Weird intermittent hum..

[pipunch]

Hey. Before i ask my question and describe my problem, the following info is probably useful:

It's a repo'd house - was empty for a year and no contact with the previous occupants.

Upstairs of house is bare floorboards and easily accessible.

We have 6 radiators - 3 upstairs and 3 downstairs. They are on microbore pipe (teed off from 22mm pipe feed and teed back to 22mm pipe return) and two get hot upstairs and only one hot downstairs. The water pump is new and the hot water works fine.

Upstairs we have nothing plugged into the plug sockets and the pump/thermostat/diverter valve hard wired in.

Downstairs we have the boiler, the oven and hob wired in on plugs, the washing machine wired in on a plug and the boiler and function controls for the heating/water are also hard wired. We have a computer plugged in and the fridge-freezer plugged in.


Ok - when we first moved in, the house was completely empty and all services shut off. We got everything working and up and running fine. Water and electric work fine, and a device my old man gave me which plugs into the sockets and tells you whether they are working is showing that all sockets are working perfectly.

On the third day we were here we were lying on the bed (after i'd put it together) about 6pm, and this weird buzzing noise started happening. It was difficult to locate, but it appeared to be coming from the floor under our bedroom. I went downstairs and i could still hear it there. I then turned everything electrical off and it was still going, and then it suddenly stopped after about 5 minutes.

Not heard anything since, and the above happened on Sunday.

This morning, i was woken up at about 9am by the same noise, albeit a little bit louder. I got the floorboards up in our room and i can see a big bunch of wires coming through the floor from the consumer unit which is under the room in the hallway by the front door. Water pipes are running alongside the main electrical wires and although the sound was difficult to pinpoint it appeared to be coming from that general area.

There is still a tiny bit of air in my heating system i would presume, as the system is only warming 3 out of 6 radiators, i don't know whether this makes a difference.

Again the sound just randomly stopped after about 5 minutes.

This isn't a huge concern it's just doing my head in not knowing what it is. Can cables hold charge even when the consumer unit is completely switched off, hence the sound not stopping when i powered off? Or is it more likely to be pipes? I thought this was the best place to ask as the sound sounds like a loud version of a humming dimmer switch or something.

Thanks in advance for any help.

ALSO - just me in the house last night and this morning. No appliances were on before i heard this sound today.

 

[flyingsparks]

If it is still doing it with the main switch off at the CU, then it is more than likely to be a plumbing issue, such as air like you mention.

 

[THRIPSTER]

Did the house have storage heaters? If so, what you can hear could be an old electro-mechanical time switch cutting in/out. Any pictures of the meter and consumer unit?

Regards

 

[pipunch]

It has old pipe work for a back boiler, but it's run by a normal combi boiler now.

Don't think it had storage heaters.

The set up is Boiler > Cylinder > Tank in loft.

I think it could be a plumbing issue because the pipes are not clipped down anywhere, but i don't get why it would be random? I heated the heating up last night and am consistently using the water (both hot and cold) and i've only heard it twice. It happened this morning 9 hours after the last tap etc was opened.

Very confused, but although i didn't turn the mains off this morning, the first time it happened i did and it was still there, but maybe 2 or 3 minutes later it stopped.

 

[skotl]

Sounds like air in the heating pipes. It will be random because it will depend on the temperature and also where the air blocks are.
I've also seen and heard pipes vibrating against flooring and joists which can cause the sound you're describing.

Having said that, you would likely only get the knocking / vibration when the heating pump is running - is the heating definitely off or on when the noise is present?

 

[Iggifer]

There is still a tiny bit of air in my heating system i would presume, as the system is only warming 3 out of 6 radiators, i don't know whether this makes a difference.

http://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

 

[viewer]

This does sound like a question for a good plumber / heating engineer. Your combi boiler - cylinder setup doesn't sound right. There are variations, but generally the combi provides all hot water and heating at mains pressure without a tank or it provides heating and the hot water is via immersion heater. An inlet to a cold water tank (eg to serve the hot water cylinder) is a common cause of vibrations as the movement on the pipe and sidewall caused by the valve closing causes a standing wave and tremor through the pipework which can last for quite a while. The solution here is to strengthen the inlet point and pipework to prevent movement.

 

[mfarrow]

Don't think it had storage heaters.

Yes but does it have Economy7?

If the incoming supply/meter isn't in the same place as your consumer unit, it could be a timer winding itself up (the old ones do that in case of a power cut, they have a mechanical mechanism as a backup), or that of your neighbours.