Heat Pump - How to use efficiently?

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#1587100 6-Jul-2016 13:33

chimera:

timmmay:

chimera:

Cheers, yeah ducted makes sense. But a floor mounted model I think, at least based on the layout at the end of our hallway, would certainly work. It was still $2k though. That covers a lot of nightly oil heater running costs over a long period. I've asked a mate who installs joinery to get me a price on double glazing the kids rooms instead. Obviously not a method of heating, but better heat retention may just be enough to take the chill off. It certainly helped doing double glazing on a large window in our stair well. Think I'll stick to oil heater for the time being as we're in the process of putting a pool in ready for summer so that in itself is a v. large expense!

PVC double glazed windows just cost me around $1600 each installed (ish), using the existing wooden frame and an "insert" method. Replacing the frame costs around $500 more and more time painting.

Size of window? Got mates rates on mine, about 1200mm high by 2100mm wide for less than half that installed (aluminium, so likely less labour than timber)

A variety of sizes. Most will be around 3x2 meters made up of one large pane and two smaller panes, one of which opens. Some are a bit bigger, some are a bit smaller. My prices include fitting, but not the touch up painting work that was required.

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#1587879 7-Jul-2016 21:17

By far the best way to heat and cool bedrooms down a hall is ducted heatpump. We have a ducted heatpump in our new house and it is brilliant. Thanks to careful design by the installer the bedrooms are about two degrees cooler than the living area which means the kids don't kick off their blankets when we are still up then freeze when we go to bed. Ducted heatpump work whether or not the door is closed. I mean seriously what's the point in heating a hallway and hoping that heat will magically go into the rooms. Yes they cost more but they are worth it....how much energy are you wasting by heating a hallway to 27 degrees to try and get the rooms warmish

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#1587911 7-Jul-2016 22:31

jonathan18: I think there's a flaw in the idea of heating one space and expecting the heat to be pushed into other rooms off this space

Yeah this is one of the big lessons we learned when we installed a heat transfer system. To truly work well you needed to have the room doors open, so the air could return/be pushed back into the lounge to replace the air being pumped out of the lounge. It was all one big circular system, and didn't work well when the return path was isolated.

I often wonder why they advertise log burner fires as being rated for 4 - 5 bedrooms, without any discussion as to how exactly this massive excess of heat in the lounge is supposed to magically transfer to the rest of the house?!

Heat pumps are essentially efficient fan heaters hanging on a wall. They're massively hyped but are essentially similar to a normal fan heater with a thermostat on them and fan speed selector. If you can use a fan heater, then you can probably use a heat pump.

I like the ability to cool, and I like the ability to dehumidify, but dehumidification only works if you pass warm air over cold coils, so the dehumidify mode is not particularly energy efficient in winter. Works well in summer though whilst you're cooling, but of course this would be of more benefit in Auckland where you get tropical humid summer nights.

chimera

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#1587925 8-Jul-2016 01:40

That's a fairly generic and inaccurate description of fan heaters vs heat pumps, you are in effect stating that they work simarly when they work completely different.

A fan heater works by convection, it uses electricity to generate energy that gets dumped onto an element which heats up then a fan blows that heated air into the room. They can only ever be 100% efficient, energy in = energy out.

Heat pumps are effectively a heat transfer system, they don't use electricity to generate heat directly. They extract warm air from outside by using a refrigerant pushed through a coil that is cooler than the outside air. When that outside air comes in contact with the coil then because heat likes to move from warmer objects to cooler objects (and bearing in mind the 2nd law of thermodynamics) we can basically "extract" that heat and transfer it to the heat pump unit to get blown into the room (consider it like the reverse of what an air conditioner does) Because they are transferring heat rather than creating it, they can be up to 300% efficient.

jonathan18

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#1587959 8-Jul-2016 09:17

Jaxson:

jonathan18: I think there's a flaw in the idea of heating one space and expecting the heat to be pushed into other rooms off this space

Yeah this is one of the big lessons we learned when we installed a heat transfer system. To truly work well you needed to have the room doors open, so the air could return/be pushed back into the lounge to replace the air being pumped out of the lounge. It was all one big circular system, and didn't work well when the return path was isolated.

I often wonder why they advertise log burner fires as being rated for 4 - 5 bedrooms, without any discussion as to how exactly this massive excess of heat in the lounge is supposed to magically transfer to the rest of the house?!

We fell for the same thing in our last house; put in a decent-capacity pellet fire, and a ducted heat transfer system into three other rooms in the house. It did SFA, and was quite possibly one of the worst purchases I've made!

My experience with houses with huge fires has been ridiculously hot lounges, and bedrooms that are hardly affected by the excess heat.

The only houses I've found that are relatively warm throughout are those using a ducted system or heaters in basically every room - using a single or few sources of heating and then relying on convection (natural or fan-assisted) to distribute it around the rest of the house just doesn't provide that consistency.

While our heatpump install was a nightmare, this is put in perspective each morning when I come back to the house from doing exercise to a toasty warm house - can't beat that feeling!

Jaxson

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#1587995 8-Jul-2016 10:20

chimera: to get blown into the room

I was referring to the actual indoor unit blowing air around the room.

Agree there are substantial differences in terms of where this heat is sourced from, but once the heat is presented to the indoor unit, it's a fan heater.

So, not denying or trying to suggest the background concept is the same at all, but just pointing out that this thing isn't going to magically heat your whole house. Inside your room, the operation of the fan heater is essentially thermostat controlled, just like a basic fan heater. If you have one in a hallway, and your bedroom doors are shut at night time, how is it going to heat your rooms etc.

To be fair also, if we want to go down the efficiency route somewhat, the 300% efficiency is under optimal conditions, where the indoor required temperature is extremely close to the outdoor temperature. Ie you want 22 inside when it's 20 outside. This efficiency drops as the difference between indoor setpoint and outside air temp changes, as well as a bunch of other environmental factors such as humidity etc. Many people get a shock when they find they are still paying quite a bit for their power with a heat pump.

A 2kw fan heater is around about $70, with zero installation costs.

A 2.5 kw Mitsubishi heat pump is around $1,850 excluding installation.

Given an efficiency of say 250% over standard resistive element electrical load, that's still a lot of time to see a pay off, given you're only saving money on the electricity used, and nothing when it's turned off.

For a small bedroom, the savings just may not be worth the upfront establishment cost.

Different for a larger area, and if you own your own home and intend on staying in it for quite some time.

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#1588081 8-Jul-2016 11:53

Jaxson:

chimera: to get blown into the room

I was referring to the actual indoor unit blowing air around the room.

Agree there are substantial differences in terms of where this heat is sourced from, but once the heat is presented to the indoor unit, it's a fan heater.

So, not denying or trying to suggest the background concept is the same at all, but just pointing out that this thing isn't going to magically heat your whole house. Inside your room, the operation of the fan heater is essentially thermostat controlled, just like a basic fan heater. If you have one in a hallway, and your bedroom doors are shut at night time, how is it going to heat your rooms etc.

To be fair also, if we want to go down the efficiency route somewhat, the 300% efficiency is under optimal conditions, where the indoor required temperature is extremely close to the outdoor temperature. Ie you want 22 inside when it's 20 outside. This efficiency drops as the difference between indoor setpoint and outside air temp changes, as well as a bunch of other environmental factors such as humidity etc. Many people get a shock when they find they are still paying quite a bit for their power with a heat pump.

A 2kw fan heater is around about $70, with zero installation costs.

A 2.5 kw Mitsubishi heat pump is around $1,850 excluding installation.

Given an efficiency of say 250% over standard resistive element electrical load, that's still a lot of time to see a pay off, given you're only saving money on the electricity used, and nothing when it's turned off.

For a small bedroom, the savings just may not be worth the upfront establishment cost.

Different for a larger area, and if you own your own home and intend on staying in it for quite some time.

I think what are referring to is pay back on investment. You can spend say $2000 (installed) on a 2.5 kW heat pump and use less electricity over it's life or buy an electric heater for say $70 and use the remaining $1930 to pay for the electricity until it balances out. But a heat pump provides cooling in summer, should be quieter, filters the air etc. It's a lifestyle / comfort choice as well as an economic choice. If you rent a property installing your own heat pump isn't usually an option as it damages the property.

The efficiency figures you are quoting are not at 'optimal' conditions they are at 'rated' conditions which are from AS/NZS 3823 which for heating is indoors 20°C and outdoor 7°C DB & 6° WB, this is a standard that all heat pumps are rated at to enable comparisons between brands.

For example a Mitsubishi Electric MSZ-GE25 has a COP of 4.47 at these rated conditions which is 447% efficient. This efficiency does drop as it gets colder but it also increases when it's warmer outside. This all depends on your local climate. The forecast for Auckland today has a high of 18°C and a low of 10°C, Christchurch has a high of 10°C and a low of 1°C so the same heat pump is more efficient today in Auckland. But in Christchurch for a house with the same size room and insulation you'd probably put in a larger 3.5kW unit so the heat output you need at low outside temperatures is available.

lissie

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#1588820 9-Jul-2016 14:26

We've had quite a journey with our house over the last year and learnt some interesting things! The layout is effectively an L with the shorter leg being a lounge with a cathedral ceiling, single glazing - and an open walk through to a dining room and kitchen. The bedrooms (2) are at the end of the corridor and quite small.

Last year we were miserable in July. The lounge had both a wood burner and a heat pump and neither could warm the area - not even with the doors closed. The bedrooms were freezing too - but we don't like heating in bedrooms.

In the last year we have replaced the windows in the bedrooms and kitchen (SE corner) with double glazed PVC - apart from actually keeping the rain out they are amazing at moderating the temperature both summer and winter.

The lounge we installed insulation by dropping the cathedral ceiling by about 30cm and installing bats under plywood. We also installed an over head fan. The windows in this part of the house is still single glazed and have the same thermal curtains.

Last weekend I hung thermal curtains over the single glazed window in the dining room (which is behind the HP and lounge on the other side of a short wall).

Last night was cold and we over-heated the lounge for the first time!

Not only does the lounge get warm using either the wood burner or the HP - having the ceiling fan on winter mode pushes the heat through the house if the doors are open.

I use one of the bedrooms as an office and on a cold day - I now just leave the HP on and the over-head fan running -its enough to keep my office warm - last year I was running the column heater all day - now I only use it at night if the doors to the lounge are closed.

So based on our experience I'd say - ceiling insulation is the most important thing - once you do that the windows become more important (adding the curtains to the last single glazed uncurtained window made a big difference)

If you can afford it replacing rubbish single glazed aluminum with PVC double-glazed with Argon fill - but if you can't invest in good curtains that touch the ground - have a lot of gather (I like 2.5 x) and ideally have a pelmet too).

I'd do all that before worrying about your heating source. I thought our HP was broken last year - had it serviced and all- now it's perfectly adequate for the space!

I help authors publish their books - DIYPublishing.co.nz

Kickinbac

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#1588861 9-Jul-2016 15:16

lissie:
We've had quite a journey with our house over the last year and learnt some interesting things! The layout is effectively an L with the shorter leg being a lounge with a cathedral ceiling, single glazing - and an open walk through to a dining room and kitchen. The bedrooms (2) are at the end of the corridor and quite small.

Last year we were miserable in July. The lounge had both a wood burner and a heat pump and neither could warm the area - not even with the doors closed. The bedrooms were freezing too - but we don't like heating in bedrooms.

In the last year we have replaced the windows in the bedrooms and kitchen (SE corner) with double glazed PVC - apart from actually keeping the rain out they are amazing at moderating the temperature both summer and winter.

The lounge we installed insulation by dropping the cathedral ceiling by about 30cm and installing bats under plywood. We also installed an over head fan. The windows in this part of the house is still single glazed and have the same thermal curtains.

Last weekend I hung thermal curtains over the single glazed window in the dining room (which is behind the HP and lounge on the other side of a short wall).

Last night was cold and we over-heated the lounge for the first time!

Not only does the lounge get warm using either the wood burner or the HP - having the ceiling fan on winter mode pushes the heat through the house if the doors are open.

I use one of the bedrooms as an office and on a cold day - I now just leave the HP on and the over-head fan running -its enough to keep my office warm - last year I was running the column heater all day - now I only use it at night if the doors to the lounge are closed.

So based on our experience I'd say - ceiling insulation is the most important thing - once you do that the windows become more important (adding the curtains to the last single glazed uncurtained window made a big difference)

If you can afford it replacing rubbish single glazed aluminum with PVC double-glazed with Argon fill - but if you can't invest in good curtains that touch the ground - have a lot of gather (I like 2.5 x) and ideally have a pelmet too).

I'd do all that before worrying about your heating source. I thought our HP was broken last year - had it serviced and all- now it's perfectly adequate for the space!

Sounds like you did good work. The insulation and curtains retain the heat. The ceiling fan disrupts the stratification. I am always concerned when I go to a home and they want a heat pump and have cathedral ceilings. Especially when its a 70's or 80's house cause I know the insulation will be inadequate and its difficult / expensive to retrofit. It usually takes more than a heat pump to solve the problem. Some people think heat pumps are a magical solution.

Jase2985

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#1588864 9-Jul-2016 15:18

so there was nothing wrong with your heatpump in the end?

lissie

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#1588907 9-Jul-2016 16:44

Sounds like you did good work. The insulation and curtains retain the heat. The ceiling fan disrupts the stratification. I am always concerned when I go to a home and they want a heat pump and have cathedral ceilings. Especially when its a 70's or 80's house cause I know the insulation will be inadequate and its difficult / expensive to retrofit. It usually takes more than a heat pump to solve the problem. Some people think heat pumps are a magical solution.

Retrofitting the insulation was actually very cheap - we weren't lovers of the dark-stained chipboard ceiling with dark struts anyways - so basically the builders put battons up across the existing struts and used them to support the bats - and then installed the plywood over the top - we were going to go with gib and plaster originally - but like the look of the ply so did that - it was cheaper as no plasterer required.

If you were handy you could do the job yourself - I think it cost us maybe about $5k? excluding the electrical

I help authors publish their books - DIYPublishing.co.nz

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lissie

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#1588908 9-Jul-2016 16:46

Jase2985:

so there was nothing wrong with your heatpump in the end?

Probably under-sized when installed - but now it's doing fine. When the log burner needs replacing in a few years we will probably replace both with flued gas heater though - that will get us some space back in the lounge - and will be the cheaper/easier option given that we have gas connected for hot water anyways so already paying the line charge.

I help authors publish their books - DIYPublishing.co.nz

Kickinbac

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#1588914 9-Jul-2016 16:57

lissie:

Sounds like you did good work. The insulation and curtains retain the heat. The ceiling fan disrupts the stratification. I am always concerned when I go to a home and they want a heat pump and have cathedral ceilings. Especially when its a 70's or 80's house cause I know the insulation will be inadequate and its difficult / expensive to retrofit. It usually takes more than a heat pump to solve the problem. Some people think heat pumps are a magical solution.

Retrofitting the insulation was actually very cheap - we weren't lovers of the dark-stained chipboard ceiling with dark struts anyways - so basically the builders put battons up across the existing struts and used them to support the bats - and then installed the plywood over the top - we were going to go with gib and plaster originally - but like the look of the ply so did that - it was cheaper as no plasterer required.

If you were handy you could do the job yourself - I think it cost us maybe about $5k? excluding the electrical

I helped a friend do this a few years ago, not difficult at all for a couple of people and a mobile scaffold. Insulation, battens and gib. They got a plasterer in to do the stopping. It made a huge difference to their place, making it both lighter and warmer.

timmmay

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#1588919 9-Jul-2016 17:14

Gas heater creates moisture as a product of combustion. Best thing I did was take out my fire, the big hole in the ceiling let so much cold air in.

Kickinbac

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#1588923 9-Jul-2016 17:21

timmmay:
Gas heater creates moisture as a product of combustion. Best thing I did was take out my fire, the big hole in the ceiling let so much cold air in.

It's not a problem if it's flued outside.

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