I posted this initially in the plumbing forum but think that the Residential HVAC forum makes more sense.
A year ago, we installed a 14 kW photovoltaic system to generate net-metered solar power. After one year, it is safe to conclude that I have excess solar generation (~ 4k kWh) and I am looking for the most financially attractive options for utilizing the excess. I am not sold on EVs for rural America but have thought of another option and would appreciate any and all opinions.
I have (2) 20 year-old 75-gallon LP fired water heaters...one is used for heating water for everyday use (showers, dishwasher, etc.) and the 2nd is a hydronic auxiliary heat backup when temperatures drop below the lower limit of my heat pump capabilities (<30˚). The hydronic unit also provides heated floors on request. We do not fire up the hydronic water heater until temperatures are forecasted to drop below that 30˚ threshold. The "traditional" water heater consumes about 350g of LP annually while the hydronic unit (as it is only used seasonally) uses around 150g of LP.
Being rural, we lose our power on occasion...it is not unusual to be out for a few days (the derecho was 8 days). The exhaust fans on both LP water heaters are connected to our 12k watt Generac standby generator as is our well pump. So we currently have hot water (and heat) during prolonged power outages. The generator was sized for the current arrangement and has no room for expansion.
My thought is to replace the "traditional" water heater with a 75-gallon heat pump electric water heater (HPWH). The annual savings of 350g of LP makes for an attractive payback, especially if one considers that my marginal electricity cost may well be $0. This type of unit would consume 1k kWh annually so I have plenty of solar capacity in the event that an EV eventually makes sense down the line.
The draw for a HPWR is too much for my generator so we would be at risk for no hot water in the event of a prolonged power outage. One possible work around involves tapping into the hydronic water heater.
Suppose that I was to have a pipe installed between the hydronic water heater and the new HPWH. In the event of a power outage I would fire up the hydronic water heater (if not already on) and turn a diverter valve to switch the HPWH supply from the well (cold) to the LP hydronic water heater (hot). In this scenario, the HPWH would not be heating water...just maintaining the temperature of the heated water provided by the hydronic water heater and providing hot water for the house.
Is there anything that I am not taking into consideration with this concept?
John
A year ago, we installed a 14 kW photovoltaic system to generate net-metered solar power. After one year, it is safe to conclude that I have excess solar generation (~ 4k kWh) and I am looking for the most financially attractive options for utilizing the excess. I am not sold on EVs for rural America but have thought of another option and would appreciate any and all opinions.
I have (2) 20 year-old 75-gallon LP fired water heaters...one is used for heating water for everyday use (showers, dishwasher, etc.) and the 2nd is a hydronic auxiliary heat backup when temperatures drop below the lower limit of my heat pump capabilities (<30˚). The hydronic unit also provides heated floors on request. We do not fire up the hydronic water heater until temperatures are forecasted to drop below that 30˚ threshold. The "traditional" water heater consumes about 350g of LP annually while the hydronic unit (as it is only used seasonally) uses around 150g of LP.
Being rural, we lose our power on occasion...it is not unusual to be out for a few days (the derecho was 8 days). The exhaust fans on both LP water heaters are connected to our 12k watt Generac standby generator as is our well pump. So we currently have hot water (and heat) during prolonged power outages. The generator was sized for the current arrangement and has no room for expansion.
My thought is to replace the "traditional" water heater with a 75-gallon heat pump electric water heater (HPWH). The annual savings of 350g of LP makes for an attractive payback, especially if one considers that my marginal electricity cost may well be $0. This type of unit would consume 1k kWh annually so I have plenty of solar capacity in the event that an EV eventually makes sense down the line.
The draw for a HPWR is too much for my generator so we would be at risk for no hot water in the event of a prolonged power outage. One possible work around involves tapping into the hydronic water heater.
Suppose that I was to have a pipe installed between the hydronic water heater and the new HPWH. In the event of a power outage I would fire up the hydronic water heater (if not already on) and turn a diverter valve to switch the HPWH supply from the well (cold) to the LP hydronic water heater (hot). In this scenario, the HPWH would not be heating water...just maintaining the temperature of the heated water provided by the hydronic water heater and providing hot water for the house.
Is there anything that I am not taking into consideration with this concept?
John
source https://hvac-talk.com/vbb/threads/2242134-Heat-Pump-Water-Heater-During-Power-Outage?goto=newpost
No comments:
Post a Comment