Gas based heating · Auckland
Underfloor and hot water from one boiler
Underfloor + hot water
This is the most common gas setup we install. The boiler is already there for the floors, and heating the hot water as well adds little extra cost.
Why it works
Floor and hot water loads
Unlike the pool combination, a slab and a cylinder are compatible loads. The boiler can serve both without either compromising the other.
Hot water takes priority
When someone runs a tap, the diverter sends everything to the cylinder for a few minutes. The slab does not cool measurably in that time.
The cylinder recovers fast
A gas boiler puts heat into a cylinder much faster than an element or a heat pump can. That means a smaller cylinder goes further.
Different temperatures, one boiler
The heating circuit runs cool for condensing; the cylinder circuit runs hotter for storage. A mixing valve on the underfloor side handles it.
One service visit
One appliance, one annual service, one certificate, one company.
One boiler — warm floors and hot water
Swipe the diagram sideways to follow the full circuit →
One boiler, one primary circuit
Gas in, flue gases out, condensate to the drain. Both jobs come off the same primary flow and return.
Balanced at the manifold
Flow and return feed every floor loop, zone by zone, from a lockable cabinet recessed into a cupboard wall.
Hot water through a coil
Primary water runs through a coil inside the cylinder and heats the stored water without mixing with it. A sensor calls the boiler.
Hot water gets priority
The cylinder is a small, short load compared with the slab, so it is heated first without a noticeable effect on the floors.
The boilers we fit
Click a boiler to see its full specifications.
From one of our installs
One gas boiler, warm floors and hot water
On this job one wall-hung gas boiler heats the underfloor heating and the hot water cylinder beside it. The boiler switches to the cylinder whenever it needs topping up, then goes back to the floor, so one appliance in a single cupboard provides both.
Cylinder or combi
Both work here
A system boiler with a stored cylinder is the usual choice. A combi — making hot water on demand with no cylinder — also runs underfloor heating and suits smaller homes.
Gas or heat pump
Gas and heat pump are not rivals in our shop — we install and service both, every week. What follows is how we actually decide.
A DuoHeat heat pump suits you if…
- You want the lowest running cost on both jobs
- Hot water is the largest part of your power bill
- There is outdoor space and a place for a cylinder
- See the heat pump version
Gas suits you if…
- Gas is at the house and the boiler is being replaced anyway
- You want fast hot water recovery, or no cylinder at all
- Plant space is limited
- Up-front cost is the constraint
If gas is already at the house and the boiler position is easy, a condensing boiler is normally cheaper to put in and more expensive to run. A heat pump is the other way round. Which wins depends on how long you are staying, what the gas connection costs, and whether you also want pool or hot water off the same plant. Ask us and we will price both.
Questions
Underfloor and hot water on gas: questions
Does the heating stop while the hot water heats?
Technically yes, for a few minutes. In practice you will never notice, because a concrete slab holding 20 °C does not cool measurably in the time it takes to have a shower.
Do I need a bigger boiler to do both?
Usually not. Because hot water is prioritised rather than simultaneous, the boiler only ever does one job at a time. It is sized on whichever load is larger, not on the sum of them.
Can I add the pool to this later?
Possibly — but a pool is a much larger load and changes the sizing. If a pool is possible in future, tell us at the start and we will leave the boiler and the pipework ready for it.
What is the annual service?
One visit. Combustion check, condensate and flue, expansion vessel, pump, zone valves, cylinder and thermostats, plus a gas soundness test. It keeps the warranty intact.
Free, no obligation
Request a quote
Send the plans, or tell us what is there now. We will price the gas option and the heat pump option side by side.