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Central heating noise

(16 Posts)
JB321 Sun 29-Oct-17 08:38:54

Hi Folks

Completely new to this forum and have very little knowledge of central heating systems hence after a bit of advice from the experts.

I have recently had a pressurised unvented hot water cylinder installed in the loft which was done to free up the airing cupboard space. This has replaced a gravity fed system. We are really pleased with everything other than the low frequency humming sound that is now resonating through the ceiling and down one wall in the main bedroom (and is bloomin annoying!!)

After doing a bit of Googling I tried turning the Grundfos pump down from setting 3 to setting 1. This immediately sorted the problem. After a few days I started worrying I might be causing problems elsewhere in the system so contacted the heating engineer who installed it who said it must be on setting 3 but didn’t really explain why.

I did say to him that all radiators in the house had continued to heat up perfectly, the water pressure in the shower and taps had been absolutely fine and it hadn’t caused any other noticeable issues.

So my question is why does the setting need to be on 3? Is this just his opinion and do other experts out there think having the pump on 1 or 2 is fine? The house is 3 bedroom with 2 showers (in case this matters)

Thanks in advance.

whiskyowl Sun 29-Oct-17 08:51:44

"Completely new to this forum and have very little knowledge of central heating systems"

This is very clear, as if you were an established Mumsnetter you would be holding firmly to the conclusion that this was the work of woo, possibly a poltergeist, and you would be unshakeable in the conclusion that it could be explained no other way. wink

I think you should ring back the engineer who installed the system and ask why it has to be set on 3 - may be that a certain level of pressure is needed or something. Though PigletJohn may be along to explain the answer in a bit. smile

johnd2 Sun 29-Oct-17 09:44:21

The humming could just be down to the pipes not clipped properly or under tension so should be fixable. Ideally the pump wouldn't be able to transfer any vibration to the pipe work but that's not usually how external pumps are done.
Regarding the main circulation pump setting, the pump needs to produce enough"head" of water to force the water around all the radiators and other heat emitters. However perhaps you adjusted a pump that circulates the water in the cylinder that improved the heat up time. What colour is the pump and any chance of a photo of the pump and of the whole cylinder?
If you adjust that, the water won't heat up as quickly, and the engineer might be sensitive about you adjusting things on the cylinder as you have to have a qualification to adjust some parts of the sealed system. Not the pump though.

PigletJohn Sun 29-Oct-17 10:20:01

If you have a cylinder, I don't believe turning the pump speed down will do any harm. If you have a larger house or bad piping design you may need it turned up to get the radiators balanced. If you have a sludge and sediment problem you should get it cleaned.

On a combi, the heat exchanger has to deliver a lot of heat very fast when running a bath, so best not to change that (you could ask the engineer at the next service) but the pump will probably be in the boiler and not accessible.

It's possible for air to collect when the pump is running slow, I have to turn mine up occasionally due to the spiral design of the boiler.

Some pumps are self-adjusting according to load, and opinions vary on whether they're more trouble than they're worth.

Good idea to add more pipe clamps. Experiment by grasping pipes firmly with a gloved hand to see if you can locate the vibrating one.

As you have an unvented cylinder I would expect your pump to be fairly new and not worn out. 20 years is a typical life but sediment or dirt in the water will wear them out faster. Modern system filters are good at trapping dirt.

JB321 Sun 29-Oct-17 11:27:36

Thanks for the quick reply guys, really appreciated.
I can’t appear to upload any images unfortunately??? They are saved in my profile if that helps but can’t upload them to thread.
I’ve checked all accessible pipework and securing it has help slightly but not really fixed the problem.

The pump is a red Grundfos FHS type LPS 40-6s/130 with 3 speed settings on the side. It is located next to the cylinder in the loft. Both pump and cylinder are brand new.

The boiler is a Worcester Bosch condensing boiler which is situated in the kitchen.

PigletJohn Sun 29-Oct-17 11:41:49

Can you check that part number? I think FHS is a chinese budget brand making copies of Grundfos. I found a listing where it is painted the same shade of red.

PigletJohn Sun 29-Oct-17 11:47:55

Could it say "UPS" not "LPS?"

And 40-60?

JB321 Sun 29-Oct-17 11:53:53

Just double checked.
On the black side it says FHS PUMPS

Underneath that is says
TYPE LPS 40-6S/130. Definitely LPS and and S after the 6


PigletJohn Sun 29-Oct-17 12:10:01

One of these then

Not one of these

I think I can guess what the difference is sad

JB321 Sun 29-Oct-17 17:33:59

Yes PigletJohn it is the eBay version which I’m guessing may be seen as an inferior product?
Do you think I’m likely to cause any issues/damage if I try running the pump on setting 2 for a while and see what happens?

PigletJohn Sun 29-Oct-17 17:43:43

I don't think so.

johnd2 Sun 29-Oct-17 18:07:12

I can't see your profile because of your privacy settings.
Use the paper clip to attach images to the thread.

PigletJohn Sun 29-Oct-17 18:19:38

I don't think profiles are visible on here.

If you aren't using the app (e.g. on a desktop) you can attach pics using "browse" beneath the message entry panel, and navigate to the directory where you have saved your pic.

I am of the opinion that the budget pump might have loose bearings, or an out-of-balance impellor, which could cause it to run noisier than the more expensive Grunfoss.

The ebay one has a 14-day return warranty, the Grunfoss one has a 2-year guarantee.

JB321 Sun 29-Oct-17 18:30:08

Think I’ve finally sussed it! confused

PigletJohn Sun 29-Oct-17 19:13:06

brace that long vertical pipe rising from the pump. It needs a sturdy piece of wood, screwed at both ends to the roof timbers. I'd try to brace it twice, once near the top and once near the pump. Also clip the lower pipes to the floor.

A good source of strong timbers is decking boards, which are about £3.50 for a cheap one.

The foam pipe lagging will prevent vibration passing into anything the pipes happen to touch. For a narrow gap, you can shave it down with a steak-knife.

You can pick up some screw-fitting pipe clamps. If you need a long stem between the wood and the pipe, get Munsen Rings (you need 22mm). They are a bit expensive.

Drill pilot holes for all screws for a strong fixing without splitting.

JB321 Mon 30-Oct-17 09:00:47

Thanks for all the advice.
Looks like I’ve got some work to do the weekend! smile
Fingers crossed it works!

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