Can electric WH power my Radiant system

kevinl

Hello,



I am building a new 1200 square foot home, one story, slab foundation. I am located in Massachusetts. The mechanicals will be in the garage. I want to have hot water supplied by an electric water tank and a separate hot water tank with a heat exchanger for my in slab radiant heat. Is this logic o.k. to proceed with? Will a system like this (electric water tank) perform well enough to heat my house? I am thinking of a "Marathon" electric water tank for domestic hot water (50-70 gallon) and a separate tank for the heat. I am not sure what size yet for the heat system.



Even though I am a fan of oil heat, I will not have the space for it and the future does not bode well for oil and I am tired of the maintenance of it. I would not consider gas or propane at all.



I look forward to any and all replies.



Thank You,



Kevin

jp_2

cart before the horse

you need to determine what the heatloss of the house is going to be, then decide if you can afford the electricity to heat it!



 you can also do it backwards, decide how much money you want to spend on electricity and determine how much the insulation will cost.



there's electric induction heaters out there that can melt a ton of steel in less than a minute, but it all cost money!



I would build it super insulated so you can use electric to heat, don't forget passive solar too.  yesterday I got free heat all day long, didn't need to light the woodstove til 2am. I live north of 47 degrees lat.

kevinl

Reply

The new house insulation will be up to local code on Cape Cod, and it is very energy conscious from what I see. From my research, once the water is heated, there is probably only a 20 degree rise in temperature needed for each cycle through the heat exchanger. I currently use oil and it is about 200 gallons per month at about $3.80 per gallon. I don't believe I would use that much electricity at .21 per kwh (current local rate). I have attached the heat calculations (I Think). I do not want to use baseboard heat, it is too unsightly, wood burning is not for me either. I am more concerned that the logic of the system can heat the house properly. If it cost a little of a premium to use electricity, it is worth it to me to save space and not have oil burner maintenance.

Ironman

Who Did Your Heat Loss?

I don't know why you would want to heat your garage, but with the figures you have, it comes to almost 62 btu's pr square foot. That's not a house insulated to code in Mass. In fact, I would doubt that any house in Mass.needs 62 btu's pr. sq. ft.



If it's insulated to code, you should be under 25 btu's pr. sq. ft. You're gonna need an accurate heat loss to determine what size boiler you need. You can't use a water heater as your primary heat source and meet code.



As far as sizing goes, and electric water heater only produce 15,358 btu's p.r hour regardless of its storage capacity. That's no where near what you would need.



As far as electric vs. oil cost, oil is a much better deal at the rate you're paying for electric. At .21c pr KW, you would pay $8.49 to get the equivalent amount of heat that a gal. of #2 fuel oil produces. Assuming an 80% efficient oil boiler, the corrected price for oil vs. electric, which is 100% efficient, would be $4.75 pr gal.



May I ask why you don't want to use gas? A small gas mod/con would be a perfect fit for radiant.

kevinl

reply

I am not sure that is a heat loss. It is a quasi calculation to install radiant by a company that sells DIY parts. They offered a free service and I let them give me their information. I am not a do-it-yourself person on a heating system, but I would like to find all the best info I can so I can specify my wants properly (and have them confirmed by the heating contractor) that they will meet the heating needs of the house. I am really interested to know if an electric water tank can supply the hot water for an in-slab system to heat the house or would I have to go to an electric boiler? Lets assume the btu loss is 24 btus per square foot as stated in the last post.



I do not want gas. To me it is too dangerous.



Thank You,



Kevin

RobbieDo

Electric Boiler

As stated before, you will not get the BTUs out of electric as you would oil. Gas is safe if its done properly, most issues are from improper installation. Laing makes a nice electric boiler check them out, I have installed many and customers are pleased. I would have a heat loss done, not heat the garage. A house that is 1200 s.f. If it was 40BTUs per s.f. Would be 48KBtu, if it wasn't insulated properly, old rule of thumb. Sometimes it's just best to get a Proffessional to do the work as they will then be responsible if it doesn't work right or something goes wrong. Sounds like it's a new build and I'm sure you want it done right and the home be comfortable. That's my opinion.

kevinl

reply

Hi Rob,



I am not building any part of my new home, I am just specifying everything I want. It is important to have major components specified (that will work) to begin with for the heat and water systems or I feel I will go down the wrong track with the heating contractor. (and yes, I will have him confirm the system will work for the house) Most heating contractors are set in their ways meaning they like to use components that they are familiar with. I could say I want radiant heat and I would be surprised with what I got. I will get the heat loss done as soon as I choose the windows and glass doors.



I am interested in the Lang model you mentioned. My goal is to use as little space as possible for my water and heat systems, keep the system all electric,have parts availability and not have breakdowns. I assume the Lang is just for the heat system? I really want to have the ability to heat my garage for many reasons and just figured I was heating the water anyways.



So could you tell me anymore about the Lang?



Thank You,



Kevin

Charlie from wmass

Kevin If you are in Mass

You would be cheaper to install a wood stove and burn dollar bills unless you are generating your own electricity.

kevinl

rely to charlie

Hi Charlie,



Thats not true. One way or another you have to pay for running your heating source. I am just looking for insight to get accomplished what I want. I am trying to get real world ideas to specify my heating system. With many ideas of real installed systems I can narrow down my choices. This gives me a knowledge base to work with the heating contractor.



I did look at the "Lang" electric "Boiler System" and it is very interesting and it does meet my needs for space saving design. Any input of components needed to assemble the "boiler" part of the system would be helpful.



Thank You,



Kevin

RobbieDo

Laing Boilers

There efficient, remember electric is 100% efficient but you don't get the same BTUs per dollar as to other forms of hearting. You have to have a well insulated area and electric not too expensive per KWH and you might be happy. I install them in a area where I live and they have municipal electric where they pay .05 cents/KWH. As far as installation, it's installed the same as any other boiler, on there site it has installation instructions. You sound like your te GC on the new building? If you have more questions let me know. You can email me through the site. Thanks

kevinl

reply to Rob

Hi Rob,



I was just looking at the Laing site and was doing a little math. I would like to figure my electric heating cost for the 9kwh model over an average winter. Please let me know if my math is correct...



9kw/h is what the unit will use in electricity per hour.



@ .20/kwh = $1.80 per hour to run

@ constant on 24 hours per day ... $1.80 x 24 = 43.20

@ constant on 30 days per month ... $43.20 x 30 = $1296.00



Now if I understand and I am correct on my calculations, what percent of an hour is a correctly sized unit estimated to run to keep a modern (new construction) house warm? 25% (15 minutes every hour)?



I think I am asking this question correctly.



Thank You,



Kevin

Charlie from wmass

Kevin if your envelope is that tight

natural gas would be about half the cost to run. What are your fuel choices? Electric is 100% efficient but it is not clean. There is a lot of fossil fuels built to produce it and there are high losses in transmitting the power to your home. That is not considered when they are promoting their product. If you were in Seattle or Quebec I would say go for it. In MA it is at least double the cost of operation. If you have any questions on the installation details I am more than happy to answer them. I am simply trying to make you aware of the cost of operation of your system choice.

Charlie from wmass

If you do not like baseboard

and you want Electric heat. http://www.suntouch.com/ This product gives you warm floors and no pipes to freeze. also no pumps to wear out or water to leak. I am not promoting heating with electric just giving you another option.

kevinl

reply

Hi Charlie,



I did look at electric mats, etc. but I am using VCT flooring through-out the house and the electric mats do not fit my need. If the flooring is ever replaced, I am confident the mats will be destroyed on a tear up.



Thank You,



Kevin

Kevin_in_Denver_2

Why settle for 100% Efficiency

With electricity, you can get 350% efficiency for a pretty small price:



http://greenbuildingindenver.blogspot.com/2009/08/mini-splits-or-ptacs-are-key-to-net.html



http://www.greenbuildingadvisor.com/blogs/dept/musings/will-minisplits-replace-forced-air-heating-and-cooling-systems



On the other hand, natural gas is staying really cheap even as oil approaches 2008 prices.   If that holds true for long, CNG will replace propane in all markets.

meplumber

Just a follow up on Kevin's post.

There are a lot of areas of the country where natural gas is not available and due to geography and population, will not be any time soon.

Gordy

Is house still in planning/Design stage?

 Or are somethings like the slab completed Kevin?

kevinl

reply

The house is not started, all plans are finished with engineering stamps and wind load calculations. Heat loss calculations are not done because of window selections have not been made yet. I am at the point of creating all my specifications for the builder.



Thank You,



Kevin

Gordy

Slab insulation

 Should be a topic covered that is mentioned under some recent threads if you care to read.  One was under "slab concrete temps", The other was under " you are using wrong slab loss calcs".  Not exact words but you will find them.



 Very important to insulate the slab correctly. Unless you want to grow tulips in December, and pay higher utilities.

Roland_18

'lectric heat

Hi Kevin,

Do you have the specifications for how the new house will be insulated? What kind of insulation? How thick? What kind of air sealing?

I wish I were in a positon to build a new house. I'm a little envious.

jp_2

correctly sized unit

at the coldest day of the year?  most say  it should run 100% of the time.



I would prefer to see it running at 90%.   giving  it a chance to keep up in  a bad winter storm with 50mph winds and 15 degrees below average coldest temperatures.

NRT_Rob

that heat loss

is a complete joke.



if you are in the standard range though, an electric water heater will not be strong enough to heat a 1200 square foot house in the northeast. You'd have to be superinsulated or rig it up to fire multiple elements at once.



If it must be electric... and be aware, that's almost twice as expensive as oil is, even today, here in the northeast unless you get a great rate on electricity... I would look at electric boilers, or heat pumps.

NRT_Rob

can't compare like that

have to do degree day analysis.



if you had a 24kBTU/hr load... and none of us knows if you do, doing a real load calculation is a must... at something like zero degree outdoor which is conservative but not stupid unless you're on the very tip of cape cod... then you're using about 2.5 Kwh per degree day.



Your area usually has about 6,000 heating degree days per year.



I'd say you'd be looking at about $2000/season in electrical costs there just for heating with a 24kBTU/hr load and 0.20/kwh. Much more in january, of course, and much less in october.



Good heat pump as others mentioned, geo exchange heat pumps or Air to water units like the Altherma can all cut that number very significantly... by 2/3rds or so, I would think.

kevinl

reply

Here is a cross section with insulation specs.

Roland_18

'lectric heat

Hi Kevin,

Thanks for posting the plan.  As you are not yet in the actual building phase, there is an excellent website for all things building related. It's called Building Science. Don't be put off by the "Science" part, most articles are written for the layman.



One article might be of particular interest to you: 



http://www.buildingscience.com/documents/guides-and-manuals/gm-read-this-before-you-design-build-renovate/view?topic=doctypes/guides-and-manuals



Near the top of the page is a prompt which indicates "download the pdf 4.8 MB " use that in order to expand the article. Enjoy !



Don't  look too hard for hot water boiler information, it seems they like forced air in Canada.