ProDave Posted August 27, 2018 Share Posted August 27, 2018 Telford 300L stainless, unvented cylinder with heat pump input coil, heated by LG 5KW air source heat pump. Was fine when first comissioned. But for the last week or so, when the heat pump is running heating the tank, the tank is making a hell of a racket. I can best describe the noise as like an old PC fan with worn out bearings grinding and rattling away. The noise is coming from within the tank, not from the pipework. So it has to be something like the heat input coil inside thew tank vibrating and resonating. It did not do this to start with. Nothing has changed. Flow rate is about 15L per minute, I can't reduce that otherwise the heat pump will trip, but even if I do reduce it, it does not stop the noise. I have tried increasing and reducing the pressure (of the heating loop) and that made no difference (can't see why it would but it was something to try) Any ideas. This is driving me nuts. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 27, 2018 Share Posted August 27, 2018 How far away is the heat pump from the tank and how well decoupled are the pipes at the heat pump end? I found that copper pipes were really good at transmitting vibration, even when going through walls and wrapped in insulation, and ended up fitting long anti-vibration loops of flexible pipe to decouple the heat pump from the copper pipes going into the house. Link to comment Share on other sites More sharing options...
ProDave Posted August 27, 2018 Author Share Posted August 27, 2018 I don't think it is the heat pump. That's about 10 metres away, and connected with flexi pipes. But crucually there is a short delay before the fan and compressor starts up, and the noise in the tank starts immediately the pump starts. So it is just the water flowing through the pumps that starts the tank making it's noise, and nothing changes when the fan and compressor start. Link to comment Share on other sites More sharing options...
Ian Posted August 27, 2018 Share Posted August 27, 2018 @ProDave Air in the system somewhere? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 27, 2018 Share Posted August 27, 2018 Could there be air in the primary circuit that's causing the noise in the coil? Link to comment Share on other sites More sharing options...
PeterW Posted August 27, 2018 Share Posted August 27, 2018 When I purged a HP coil I got a fair bit of noise from the tank - worth checking for air or at least checking any AAV is open correctly. Link to comment Share on other sites More sharing options...
ProDave Posted August 27, 2018 Author Share Posted August 27, 2018 Automatic air bleed valves on all the high points of the pipework. It did take a while for the last of the air to gradually bleed out, but the bottles are not collecting any more air now and the pressure has stopped dropping, so I am confident there is no air. I was wondering if the LACK of air now is what started it making the noise. Link to comment Share on other sites More sharing options...
Alexphd1 Posted August 27, 2018 Share Posted August 27, 2018 We once had a sticky valve on the pressure reducing valve that comes with a UVC. Made a slightly different nose as you are describing but worth checking. Link to comment Share on other sites More sharing options...
ProDave Posted August 27, 2018 Author Share Posted August 27, 2018 The noise is not related to domestic hot water flow. It is the sealed system primary flow from the heat pump to the heat input coil that is causing the noise. Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 27, 2018 Share Posted August 27, 2018 Whilst it is running and making the noise, go around the various sections of flow and return pipework and grab hold of them tight, pushing or pulling as forcibly as possible. Get someone to listen whilst this is being done, all the way back to the HP. Resonance thats generated in such a system will eminate from very strange places, often not where they're being generated. Number one culprit would be the NRV or the inline strainer. Grab the zone valve also, and see if thats causing it. Link to comment Share on other sites More sharing options...
joe90 Posted August 28, 2018 Share Posted August 28, 2018 Any luck Dave? (I am getting worried as I hear horror stories about people’s ASHP and I am yet to fire mine up ?) Link to comment Share on other sites More sharing options...
ProDave Posted August 28, 2018 Author Share Posted August 28, 2018 No, no luck. I can hold, push, pull, wiggle or otherwise manipulate the pipes and it makes not a jot of difference. I can't feel any vibration in the pipes. It's not affecting operation, just making me think I need to sound proof the airing cupboard that will eventually be built around it. Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 28, 2018 Share Posted August 28, 2018 On 27/08/2018 at 09:00, ProDave said: Any ideas. This is driving me nuts. Was this purchased new in the BH-Telford 'deal'? Ask for it to be replaced. Link to comment Share on other sites More sharing options...
ProDave Posted August 28, 2018 Author Share Posted August 28, 2018 39 minutes ago, Nickfromwales said: Was this purchased new in the BH-Telford 'deal'? Ask for it to be replaced. No it was purchased new 3 or 4 months ago direct from Cylinders 2 go. Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 28, 2018 Share Posted August 28, 2018 2 minutes ago, ProDave said: No it was purchased new 3 or 4 months ago direct from Cylinders 2 go. Return it as faulty Link to comment Share on other sites More sharing options...
ProDave Posted August 28, 2018 Author Share Posted August 28, 2018 6 minutes ago, Nickfromwales said: Return it as faulty Are you serious? Swapping it was not on my "to do" list. But time to have a chat with Trevor? Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 28, 2018 Share Posted August 28, 2018 If its that noisy, and your as sure as you can be that its coming from the HP coil, then too damn right. What if it gets worse? The last time I had a warranty claim with telford, prob over 8 years ago ( and not really a fault more my blagging as the EV had gone and popped the UVC ) they dropped off the new one and waited to collect the old one. 1 Link to comment Share on other sites More sharing options...
ProDave Posted October 5, 2018 Author Share Posted October 5, 2018 So I have finally got around to trying to investigate this. The one thing I wanted to eliminate before I contact the cylinder manufacturer, is the automatic bypass valve. This is situated in the airing cupboard between the flow and return pipes, immediately before the 2 port motorised valve for the cyilinder, this puts it as far from the heat pump as possible. Adjusting the ABV does not stop the cylinder noise, but it goes through a transition as you close the ABV down you momentarily get silence before the noise starts up again a few seconds later. It is impossible to find a setting where it remains silent. To replace the ABV is not easy, will need a bit of pipework stripped down (didn't think that through enough) so I pondered what I could do to eliminate it. Well what I have done, is remove the top of the ABV, remove it's spring and plunger and put it back together. So now it won't be operating as an ABV but as a permanent bypass and probably way too much bypass. The result. Totally silent hot water heating. Hot water still seems to heat up okay in spite of almost certainly too much bypass. I assume convection ensures enough flows through the heat input coil rather than all bypassing? No detrimental affect noticed on space heating. Even with too much bypass, the manifold pumps seem to ensure enough circulates through the UFH and it maintains it's temperature. What now? Leave it like that? Replace with a new (different make) ABV? replace with a gate valve to give manually adjusted fixed bypass? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 5, 2018 Share Posted October 5, 2018 Good that you've found the cause. As it's working I'd leave it. The chances are that your pipe work may well have created a low loss header, where there is a hydraulic preference to go straight across the top of the bypass. Link to comment Share on other sites More sharing options...
ProDave Posted October 5, 2018 Author Share Posted October 5, 2018 7 minutes ago, JSHarris said: Good that you've found the cause. As it's working I'd leave it. The chances are that your pipe work may well have created a low loss header, where there is a hydraulic preference to go straight across the top of the bypass. You could be right. That is the flow and return both coming up out of the floor and 3/4 of the way up the cylinder to where the coil connections are. The ABV is connected between these just above the floor. Above that and to the right is the 2 port motorised valve for hot water The flow rate is relatively high at 15l/min so water is indeed more likely to go straight on, rather than make a 90 degree turn to pass through the (now nobbled) ABV. My guess is the noise was an unfortunate resonance thing, with the workings of the ABV oscillating at the resonant frequency of the coil and making it vibrate. No ill effects so I will see how it goes. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 5, 2018 Share Posted October 5, 2018 With those straight runs at the tees at either end you have two hydraulic switches that will preferentially flow straight across, so I'm sure the system will work fine without the valve doing anything. Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 6, 2018 Share Posted October 6, 2018 Last one I had issue with was a non return single check valve on the hot return. As it was directly after a 90o bend the water was causing the valve to oscillate and just moving it a few inches further from the bend made it go silent. Funny thing, water ( or hydraulic dynamics ? ). Link to comment Share on other sites More sharing options...
ProDave Posted October 6, 2018 Author Share Posted October 6, 2018 4 hours ago, Nickfromwales said: Last one I had issue with was a non return single check valve on the hot return. As it was directly after a 90o bend the water was causing the valve to oscillate and just moving it a few inches further from the bend made it go silent. Funny thing, water ( or hydraulic dynamics ? ). So the message to anyone reading and about to do their plumbing is DO NOT put the ABV right in between two 90 degree bends. All seems to be working fine and silently now, both HW and heating working as they should. So I will leave it as it is. Link to comment Share on other sites More sharing options...
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