Pump runs continuously in new installation

jammydodger · 27 Feb 2021

Just had our Keston C40 system boiler replaced with a Keston Heat2 45kW heat-only boiler and Yonos Pico pump. The pump runs all the time, even hours after the boiler has gone into standby. Is this normal for a modern boiler with an intelligent pump? The pump displays its power consumption on a small screen, and when the system's been off for a while, the reading is 12W, which is probably low enough to ignore. But something tells me something's not quite right. Any ideas?

muggles · 27 Feb 2021

The pump should ideally be wired back to the boiler for the boiler to control. Is it?

jammydodger · 27 Feb 2021

Yes muggles, the pump is wired straight into the boiler. It's a closed (pressurised) system serving HW and rads with a motorised valve.

muggles · 27 Feb 2021

Could be a PCB fault then. Don't think the pump overrun time is adjustable. @shambolic any thoughts?

ianmcd · 27 Feb 2021

Check the temp that the frost setting is set to on the boiler interface

jammydodger · 27 Feb 2021

Okay I'll do that later. In the meantime I've noticed the boiler panel says:
Operation: Standby
Flow setp.: 0.0C
Flow temp.: 32.9C

ianmcd · 27 Feb 2021

If the flow temp is 32.9C then the burner must be coming on too, is the 3 port valve wired into the boiler direct ?

jammydodger · 27 Feb 2021

Sorry, there are actually 2 valves/actuators, both wired into a junction box along with cables to the programmer and the boiler. The boiler is working fine, firing up when it's supposed to. It's just that the pump remains on all the time, and I'm not sure if that's right.

ianmcd · 27 Feb 2021

jammydodger said:
system serving HW and rads with a motorised valve.

See that would tell us you have a Y plan

jammydodger said:
Sorry, there are actually 2 valves/actuators, both wired into a junction box along with cables to the programmer and the boiler.

Where you actually have an S plan

Yours is quite a complex boiler electronically wise, and has many setups you need to be more carefull what you respond when asked, post pics of everything you have control wise, do you have weather compensationm when no demand but pump is running post a pic of the boiler screen showing boiler status

D_Hailsham · 28 Feb 2021

Despite being called a "heat only" boiler, which usually means it's open-vent with an external pump, the Keston Heat2 is actually a "system" boiler with a built-in pump. Is this the Yonos Pico pump you mention? Or is that a second, external, pump fitted because you have a very large installation (most domestic properties do not require a 45 kW boiler!).

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Pump runs continuously in new installation

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