Heat Pump Thoughts

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#1341975 13-Jul-2015 10:03

I'm making assumptiosn because it's really hard to get unbiased advice on heating! I'd love to pay an independent expert to advise on ALL heating options - but all the ones I've met are selling either gas or electric!

If anyone has got any suggestions on how to get independent expert advice on this Im all ears!

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Hammerer

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#1341976 13-Jul-2015 10:05

It's quite simple if we ignore the complexities of room shape and size, thermal differentials and the like. If you only use a heat pump for heating then a floor-level unit will be better than a unit up on the wall or with heat vents in the ceiling. If you only use it for cooling then it will be better better at or above head height.

The main reason is that warm air is lighter than cooler air so it rises to the ceiling. Likewise cool air is denser than warm air so it falls to the floor. This means that positioning the heaters to use the natural flow will make it easier to mix the air to get the result you desire.

The fans in the units do allow the heating or cooling air to move against the natural convection flows but, in general, it will not be very efficient or very effective for one heater to blow air into every part of the room.

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#1341982 13-Jul-2015 10:16

room shape and size make a huge difference, and you need to understand fluid dynamics of hot and cold air to work out the best source of heating for your non standard shaped room. yes its hard to get unbiased advice as everyone you ask has an agenda to try and sell you something.

maybe a ceiling fan is all you need to help bring the hot air back down to where you are, or maybe a heat pump is not the best option, i dont know if a gas heater will be any different unless its a very high kw unit. A typical wood fire has 2x the heat output of a heat pump, but lack cooling and the ability to distribute its heat.

cost wise they probably end up costing about the same to run but im not speaking from first hand experience here im just basing it on cost per kw figures.

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#1341987 13-Jul-2015 10:26

lissie:
Jase2985:
lissie: Carrier 6kw heating - the room isn't huge 5m x 5.3m - open (thru an archway to a dining room about 3.2 x 2m The log burner warms it easily - indeed so does the 2.5 kw fan heater I have! Large windows single glazed, the cathedral ceiling appears to have no insulation - going to fix both of those things before we do anything with heating.

a fire will work much more effectively because its rated at soemthing like 15+kw so it heats quickly, the problem is over heating.

the electric fan quick because its on the ground at the lowest point heating the coolest air. the hot air rises forcing cooler air down to the floor where it is heated again

The heat pump, because its high on the wall will struggle to heat the lowest air and because you have high ceilings it just ends up heating the air above head height. maybe try a ceiling fan or point the heat pumps directional vanes at the ground to try and stir the air up a little more.

That makes sense - not that we've had problems with over-heating with the log burner- and I totally agree it makes no sense to mount a heater high on the wall - so why are most HP installed like that? That's how they are instaled overseas - but that's for use as air conditioning! As they are marketed as heaters here Idon't understand why they are aren't installed at floor level

lissie, you're right. If the fan in your heat pump really can't blow the air to floor level (most can blow air 3-5 metres) then another fan should help.

lissie:
Jase2985:
lissie: That makes sense - not that we've had problems with over-heating with the log burner- and I totally agree it makes no sense to mount a heater high on the wall - so why are most HP installed like that? That's how they are instaled overseas - but that's for use as air conditioning! As they are marketed as heaters here Idon't understand why they are aren't installed at floor level

Because most people dont have high ceilings as the standard ceiling height in NZ is 2.4m. It doesnt take long to heat a normal sized room.

also im pretty sure they are designed to work best from 6-10in from the ceiling height and it also means they can be mounted over a window/door and you can place furniture under them and your not wasting floor space by having them at floor level.

That makes less sense - even if the windows were double glazed - and most NZ houses aren't - the heat is going straight out the window! Anyway you can just as easily place a heater below a window (see any UK house with radiators)

The rest of the house is 2.4m - just not this room! We are retrofitting insulation (on the inside) and installing a ceiling fan (to help the log burner) - which may help the HP - but at this point it's very close call as to whether we regain the wall space by removing it and installing a gas bayonet for gas.

Yeah I hear you about wall space though - I'm getting rid of the wall lights to regain that!

The heat doesn't go straight out the window unless the air is blown directly onto the window. Normally it will be blown into the room and from there it flows to the cooler/ lower pressure areas outside the heated zone. More often than not this warmer airflow will counteract the downward airflow of cooler air from the exterior windows/walls and reduce heat losses - this is because heat transfer rates increase as air flow increases. In some circumstances the blown air can also function like an air curtain (they blow heated air downwards in a doorway to keep colder air out, e.g. at a retail store) to contain the coldest layers of air that form next to the window.

bongojona

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#1341991 13-Jul-2015 10:33

We have a 1 year old Toshiba pump in our living room. The supplier ran out of the model we originally wanted so they they gave us a larger model for a discount. Worked out pretty well as it doesn't need to be on full power (or anywhere near) to heat the whole living space (living room, kitchen, dining) quickly.

This makes it very quiet most of the time, only turns up the fan for a few minutes at the start or if my wife uses the remote...

We had it on 18-19c all day yesterday and you would hardly notice it was on. I did notice when walking down to the bedrooom though...

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#1341994 13-Jul-2015 10:35

Jase2985:

... i dont know if a gas heater will be any different unless its a very high kw unit. A typical wood fire has 2x the heat output of a heat pump, but lack cooling and the ability to distribute its heat.

cost wise they probably end up costing about the same to run but im not speaking from first hand experience here im just basing it on cost per kw figures.

An unflued gas heater, which is what a bayonet fitting provides, introduces a lot of moisture from burning gas (LPG/CNG) that reduces the efficiency of heating because that water also has to be heated. I would always use a flued gas heater in New Zealand so that most of the moisture is vented outside the house. Overseas it can be a different situation. For example, in the centre of large land masses such as in central Asia the winter air is very dry so an unflued gas heater is helpful to humidify the air - that's why people dry their washing inside the house. NZ does not have this problem as our air is quite humid all year round. Central Otago might be the one exception but I doubt it.

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#1342027 13-Jul-2015 11:07

cldlr76: Thanks for the replies,

We have briefly looked at a ducted system but not in any detail, so it could be an option. Are they cost effective from a hardware/installation point of view compared to separate units? We also had limited it down to fujitsu and Mitsubishi but has mentioned currently leaning towards Mitsubishi but certainly open to other suggestions

We are in Auckland and the area mentioned above is a 2nd story about 65sqm with slopped ceilings with a max height of 2.9m. There is a reasonable amount of windows which are all single glazed with decent curtains. The walls are insulated with R2.6 pink batts. On the same 2nd story there are bathrooms and bedrooms totalling about another 100sqm that currently don't have insulation but will do and we will also be wanting to heat/cool that area in the future as well. There is also currently an HRV system installed as well.

We've recently decided to install a ducted heatpump system throughout the house (in fact I'm asking for some advice re choosing this on another thread), and personally I think it seems pretty good value for money, given the impact it'll have on the usability of the house. Prices of two quotes range from $10,000 to $14,000, but remember that's to heat the whole house (c. 160m2) with eight ducts, with the top price being a wifi-controlled multi-zoned unit with two established zones (and a cost of under $300 per zone to add in additional zones [up to eight] should we want to do so).

We stupidly put a large heatpump in the hall, hoping it would heat the side of the house with the bedrooms, but the reality is it really warms half the hall. It's useful when used in conjunction with the woodburner or gas fire, simply to help distribute heat around the whole house. That said, the bedrooms are never particularly warm in winter even with both forms of heating going.

The ducted system will allow each and every room to be warm - including at night. Given it's not attempting to force all its air out of one location, ducted systems are also not nearly as irritating to sit under (compared to a high-wall say). I really dislike the heat from a standard wall-mounted heatpump, but have none of this issue with that from a ducted system (given it's not a huge wall of air, and is evenly distributed around the heated space, whereas wall-located heatpumps I find tend to resuly in quite uneven heat). It also means all you have is a vent or two in the ceiling of each room - which personally I find far less invasive and ugly than a wall-located heatpump.

Fancier models with zones (eg the Daikin I mention in that other thread) also mean you can control which areas are heated and when; all units do allow some control by limiting airflow out of each vent, but I understand reducing airflow too much can place strain on the system if the fan speed isn't reduced (for most bar that Daikin the fan speed isn't automatically reduced, as essentially the damper system is independent from the heatpump).

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#1342076 13-Jul-2015 12:08

How many kW will your ducted unit put out

jonathan18

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#1342081 13-Jul-2015 12:21

joker97: How many kW will your ducted unit put out

All three installers are looking at units around the 15 kW size; the one we're likely to pick, given its ability to fully control zones and that it comes with built-in wifi access (Daikin FDYQT125L), is cooling 12.5 (EER 3.4) heating 15 (COP 3.96).

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#1342106 13-Jul-2015 12:51

You should probably move the ducted conversation to that thread.

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#1342147 13-Jul-2015 13:23

timmmay: You should probably move the ducted conversation to that thread.

Apologies. I was just responding to the OP's comments re a ducted solution, and his questions regarding the relative cost of this. Given my own experience of thinking a standard wall unit could be a panacea for our problems, I was just wanting to provide some more information so he too doesn't end up with a solution that fails to deliver as hoped, and then having to spend more money to fix it later on. I can't imagine we'll get much money for the 8kW unit we'll have taken out when the ducted one goes in!

Gilco2

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#1342159 13-Jul-2015 13:31

Not 100% keen on heatpumps. We have Mitsubishi since 2006. Works well as aircon and heat in during day and evening when cold. However cold mornings when you need it, you sit around shivering for half hour or more while waiting for it to de ice. This is at Papamoa and outside temps 3 to 5 deg. Supposed to be okay to minus 5. Hat the agent/installer check it out and all okay still so just have to put up with it and shiver in mornings

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#1342167 13-Jul-2015 13:37

Hence you set the timer to come on half an hour before you get up....

If I have a heat pump that works in Dunedin (Toshiba) as much as I like the place, it can get pretty damn cold here in winter. Below about 3 degrees it goes into defrost maybe once every 3/4 of an hour but still keeps the place warm. This is a 100m2 built in 1935 so no wall insulation or double glazing.

It's hard to believe people have correctly sized correctly working units in Wellington that they can't get any heat out of.

Folks have a Fujitsu E3 in their new house here in Dunedin, it heats 2 lounges, dining, scullery and kitchen just fine.

lissie

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#1342173 13-Jul-2015 13:45

lxsw20: Hence you set the timer to come on half an hour before you get up....

If I have a heat pump that works in Dunedin (Toshiba) as much as I like the place, it can get pretty damn cold here in winter. Below about 3 degrees it goes into defrost maybe once every 3/4 of an hour but still keeps the place warm. This is a 100m2 built in 1935 so no wall insulation or double glazing.

It's hard to believe people have correctly sized correctly working units in Wellington that they can't get any heat out of.

Folks have a Fujitsu E3 in their new house here in Dunedin, it heats 2 lounges, dining, scullery and kitchen just fine.

I just asked on a local FB group (Wgtn) for advice on a local service agent- and I have lots of people saying that htere's dont' work in the mornings or when it's "too cold" either!

It's clearly not an isolated issue.

Mine is working fine now that the sun is flooding into the room - it's great between about lunchtime and 7pm!

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#1342177 13-Jul-2015 13:48

My car looked like a giant popsical this morning yet the heat pump had the place nice and warm by the time I got up this morning with it only being on for half an hour.

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