Rattling noise from central heating pump

Graeme1978uk

Ok, if I ramp either of the zone thermostats up via the app on my phone, this is what happens.

1. The wall thermostat clicks
2. The pump starts and at the same time, the Honeywell zone valve ‘clicks’
3. The boiler fires up

There’s only a few seconds for this process to complete but definitely occurs in that order.

The Honeywell valves only ever seem to make that whirring sound when the thermostat reaches the required temperature and the system is turning off.

Ibrahim5

I have almost exactly the same system. On my boiler instructions it was very clear that the boiler must control the pump. I got the cowboys back to rewire it. When the zone valves close the pump runs on and the flow goes through the bypass. The noise would be quite load but my Wilo slows down so it goes quiet and pump power consumption reduces.

Ibrahim5

Our cowboys also fitted a TRV on the wrong end of the radiator. It made a racket when the room got up to temperature. I just opened that valve fully and adjusted the lockshield valve until the temperature was reasonable.

Bendy_House

Graeme1978uk said:

Ok, if I ramp either of the zone thermostats up via the app on my phone, this is what happens.

1. The wall thermostat clicks
2. The pump starts and at the same time, the Honeywell zone valve ‘clicks’
3. The boiler fires up

There’s only a few seconds for this process to complete but definitely occurs in that order.

The Honeywell valves only ever seem to make that whirring sound when the thermostat reaches the required temperature and the system is turning off.

"The wall thermostat clicks. The pump starts and at the same time the Honeywell zone valve 'clicks'."

The zone valve should take a brief period - a couple of seconds? - to move to the open position and to 'click'. It does 'whirrrr' during this, tho' it might be fairly quiet. So, the sequence of the valve operation is still a bit uncertain.

There's another way to tell; if you look at the end of the valve, on the metal top box part, you'll find a metal lever with 'Auto' at one end and 'Manual' and/or 'Open' at the other end. When the valve is powered off and therefore closed, this lever will be firm against the 'Auto end. (Try pushing it slowly but firmly towards 'Manual' - it makes a whirrrr, and you might hear the click when you reach the far end? Release it, and it'll return under spring pressure with a definite whirrrr. (Make sure you don't get the lever caught under the hook in the slot! If it does, you'll need to release it - peasy.)

Ok, just to be certain, could you repeat the test, but FIRST check that the zone valve IS tightly at 'Auto'? Now tweak yer App, listen for the room 'stat 'click', and there should be a 1-2 second zone valve movement before it goes 'click'. Again, try and confirm whether the pump fires up immediately when the wall 'stat clicks, or when the valve clicks.

Ibrahim's report is interesting, and it does sound like your initial description - ie. the pump comes on independently of the boiler, and before it. That is not good.

s I understand it, the pump should either (a) be switched at the same time as the boiler, by the action of the zone valve 'click' (ie, both come on only AFTER the valve has opened, and go off BEFORE the zone valve closes), or (b) the pump is controlled by the boiler (in more advanced systems), but again the pump shouldn't come on until the zone valve has opened. 

Bendy_House

Ibrahim5 said:

I have almost exactly the same system. On my boiler instructions it was very clear that the boiler must control the pump. I got the cowboys back to rewire it. When the zone valves close the pump runs on and the flow goes through the bypass. The noise would be quite load but my Wilo slows down so it goes quiet and pump power consumption reduces.

That's interesting - thanks Ibrahim.

With boilers that control the pump, this is used for pump 'overrun' situations, where, for example, the boiler still has a load of heated water in it that it wants to shift before it shuts down. So when the boiler has been told the room is warm enough, the boiler flame shuts off, but the pump keeps running until all the water inside has been dispersed.

What were your symptoms before they came back to rewire the control?

Bendy_House

Graeme, have you told us the make and model of boiler? Thanks.

Ibrahim5

Bendy_House said:

Ibrahim5 said:

I have almost exactly the same system. On my boiler instructions it was very clear that the boiler must control the pump. I got the cowboys back to rewire it. When the zone valves close the pump runs on and the flow goes through the bypass. The noise would be quite load but my Wilo slows down so it goes quiet and pump power consumption reduces.

That's interesting - thanks Ibrahim.

With boilers that control the pump, this is used for pump 'overrun' situations, where, for example, the boiler still has a load of heated water in it that it wants to shift before it shuts down. So when the boiler has been told the room is warm enough, the boiler flame shuts off, but the pump keeps running until all the water inside has been dispersed.

What were your symptoms before they came back to rewire the control?

I was just trying to understand the wiring so I could maintain it myself. Although an expensive house they had fitted the cheapest pump you could buy and it was set to maximum. It was quite noisy. I asked the builders if it could be made quieter. There was nothing they could do. So I researched it myself and fitted quality pumps that could be adjusted so they were quiet but still had enough flow to work. I have a Glowworm boiler. I phoned them up when I discovered that the cowboys hadn't wired it correctly. They said the boiler must control the pump to protect the cast iron heat exchanger. I never really liked the bypass. Seemed wasteful. I don't think the building regs permit them.

Ibrahim5

I originally swapped it for a Grundfos alpha. I now have the Wilo. I get it to maintain a constant pressure. Really like it. Prefer it to the Grundfos.

Bendy_House

Ibrahim5 said:

Bendy_House said:

Ibrahim5 said:

I have almost exactly the same system. On my boiler instructions it was very clear that the boiler must control the pump. I got the cowboys back to rewire it. When the zone valves close the pump runs on and the flow goes through the bypass. The noise would be quite load but my Wilo slows down so it goes quiet and pump power consumption reduces.

That's interesting - thanks Ibrahim.

With boilers that control the pump, this is used for pump 'overrun' situations, where, for example, the boiler still has a load of heated water in it that it wants to shift before it shuts down. So when the boiler has been told the room is warm enough, the boiler flame shuts off, but the pump keeps running until all the water inside has been dispersed.

What were your symptoms before they came back to rewire the control?

I was just trying to understand the wiring so I could maintain it myself. Although an expensive house they had fitted the cheapest pump you could buy and it was set to maximum. It was quite noisy. I asked the builders if it could be made quieter. There was nothing they could do. So I researched it myself and fitted quality pumps that could be adjusted so they were quiet but still had enough flow to work. I have a Glowworm boiler. I phoned them up when I discovered that the cowboys hadn't wired it correctly. They said the boiler must control the pump to protect the cast iron heat exchanger. I never really liked the bypass. Seemed wasteful. I don't think the building regs permit them.

Which model of GlowWorm, and roughly how old is it?

Bendy_House

Ibrahim5 said:

I originally swapped it for a Grundfos alpha. I now have the Wilo. I get it to maintain a constant pressure. Really like it. Prefer it to the Grundfos.

Grundfos used to be the default choice of pump. Wilo are also respected. The G Alpha can be delicate, tho', and the electronics can be affected by leccy spikes - according to some reports at least.

Are you familiar with the valve lever on the Honeywell? That should help determine whether it really does open first before the pump comes on.