I am keen to get rid of gas underfloor heating although it works well. I have had a quote to replace the system with an ACTRON Air 13kw ESP plus system with 3 zones. The total quote is $13,860. An unzoned system by Toshiba was quoted at $8,400 plus GST.
I havent been able to find impartial information on which I could base a decision.( We already have 8 solar panels and solar hot water on the roof of our 4 bedroom double brick old refrigerator of a house in Sydney, so don’t need air con .) Can Choice Community help?
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Hi @pmslaytor, welcome to the community.
If you don’t want aircon and have been happy with gas underfloor heating in the past, have you thought about turning it into a solar run system?
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The gas heater for the underfloor hydronics can be replaced with a high efficiency electric heat pump. It will provide the same great benefits of the existing underfloor system at potentially a lower cost. IE retain the underfloor hydronics and replace the gas heater?
EG
The only benefit of a reverse cycle air conditioning system is the ability to cool and dehumidify effectively in summer as well as heat in winter. Although RC air conditioners can dry the winter air more than is comfortable.
My past experience of living in Sydney is of a relatively mild climate, unless one lives away from the coast.
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Our house is not based on a concrete slab, so I dont think this would work. am I right? It is an old (1909) house built on brick piles, with wooden floors.
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Is what you are describing a ducted heating system, using gas with an external heating unit? Whether the ducts are installed in the roof space or under floor space, both are options with ducted systems.
‘Underfloor’ may be how your system is described by the installer but a description which is a little confusing. Underfloor heating is generally associated with hydronic heating using recirculated hot water and pipe/tube imbedded under the floor. Hydronic heating often uses gas as a heat source for the ‘boiler’.
Assuming your heating system is a ‘ducted’ system it would be reasonable to consider an upgrade or replacement of the gas heater with an electric powered heat pump. Any supplier of ducted air conditioning should be able to offer a replacement. It’s likely they will offer a replacement that can heat and cool as needed.
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Underfloor heating for timber floors will work see…
It really depends on you budget and type of heating you are after (instantaneous, constant etc).
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Similar issue- have gas fired furnace for extensive ducted sub-floor heating- wish to replace with a heat pump- but indications are that the existing ducting is sub standard and would have to be replaced at a major cost- is this mandatory i wonder?
Not mandatory - it’s a common guide, but it may be worthwhile. It’s understandable to question whether the business offering the replacement for your gas heater taking advantage to upsell new ducting? The replacement of the ducting is labour intensive and as you note a major cost to replace.
There’s differing views to be found across the internet, many of which may relate to climate zones very different to Australia. It’s worth taking some time to review prior posts if not already done. I also found the following of general interest, being a relatively independent source. https://www.nrel.gov/docs/fy02osti/31318.pdf
To consider:
Is the existing ducting in good condition - no leakage and well insulated? It might require a survey with a thermal imaging camera (if in doubt) to identify any issues, whether it is serviceable as is or a repair is better than replacement.
To note many general recommendations are to replace ducting with larger when upgrading to a heat pump. Energy efficiency is a much higher priority today than when most older systems were installed. Australians anecdotally have been seen as a market that is excessively purchase price conscious, hence cheaper is best. Hence under sizing and low quality insulation are more common, given many systems were only ever needed for a short portion of the year. Gas was also very cheap mitigating any losses due to lower standards of the install. New larger ducts will reduce the airflow power losses (it’s a cube law) and are likely better insulated reducing heat loss. Energy is no longer as cheap as it once was making efficiency more valuable.
One could suggest the existing ducts will service a replacement by a heat pump. The unknown is whether the existing ducting will cause any unacceptable restriction to the maximum airflow through the heat pump. The heat pump manufacturer will have charts for the design air pressure air flow volume (rate) for the heat pump/system fan at rated output. These can be compared with the existing gas heater specifications (if available).
While the airflow capacity of your homes ducting can be estimated by calculation, it is also possible to assess its operating condition (pressure loss and implied flow rate from the fan curves). As is by measuring the differential pressure at the fan at maximum speed, with all in home vents dampers etc fully open. This may assist in deciding which way to go.
If the intent is to also use the heat pump for cooling in summer there will be other factors to consider. This might include condensation risks or drainage from the ducts, depending on the install and product now in place.
All of the preceding should not be taken as offering professional advice. A professional assessment of your actual home, ductwork and needs would require a HVAC professional to complete an assessment using full details of the existing install and future needs (at a cost that might not find favour). An alternative for the average consumer is to compare multiple quotes from reliable suppliers, and question every difference.
Addendum: “food for your thoughts”
If I was in a similar situation, and the existing ducts were in good serviceable condition. I’d wonder if it was wise to look to spending extra on improving the homes insulation. Improving the insulation and reducing heat losses could support purchasing a lower capacity heat pump (which would not need as large a duct size) to replace the gas heater. The saving in the cost of the heat pump, running costs from needing less heating and avoided duct upgrade could provide a better outcome. It would need some professional HVAC expertise to help to decide. Possibly not available from the local businesses intent on selling a new heat pump and ducting. YMMV
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Thanks for that comprehenive response
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