Something tells me that fastening an otherwise opening window to remain shut is not going to be acceptable for the regulations! I too had very little scope to move the siting of my ASHP short of using extensive wiring and pipework to site it down the garden. I could not have a Vaillant ASHP in my situation as there is a door and an opening window plus drains and went with a Daikin Monobloc with R32 which was permissible and available. Regards, Toodles.

Propane (R290) sinks, under a window is allowed so far as I am aware.

@jamespa From the suppliers I understand this regulation may change due to the small R290 charge. However I also have a drain close by!  Frankly I would think what the drain contains is more likely to generate methane than the ASHP would leak. Then with this and the battery placement regs I am beginning to wonder why I am bothering. These ASHP machines are so damn big the Samsung R290 one is a bit smaller.

Posted by: @jancold

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@jamespa From the suppliers I understand this regulation may change due to the small R290 charge. However I also have a drain close by!  Frankly I would think what the drain contains is more likely to generate methane than the ASHP would leak. Then with this and the battery placement regs I am beginning to wonder why I am bothering. These ASHP machines are so damn big the Samsung R290 one is a bit smaller.

They are large because a) they have to move a lot of air and b) they need sound insulation.  That is probably not going to change a lot!

I have also seen it said many times that the regs may change because of the small R290 charge, given that we have unrestricted amounts of methane piped into our houses without worrying too much, and can store 13kg containers of propane on a boat or caravan, the fuss over the small amount in an ashp is out of proportion.  But that is true of several things about ASHPs, its almost as if there is a lobby that doesn't want them to be installed!

Notwithstanding this, you say that the best place for you is under a window and the regs don't, so far as I can see, stop you putting it under a window.  Could the drain be blocked up or moved?  Personally I would be reluctant to compromise location on the basis of a drain unless it was really impossible to divert it.

I am in a similar position and my R290 ASHP will be going under the window and a drain moved/blocked up (if I can get planning consent, sadly my LPA, run by the 'Green' party', has policies which make it almost impossible to install a heat pump unless its under permitted development).

We dodged the bullet since we had a non-opening window fitted where we hope the pump will go. It was by accident rather than advanced knowledge of the non-opening aspect. We had it non opening because of security on the ground floor.

The building regs are inconsistent between fire, ventilation and insulation. I discovered the non ventilation aspect when researching the position the central heating vent had to be.

BTW it isn’t as expensive  to change a window panel as a whole frame!

@judith Interesting. Not all my windows on the ground floor  open but they look like they could, I forget the term, frame within frame?. The non  opening ones are screwed to the frame and the glass fitted. So I can remove the glass on this one and screw it shut, and disable the handle. Since I fitted all my windows (before Fensa) I am familiar with them. The next thing is what to do to make the drain acceptable. Some polystyrene and a thin  covering  of concrete so I can open it later if I want!

@jancold I suspect all they’ll look at is whether there is a handle!

Posted by: @jancold

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@judith Interesting. Not all my windows on the ground floor  open but they look like they could, I forget the term, frame within frame?. The non  opening ones are screwed to the frame and the glass fitted. So I can remove the glass on this one and screw it shut, and disable the handle. Since I fitted all my windows (before Fensa) I am familiar with them. The next thing is what to do to make the drain acceptable. Some polystyrene and a thin  covering  of concrete so I can open it later if I want!

Who is telling you that under a window is unacceptable and why?  I am concerned because I am being told that underneath a window (opening or not) is ok (and that is clearly what the vaillant manual implies).

What regulation are they quoting. 

@jamespa this morning we were told that up to the window cill is ok, in Vaillant’s new advice.

my other comment would apply if anyone considered that the propane in an ashp was equivalent to storage of lpg cylinders (surely not!)

In which case distances to opening windows do apply. You never know when you’re going to get a jobs-worth though. Common sense is rare not common.

Posted by: @judith

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@jamespa this morning we were told that up to the window cill is ok, in Vaillant’s new advice.

my other comment would apply if anyone considered that the propane in an ashp was equivalent to storage of lpg cylinders (surely not!)

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In which case distances to opening windows do apply. You never know when you’re going to get a jobs-worth though. Common sense is rare not common.

New advice from Vaillant is consistent with their own documentation  

I can see an argument for there being a gap above an LPG cylinder.  These are under significant pressure and have a significant charge and the most likely failure point is the valve right at the top.  So the gas could just be projected upwards a bit before falling.  The diagram allows 300mm above (but that still means you can store a short LPG cannister, eg 13kG , below a window.

In an ashp the failure is likely to be contained within the box so gas will start falling before it exits the box.  Also the charge is much smaller.

As you say common sense is rare not common; but the Vaillant manual (don't know about others) is very clear to my mind in showing the protection zone extending to the side but not above the unit.  Installers are sticklers for slavishly following the manuals, or is that only when it suits them?.

@jamespa I notice they talk of untrapped drain or cellar entry. I'm pretty sure my rainwater drains connect to the main sewer so surely they must have a trap? So they should not be a problem?