I’m having a new home built in Northern Minnesota. The home is going to be built to be very efficient and to the standards of the local Electric power company which will give considerable rebates if we meet all their criteria. The home must first be heated electrically to qualify for the program. I want to have infloor heat throughout the home. How should the fluid in the infloor be heated electrically? I currently have an efficient gas boiler which I am happy with but to get any rebates I must use electric.
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It would make the most sense to skip any "fluid" and just use heating cables.
Heat scource
You can use a ground scource heat pump with radiant floor heating. Even an air to air heat pump will work. If gas is available you can use either type heat pump with gas as the alternate scource (back up heat scource). The se are called hybrid systems, but meet most "all electric home" requirements.
Radiant floor heat with electric cableing would be a real energy hog. They are fine for small tile floor areas that have intermitant use, but a whole house with radiant floor cable matts would spin your meter like a top.
Radiant floor heating with cables would be no more of an "energy hog" than radiant floor heating using an electric boiler.
You guys are all missing the point...
He wants an Electrical Hot water system JUST LONG ENOUGHT to get the energy rebates from his POCO, after which he will go back to using his fancy gas system.
You can't resell buried heat cables on EBay!
Huh?
He is building a new home, but is happy with his hot water boiler system in his current home. He didn't sy if gas was available at the new home site. May or may not be, but the credits are for an efficent all electric home. Most of those programs include hybrid gas/electric system or propane/electric systems. He can have both, and if his electric rates are low enough may save energy cost running GSHP instead of gas.
Efficiency
By definition electrict heat is 100% efficient. I can't argue that. Why then aren't there more and more homes with all electrict (resistance) heat being built? Maybe it is because energy cost have driven that option to the side lines. A GSHP is touted to be 300% efficient (I don't agree with that numbr) when you use the electric heat as the standard.
I put one in a home 20 years ago and we have tracted the utiliy cost for that same period of time. We have also compared it to the homes in the same developement. Any guess as to the lowest average energy usage> Hands down the GSHP wins, even when stacked up agianst smaller homes. Maybe I just did a better job of building the home, but I don't think so. I did a good job, sure, but knowing what I've learned in the last 20 years, I could have done a heck of a lot better.
Touting all electric resistance heat as being the "best" way to supply his needs is just plane wrong. He knows ng is a cheaper scource of energy, even though it is not as efficient as electric heat. It just cost so much less that a 90+ efficiency rating still beat the operating cost socks off striaght electric.
I'm not trying to flame you with any of this. I'm just trying to present the op with options that have worked for me and many others. His choice will be made based on what he learns , and what fits his means.
Yeah, I should have explicitly said all resistance heating is 100% efficient. (This is what I meant to say.) A heat pump (ground source or otherwise) is generally more than 100% efficient and is another option.
(I thought I was replying to Bob's post, but apparently punched the wrong Reply button.)
For the OP, the electric utility is the best first source for info on options. They will have data on how well heat pumps perform in his area, applicable regulations (the well option may not be allowed), and other relevant data.
What size is the lot and what is the ground like? If you can go with a ground source heat pump (otherwise known as geothermal) you can easily connect it to your radiant floor system. The side benefit of this system is you can also connect it to an air handler for air conditioning in the summer and the heat collected from the house in the air mode can be dumped into a domestic hotwater heater giving you virtually free hot water while you are air conditioning. The downside is you need plenty of ground to put in the loops (or you have to drill wells which is a whole lot more expensive.)
Heat source
The new home will be much tighter and built to the electric company's specs. To get their rebates, the home must be heated electrically. They have programs for "dual fuel" which means I can heat with other systems if they turn the electric off for certain high peak times. To qualify for the reduced rate of electricity with a "dual fuel " system I must have an alternate way to heat other than with the "dual fuel" electricity which comes through a separate meter. What I really need to know is the type or brand or method of heating liquid electrically to run through my "infloor radiant" heating system. If I could use gas to heat the liquid, I would but to recieve benefits from this program I must use Electricity as the prime energy source. To answer another persons question, Natural Gas is available at the building site. The lot is rather small (100x 150) and heavily wooded which I assume would limit the placement of coils for the Geothermal systems available.
Bob
A deep well would be a thought-worth asking about.
From the standpoint of how to heat water with electricity, it basically doesn't matter -- all units will be essentially 100% efficient.
It's really an issue of picking a heater that has the necessary capacity and reasonably long life. A standard domestic water heater is not out of the question, though you may want to invest in a small electric "boiler", especially since that may give you more options for zoning, etc.
Note that in a highly insulated home good air handling is important. You need to move heat (eg, from the sun through the windows) to areas that need it, and generally avoid "stagnant" air.
GSHP loops.
Go vertical and you only need about 15' between loops. I have a five ton WaterFurnace system. My loops start 20' from my foundation wall and are spaced 15' apaart in a pentagon patern, 165' deep each through dense clay and layer upon layer of solid rock. My system is forced air, but could just have easily been a radiant floor heating system. I opted for the forced air system because I am in a mixed heating/cooling climate with the weighted side being on the cooling degree days with high humidity. That means an air handler and duct work, so radiant floor heating would have only added to my cost. My system is not a simple system, with three seperate heating/cooling zones, tow stage compressors, and with floor trusses, supply and return ducts are all hard systems fit into the trusses. I am all electric. No ng available here and propane is to unregulated for my financial risk taking. I do have to other building on propane, but they are never occuppied more than a few hours a day or a few days a week, so I have yet to use over 200 gal a heating season.
Talk to your utility company about the GSHP. They likely have a list of HVAC companies that have met thier requirements for home owners to qualify for the rebates. Get the list, get referances, visit with HO if you can and look at the completed jobs.
My system cost was a little over $5k per ton, but as I said it is a little "over the top" for residential. My annualized heating cooling cost should be just a little over $500 per year if everything works as modeled using "standard construction methods. I expect to do better. That $500+ is for a 2400 sf home with a 2300sf walkout basement. All conditioned space.
In your area I would think you would give GSHP a hard look. A good HVAC company can take your plans and do a load calculation from them. After that it is amatter of plugging in fuel cost, system efficencies, etc and crunching numbers. In the end the rebates are nice, but what you really want is a system that works and keeps your operating cost the lowest it can possibly be. Energy in any form is not going to ever get cheaper in the future. Recognize that and plan to minimize the impact that will have on you and your family.
Given that you cool more than heat, did you opt for the hot water system to recover the waste heat?
BTW, I agree the GSHP is almost ideal for what he has in mind. It can cover both the radiant heat and cooling. No need for a backup heat source (if the GSHP isn't working the backup source won't work either unless you are talking woodstove).
Millivolt propane stove is a grid down alternate.
I have a millivolt controlled propane stove with a pilot light that I keep just because it needs no power to run, and before they double fed the power to town, we used to have long periods, (76-hours one January), with the power down.
The little fella won't heat the whole house, but it will keep things from freezing.
All of the GSHP I have seen or read about use the D-super heat loop into water heater to give you "free hot water" durring the cooling season. There is really not much to it. A simple loop installs in place of the drain valve of the wter heater. The glycol mix of the GSHP circulates through it and heats the water.
There was no upcharge on either of the systems I have had installed for the D-super heat loop.
GSHP
I think I am going to explore the Geothermal a bit more. The heating contractor tells me that a vertical system is quite a bit more costly for whatever reason. Having it also heat my domestic would be a plus. I am using a Amtrol Hot water maker now with my system and it works well.
there's no reason both heat sources can't be plumbed in the same hydronic floor heat system...in fact the electric boiler will be a great backup if your gas boiler ever goes down in cold weather.
I don't see the long-term costs of in-slab electric coils being worth it - the coils won't last forever and then what - anyone who has delt with in-slab open circuits knows what a pain in the rear that can be in the best situations.
Cheers!
Don
Electric boiler
Does anyone have a Brand Name for a good electric boiler?
Concur that a water to water GSHP is the way to go. Even better would be if you have a good well and a pond to do a 'pump & dump'.
Like I implied earlier, certain well options may not be allowed, depending on locality.