Buzzing from three way valve actuator

[Ray1000]

Occasionally we get a buzzing from the three way valve. It can be stopped by turning the power off to the central heating, and stays silent when the power is restored

The hot water was on 6am to 7am this morning then CH on for 30 mins at 7:30am ... the noise was noticed at 11am but it may have been there since 8am .

If you turned the CH off when the HW was already off the valve does not return to the initial start position. Power is still applied through the grey wire from the HW OFF terminal to the motor and holds the valve at the CH position. This is how it is designed to function. I gather the buzzing is caused by the motor.
To prove it, turn the CH off first followed shortly by HW the motors power will be cut off and motor/valve will drop back to initial start position and buzzing will cease.

I'm not sure if this answer in another thread applies to ours?

Thank you for your help

Ray

 

[stem]

Under certain conditions, for example when the heating demand is removed by the controls, and there is already no demand for hot water, the valve will remain in the heating only position with the motor fully energised. The boiler and pump will be off so the radiators won't actually heat up, but the valve will remain in this position until there is a hot water demand, then it will move away from the heating only position. So, it could be energised all night for example, until the hot water comes on in the morning. In this position it is quite common for the AC synchronous motor to buzz. The buzzing may not be continuous during this time it may come and go.

Turning off the mains supply to the heating system, removes power from the motor and the valve moves across to hot water only position, where it will stay even when mains power is restored, until the time when there is a demand for central heating and the motor will be come energised once again.

So really what @MANDATE said.

 

[Ray1000]

Thank you very much for the reply.

Q1. Is it using more electricity if it's energised?
Q2. Is it using more electricity still when it's energised and buzzing?

We have our water on 6 to7am only - and I don't know if the tank stat knocks it off before the Nest does.
The heating is on in the evening so if I understand correctly we are prime targets for being energised all night.

Q3. Presumably, flicking the CH Fused Spur off and back on last thing at night would knock the energised power off and position the valve ready for the following mornings hot water?

Ray

 

[flameport]

Q1. Is it using more electricity if it's energised?
Q2. Is it using more electricity still when it's energised and buzzing?

The motor in it uses about 6 watts, or about 1p for every 5 hours it's on.
The buzzing is because the motor or other parts are wearing out, it does not affect the power consumption.

 

[Ray1000]

Thank you, it was renewed in 2019 !
Ray

 

[stem]

We have our water on 6 to7am only - and I don't know if the tank stat knocks it off before the Nest does.

Probably it does. Typically the hot water cylinder is up to temperature, and the hot water cylinder thermostat has already turned the hot water off before before the programmer (Nest) does.

The heating is on in the evening so if I understand correctly we are prime targets for being energised all night.

Yes, but it's the same for most people, because the hot water cylinder heats fairly quickly and is well insulated the hot water is off most of the time. The central heating is usually the last thing running in most cases.

The upside is that in the summer, when the central heating isn't being used, the valve will sit in the hot water position permanently and never be energised at all.

 

[Ray1000]

I understand, thank you again.
Ray

 

[Harry Bloomfield]

Q3. Presumably, flicking the CH Fused Spur off and back on last thing at night would knock the energised power off and position the valve ready for the following mornings hot water?

Following an off, the actuator will spring return to it's default position of HW. When you switch back on, the actuator will assume it's position based on what the demand is at the time of switch on, be it HW, HW + CH, or CH only.

If the motor is powered to reach HW + CH (mid position), or CH, then when it reaches those positions, the motor is deliberately stalled - so as to just be able to hold the position. Basically, the actuator motor powers to wind up against a spring - if power is removed, the actuator will return back to the HW position.

The motor needing to be powered for a CH demand, and the constant back and forth movement, every time there a demand for CH, means considerable wear on the actuator. A more interesting and better design of 3-port actuator, is one called the MOMO.

The MOMO actuator, is electrically compatible to the spring return, but needs a matching water valve. Rather than using a spring return system, the motor only runs when a change in valve position is needed, between times, the actuator stays put in the last used position. Basically, the mechanism is under much less stress, because it's not constantly fighting a spring, and the motor lasts much longer, because it is only powered when a position change is needed.

A downside of the MOMO, is that because they are electronically more complex, they are rather more susceptible to water damage, so ideally need to be mounted actuator uppermost, so the electronics are given some protection by the plastic cover.

 

[Ray1000]

Thank you for your help Harry

Ray