Heat Pump Placement Confusion

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auccl799

2 posts

Wannabe Geek

#214486 14-May-2017 13:24

First time poster - please let me know if I can do this better.

My husband and I have recently bought our first home, a 1979 hardiplank in Hamilton. We are looking at getting a heat pump installed but after getting quotes from three different builders are now totally confused about size, location and placement height!

The main confusion is around placement - one installer told us that the indoor part of a high wall heat pump "should not be placed higher than the top of a window". Most heat pumps we've ever seen are higher than the top of a window. I've tried googling but everything I've found discusses placement of the outside part, not the inside. Is this a new recommendation or has there been a miscommunication and they mean "don't install it above a window" - any ideas?

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20003 posts

Uber Geek

#1781915 14-May-2017 13:30

The problem with installers, is that they all seem to have conflicting solutions. I guess they have a bias towards their particular system. It is very difficult to get independent advice apart from using a heating expert or house designer.

I think it also depends on how high your ceiling is, as to how high it should be placed, as it probably needs a clearance above it? Being a house of that age which will be leaking air, you may benefit from a floor unit.

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auccl799

2 posts

Wannabe Geek

#1781922 14-May-2017 13:42

You might be on to something with the clearance - it's a 2.4 metre stud. We hadn't considered a floor unit because we don't really have the floor space.

vexxxboy

4229 posts

Uber Geek

#1781926 14-May-2017 13:59

mine was installed above the window in the lounge area , but it was a case of having to as we have french doors down 1 wall and the couch and large windows the other side down the other wall so it had to go in the 2 foot space above the window. It's been there for 5 years and we have had no problem with it. The installer had no problem with it going there.

Common sense is not as common as you think.

shk292

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#1781928 14-May-2017 14:06

All of ours are above window-level, and two of them are actually above windows. They all work fine. I wouldn't want to sacrifice low-level wall space for a heat pump unless it makes a huge difference to efficiency/effectiveness

rscole86

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#1781929 14-May-2017 14:20

Our ceiling height is 2.4m, and the top of the wall unit is mounted 10cm down from the ceiling and the unit is 33cm high. We got a certified Mitsubishi Electric installer to put our heat pump in. Most our windows more or less end up at ceiling height.

timmmay

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#1781931 14-May-2017 14:24

Floor units are quieter, as they have large fans that move more air at lower speeds. Buy the largest rated unit you can afford, it'll be more efficient than a smaller unit.

mattwnz

20003 posts

Uber Geek

#1782010 14-May-2017 17:20

You an also go for a ceiling one. Although IMO they are very ugly. I personally like the high wall ones, and the silver or black ones. The white ones tend to go yellow after a while.

scuwp

3868 posts

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#1782015 14-May-2017 17:26

We have a ceiling cassette. Great if you don't have wall space or if it's on an internal wall that needs a condeser drain installed. As for looks that's a matter of personal preference. I can't imagine a wall mounted one that's lower than window height. Can't say I have ever seen such a thing.

Lazy is such an ugly word, I prefer to call it selective participation

timmmay

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#1782020 14-May-2017 17:34

mattwnz:

You an also go for a ceiling one. Although IMO they are very ugly. I personally like the high wall ones, and the silver or black ones. The white ones tend to go yellow after a while.

Part of our white one is going yellow, the part that directs the heat.

Fred99

13684 posts

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#1782198 15-May-2017 08:52

timmmay:

Floor units are quieter, as they have large fans that move more air at lower speeds. Buy the largest rated unit you can afford, it'll be more efficient than a smaller unit.

Is this correct?

The standard advice being given seems to be to calculate size based on house type, room size, part of the country you're in etc, then go for something "a bit" larger - not as large as possible.

Looking at a manufacturer's spec sheet for all models "same type / different capacity", COP tends to drop as capacity increases. For example from what I'm looking at, a 3.6KW unit has COP of 5.8, the 5.0KW version a COP of 5.0, the 6.3KW version a COP of 4.6.

People seem to refer to the "installer's" advice, but it's probably the supplier as agent for the manufacturer who's carrying the can for warranty if an under-specced unit isn't performing or fails under warranty (or under CGA). The installers seem to be mainly self-employed contractors around here.

timmmay

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#1782222 15-May-2017 09:16

Well you wouldn't buy a 15kw unit to heat your bathroom. Yes the COP does drop with larger units, but if you're running a small unit on high power all the time what I read is it's less efficient. A larger unit running on a lower speed uses less power, even with the lower COP. The larger units have a bigger outdoor unit, larger fan, so it can push more air through.

sbiddle

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#1782225 15-May-2017 09:19

We have a floor mount and find it the best solution. A wall mount couldn't have worked on an internal wall anyway as it couldn't be a simple back to back solution and in our house the location of the floor mount in a hallway was the best location for a heat pump.

I think a lot of people completely overlook them as a solution, and you will also find different views on them but it's worth considering some basics of physics when you're looking at options. Warm air rises, and cold air stays down low in a room. If you've got a floor mount unit it's drawing in that cold air from near the floor and heating it, where as a high mounted unit is drawing in the warmest air in the room. If you're trying to cool a room then mounting a unit higher is the most logical, whereas if you're trying to heat a room having something lower down makes the most sense.

DarthKermit

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#1782231 15-May-2017 09:30

Had that when we got one installed in the lounge. We also inquired about a unit for the hallway. Three different install guys had three different ideas and suggested locations for the hall unit. Which one is 'correct'?

Fred99

13684 posts

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#1782475 15-May-2017 12:17

timmmay:

Well you wouldn't buy a 15kw unit to heat your bathroom. Yes the COP does drop with larger units, but if you're running a small unit on high power all the time what I read is it's less efficient. A larger unit running on a lower speed uses less power, even with the lower COP. The larger units have a bigger outdoor unit, larger fan, so it can push more air through.

Well actually I don't think that's correct, one of the main points of energy loss is the DC motor which will have an optimum efficiency with a specific RPM/load curve, below which the efficiency drops off, so an over-specced unit would not only be less efficient COP optimum, but less efficient when running under low load - which is what they're doing most of the time. (ie at optimal load, the motor may be 80% efficient, at low load/rpm when the heat pump is idling, the efficiency may be half that). I suspect that a "3KW" unit pumping out 2/3 max capacity at 2KW is going to be quite a lot more efficient than a 10KW unit running at 1/5 capacity to produce the same amount of heat.

I believe that the advice that the optimum sized unit should be based on calculation with a small margin above is the correct advice - contrary to what you are saying.

Clearly from examples people are giving above, then there's a hell of a lot of variation in advice, I guess there's possibly some "upselling" going on - making extra money by selling people more than they need (or makes sense).

So dealing with a reputable company and taking their advice - even if you think you can work it out yourself - is a good idea - also to discuss options for wall vs floor mount etc, taking into account how they're going to run services etc through walls, under floors, or in ceiling space.

timmmay

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#1782482 15-May-2017 12:36

Fred99:

Well actually I don't think that's correct, one of the main points of energy loss is the DC motor which will have an optimum efficiency with a specific RPM/load curve, below which the efficiency drops off, so an over-specced unit would not only be less efficient COP optimum, but less efficient when running under low load - which is what they're doing most of the time. (ie at optimal load, the motor may be 80% efficient, at low load/rpm when the heat pump is idling, the efficiency may be half that). I suspect that a "3KW" unit pumping out 2/3 max capacity at 2KW is going to be quite a lot more efficient than a 10KW unit running at 1/5 capacity to produce the same amount of heat.

I believe that the advice that the optimum sized unit should be based on calculation with a small margin above is the correct advice - contrary to what you are saying.

Clearly from examples people are giving above, then there's a hell of a lot of variation in advice, I guess there's possibly some "upselling" going on - making extra money by selling people more than they need (or makes sense).

So dealing with a reputable company and taking their advice - even if you think you can work it out yourself - is a good idea - also to discuss options for wall vs floor mount etc, taking into account how they're going to run services etc through walls, under floors, or in ceiling space.

I'm not an expert in this area, I'm just relaying what I read when I was looking. Very happy to be corrected here.

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