As a secondary, how is your water temperature, as you know my sensor was moved to bottom of cylinder yesterday, 2 hours gets to 46 degrees, 3 hours gets to 46 degrees, just boosting to see if i can get to 50? I’m not convinced it will get there. It might shall see!! 
just wondered if people get to 50 on the cosy 12?

@l2jad Must admit my water is lovely and hot. It is switched on for an hour only and gets to temp quickly. Set at 50.

When sensor was at top it got hot very quickly. Not over bothered as we have a lot of hot water. Just seems to get to a temperature and doesn’t get hotter. 

i’m guessing over the next few days as water in tanks start point is warmer it will sort.

pre move of sensor two showers and water was cold 😉

Posted by: @l2jad

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As a secondary, how is your water temperature, as you know my sensor was moved to bottom of cylinder yesterday, 2 hours gets to 46 degrees, 3 hours gets to 46 degrees, just boosting to see if i can get to 50? I’m not convinced it will get there. It might shall see!! 
just wondered if people get to 50 on the cosy 12?

The Cosys are/should be capable of heating the tank of water to over 50c, including doing a legionella cycle if you want it.  If it's heating a full tank of cold water it may take more than 2 hours, I don't know, but I assume your schedule for hot water is set with the desired temp to reach.  We have ours set at 45c, usually reaches 46c/47c in one hour; never run a legionella cycle.  There is just the two of us with a 250L tank so we don't get anywhere near emptying it with two showers a day and typical other hot water usage.  I'd say it is never heating from fully cold though, even if my wife chooses to have a bath.

The fact that it is only reaching 46c after two hours and no difference after 3 hours is a bit strange though.  However, I would add this: you can only validly check the temp the app is reporting in the morning BEFORE anyone uses any hot water AND nobody is using hot water whilst you are heating it.  Once that happens, the app is reporting the temperature of the water mixed with cold - e.g. our shower has only been used once today and there's been a bit of hot water usage rinsing cups and brushing teeth: the reported temperature in the app is 26.4c!  It would have been 46/47c first thing and there is still plenty of hot water left at that temperature.

Hi all,

Just an update on where we are with the "Constant Hum" issue. An Octo engineer attended on the 24th February and discovered that one of the tanks (I believe it's the volumizser) had not been bled properly and was half full of air.

Almost a week later the internal Grundfos circulation pump finally stopped. The reduction in noise was so significant that I noticed it immediately from an upstairs bedroom. At first I wondered if the pump had burnt out from running constantly but I triggered a heating boost through the app and it started up again. So it looks like that problem has been resolved.

Unfortunately we are still disappointed with the amount of noise coming from the Cosy 12 itself. Due to the warmer weather the heat pump is not working as hard as when it was first installed but this morning whilst it was heating the hot water it was still well above the advertised 60dB level.

Hope this helps

@dedwards I'm glad to hear some your issues have been resolved.

Unfortunately none of my issues have been resolved so far. After the umpteenth visit from a Octopus engineer, they rebalanced and bled the radiators in the hope that it would reduce the noise. They've also said they'll change my circulation pump on Wednesday, and that should help reduce the noise.

@Mars, I remember you were quite interested in the buffer/volumizer situation. They insist that a buffer is the right setup for my system, given the layout and pipe lengths and angles.

They've so far offered no solutions for the sound from the outside unit, the water hammer (which was introduced with the installation of the heat pump), nor have they offered to even investigate the ringing/hissing/resonating from the radiators and pipes. 

The resonating is so bad that I can't sleep comfortably anywhere in the house. I have developed some kind of ear condition from all the noise. I get an intense burning sensation in my ears after a few minutes near any moderate/high noise environment. I know it's the resonating that's doing the damage, because if I spend some time in my study, the damage is mainly to one ear, which faces the wall with the pipes inside it.

I also found that if I get out of the house for a couple of mins, the pain in my ears go down a lot. I have now resorted to spending as much time as possible outside the house, mostly working in libraries. Sometimes I just go for a walk at night, just to feel some relief from the buzzing and ringing.

This has taken an immense mental and physical toll on me. I have threatened to write to MCS/HIES but never followed through. As of this week, I have threatened to have a third party heating engineer rip the thing out and install a boiler.

I have contacted a local heating engineer who does boilers and heat pumps, to have a look at the system. I am now considering paying up Octopus, and then spending extra to have someone else replace it all with a boiler, and another set of smaller radiators.

I never imagined installing a heat pump could go so wrong.

Posted by: @razz

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I have contacted a local heating engineer who does boilers and heat pumps, to have a look at the system. I am now considering paying up Octopus, and then spending extra to have someone else replace it all with a boiler, and another set of smaller radiators.

If you do go down this route:

• No need to switch to smaller radiators, you can just operate the boiler at a lower temp which will be both more efficient and more comfortable.
• If the water hammer is in your hot or cold water system not the central heating  then swapping to a boiler WONT fix that unless the plumber also reverts you to an indirect water system, which unless you instruct them specifically they are almost certain not to do.

@jamespa Thanks for the heads up on the boiler vs HP radiator sizing. Not having to replace the radiators again would be a big help.

You've got the right person. The water hammer started with the installation of the HP. I did think mine was a shared water feed, but I don't actually know. I have a separate meter. I do remember you pointing out that the issue is unlikely to be related to the HP. 

After reading some stuff on here, I thought mine was an indirect system, but the Octopus installers assured me that it was already a mains supply system. So that's not a likely culprit for the issues.

BTW, one of the possible reasons given online for the hissing, resonating sounds is that radiators need higher flow rates with heat pumps, which could be the cause of this strange resonating sound throughout the house. Do you think that holds up?

Also, reinstalling a boiler just doesn't seem wise in the current climate, and the trajectory of technology. I imagine I'll have to install an electric heating system sooner or later.

If Octopus were at least a little more agile(🙄) with their responses, I might get the HP working properly or replace it with a boiler. Instead, I'm left to suffer while they give me appointment weeks down the line.

Posted by: @razz

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After reading some stuff on here, I thought mine was an indirect system, but the Octopus installers assured me that it was already a mains supply system. So that's not a likely culprit for the issues.

Are they saying that your original system (pre heat pump) was direct (mains pressure).  If so you wouldn't have had any tank in the loft and you shouldn't have seen a change in water pressure at the taps when the new system was installed.  Was that the case?

Either way if its water hammer in the DHW or cold water its not a function of the ASHP, so switching to a boiler wont fix it!

Posted by: @razz

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BTW, one of the possible reasons given online for the hissing, resonating sounds is that radiators need higher flow rates with heat pumps, which could be the cause of this strange resonating sound throughout the house. Do you think that holds up?

It is true that heat pumps are generally designed to have higher flow rates because they are generally designed to operate at deltaT.  

However if correctly designed and properly bled then it shouldn't be a major problem. 

Hissing is most likely air trapped.  Have you bled the system several times, thoroughly?   From what I recall the main noise source is the secondary pump.  Frankly the best would be to design it, and the buffer, out.  Perhaps Octopus can be persuaded to do that.  Alternatively some rooting around in the region of the pump may reveal something you can either bolt down or unbolt to reduce the transmission.  Possibly putting flexis on the secondary pump might help, or noise insulation around it.  These things can be difficult to track down but its a bit radical to chuck it all out for a noisy pump that could almost certainly be relocated, replaced with a quieter one (I have heard it said that Wilo are quieter than Grundfoss, but have no evidence to back this up) or designed out.

Posted by: @jamespa

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Are they saying that your original system (pre heat pump) was direct (mains pressure).  If so you wouldn't have had any tank in the loft and you shouldn't have seen a change in water pressure at the taps when the new system was installed.  Was that the case?

 

Yes, that's right. 

Posted by: @jamespa

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Either way if its water hammer in the DHW or cold water its not a function of the ASHP, so switching to a boiler wont fix it!

I guess it could really just be coincidental that the hammering started at the same time as the HP install. Maybe something got kocked loose while they turned off the water and turned it back on.

Posted by: @jamespa

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Hissing is most likely air trapped.  Have you bled the system several times, thoroughly? 

I have not. Octopus engineer did it on Friday, when he did the rebalance. It seems to have made things worse with the ringing, maybe I'm more sensitive to it now, cos of my ear issue. I'll have a go at bleeding the radiators tomorrow.

IIRC, you told me how to balance the radiators myself, and Octopus told me not to, as it's a complicated process.

Posted by: @jamespa

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From what I recall the main noise source is the secondary pump

It was, which is why I've been sleeping in the front living room, away from the noise, but lately the radiator ringing or resonance (not exactly whistling), got too much in that room, and I fled back my bedroom, as the hum of the circulation pump is less painful than the radiator resonance.

Posted by: @jamespa

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Perhaps Octopus can be persuaded to do that.  Alternatively some rooting around in the region of the pump may reveal something you can either bolt down or unbolt to reduce the transmission.  Possibly putting flexis on the secondary pump might help, or noise insulation around it.  These things can be difficult to track down but its a bit radical to chuck it all out for a noisy pump that could almost certainly be relocated, replaced with a quieter one (I have heard it said that Wilo are quieter than Grundfoss, but have no evidence to back this up) or designed out.

Octopus have said the buffer is necessary, not even going to change to a volumizer. They said they'd install a new circulation pump, but didnt mention anything else.

The issue isn't just the circulation pump, every part of the system is nosy, and as of a few days ago, the ringing from the radiators is the main issue. It's literally causing ear damage, and it's in every room, so I can't escape anywhere.

I found this thread on reddit:
https://www.reddit.com/r/ukheatpumps/comments/1r97882/noisy_home_not_the_heat_pump/

Does this seem like something I should ask from Octopus?
https://www.reddit.com/r/ukheatpumps/comments/1r97882/noisy_home_not_the_heat_pump/o6engbb/