Air-to-water heat pump failure

May 16, 2010 · Posted in Construction, Lessons Learned from a Green Building Project

My family built a new home in 2004, and given my long professional background in energy efficiency, it was only natural to include as many energy features as we could afford. I’ve always recognized that home efficiency starts with a tight, well-insulated building envelope. We selected a general contractor that impressed me with his knowledge of building science and a long history of building homes ahead of the curve. Although not a builder myself, I’ve worked with them for many years. I’ve always believed that a builder develops a “system” that works for him or her, and that as a client I would be wise to adopt that system. In this case the system included hydronic radiant floors driven by an air-to-water heat pump. When our house was built this contractor had already installed several of these systems with good results. Ours was to be the first of many problematic systems over the next several years.

Repeated failures and costly repairs over the last four years have prompted us to seek estimates for a replacement. We might consider another brand of air-to-water heat pump (aka reverse cycle chiller) or we may simply convert the system to a gas-fired tankless water heater.

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The original system (above) was installed in late 2004 by our general contractor. The system is a standard York heat pump mated to a heat exchanger made by Aqua Products.

A Good Beginning

The first heating season was trouble free and the system performed very efficiently. The coefficient of performance was measured 3.5 at 49°F. Even when temperatures dropped to the single digits, the system was able to heat the 1800 sq. ft. home without backup heat. After that first heating season we were pleased and optimistic.

Trouble Brews

In November of 2005, the system died. During this time, the house was heated by a single 4.5 KW electric element in the standard electric water heater that serves as the storage tank. In a perverse way, this was instructive. We were able to measure how much heating energy is required without the extra efficiency of the heat pump.

We called in a well-regarded heating contractor. Several months passed as the system was diagnosed and finally York agreed to provide a replacement compressor, while the local distributor paid the labor costs to install it. The work was finally completed in April 2006, two weeks before we shut the system down for the season. While the system is capable of mechanical cooling, we seldom use it. The new compressor performed well during the following heating season, and again we were optimistic.

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Another Compressor Fails

The system stopped working again in November of 2007 due to a failed compressor. This time York agreed to replace the entire outdoor unit with a highly efficient member of the Affinity line. We paid our heating contractor for the labor. The work was completed in February of 2008. For the second time, the system was out of commission during the coldest part of the winter.

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Just a week later, this new unit stopped functioning during a moderate cold snap — the temperature dropped to the mid 20s. York’s factory representative was in town to meet with a group of HVAC contractors who had been experiencing problems with air-to-water heat pump systems. He dropped by to take a look and declared that all was well.

In December 2008, about six weeks after the system began operating for the season, the system began to cut out. The diagnostic code indicated high discharge line temperature. The York factory representative again visited the system along with local HVAC technicians. He suggested that the liquid line sensor be moved to a different location. That change has not prevented repeated cut outs, all showing the same high discharge line temperature code. Actually, it seems that the cut outs are more frequent now.

All these problems have occurred within the York heat pump, so we have asked that York cover the materials and labor to fix it. Citing the warranty, which does not cover labor, York has offered only to supply replacement parts.

We have decided not to invest any more of our own money in the York/Aqua Products system, and have started to research a replacement system. We might consider other reverse cycle chillers now available from Daikin and Unico. On the other hand, we may just install a gas-fired tankless water heater.

(Note: This post was originally written in late 2009. Since then there has been a new development and the heat pump may be fixed.)

— Bruce Sullivan

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Comments

3 Responses to “Air-to-water heat pump failure”

Fire Fly on September 20th, 2010 6:49 am

When properly installed, an air source heat pump will effectively deliver one and a half to three times more heat energy to your home than the electrical energy it consumes.

why not maybe try a fire fly heat pump instead?
air water heat pump on October 2nd, 2010 6:39 am

I notice the brand of your heat pump is “york”. I advice another specialized air-water heat pump brand “wave”. just google it for your information,
brian tausch on December 26th, 2010 8:03 pm

i always to get the outside temp senors cut off at 34 degree that to shut down the heat pumps before the cold weather runs down to deep frezze and heat pumps need to be rest and off under cold 35 degree senor and the outside temp senor will call to the elecrtic heater or hybird gas furnace heater to get that heat on when the higher eff heat pump is off. when the outside going warm and outside temp senor 35 degree will go kick in with the heat pump running (make sure snow must remove off the heat pumps in warm weather) heat pump only better eff zone in 35 to 65 degree. heat pump going to easy running and will give high hot air out of vents or get water hot in the better warmer weather is 50 to 55 degree better than the gas furance or elecrtic heaters. outside senor can save the heat pumps life and those heat pumps going longer last up to 10 years and 20 years with lower the thermost down. I have oldest heat pump 30 years old that i took care of that heat pumps.