CHOICE membership

Ducted heating unit

We have a 25yo Stadt heating unit that requires coaxing most mornings to fire up. Had the pcb board replaced some 5+ years ago. Figure it might be coming up for a replacement…
Choice doesn’t seem to have tested ducted heaters and the productreview website is, as often the case, riddled with dissatisfied consumers.
Can anyone recommend a brand/model??

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Is this gas fired? Would you consider replacing it with a heat pump or aircon? It may save you on running costs.

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I’m not against the idea, but I’m not sure it’s practical. An article I read somewhere in Choice suggested multiple split systems would be cheaper to run than ducted reverse cycle. Apart from a new power run from the fuse box, I imagine we’d need to go 3phase as well. We’re a retired couple and in winter we run the gas ducted to take the chill off the house until 7pm at which point we generally retire to the family room and use the split system to warm the room (rather than the entire house). We recently went to a instantaneous gas HWS, and we’re also pretty committed to the gas cooktop:-)

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The new circuit would be part of the cost. I am not an aircon technician but I doubt you would need to go three phase, that seems to be the case with large commercial systems for buildings much bigger than the usual house.

It may be worth the trouble of costing various technologies over their lifetime to see which is cheaper taking into account the upfront cost and running costs. Unless you get some real numbers to compare we are all guessing.

Gas was all the rage 20-30 years ago when Oz had very cheap gas. Since then the cost of installing aircon has gone down and the efficiency up while the price of gas has doubled or more, so you may get a different answer than the one you expect. I don’t know if this is important to you but aircon also has the advantage that it can run off your own solar panels giving you more own-use of the power you generate. Also in future as the reticulated power converts to renewable energy aircon can take advantage of that where gas will always be generating greenhouse gases during production and during your use of it.

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The reason Splits vs Ducted running costs are that with Ducted it has a a set pressure flow it looks for, if too much back pressure it opens at least one duct to reduce that back pressure (this duct/s are usually set ducts ie they are specifically chosen and marked in the controller). It has to have access to returns which feed the air back over the coils, so doors need to have space under them or returns placed in the rooms for proper circulation and the fan has to work to draw that air into the returns (uses a bit of power, more so than a split in a room). Even though most are inverter Tech, a 11 or so kW unit will be using a lot more power than a typical room Split of 2 - 3 kW just to heat/cool one bedroom (in part because of the pressure relief system). So say you want to heat 2 or 3 rooms at the same time you will be using around 6-9 kW (if at max) with Splits, with ducted this will be around 10-11 kW (at Max if a 11kW system). Generally with ducted you have one temp sensor so depending of it’s placement a ducted unit may run harder because it is not getting correct temp values for the room you are trying to cool or warm. Splits because they tend to be room specific they tend to get temp control judged better. Of course if you have a bigger room then running costs for that room will be more equal.

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Since the question comes from a retired couple I feel incumbent to add context that might or might not be relevant.

When we reach a certain age more and more products are likely to outlive us, so the whole of life costs are not as important as installation and cash flow to run them.

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Good point Phil but the value of the estate is also a consideration. I am of an age when I have started thinking about these things too. Another consideration is the environment. I regret now replacing our gas system a few years back as ultimatley they are producing CO2 and contributing to warming, whereas an electric unit can (potentially) be powered by renewable sources - including dometic solar. Also, I doubt gas wil get any cheaper, whereas I think the oppostie is true of electricity. Reverse cycle units seem to be the obvoius choice, but a little research may identify other options. They do offer the opportunity to localise heating to reduce consumptoin, rather than heat the hwoel house whne it is not required too. Ultimately they would add value to the property, whereas a gas unit may be less deisrabe, particulary in a few years.

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[quote=“grahroll, post:5, topic:24400”]
It has to have access to returns which feed the air back over the coils, so doors need to have space under them or returns placed in the rooms for proper circulation and the fan has to work to draw that air into the returns (uses a bit of power, more so than a split in a room).

We had ducted reverse cycle installed. The plan was to split the return air either side of a sliding door (dining/family/kitchen area plus a lounge room and bedroom on one side, and 3 bedrooms with a small hallway on the other side). After installation, we found that they had put just one large return in the hallway ceiling. The explanation was that a return in the dining/family/kitchen area would be too close to the inflow duct. An early-to-bed occupant of the nearest bedroom likes the sliding door closed to reduce noise and light, which is why I wanted the return air to be split either side of the door. The air/con fan obviously has to work hard if it is fully closed as air from two-thirds of the house would have to squeeze under the sliding door. I routinely have to slide the door open a couple of cms. It sounds as though the energy use would be increased if this wasn’t done, as well as possibly shortening the life of the air/con. Any other suggestions?

Two returns would have worked. As well the temp control should have been placed to ensure as even a temp was maintained as possible. If it isn’t too difficult just get a second return placed the other side of the sliding door and connect the tubing to the existing return ducting. You could also have a louvered vent placed in the sliding door so that it cuts the light but allows free movement of air either side of the door.

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Thanks for that. I think an extra return would be the better option, and I just need to be more forceful in requesting same (the air/con company was not at all keen to do so earlier).

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