radiators will start getting hot again.

The boiler stays firing throughout from initial thermostat change until i switch it off. 

I don’t understand what on earth is going on, whether it’s my boiler or thermostat?!?!?

Please help me before I go crazy lol

macman

Is there a max temp programmed into the Nest?
What internal temp are you trying to achieve?
It's not likely to be the boiler, because that should simply act dumb and merely respond to calls for heat from the programmer as commanded.
What does your installer say about this issue?

Money_Grabber13579

If the boiler continues to fire continuously, that suggests that there is a demand for heat somewhere, at all points. So if you only have one nest, I can’t see how it is the nest turning the heat on and off? So I’d have thought it must be something to do with one or more radiator thermostats, faulty or otherwise.

Le_Kirk

Is the boiler reaching the set/maximum temperature of the water?

macman

Le_Kirk said:

Is the boiler reaching the set/maximum temperature of the water?

The Greenstar 8000 is a combi.

coffeehound

I don't understand the bit where the boiler is still firing but the rads are cool.  AFAIKS the only thing that could do this is the TRVs.  Are they 'smart' and connected to the nest?

Le_Kirk

macman said:

Le_Kirk said:

Is the boiler reaching the set/maximum temperature of the water?

The Greenstar 8000 is a combi.

Yep but if the circulating water for the radiators is reaching the temperature set by the boiler control system, the boiler will modulate to low (or off if not modulating) and the will rooms will cool down.