Hi,

I am installing a system and the homeowner just informed me that he wants to hook his geo unit up to a seperate meter he is having installed.  The power company will offer him an "off peak"  discounted rate and he wants to hook up his five ton geo unit and 15kw auxilary heat to this cheaper meter.  Sounds like a clever idea, but when I contacted the power company they said that this "off peak"  power could be shut of for unpredictable periods of time but never more than six hours straight.  This is a 3,400 square foot  two story house with a gas fireplace on the second floor.  The homeowner is pretty determined to use this cheaper power.  Is there any other way to do this other than hooking up a gas furnace that would heat his house when the "off peak" power gets shut off for six straight hours and its ten below outside.   Thanks. 

Maybe an electrician can make it possible to use regular power when the off peak is not available.

Such an arrangement might violate the terms of the off-peak metering since it would subvert the utility's attempt to shed load during peaks. It would have been against the rules for me when I had a separate off-peak meter near Philly in the early 1990s.

Consider leaving the aux on peak and the unit off peak?

Is there room in the basement for a 1000-2000 gallon tank of water in the basement to serve as heat storage?

In heating dominated climates such as MI for me or WI for you most of these interuptable service systems tend to be active in the summer (ac season) and dormant in the winter. Other thougts are that night time or peak load for the heat pump are least likely interuptions.
You might try it and with all the usual disclaimers. In MI if folks want interuptable service, I insist on a larger unit for recovery (which negates much of their savings).
Or convince them that a gas furnace with a split system is the way to go.
Good Luck,
Joe

We actually have this on our system. But we also have a natural gas 30,000 btu fireplace in the main living space. We are in Wisconsin (WPS) and rarely have it shut off in winter. I see they have a scheduled shut off on the 30th, odd, that is the first winter one I have seen, although it is unseasonable warm right now. My guess is they are moving / upgrading some lines or something.

If they want to do it make sure they understand they could get cold and has been mentioned when it does come back on the aux heat will likely run and eat up a months of energy savings. Either that or disable the aux and let it take a day to get back up to temp. We also have 16,000 gallons of hot water in the basement so our house doesn't have a fast swing and will stay at temp for quite a while.

We are in Duluth Minnesota. Our geothermal (7 ton) compressor is connected to 'off peak' electricity which we pay at half the rate of the non-interruptible power. Our geo installer put in a gas tankless water heater on the hydronic circuit. It has never come on. I 'exercise' it monthly to be sure it will work. I also put in a backup generator for our fairly frequent power outages (in the non interruptible service). The generator will run the circulating pumps and water heater circuitry, but isn't big enough to power the geo compressor.

Rolling blackouts are usually related to the cooling season, not the heating system.  The power company isn't going to save all that much energy by shutting down his system in the winter, since most people are heating with oil and gas.  While there nothing preventing them from invoking there right to shut down his system when it's 10 below outside, the event would be so rare that it wouldn't justify the cost of installing a dual system.  

I would not assume anything other than what is written in the rate tariff terms and conditions. If they are legally allowed to interrupt the service all night during a cold snap, prudence dictates designing for that circumstance, and the design had best be automatic in nature, that is it can't assume the homeowner will be present to take whatever mitigating action is planned.

A single bad unattended frozen plumbing incident will gobble up a lifetime of energy savings.

The homeowner spoke with the power company and has decided to install a gas backup furnace. I agree with engineer that assumptions can get people into trouble... big trouble if its ten below zero. The homewoner still may have a few issues with ac if his power gets shut off in the summer, but I feel in my climate this is much more bearable especially if he installs a window unit or something. The homeowner has also decided to put radiant in his basement, so the idea of putting in some kind of backup water heater for the radiant system seems like an interesting option to me as well.

The bonus to this design is the ability to keep the house warm witha portable generator.
j

The entire point of power metering is to reduce the electrical demands on the power company, him tossing in 4 window units and turning them on defeats the entire purpose of the program.  I would imagine that the power company wouldn't be too happy if everytime they turned off his Geo system power that his standard power usage spikes.