Central heating vs heat pumps.

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#1845667 12-Aug-2017 21:21

I have an 8 year old Daikin still working just fine. It had the compressor replaced after a few years because it was making a strange noise.

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shk292

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#1845681 12-Aug-2017 22:38

One consideration is that you're meant to get gas heating systems serviced every year, but heat pumps are pretty much maintenance free except for cleaning the air filters with a vacuum cleaner every few months

timmmay

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#1845696 13-Aug-2017 07:50

The heat pump firms all want you to pay them $150 a year per heat pump to "service" them. I watched them once. All they do is clean the filter and hose the outdoor unit. I don't pay them to do that any more, I do it myself. The warranty doesn't depend on "servicing".

mentalinc

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#1845730 13-Aug-2017 09:42

The cleans we've had done they pull the indoor unit into pieces and clean them with some sort of cleaner, and same outside, takes them around an hour or so...

Think you got ripped off if they only did a quick clean.

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mwm42

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#1846458 14-Aug-2017 15:40

I am hoping to install a heat pump system to replace oil-fired ducted central heating in our house near Eastbourne, facing south and in bush, therefore very humid.

We built in 1964, haven't used the furnace since the mid 70s, The ducting was very effective - it's two-storey with a lounge-dining area just under 40 square metres, normal stud height, and 3 bedrooms directly underneath. A single duct at ceiling level in bedrooms, 2 ducts at floor level in lounge and 1 in dining area.

Playroom, toilet and kitchen extend at the 2nd storey height, with workshop underneath including furnace; these will rely on spot-heating if at all.

So I want to replace the furnace with a heat pump sized to heat the lounge to around 20 degrees. I use a pyroclassic wood burner on cold days or when the spot price is high (I’m on Flick Electricity).

Only the main bedroom would be heated at all – I’d close off the other bedroom vents.

Our humidity is very high - several litres/day in portable dehumidifiers - up to 10 litres as I recall in early summer, and around 2 litres/day in winter. I expect therefore that the outdoor unit will ice up badly in winter. Therefore I would want to add a separate dehumidifier, thus ducting dehumidified air. IS THAT POSSIBLE?

timmmay

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#1846463 14-Aug-2017 15:52

You possibly need to talk to a heating and ventilation company. Dehumidifiers are generally a sign that there's a deeper problem to be solved, but if you live in a very humid area it might be that you do need a dehumidifier. You might be able to pipe in drier air from somewhere away from the house, or a ceiling cavity.

My house used to be quite moist inside. We had a plastic ground sheet laid down under the house, a small fresh air ventilation system put in, problem solved. We of course ventilate the bathroom and kitchen with fans. If it's damp outside your house you might not want to replace the air constantly, but someone would probably have to look into and think about that.

Aredwood

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#1846687 14-Aug-2017 20:39

mwm42:

I am hoping to install a heat pump system to replace oil-fired ducted central heating in our house near Eastbourne, facing south and in bush, therefore very humid.

We built in 1964, haven't used the furnace since the mid 70s, The ducting was very effective - it's two-storey with a lounge-dining area just under 40 square metres, normal stud height, and 3 bedrooms directly underneath. A single duct at ceiling level in bedrooms, 2 ducts at floor level in lounge and 1 in dining area.

Playroom, toilet and kitchen extend at the 2nd storey height, with workshop underneath including furnace; these will rely on spot-heating if at all.

So I want to replace the furnace with a heat pump sized to heat the lounge to around 20 degrees. I use a pyroclassic wood burner on cold days or when the spot price is high (I’m on Flick Electricity).

Only the main bedroom would be heated at all – I’d close off the other bedroom vents.

Our humidity is very high - several litres/day in portable dehumidifiers - up to 10 litres as I recall in early summer, and around 2 litres/day in winter. I expect therefore that the outdoor unit will ice up badly in winter. Therefore I would want to add a separate dehumidifier, thus ducting dehumidified air. IS THAT POSSIBLE?

It sounds like the outside of your house is very damp due to the trees and not much sun. Therefore a ventilation system that only brings in outside air will be a waste of time and money. The ducted heatpump system sounds like a good idea for your house. It will dehumidify in summer when you are using the aircon, And if you don't need heating, make sure the system you get can be set to a "fan only" mode. So you can run a dehumidifier in the lounge or another room away from the bedrooms, and use the heatpump system to deliver dehumidified air to the bedrooms.

The biggest problem will be thermostat placement. Where is / was the thermostat for the oil fired system?

mdf

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#1846693 14-Aug-2017 20:58

@mwm42 - what size is your ducting? If dampness is a problem (all over the house?) but you only want to heat specific rooms, you might find it more cost effective to plug in a ventilation system to the ducting and just use ordinary heat pumps in the rooms to be heated. You can get a smartvent system from Bunnings and install it yourself if you were so inclined. They start around $1,000 I think.

Separate but related topic. Any chance the motor in your old furnace still goes? I'm on the look out for old induction motors if you wanted to flick it off.

mdf

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#1846694 14-Aug-2017 21:01

And having reread your question, the Mitsubishi Lossnay range does dehumidification and heat pumpery.

Aredwood

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#1846703 14-Aug-2017 21:21

mdf:

And having reread your question, the Mitsubishi Lossnay range does dehumidification and heat pumpery.

There is nothing on that site about true dehumidification. Apart from saying that a heatpump will dehumidify when used for cooling. It only says "assists moisture control" and "extracts moist air". Which is not going to help if the outside air is also moist.

mdf

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#1846750 14-Aug-2017 22:35

Aredwood:

mdf:

And having reread your question, the Mitsubishi Lossnay range does dehumidification and heat pumpery.

There is nothing on that site about true dehumidification. Apart from saying that a heatpump will dehumidify when used for cooling. It only says "assists moisture control" and "extracts moist air". Which is not going to help if the outside air is also moist.

I thought that part of the idea behind the heat exchanger was that any (well, some) moisture would be condensed out before being circulated. No?

Aredwood

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#1846771 14-Aug-2017 23:22

mdf:

I thought that part of the idea behind the heat exchanger was that any (well, some) moisture would be condensed out before being circulated. No?

The Lossnay heat exchanger is only for exchanging heat between the incoming and outgoing airstreams. When the house is warmer than outside, the incoming cold air is pre heated by the heat in the air that is getting expelled outside. It is intended mainly as a way of reducing heat loss, and during summer, allowing you to have ventilation without adding to aircon load from having to cool down hot air introduced from outside.

There is actually a paper Lossnay heat exchanger core available that allows humidity to be exchanged - it is intended for very dry climates, where low indoor humidity is a problem. But my understanding is a plastic core in used in NZ - no humidity exchange.

Either way it can only remove moisture when outside air has less moisture than inside air.

Kickinbac

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#1849025 19-Aug-2017 23:48

Aredwood:
mdf:

I thought that part of the idea behind the heat exchanger was that any (well, some) moisture would be condensed out before being circulated. No?

The Lossnay heat exchanger is only for exchanging heat between the incoming and outgoing airstreams. When the house is warmer than outside, the incoming cold air is pre heated by the heat in the air that is getting expelled outside. It is intended mainly as a way of reducing heat loss, and during summer, allowing you to have ventilation without adding to aircon load from having to cool down hot air introduced from outside.

There is actually a paper Lossnay heat exchanger core available that allows humidity to be exchanged - it is intended for very dry climates, where low indoor humidity is a problem. But my understanding is a plastic core in used in NZ - no humidity exchange.

Either way it can only remove moisture when outside air has less moisture than inside air.

Mitsubishi Electric do two types of heat exchanger cores in NZ. The majority are the paper core which allows moisture to pass between the air streams. They have one model with a non permeable core aimed at extracting from wet areas such as bathrooms and kitchens.

Quinny

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#1849314 20-Aug-2017 17:59

Christchurch so gas is s**t horrible expensive (ie lpg brought down to South Island at 49c per day for reticulated plus 19c a unit) but I still love the gas hot water as set at 46 deg it is perfect and hot every time whenever. I have the Escea dual sided DX1000 which is a metre wide and worth every cent of the $15000 it cost installed with 5 ducts. I hate cleaning a gas hob so went induction as the nice flat F&P model you cannot get in the South Island. I also added 4 stand alone heat pumps on a super efficient Dakin multi unit which idles very low. No I dont leave things running just turn on and use when need. The Escea can move the temp in the massive open area (house is 230sqm) 5 degrees in approx 10-15 minutes and then usually I turn it off. A raging storm can have all the glass area curtains open (and it is masses of glass) and between the fire and largest heat pump you roast.

I looked at all sorts of options and 4 years later can say I have a perfect setup for me. The gas fire is stunning visually with zero work needed (recent queues for firewood down here) and stand alone heat pumps mean warm is where needed and off where not. No cold zones. I sent them at 20-22 and turn off as soon as room is warm. Gas bill is about 60-80 in summer and max of 120-140 in winter. power is still high at about 120-140 year round but then we are electronic city here with more tvs, servers and toys than most households. I grew up with ducted diesel at my parents and have had horrible experiences with ducted heat pumps and cold zones so was never going to put that in. All up on build I think it was about 10k for the 4 heat pumps on top of the gas fire.

Aredwood

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#1849345 20-Aug-2017 19:25

Kickinbac:

Mitsubishi Electric do two types of heat exchanger cores in NZ. The majority are the paper core which allows moisture to pass between the air streams. They have one model with a non permeable core aimed at extracting from wet areas such as bathrooms and kitchens.

Wait what?? I don't see the point of using the paper core heat exchanger in NZ. Do people in NZ actually have problems with low indoor humidity? I get that in alot of other countries low indoor humidity is a problem. But I struggle to see the use case in NZ of a ventilation system that is designed to remove less moisture from the house that it otherwise could.

Im interested to hear your thoughts @kickinbac

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