Grant R290 Noise During DHW

Hardware Heatpump
1

Hi all, I’ve got a strange bang/groan noise occasionally when running the DHW cycle on a newly installed Grant R290 9kw. Until 5 days ago the ASHP ran only DHW, but we had a day where internal temps were a bit low so I thought I’d turn the CH on, somewhat for heat and somewhat to just get used to controlling the system.

Since that day I’ve had 3 occasions where the DHW charge will make a pretty horrible bang/creak sound - I think something is going a bit weird with the controller, here is the first time it happened:

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Notice how the system goes to DHW, then back to CH, then back to DHW? The bang occurs when moving back to DHW, so around the 23:38 mark in this instance.

Looking back before I had CH enabled, I have not seen one example of it doing this strange dance, and I never heard a bang.

I noticed something, possible this is co-incidence, but I have other periods during normal CH operation where the flow rate goes to the exact same amount - 30 l/s:

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These windows are accompanied with the compressor going to 60hz, I read the manual which says this:

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Now, these windows during CH seem to be about 7 mins and I think the compressor Hz matches the state described above.

This might be reaching a little bit, but the compressor indeed will be running at very low levels for a lot of the day right now - 15Hz for the vast majority, and it does seem the 3 occurrences of these bangs happen when DHW runs when CH would otherwise be running.

Anyone have any ideas or input? Not sure if I’m correlating two unrelated things, but it seems a little bit suspicious.

@glyn.hudson @Durruti you may have some ideas as I know you have Grants, in fact Matt, I notice you have a similar thing in your data:

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1 Like
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I have the 9kW unit, and have not noticed the bang you mention (yet), though since I started CH use I do see the regular oil recovery spikes (every 3+ hours in my case, not actually 4). Obviously never happened with DHW only, since the compressor mostly runs full bore then. my cutover from CH to DHW happens mostly at 4AM (cheap power), since one during the day would quite likely find CH off anyway, right now.

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Cheers Dave, is your system on heatpumpmonitor? I notice a strange shift - it goes from CH to DHW, then after 8 mins (ish) back to CH and then back to DHW. I actually get two bangs now - one on the initial switch to DHW, my suspicion with that one is that the pump is running so there is water hammer whilst the valve is switching (because the pump is running). The second one - well I suppose that maybe could be the issue because the pump is running much harder, the second bangs are very loud!

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No, not on heatpumpmonitor.org. I was awake at 6am, with streaming cold, and heard the ‘bonk bonk’ noise. Only happens if CH was active when dhw starts. I suspect is the 3WV trying to switch with 1.3 bar of water pump going thru it.

The second switch I can explain.. DHW runs the compressor up to max, which is when it is going to frost up. At that point, maybe a few minutes in, you get a fan stop, and the valve flips back to CH for defrost cycle, then back to DHW. Needs 5c outside and high humidity for best (worst) effect. Can monitor it all in HA (negative COP and all, though econet merely says zero).

Since I have manual control (via HA) I could stop CH heating (and thus the water pump) before I turn dhw on, but that won’t help with to/from defrost valve switches, and won’t work for most people who use hysteresis and the controller to start dhw cycle. Maybe there is a firmware fix, or maybe a better 3 way valve?

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Mine happens even when it’s warm outside though, I observed it happening the other day when it was 12c outside.

So what I’ve done is used the scheduling to turn CH off half an hour before DHW and this has totally stopped (so far anyway) the second “about 8 minutes in” weird switch / big bang, so it seems if not running CH directly before DHW it doesn’t happen.

Mine makes two noises basically:

  • A thud on very initial switch to DHW - water pump is always running so assume this is some result of that, it’s worse sometimes though, unsure why
  • The 8 minutes in big bang - as mentioned above

What valve are you on? I am going to get mine swapped - mine is an EPH Divert Pro (B328DIv) which from what I have read is potentially not very suitable for this heat pump. It seems ideally it should be a ball valve or at the least have a bypass (mine has no bypass).

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This is my valve, which clunks

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This is a sprung return valve, these valves slam shut with a spring mechanism. This is what will be causing the banging. They are not the best choice for a high flow rate heat pump. Rotary valves e.g ESBE are a better option.

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The EPH divert pro is also a sprung return valve.

I fitted an ESBE MBA132 on my system, which is a rotary valve. It’s totally silent when it moves from CH to DHW and back again.

This is a good video from @MWPHS explain how to wire it:

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@glyn.hudson do you have a bypass on your setup? I don’t right now. I’m asking the installer to move to an Esbe VRG231 as I don’t have room for the MBA132 or the Honeywell, and I’m wondering whether I should have a bypass as well. Looks to me like others with decent valves don’t.

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No, a bypass shouldn’t be needed on a heat pump system, there’s no reason for it.

The VRG231 is a good valve.

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@GSV3MiaC Did you say in the other thread that grant themselves fitted this? I’m curious because apparently the HPID120 is supplied with Grants “UK Heat Pump Installation Pack C”, so if Grant themselves fitted yours (i.e not their sortof “official” valve) that seems surprising.

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No it was not a Grant fitment, it was picked by my installer, though I am informed the Grant one is, also sprung return, so could have the same problem.

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Well I’m getting an Esbe fitted tomorrow so hopefully I’m all good after that. I’ve been having to turn the heat pump off via schedule 30 mins before to avoid the defrost during DHW which is causing the main issue

1 Like
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I’ve been using home assistant to turn ch off just 2 mins before dhw starts, and my clonking has gone away. Dont see (hear) it happening during dhw run, even if the pump does a defrost (which it often seems to, when the compressor ramps up hard), though to be fair I am often asleep at nighttime dhw reheat. Maybe defrost valve change over doesn’t happen at max water pump speed, or maybe I just missed it. My esbe valve will wait until spring drain Down. :slightly_smiling_face:

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I’ve had mine swapped, I would say I don’t hear it any more but I have noticed that it hasn’t been doing the weird defrost 10 mins after switch to DHW, probably due to me upgrading the controller with the latest version and switching to quiet mode level 2. I suppose mine did do a small clonk on initial switch to DHW and it hasn’t been doing that, so that’s a plus.

So, I would say the valve is working but I’ve no clue! It looks pretty though…

I’ve also had a spirovent fitted which (touch wood) has fixed my air issues, though again… I have also changed something else at the same time by reducing my DHW temp, so that will certainly have affected things. That said, whenever I used the bleed valve on my filter it would always have air in, and now it never does, so it has probably worked.

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in fact, @glyn.hudson are you ok to review my system for inclusion on heatpumpmonitor.org? I’ve put it on now it seems to be behaving :slight_smile: (it is currently waiting for review)

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Great. I’ve also noticed my 9kW HP290 often does a defrost at the beginning of a DHW cycle. I’m also running quiet mode. It doesn’t seem to be a big problem, overall DHW gets good performance.

Done: https://heatpumpmonitor.org/system/view?id=862

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Cheers!

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Just in case anyone else gets this - in summary, I didn’t realise what I was seeing was a defrost cycle (too green with the heat pump at that time!), which for some reason this unit does about 10 mins in to a DHW run under certain circumstances, I assume to do with coil temp, effectively for me it did it if space heating was running immediately before, although I did notice it happen even if it has been running as much as 15 minutes before. It seems not to happen when I have quiet mode enabled, maybe again due to lower coil temp due to lower compressor hz? All guesses really, ultimately “it went in to defrost”.

Couple this with an incorrect diverter valve being used in my installation (an EPH divert pro, which does not seem suitable for the task) coupled with no bypass. Seems the EPH either temporarily blocked the flow, or slammed to one side due to a high flow of water, or both. Either way, it was not suitable for my install.

Have replaced with an ESBE valve which has at least solved the clunking when switching to DHW, I haven’t yet seen the defrost so I’ll update this resolution if it turns out to be wrong, but I would be very surprised if that is the case.