We have a rushing noise in most radiators, all valves are open, everything well bled and it appeared after I modified the system to a 3 port buffer with the pump in the piping out to the radiators. Unfortunately the radiators are fed with drops from the loft (2 storey house, mainly plastic piping) so it’s working quite hard even on its second speed. Tried reducing pump speed further but results in poor circulation.
Most noticeable when laying in bed…hence the complaints from other family members!
Anyone managed to solve a similar problem?
Dear @JPB,
As a matter of fact, I had a rushing noise too. I had to change the water flow of the radiator zone to almost eliminate the noise. Now it’s not even audible but for the moment it starts and stops.
The pressure in the tube was too high, causing friction and hence, noise.
Hope that helps.
Cheers
Pump wearing out. It was an old Grundfos pump that I think was the original one fitted to the system when it was installed in the 1980s. After I rearranged the piping in the noughties it was used just for DHW. Last year it started making a noise that could be heard from all radiators. It sounded very similar to a whooshing sound, but it was the pump bearings finally expiring, replaced pump, all well.
Turbulent Flow. When I fitted my heatpump a few years ago there was much whooshing from the pipes and radiators. This is because the flow rate had been upped by 3 to 4 times to match the flow rate stated in the heatpump data sheet. Of course, my nice, quiet laminar flow for the boiler was now replaced by turbulent flow everywhere, hence the white noise whooshing sound. It turns out you only need enough flow to transport the heat you are generating, and the flow on the data sheet is only relevant if you are trying to extract the maximum output. So a PWM controller for the pump now runs it just fast enough to transport the required heat and silence is restored. The PWM has a maximum limit just below the onset of turbulent flow, so you can’t get the rated maximum output from the heat pump, but it just means it takes longer to heat up.
So in summary, pump on the way out or turbulent flow due to too high a flow rate.
Thanks…turbulent flow…reckon your right, certainly improves if the speed is turned down.
It happened after I modified the system from direct to a 3 pipe buffer to combat excess cycling as my HP is a size too large (got 8kw should have been 6) and struggles to modulate far enough down, added the second pump and buffer and the HP is now happy.
Think I’ll try reducing the flow further when we start the next season or some other suitable time…more experiments!
We had this on one of our rads post Octopus install. We have a small radiator at the top of her stairs, no TRV, only lock shields both sides. The noise wasn’t there before the install with our old oil boiler.
It was surprisingly loud.
Octopus plumber came back and just tweaked the lock shield on the incoming water side of that rad ever so slightly and the noise disappeared.
I’ve had a similar issue since heat pump install that I’m still looking to resolve. There’s a rushing noise from some of the pipework. At times, I’ve even had the pipes resonating in a couple of places. I put it down to turbulent flow.
I’m hoping to do some repiping this summer. Most of the noise seems to come from a few elbows under the floorboards so I might get some large radius elbows that I’ve seen online and see if it helps. Failing that, I might put PEX in some sections to reduce the number of elbows needed.
I’ve even been toying with the idea of using a 10 way underfloor heating manifold and using a seperate pex run for each radiator so that I can monitor and adjust individual flow rates easily. Very drastic, not even sure if it will work, but it sounds fun
I always wonder why measureing flow rates to radiators is so difficult? Adjuating for dt is less accurate and takes a long time to settle after adjusting. Flow rate measurment is instantaneous and independent of flow temps.
That’s exactly what I would do if starting from scratch. You can have big pipes (22/28mm) to/from the heatpump to manifold to support the high flow rate required by the heatpump. Then thinner pipes to each individual radiator. Those thin pipes only need to support the flow rate for one radiator, so the velocity in both sections should be low enough to maintain laninar flow everywhere.
