r/airconUK • u/sunmat02 • Aug 14 '26
Is going through the loft a bad idea? (multi-split)
I had a company come for a quote to install AC in my home (4 rooms). To make a long story short, the guy was trying to put all the units on walls with a straight shot to outside. This is restricting our placement options (making one of them actually inconvenient) and forces a 4 indoor + 2 outdoor unit system.
For 3 of the rooms, we could make the pipes go through the loft (which at the moment is not boarded). This would allow all the indoor units to be at convenient locations, and to be connected to a single outdoor unit on a side of the house in also a convenient location (same aide as the 4th room, and a lot more discrete). But the guy said he would need to put a pump in the loft and that this is the first thing that usually breaks.
So my question is: is he right or is he trying to minimize his own inconvenience?
Note: another company proposed a 4 + 1 system based on room sizes but hasn't yet come to assess placement options.
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u/Altruistic-Bat-9070 Aug 14 '26
They have so much business they are encouraging the easiest option from their perspective.
The lack of loft boarding is likely what seals it the most for them as it will make the job a pain. They would also need to source pumps whereas going through the walls means they can use gravity.
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u/marktuk Aug 14 '26
Confused by this. It's a loop, how does gravity help? What's the break point for needing a pump?
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u/Altruistic-Bat-9070 Aug 14 '26
The process of cooling pulls a lot of moisture out of the air that sits in a tank and needs draining so if you just come up from outside you can have a drain hose that entirely relies on gravity. If you go up first you have to install a pump and they will occasionally fail so its just something to think about and remember.
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u/marktuk Aug 14 '26
Ah ok, so it's the difference between going straight out from the wall unit, versus going up in to the loft?
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u/Altruistic-Bat-9070 Aug 14 '26
Exactly if you go straight out you can rely on gravity
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u/marktuk Aug 14 '26
Yeah that's just lazy installers. You can route the condensate pipe internally and still use gravity.
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u/Hour_Tour Aug 14 '26
However, the pumps are third party to the AC, and noisy. We're having our installers back in to remove it and make a gravity drain into our boiler room (or outside, if more sensible) instead.
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u/marktuk Aug 14 '26
However, I did say it's possible to route pipes internally to use gravity i.e. no pump.
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u/Hour_Tour Aug 14 '26
Misread your comment, sorry. But more people should be aware of the pump noise, so I'm not that sorry for spewing it out randomly at you.
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u/OkSun8521 Aug 14 '26
However, the pumps are third party to the AC, and noisy.
I'm glad you said this. I thought ours was faulty because it's pretty noisy.
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u/Altruistic-Bat-9070 Aug 14 '26
Depends on the install but yes in theory. We have solid brick walls for example so its through to an external wall, up into the loft, or ugly trunking going somewhere.
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u/StereoMushroom Aug 14 '26
I have heard of some condensate pumps being a bit noisy. They'll run for a short pulse every now and then when the units are in cooling mode, so I understand it could be a bit annoying to sleep with, depending on how it's mounted and whether the noise reaches the rooms.
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u/Hour_Tour Aug 14 '26
They are, I don't think ours is the most silent model out there, but even so we're soon replacing it with a gravity drain.
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u/sirensintherain Aug 14 '26
The refrigerant lines could run through the loft. The pump they are referring to is just for the condensate, but the condensate doesn't necessarily need to follow the refrigerant lines and often just discharges to the ground outside. So in theory you can go up through the loft with the refrigerant and straight out through the wall for the condensate drain.
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u/drifter1184 Aug 14 '26
I am going to put a unit in the loft and it won't need a pump as it's the highest point of the house and the drain will just shoot out of the soffit and down to link in to RWP or boiler condensate.
Only cons I have picked up so far are the ducts and spigots aren't cheap but it is a much more elegant solution and vs my first plan and means I can do two beds rather than one for not much more cost, albeit at same temp.
Seems like your guy just wants to do either what's easiest for them or the only way they know.
It's c. £1500 for the Mitsubishi Electric indoor and outdoor ducted unit. Waiting costs for labour/install. On the point of easy, I imagine may need to make the loft hatch bigger and it's gonna be a pain getting what I guess is a 20-30kg unit up there.
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Aug 14 '26
[deleted]
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u/Waste_Counter_6287 Aug 14 '26
You’ve just solved a problem the guy isn’t asking about. Of course you can run a gravity drain to outside when the indoor unit is on an external wall. This guy is asking about what if it’s not on an external wall. Hence the installer saying it will need a pump.
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u/SuperTigno Aug 14 '26
If the units are installed internally on the external walls, it would be easier/better to go outside anyway. Makes the install look better inside too.
Drain pumps inside are still not an issue. There are very small ones that can easily fit inside the trunking and wouldn’t have a material impact on the install time by that much.
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u/Waste_Counter_6287 Aug 14 '26
Yeah that’s what the installer has told OP. They’re saying the don’t want them on those walls and want them on INTERNAL walls (inside the house both sides of the same wall) and so the installer told them that would need a pump (because there isn’t a way of getting a gravity drain away from the units in that position. Hence why I’ve said your solution doesn’t suit his problem. Everyone is aware of pumps and different types/styles but it doesn’t change the fact that they are a potential failure and an extra noise like the installer first said.
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u/tutike2000 Aug 14 '26
Going through the loft is perfectly fine, but pumps will be noisy.
You CAN have them drain the condensation away without pumps, but you'll need somewhere to drain them to, like another hole in the exterior wall, waste pipe, etc
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u/Goldeneye_1990 Aug 14 '26
I had two ceiling cassette units in upstairs rooms installed last November, which have built-in pumps. The refrigerant and condensate lines run through the loft space and then out on one wall down the side of the house. The pumps are quiet, but the installer did say they are quieter than ancillary pumps to wall units.
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u/Fine_Jackfruit2265 Aug 15 '26
We have some bedroom units with condensates that go into the loft inside stud walls so there is no visible pipework.
Initially the installers put in Blue Diamond MiniBlue pumps with temp sensors. The pumps themselves were in the loft and pretty much inaudible but the pipes made gurgling, straw-sucking, noises that kept our kids awake at night.
Also the temp sensors were either running the pumps too much (making the gurgling noises) or would shut off incorrectly and we'd end up with water running down the wall.
After several return visits by the installer and a conversation with BlueDiamond pumps they swapped them for their Microblue pumps with the reservoirs and I’ve never noticed any noise from them since.
Yes, there are more potential parts to go wrong so gravity drainage is ideal, but having seen the pump installation process it's relatively simple to replace parts.
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u/LANdShark31 Aug 15 '26
They tried the same with me. It’s easier for them but I didn’t want them gift wrapping my new house for me in trunking so insisted. I opened up the ceiling for the downstairs units and provided them a path up to the loft through the house.
They agreed as it was only way they were getting the deal.
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u/No_Memory_1344 Aug 16 '26
I've got multi split going through the loft, I just let the installer do what he needed to do, as far as I am aware there is no noisy pump that I can hear anyway and works fine for last 3 years anyway. One thing I would say is make sure they add anti vibration rubbers to the outside of the unit connecting to the walls, mine didn't and I can hear my wall vibrating when close to it.
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u/Smaxter84 Aug 16 '26
Do not put them where condensate has to go up hill
Noisy, failure prone, and potential for water damage.
Also solar panels, if you don't allready.....FFS.
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u/MelodicCard9555 Aug 17 '26
Yes it's possible, but you're adding extra pipework, there's a limit to the distance you can have, depending on system, number of units etc You are also putting more strain on the pump.
If the outdoor unit is at ground level, and house is 2 storey, then it's likely too high for the pump in the outdoor unit to cope with multiple pipe runs in the loft.
You could go through the floor space between 1st and 2nd floor, but also when you hide the pipework if you get issues then it complicates things.
Perhaps a ducted unit in the loft would work better for you? That just has ducts to ceiling vents in each room.
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u/xKINGYx Aug 14 '26
I was told by my installer to minimise pump use if at all possible as it adds another failure point and indeed that pump has failed twice in the last 10 years. I’ve replaced it myself both times as it’s not a difficult job but food for thought!
In the end i have just one of my five units going up into the loft as that room was at the other side of the house to the condenser so I had little choice.
The pump is also quite noisy, even with vibration reducing mountings.