Heat transfer kits that duct warm air from the lounge to the bedrooms run on a fan. Some fireplaces have a built-in blower. Wetbacks that heat the hot water cylinder may rely on a circulating pump, and some households run a wetback into radiators with a pump as well. In an outage the fire still burns, but the lounge overheats, the bedrooms stay cold and the wetback can be left without circulation.
A pumped wetback system that loses circulation while the fire is roaring can overheat. Most are designed with safety features for this, and you should follow your installer's advice on running the fire during an outage. With the battery and inverter in UPS mode, the circulating pump simply does not stop, so the system behaves as designed. The fuel cell keeps the battery charged from stored hydrogen through a multi-day outage.
How it works →
Transfer fans, blowers and pumps are small loads that barely register against 15 kW continuous output, so they run alongside the fridge, lights and router without any juggling. Charging happens on cheap night-rate power or from wind or micro-hydro, and because round-trip efficiency is 30% or less, the system is for the outage, not for everyday running. A good firewood stack and steady power together make for a comfortable storm.
Follow your installer's and manufacturer's advice, because pumped systems differ. The system is designed to keep the circulating pump powered through an outage, so the wetback behaves as it would on grid power.
Yes. It is a small load, well within what the battery and fuel cell are designed to supply. It keeps moving warm air to the bedrooms while the rest of the house runs normally.
Many people keep both. The wood burner gives heat without power and the system keeps the fans, pumps and the rest of the house going. Together they cover a long winter outage well.
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