How many radiators MUST be on when the boiler is set to heat the system?

[wuwyam]

Hi. Just had eleven new rads fitted to work with an older but verified suitable boiler. At first firing I had only one rad open and the rest closed. Four other rads warmed up while set to zero. In other words the valves at these four rads are effectively open while set to zero. The boiler was making an unusual slightly rattly noise. Have I damaged the valves and the boiler by making the pump work too hard? That's the question. I've since been told that it's a mistake to only have one rad open, that maybe three other should be set to FROST in order to allow enough flow in the system. Thanks guys.

 

[Harry Bloomfield]

I've since been told that it's a mistake to only have one rad open, that maybe three other should be set to FROST in order to allow enough flow in the system. Thanks guys.

When set to frost, TRV's only open when the room is below around 5C, above that they are closed, so you were misinformed. Modern boilers only need one radiator open as a bypass, to ensure there is always some flow through the boiler, but what actual boiler do you have?

 

[Madrab]

A boiler should happily run with no rads on, it just won't run for long. 1 rad is enough for a system to circulate and heat up but depending on how far along the system it is will determine how long the boiler runs before it reaches temp and shuts down

 

[Madrab]

I've since been told that it's a mistake to only have one rad open

Who told you that? A boiler can be set to run with no rads open, it just won't run for long and should just shut down. 1 rad is enough for a system to circulate and warm up but depending on how far along the system it is will determine how long the boiler runs before it reaches temp and shuts down.

When it comes to properly commissioning then that's different

 

[wuwyam]

Guys. I really appreciate you taking the time. Harry, boiler is a Greenstar 32CDi Compact ErP condensing Combi. Eleven rads between ground and first floor in a bungalow. Radiorentalrabberto.....Not sure what you mean about commissioning (don't get mad) but yes I get the rest of it. Makes sense. Seriously thanks.

 

[Madrab]

Not sure what you mean about commissioning

When a new system is commissioned, you run it under full load with all the rads on to ensure everything warms up properly and the system performs correctly, making adjustments to temps, flow and balancing where necessary.

Part of the install of the new rads, whoever did that, should have recommission the system to ensure everything is working as expected. Part of that would have identified the faulty TRV's and remedial work could have been performed to sort it out.

 

[wuwyam]

They say they are coming back to replace the faulty valves. Thanks again Rab