Yeah, just that really. I originally thought we would position it miles away (well 25m). But that wouldn't be so convenient and we couldn't install it until close to the end of the build as that's where the site hut is. We could position it about 7m from the kitchen and guest bedroom. My wife is fairly sensitive to noise. Would 7m work, do you think?

It very much depends on the noise output of the heat pump. This is always found in the specifications and you can use the mcs sound calculator to provide results for you. Measure from the heat pump to 1m perpendicular to the window door in question.

Also depends on your windows and whether you routinely sleep with them open? Good windows, usually closed will block most normal heat pump noises (in a well specified/setup system)

>>> mcs sound calc

Ah, good point.

So,

i.e. 52 + 10 log10 ( 3 (for grass) / (4 . pi . 5^2 )) - 0 (5m because distance is to 1m point and leaving a 1m gap to the hedge)

= 31.8 dB(A)

So, within the MCS limit of 37dB(A).

But, I have no idea really how loud that is.

Windows will be 21 degrees triple glazed but we do sleep with the windows open. Also, this is a quiet country location, so there's not much background noise.

Also makes a big difference how you actually run the heat pump, if slow and steady on WC it will just modulate down and be almost silent except for the coldest days.

But you will also be running flat out doing DHW reheats, so timings makes a difference. And if you run in cheap time periods mostly, your heat pump could run at full load for an hour or 2.

If your having a shed, stick it behind that. Out the way a d noise has a barrier.

We always used to have windows open but have found that with mvhr we prefer not to.

Ours is 12m away from house....you can come listen!

1 hour ago, Alan Ambrose said:

Windows will be 21 degrees triple glazed but we do sleep with the windows open.

@G and J

Would I be right in thinking you can’t hear it at all?

Not at all. Never in the house, and only if standing on top of it in the garden, and then it's pretty quiet.

Mine is 400mm away from the outside of the bedroom wall, icf wall,

you have to walk outside and get to within 1m of the heat pump to actually know it’s running.

Panasonic unit.

There are different types of noise. There's the noise of the fan moving air, then the vibrational noise of the compressor, pump, and fan.

You can reduce transfer of vibrational noise to the house by mounting the unit on shock absorbing mounts, on a frame that is not mechanically coupled to the adjacent wall or slab (it goes without saying you wouldn't mount it onto the wall). Also, many years ago someone (Jeremy Harris, I think) mentioned that flexi connections transfer vibration/noise unless they're installed with sufficient slack (e.g., with a significant downward bight), so keep that in mind.

The noise of the air itself is much less likely to wake someone up.

3 hours ago, Russell griffiths said:

you have to walk outside and get to within 1m of the heat pump to actually know it’s running.

Panasonic unit.

Same - we have an 11 year old, 5 kW Panasonic Aquarea unit. It's so quiet when heating the house that I generally can't tell whether it's on unless I feel for the draft from the fan. To be fair, I'm not generally out there when it's producing DHW in the cheap period leading up to 5:30 in the morning, when I imagine its louder. We also have large trees right beside us, so if there's any wind at all, the sound of the leaves rustling completely covers any sound from the unit.

We're lucky enough that ours is installed on the other side of an attached garage, so we don't hear it at all.

3 hours ago, Russell griffiths said:

Mine is 400mm away from the outside of the bedroom wall, icf wall,

you have to walk outside and get to within 1m of the heat pump to actually know it’s running.

Panosonic unit.

even at less than 4°C ? The fan speeds up giving a low pitched wooshing sound and could be intrusive at night next to a bedroom window.