Anyone fitted a pre-charged aircon unit?

[Miek]

47 minutes ago, JSHarris said:

I've ended up buying a vacuum pump and set of gauges and hoses for less than £70 delivered

That is a lot cheaper than i had expected. I wonder how good a vacuum it will pull? Look forward to hearing from you.... 

[Jeremy Harris]

7 minutes ago, Miek said:

That is a lot cheaper than i had expected. I wonder how good a vacuum it will pull? Look forward to hearing from you.... 

 

It was a lot cheaper than I expected, too!   The spec says it will pull down to 3 Pa to 5 Pa, which should be fine.  It's a fairly standard single stage rotary vane pump, running in an oil bath, so not much to go wrong, really.  The main downside is that it's only 1/4hp, so will be a bit slow to pump the system down.  As this is a DIY job on a small system I doubt it will be an issue, plus I'm in no hurry, so a few minutes longer to pump the system down is neither here nor there.

[Jeremy Harris]

Just to close this off, I finished commissioning the Toshiba unit this afternoon (good timing, probably the hottest day of the year).  It was delayed by me not realising I needed an adapter to allow the pressure gauge I'd bought to fit the test port on the outdoor unit - took a week to arrive.  It was also a bit of a palaver hoisting the 23kg outdoor unit up on to the wall bracket.  Apart from that these things are pretty easy to connect up and get going.

 

I bought a package which consisted of an indoor unit (with remote), an outdoor unit, 4m of insulated pipework, with pre-flared ends, and a wall mounting bracket for the outdoor unit.  I had to buy a length of 3 core 1.5mm² flex, plus a length of outdoor-rated 4 core 1.5mm² flex.  I also chose to buy a vacuum pump, pump oil and a set of test gauges.  Total cost for everything came to:

 

Toshiba MIRAI RAS-10BKVG-E 2.5Kw/9000Btu outdoor and indoor unit, inc. shipping and VAT £574.08

4m pipe set  £62

Wall mounting bracket  £21.15

Trunking for pipework and cables  £32

Cables  £15

10m of 16mm bore water drain pipe  £16.99

 

Total for parts used in installation £721.22

 

In addition, I had to add another double gang outlet to the upstairs ring final, tucked away in the service room.  I happened to have a spare metaclad one, and the cable was easy to get at, so it was only a ten minute job.  The unit plugs in and works fine on a 10 A fuse in an ordinary plug (the indoor unit is designed to accept flex, rather than T&E).

 

I also chose to buy a vacuum pump for £42.99, plus a set of test gauges for £25, some vacuum oil for £6.25 and an adapter to convert 1/4" to 5/16" for £5.18, so £79.42 on tools.  I'd be happy to lend these out if anyone wants to have a go at installing one of these things - not easy to post, though, as the pump is now full of oil.

 

Installation was not difficult, but hampered by doing the job on my own.  Coming up with a way to hoist the outdoor unit up on to the wall bracket, mounted just under the eaves, took the best part of a day, and was a real faff.  The rest was pretty easy, run a duct through the wall (a bit of 68mm drain pipe is ideal), screw the indoor unit to the wall and hook it into place.  Carefully unroll the copper pipes and feed them through the wall and connect them to the short pipes that come out of the back of the indoor unit.  Connect up the 16mm drain pipe and run that outside and down to just above ground level.  Connect the 3 core cable and 4 core cable to the indoor unit, and run the 3 core to a 13 A plug somewhere easily accessible.  Run the 4 core cable outside with the pipes.  Connect up the pipes to the outdoor unit, with a bit of vacuum oil on the threads and flare fittings and tighten them up.  Connect up the test gauge and vacuum pump to the test port on the outdoor unit and pump the system down to vacuum, checking for leaks by turning the pump off, closing the valve on the test gauge and waiting to see if the pressure rises.  If all is leak tight pump the system for around 15 minutes, to get any water out of the pipework, then turn the pump off and leave the system under vacuum for a while as a further test for leaks (I left it for over an hour whilst I had lunch).

 

If all is well, then wire the 4 core cable to the outdoor unit, remove the test gauge, cap the test port and remove the caps over the gas valves.  Open these to let gas into the system with a 5mm Allen key, then replace the caps and do them up tightly.  Turn on the power and it should work.

 

It seems to be working very well, and is extremely quiet, even when running flat out.  The bedroom temperature is now heading for 18°C, so we should be able to get a good nights sleep.  I think my timing has to be just about spot on, getting this running on a day like today.  Time for a nice cold glass of wine...

[ProDave]

I would be interested to hear if cooling during the day (while the PV is generating) and turning it off at night is okay, i.e.does it stay cool over night.

 

Previously in our old 1930's house we tried a portable aircon unit but the house leaked heat so quick that if you turned it off the room was warm again in half an hour, so it was a choice of be over hot, or put up with the noise to keep it going over night.

[Jeremy Harris]

2 minutes ago, ProDave said:

I would be interested to hear if cooling during the day (while the PV is generating) and turning it off at night is okay, i.e.does it stay cool over night.

 

Previously in our old 1930's house we tried a portable aircon unit but the house leaked heat so quick that if you turned it off the room was warm again in half an hour, so it was a choice of be over hot, or put up with the noise to keep it going over night.

 

Tonight will be the test for this! 

 

The plan is to cool the bedroom right down, then turn the air con off and see if just the MVHR will keep it cool.  If push comes to shove I can leave the air con on it's lowest setting, at ~23dB it's virtually silent as far as either of us can tell.  The considered view at the moment is that it won't disturb sleep at all it's that quiet, but the real test will be to try it.

 

Flat out on it's highest setting it seems to draw about 650 W, which won't have any effect on our electricity usage if we only run it during daylight ours.  Usually the temperature drops a bit at night, although the forecast here is saying that it will only dip to about 19°C, which for us probably means over 20°C.

[MrMagic]

Well done @JSHarris.. just in time too!!

 

Even in my leaky old house it only runs the compressor for 10-15mins every hour or so to maintain temperature...we turn ours on around 5-6pm so that it's nice and cold come bedtime and also the noisiest bit is over to give the neighbours some peace if they have their windows open.

 

 

(Orange line is power household power draw)

 

Edited July 23, 2019 by MrMagic

[joth]

@JSHarris

Congrats on the install and hope you're enjoying a nice comfortable sleep!

 

With the benefit of now having installed it and hindsight, what steps would you have made to future proof for this job when carrying out the original build?

Are the A/c pipes the same for all manufacturers, so preinstalling it is a safe bet without knowing what unit will use it?

Is the 10m limit for each of the pair, or total distance around the loop?

 

My own thought would be an ducted internal unit in the loft and drop a duct down to each bedroom. So it's just a matter of pre-running pipes from service room up the riser to the loft. 

I *could* preemptively run them right out to the flat roof and seal them up somehow, but seems odd to add an extra penetration in the airtight layer until actually needing it.

Edited July 24, 2019 by joth

[Jeremy Harris]

Thanks, @joth, the unit seems to work fine. 

 

My main regret is in not having realised that we might need more cooling earlier, and including ducts to run the pipes and cables during first fix.  What I should have done, perhaps, is just make provision for running pipes from the UFH up to fan coil units, together with cabling, as we have lots of spare cooling capacity from the main ASHP, all we need is more cooling upstairs (downstairs seems fine with just the floor cooling).

 

You could run insulated 1/4" and 3/8" copper pipes in, ready to be flared and connected, as that seems to be the standard size for small to medium power indoor units.  I'm afraid I don't know how the multi-split systems are connected, but would assume that they have a radial piping system from the outdoor unit.  The copper piping is reasonably flexible, if a bit awkward to handle, so pre-installing it may make sense, rather than just putting ducts in place.

[joth]

@JSHarris great, thanks very much for that.

I'm already going to have a water pipe loop from the ASHP to the loft anyway, as the plan is to heat upstairs via a split manifold arrangement, so I should probably just stop worrying and focus on that. When you've been lying awake sweating for 3 hours it's easy to think of ways to over provision everything!

 

 

[Jeremy Harris]

14 hours ago, ProDave said:

I would be interested to hear if cooling during the day (while the PV is generating) and turning it off at night is okay, i.e.does it stay cool over night.

 

Previously in our old 1930's house we tried a portable aircon unit but the house leaked heat so quick that if you turned it off the room was warm again in half an hour, so it was a choice of be over hot, or put up with the noise to keep it going over night.

 

After one night, the answer is a partial yes, turning the air con off during the night does sort of work, but the bedroom was up at about 22°C this morning.  Not too bad, but a quick wander around with the IR thermometer shows that the walls are all sitting at around 22.5°C, even those on the North side, so my guess is that a few hours of running the air con yesterday evening didn't take much heat from the internal structure, and that just radiated heat back into the room through the night. 

 

We could leave the unit on all night, at it's lowest setting, but I'm going to try just keeping it on all day today, to remove as much heat as possible from the internal structure, furnishings etc, and see what that does.  I suspect I can get it to work much like the under floor cooling, by sucking heat out during the day, when the PV is generating, with the house then remaining cool overnight.

 

[MrMagic]

Re: Multi-split - for the one I have at least it's radials from the outside unit. i.e. if you have a 3 way outdoor unit, feeding three indoor units, you need a pair of pipes for each, 6 pipes in total (+3 control/power wires, +3 condensate drains). Running internally would go some way to avoiding the 'office block / kebab shop' look on the outside.

 

But I guess if you're building from scratch and could design a system whereby the A/W ASHP also did cooling via fan coil units, you could minimise extra services and pipework.

 

The world is getting hotter... I think it's certainly prudent to factor in cooling from the start.

 

[jack]

1 hour ago, MrMagic said:

The world is getting hotter... I think it's certainly prudent to factor in cooling from the start.

 

Couldn't agree more with this. When it's cold you can turn up the heating and put on a jumper. When it's hot, other than a fan, there's little you can do to cool down short of some sort of active cooling.

 

For me, it's exacerbated by working from home. I know from experience that my productivity drops precipitously when it gets hot.

[Jeremy Harris]

Trying an experiment this morning, leaving the bedroom door wide open with the air con running.  I have to say it's very effective at cooling the top of our entrance hall as well as the bedroom.  Ideally I'd have fitted some sort of cooling unit at the top of the hall (it's around 6m high and in the centre of the house), something that would have been easy to make provision for at first fix.  However, it seems as if just leaving the bedroom door open does almost as good a job.  The bedroom's back down to 19°C again, whilst downstairs is sitting at 21°C, but will probably cool down a bit, as the floor cooling only came on about 20 minutes ago.

 

I'm hoping that if I can hold the bedroom temperature at around 19°C all day, this may cool the internal fabric down and so keep the bedroom cool over night.  Pretty humid here this morning, after the rain last night, makes it feel a lot warmer outside than it really is.  I've just been out, putting the finishing touches to the air con installation (fitting trunking over the pipes and cable) and was glad to get back indoors.

[jack]

Not a moment too soon to have installed an aircon unit. 35°C here tomorrow!

[Ferdinand]

Do the pipes running to the external unit need insulating if they are running a few meters outside?

 

Logic says yes, but do they come insulated as an option?

 

I think I am heading for doing the same as Jeremy here. Should I start a mini-project thread, or continue here?

 

Ferdinand

Edited July 24, 2019 by Ferdinand

[Jeremy Harris]

38 minutes ago, Ferdinand said:

Do the pipes running to the external unit need insulating if they are running a few meters outside?

 

Logic says yes, but do they come insulated as an option?

 

I think I am heading for doing the same as Jeremy here. Should I start a mini-project thread, or continue here?

 

Ferdinand

 

 

The pipes I bought came pre-insulated and made to length.  Where they run outside they need additional protection.  I used a "bear paw": https://www.saturnsales.co.uk/Inoac-Trunking-Outlet-Cover-NW75.html  plus runs of the matching trunking: https://www.saturnsales.co.uk/Inoac-CD75-Air-Conditioning-Trunking.html

 

You're welcome to borrow my pump and gauge set, although getting it to you might be a challenge, as the pump is filled with vacuum oil.

[Ferdinand]

How do these units work wrt to doing several rooms?

 

I ask because mine is a lounge - conservatory - kitchen-diner, with external quality patio doors at each room division (translation: the last owner did not get around to building the conservatory in the "L" between the two due to running out of getting-his-money-back on sale, which is fair enough). There is also a bedroom above that might be easiest to reach from this side.

 

(The rest of the house could be reached OK from the other side as there is a garage and garden corridor the full depth of the house. 

Presumably they come with several pairs of outlets, and the pipes can then be run to several of the indoor-half. Or you rely on natural flow between the rooms.

 

Or alternatively set up a tree type set of pipes on both the in and out halves, but that would then bring in balancing issues I assume. Has anyone done this? Or is it a bonkers idea?

 

Ferdinand

 

 

Edited July 25, 2019 by Ferdinand

[Jeremy Harris]

2 minutes ago, Ferdinand said:

How do these units work wrt to doing several rooms?

 

I ask because mine is a lounge - conservatory - kitchen-diner, with external quality patio doors at each room division (translation: the last owner did not get around to building the conservatory in the "L" between the two due to running out of getting-his-money-back on sale, which is fair enough). There is also a bedroom above that might be easiest to reach from this side.

 

(The rest of the house could be reached OK from the other side as there is a garage and garden corridor the full depth of the house. 

Presumably they come with several pairs of outlets, and the pipes can then be run to several of the indoor-half. Or you rely on natural flow between the rooms.

 

Or alternatively set up a tree type set of pipes on both the in and out halves, but that would then bring in balancing issues I assume. Has anyone done this? Or is it a bonkers idea?

 

Ferdinand

 

 

 

 

If you want to do several rooms that aren't well interconnected, then you need a multi-split.  Essentially the same indoor units, but the outdoor unit has provision to attach several sets of pipework.  In principle it's little different to installing a single mini-split, just a bit more pipework to run and connect up.

[Vijay]

I had to throw the big heavy AC unit on last night just to cool the dog down and I wondered if it was possible to include an AC unit into a MVHR system. So the intake air is cooled down and spread to different rooms?

[Jeremy Harris]

16 minutes ago, Vijay said:

I had to throw the big heavy AC unit on last night just to cool the dog down and I wondered if it was possible to include an AC unit into a MVHR system. So the intake air is cooled down and spread to different rooms?

 

 

Our MVHR has exactly this, a built-in air-to-air heat pump that can either cool or heat the fresh air supplied to the rooms.  The snag is that MVHR only moves a small amount of air, and air is a lousy way to move heat around, as it has a low heat capacity, so the best the cooled MVHR can manage is maybe a couple of hundred watts of cooling per room, even at boost flow rates.  This is enough to make a useful difference if the weather is warm, but not very hot, but not enough to make a useful difference in really hot weather.

[Ferdinand]

Another basic question.

 

Can the inside half of these units be mounted vertically, or the pipes fed in from the end not the back?

 

My 400-500mm width of wall where it has to go, which actually has a drainpipe on it as well, is going to be a big constraint if I am not careful.

 

Whilst one can build a custom shelf unit to hide it, far better if the unit can mount suitably.

 

Ferdinand

Edited July 25, 2019 by Ferdinand

[Jeremy Harris]

Just now, Ferdinand said:

Another basic question.

 

Can the inside half of these units be mounted vertically, or the pipes fed in from the end not the back?

 

My 400-500mm width of wall where it has to go, which actually has a drainpipe on it as well, is going to be a constraint.

 

Whilst one can build a custom shelf unit to hide it, far better if the unit can mount suitably.

 

Ferdinand

 

 

Not as far as I know, as this would upset the condensate drain arrangement.  There's an internal drainage tray that collects the condensate with a 16mm bore pipe that runs from this to outside, along with the two refrigerant pipes.  The pipes can be fed out from either end behind, or projecting down out of the base of the wall unit, as there are cut outs in the underside to allow this.  The top of the indoor unit is the air intake, so needs to be kept clear from obstructions. 

[Ferdinand]

Just now, JSHarris said:

 

 

Not as far as I know, as this would upset the condensate drain arrangement.  There's an internal drainage tray that collects the condensate with a 16mm bore pipe that runs from this to outside, along with the two refrigerant pipes.  The pipes can be fed out from either end behind, or projecting down out of the base of the wall unit, as there are cut outs in the underside to allow this.  The top of the indoor unit is the air intake, so needs to be kept clear from obstructions. 

 

Yes, just talked to a chap, and it would need to be a tower unit.

 

It seems that there is flexibility for the pipes.

 

F

[MikeSharp01]

On 24/07/2019 at 07:03, JSHarris said:

My main regret is in not having realised that we might need more cooling earlier, and including ducts to run the pipes and cables during first fix.  What I should have done, perhaps, is just make provision for running pipes from the UFH up to fan coil units, together with cabling, as we have lots of spare cooling capacity from the main ASHP, all we need is more cooling upstairs (downstairs seems fine with just the floor cooling).

So running some UFH tails, from the ASHP, to some MVHR in duct fan coil units for the upstairs MVHR junction box would make sense then? I guess you may need a couple of coil units in the line to get enough throughout / output. As you say if you have spare capacity, those of us following along can avoid the need for air conditioning units all over the place. Sorry - do you have an stack ventilation upstairs? 

Edited August 14, 2019 by MikeSharp01
final question

[Jeremy Harris]

6 minutes ago, MikeSharp01 said:

So running some UFH tails, from the ASHP, to some MVHR in duct fan coil units for the upstairs MVHR junction box would make sense then? I guess you may need a couple of coil units in the line to get enough throughout / output. As you say if you have spare capacity, those of us following along can avoid the need for air conditioning units all over the place. Sorry - do you have an stack ventilation upstairs? 

 

I think it would be worth adding duct cooling upstairs, would probably work OK to keep the bedrooms cooler.  My only reservation would be whether or not duct cooling would be powerful enough in really hot weather, as it will be limited by the relatively low air flow rate.  

 

A better way to build in cooling provision might be to use recirculating fan coil units fed from chilled water upstairs.  These could heat or cool, and being separate from the MVHR would be a great deal more effective at pumping heat out.  The only thing to watch for if fitting fan coil units is the need for a condensate drain, but that's no different to our split air con unit (a surprisingly large amount of water comes out of the drain).

 

The only form of ventilation in the house is MVHR, but we do have a Genvex unit that has a built-in air-to-air heat pump, so that can cool or heat the fresh air supply.  The heat pump is fairly small, about 1.5 kW output, and doesn't have enough capacity to cool the house in hot weather, although it does help a bit..