Power outages | Mikko Kulmala's air-to-water heat pump froze dramatically, quick action prevented costly destruction

from Kerava Mikko Kulmala was on Thursday evening at the Joker's latkämatsi in Helsinki's ice hall, when the electricity went out at home.

As a result of a power outage, the air-to-water heat pump of the detached house in Kulmala shut down and the water in the pipes froze. The situation was getting worse.

“The danger was the pipes and the heat exchanger cracking. It has been in the mind that this could happen,” says Kulmala.

Water circulates in the outdoor unit of Kulmala's air-to-water heat pump, while many air-to-air heat pumps circulate non-freezing refrigerant.

Helsingin Sanomat wrote on Thursday evening, that in Kerava the electricity was cut off for approximately 14,000 customers due to a fault in the substation's main transformer for three hours at the longest.

Kulmala received a message about a power outage on the way home. The electricity had been out in his house for about an hour.

After Kulmala returned home, he started defrosting the heat pump.

“I made a tent out of tarps around the pump and put a heat fan inside it. I defrosted the pump until half past two at night.”

The air-to-water heat pump is the main heat source of a single-family house.

“If I hadn't acted quickly, the pump would have broken down and caused costs of several thousand euros. Now we would have to use a backup system, i.e. direct electric heating.”

Private house the internal temperature was not affected by the power outage.

“The heat stays in a stone house for a long time. We have also had the fireplace on the whole time.”

According to Kulmala, the heat pump, which has been in use for five years, has never frozen before. The water circulation of the pump will not freeze if it is kept running in freezing temperatures. The floor heating of the house runs on water.

According to Kulmala, the compressor, or air pump, stops working at around 20 degrees below zero. However, water circulation pumps are popular these days.

“Water-circulating pumps have good efficiency, but there is a risk of freezing. The new pumps withstand frost better.”

Movement or going to lätkämatsi, however, the cold weather does not limit Kulmala. Fortunately, power outages during severe frosts are quite rare.

The regulation of electricity, which was discussed last year, has made Kulmala think. According to him, the heat pump freezes in these freezing temperatures during a power outage for more than an hour.

“In that case, the outdoor unit must be emptied of water and filled again. It's a pretty big show, but you can do it.”

Correction 6.1. at 8:33 am: Corrected the word Air heat pump in the title to air water heat pump.