Wall heaters maybe a solution?

[Bone1099]

I'll start with the basics. Roughly 1800 sq ft home external chimney all the way in one end of the house. Fisher fireplace insert installed in the dining area in that fireplace. Bedrooms down the hall in the other end of the house. Insert is primary heat source but I am plagued by cold master bathroom and kinda cool bedroom. floor plan wasnt intended for the pirmary heat source to come from the fireplace. every year i experiment with different combinations of ceiing fans and box fans in the hallway to move the cool air to the warm roomand with much frustration. So i have always thought i would add an in the attic insulated duct with an inline fan to pull warm air from ceiling in dining room (which has plenty) back to the cooler rooms in the house. But recently i ve been seeing advertisements for these high efficiency Quartz and what not heaters. So i get to thinking i migh could run one of those about as cheap as i could run a ducted fan. So with a bit of shopping around i found this heater called envi. it fits on the wall uses plug in or may be hard wired claims its only 475 watts and will heat 150 square feet. Im kinda skeptical but theyre pretty cheap and easy if they wouldnt use too much power I could see me using two of them. But if anyone has used heard of or even knows someone who thinks they know. please have at it.

 

[woodgeek]

A common discussion here. Space heaters are a great stopgap solution to your problem, or on a timer could warm up your bathroom in the AM, but all electric heaters will cost the same per BTU, even the super expensive ones. They are all scams, unless you are happy to pay for the pretty box. So, if you are cold, get a cheap space heater and use it...if your central heat is $$ you will still be saving by running the insert to cover the other end of the house.

As for ducted fan distribution....there are folks here who have done it. You can run either heated or cold air (in the opposite direction). You need to make an airtight system, and will want to insulate the ducting to R-8 or better if it is in an unconditioned space. The cost to run the blower is not zero, but should be a lot less than the heating value obtained. The formula to keep in mind is:

BTU/h = (temp difference)*(cu ft per minute), approximately.

So, if your dining room were 20°F warmer than your bedroom, and you pushed 250 CFM, you would move 5000 BTU/h, the same as a space heater on 'high'. If you pushed 100 cfm, then it would be like that envi. Of course, your dining room might only be 10°F warmer, then you have to halve the numbers. To get these sorts of cfm, you will need a good sized duct and blower, not a wimpy little thing and a 4" duct.

You can def see why pushing the heat in open plans with fans (huge cfm for the effort) works so well. IN your case, I assume you tried pushing the cold air to the stove along the hallway floor?

 

[jebatty]

... and whatever hot air you push from one room will be cooler by the same btu's, + losses in moving the air, as the new area being heated. Another question might be "what's wrong with cool bedrooms?" Right now its -20F outside, main living area of living room, dining room and kitchen is 68F and rising (added wood to the living room stove 1 hour ago), and bedroom is 63F -- great sleeping temp. The stove is the only source of heat for 1500 sq ft home.

 

[Highbeam]

Skip the portable plug in heaters and mount up a hardwired electric wall heater. You know, the cadet or king brand ones that look like white metal grilles mounted flush with the wall. These things are controlled by a wall mounted thermostat in each room. You can choose how many watts you want and they are cheap and easy to install. I have these heaters in each bedroom set to come on at 55 degrees during sleeping hours only. When the kids were really young their heaters were set to come on at 65.

If you must set up electric heat, these heaters are the safest, easiest to control, and most reliable.

So long as I keep the fire burning the rooms never drop below 65 and that is about 10 degrees cooler than the stove room. People that heat with woodstoves do not have homes with consistent temperatures room to room. Like JeBatty, we like cooler sleeping rooms.

 

[pen]

The consistency of the 2 star or less reviews I see on this product (assuming I'm looking at the same one you are) on amazon.com tell me that it's a product that I would not consider buying.

I'm with highbeam, put a hardwired electric radiator in here and be done. Safe and they will work. Running duct work from a wood stove that is not meant to have duct work run to it often ends in less than desired results as well as installations that are unsafe / do not meet code.

pen

 

[Bone1099]

I agree with the cooler sleeping areas. Yes the box fan was moving cold air to warm room. Incedentally my house is already outfitted with hard wired wall heaters in each room. Somehow i just look at those things burning red and it seems like i can feel the wind rushing off the disc in my meter. So all electric heaters are same efficiency? I just cant get my mind around that. Im not saying i dont beleive it. Its just hard for me to grasp that in the past 30-40 years no one has come up with a more efficient way to turn electricity into heat. Or maybe im looking at it backwards. So is there any energy lost with an electric heater? If not then why do i even own a heat pump? Or maybe im still not getting it. lets discuss this further please. I like thinking im pretty smart. So im willing to listen and learn from those of you who have more knowledge than me in this area.

I just alwasys thought of wall heaters as archaic devices that looked terrible (except for the fact that no one notices them on the wall if they're turned off) I have lived in this house for seven years and havent used but one of those things in the whole seven years. That is the one in the cold bathroom i'm complaining about (man im starting to feel like an idiot) I have a house full of these things that i have refused to turn on just because i always thought they were terrible inefficient devices. someone please catch me if i am way off base here. But im starting to think that i couldnt see the solution to my problem while it was literally poking me in the eye.

 

[Bone1099]

The idea behind the duct work was to install a large register in the ceiling just above the insert area and take advantage of some of that super warm air hovering near the ceiling and also provide a means to move warm air to the bedroms and allow the cooler air from those bedrooms return via the hallway. Never intended to connect directly to the insert.

 

[woodgeek]

Aaaah. When I saw your location I wondered if you had a heat pump. So, all electric heaters have the same efficiency...about 100% turning 1 kWh to 3414 BTUs. So, yes, they have invented a more efficient way of turning electricity to heat--the much maligned, much misunderstood heat pump. The eff depends on the outside temp, but a recent vintage one properly installed, in your climate should be able to cover all (or nearly all) your heating needs and cost only 40% as much to run as those wall/space heaters. IOW, eff should be ~250% averaged over the season. When temps are above 40°F, the eff is probably closer to 350%.

If the HP is not doing the job, or costing too much (e.g. the electric backup is kicking on a lot), then you need to get it fixed (or replaced if its really old).

 

[rwhite]

Remember the WAV (think wave) formula. Watts=Amps x Volts. Volts is the potential to produce energy, amps is the flow, and watts is the measure of energy used. So a 120v space heater set at max (1500w) will have an amp measure of 1500/120= 12.5 amps. A 240v heater set at the same wattage will be 1/2 the flow of electricity. 1500/240= 6.25 amps. Those hardwired baseboard heaters are using 1/2 the electricity that a 120v plug in heater will use to produce the same heat.

Now the difference in heaters. 120v only has the potential to do so much work. And a standard 15amp wall plug can only send so many watts through it. So with 120v and 15 amps beings constants the max wattage you can get from it would be 1800. So thats why all space heaters have the exact same potential.

Efficiency of any heating device is measures in the the heat produced - heat loss = usuable heat. Electric is the most efficient heat there is. All the heat produced is captured within the home. So how efficient a device is has nothing to do with cost to run. So while an electric heater may be more effiecent it also may be more costly.

 

[jebatty]

Those hardwired [240v] baseboard heaters are using 1/2 the electricity that a 120v plug in heater will use to produce the same heat.

Not true, unless they also are using 1/2 the watts. Go back to your WAV formula. A 1500W 120V electric heater is using the same amount of electricity as a 1500W 240V heater.

 

[jharkin]

rwhite...

IMHO I think you are confusing the issue a bit. the fact that the amp draw halves at 240v has no bearing on the amount of energy used - and its the energy consumption (watts) that determines cost to operate and the amount of source energy put in at the generation plant to deliver that electric power. The benefit is that the lower amp draw allows you to use smaller gauge wiring, switches and connections as NEC allowable wire capacity scales with the amp draw, not the voltage for our purposes (increasing voltage requires heavier insulation but that difference is a non issue in residential applications as most wire and switches are rated well above 240v already).

So bottom line is, the benefit of using 240v is lower upfront cost and complexity on the install. There is NO difference in efficiency or cost to operate on a BTU for BTU basis.

I would also say that to say efficiency has no bearing on cost is a gross oversimplification. Efficiency is a very important factor where the net cost is the product of the input cost of the fuel times the over all system efficiency. In the case of fuel burning appliances that system efficiency is easy to identify - its just the losses up the flue. For electric its trickier... maybe the source fuel is natural gas, very inexpensive. But then you have to add up thermal losses in the generation plant, transmission loses in the grid, etc - by the time your done at best 40% of the energy potential of that NG made it into electricity to run your "100%" space heater, whereas if you have a NG condensing boiler in the basement you might get a true system efficiency over 90%.


...

Back to the OP. One lesson here is that as a society when we discovered centralized heating we managed to forget how to build houses to take good advantage of source heat. Back in the colonial days they built homes with interior central chimneys, multiple stories, low ceilings and a lot of small rooms with doors for a reason. Its a LOT easier to heat with point sources of heat that way. The modern single story ranch house with one chimney at the end is just simply not designed with space heating in mind.

 

[thinkxingu]

Add electric baseboard with new thermostats: 1. They'll only run when you want them to (programmable and setable), and 2. NEAT: the new electric baseboard thermostats 'pulse' electricity to the baseboards. I didn't know about this until about the end of our first winter, when we saw our electric bills drop like a stone: while in the basement, trying to find an RC part I had dropped, I heard an electric noise come from the baseboard for a few seconds. I stopped to listen, and then did some research, and this is what I found when speaking to people: Electric baseboards get hot almost instantly, so any power sent to them after a short period of time is wasted. So, the new thermostats pulse power to the baseboard for a few seconds and then shut off. The result is almost a 50% reduction in power use when added to the programming.

NOW, this all seems to make sense to me, and it makes sense with my electric bills, what I've read, and what I've heard from my gear, but can anyone confirm?
In any case, it costs me around $215/mth for 12 months to run an all electric, well-insulated, home in southern NH.

S

 

[jebatty]

Electric baseboards get hot almost instantly, so any power sent to them after a short period of time is wasted. So, the new thermostats pulse power to the baseboard for a few seconds and then shut off. The result is almost a 50% reduction in power use when added to the programming.

NOW, this all seems to make sense to me, and it makes sense with my electric bills, what I’ve read, and what I’ve heard from my gear, but can anyone confirm?

Yes and no, and I will venture an opinion, although I'm not familiar with these. Resistance heating is almost 100% efficient at the baseboard, and btuh output is at the rate of 3412/kwh. So, on the btuh level there is no change. But by pulsing (similar to a modulating boiler) the baseboard is only delivering the heat needed to provide the desired comfort level, and delivering it at a more uniform rate. An on-off baseboard undershoots and then comes "on" and then overshoots and then goes "off," room temperature as sensed by the thermostat and probably felt by the person is somewhat variable, too cool, too hot, and uncomfortable, and the "wasted" power/heat is in the perceived comfort level by reason of the undershoot and the overshoot, that is, heat not needed. So pulsing delivers more comfort through consistency, resulting in less use of electricity. It may be more technical than this, but I think the reason is similar to why a modulating boiler at a lower btuh output may replace a non-modulating boiler with a higher btuh output, and also why a wood gasification boiler with storage to provide consistent, radiant heat, may be of a lower btuh output than a gas or oil boiler that is non-modulating. Condensing boiler add another level of heat extraction, but I don't think they are relevant to this discussion.

 

[jharkin]

jebatty has it right. Its the full on / full off cycling that causes overshoot wasting energy. During the on cycle the extra electricity is not really wasted, it keeps making the element hotter until it either reaches a steady state where the amount of energy in equals the energy out in convection to room air - OR - the thermal limit switch kicks in and cuts the power.

I suspect what the new units have is a switching power supply that allows you to power the heater at some intermediate strength.. Switching power supplies use transistors to just turn the juice on and off in very fast pulses- say you have 120v input, if you have it on for 5 ms then off for 5ms then on etc... on average you get the equivalent of 60v or half the power. The unit is probably continuously variable from anything ranging from 0v to the full line voltage. This will allow the unit to continuously vary the heat output and keep close to the thermostat set point without overshoot/recovery. It is exactly the same objective as a modulating boiler with outdoor reset, as you suspect.

Now, we could do this before switching power supplies where invented using a rheostat... the downside is a reostat dumps the excess power into a resistor that heats up so really you are still dissipating the same amount of input energy into heat - making it pointless for controlling a heater....

BTW, moving from rheostats to switching power supplies is also the reason why modern light dimmers are so much more efficient and don't heat up, and how we build laptop power supplies and cell phone chargers that don't need heavy iron transformers.

 

[CTYank]

There is a safety problem with plug-in electric heaters. They draw so much load current for such long periods (typically) that the metal surface of the plug blades gets hot and oxidized. Resistance there increases, leading to increasing voltage drop and more heating. Eventually fire.

Some fire marshals will not allow them in certain environments, like foot-warmers for women desk-riders with perpetually cold feet.

 

[semipro]

There is a safety problem with plug-in electric heaters. They draw so much load current for such long periods (typically) that the metal surface of the plug blades gets hot and oxidized. Resistance there increases, leading to increasing voltage drop and more heating. Eventually fire.

Some fire marshals will not allow them in certain environments, like foot-warmers for women desk-riders with perpetually cold feet.

+1
There are some really poorly engineered space heaters out there. We had one recently that heated the cord up so hot that we returned it as defective.
It does depend on the model and how much power they use.
I'm sitting at my desk with a low wattage IR panel in front of my feet that uses only 150 watts and it warms my feet and legs very well.
Many space heaters require 10 times that amount of power.

Link to panel heater if interested: http://www.amazon.com/Indus-Tool-CL-Flat-Panel-150-Watt-Radiant/dp/B0009HMFPM

 

[Highbeam]

All resistance heat is nearly 100% efficient. All forms are nearly the same. Wall heaters, baseboards, portables, water heaters, and central electric furnaces.

You can also use that electricity to run a heat pump that uses the supplied electricity to extract heat from the outside air. This marvelous device actually delivers more energy to the home than you gave it from your power supply by stealing heat from the outside air. This means that it can be better than 100% efficient. It can be 300% efficient. That's cool and everyone should use one to heat there homes so long as there is some heat in the outside air. It is really hard for the heat pump device to steal heat from the outside air when there is very little heat to be had. Modern heat pumps are better about this and can do the job well into the teens but at some low temperature you will need some other form of energy to supplement.

Don't get bogged down by these discussions of watts, resistance, and volts. Use your wall heaters if you need them. You can take off the grill and determine the wattage of the heater which might be 3800 watts on a typical 220 volt, 20 amp, heater circuit. In my area with 10 cent per kWh power, the heater only costs 38 cents an hour to run. That's cheap and you already have the heater installed. I wouldn't use electric resistance heat for primary heat but many folks do. I find them to be the perfect backup heat source since they require no maintenance and no floor space.

 

[rwhite]

Those hardwired [240v] baseboard heaters are using 1/2 the electricity that a 120v plug in heater will use to produce the same heat.

Not true, unless they also are using 1/2 the watts. Go back to your WAV formula. A 1500W 120V electric heater is using the same amount of electricity as a 1500W 240V heater.

You are correct. Sorry for the confusion. I falsely assumed that 1/2 the draw would equate to 1/2 the use. But you are correct that watts are watts regardless of volts. Given that you are correct and the BTU cost is the same regardless of voltage does a 240v heater produce the same BTU's as a 120v in 1/2 the time?

 

[Bone1099]

Kinda like sipping from a fire hose but thats why i love this place. I may just be over thinking this cuz my primary heat source is wood. The circa 1985ish heat pump rarely gets turned on. and i already have the electric wall heaters installed i think ill just vacuum them out a bit and try em to keep the chill at bay in the bathroom and one bedroom. Only gonna run two and they have thermostats so maybe they wont eat me alive.

 

[jebatty]

... does a 240v heater produce the same BTU’s as a 120v in 1/2 the time?

Yes and no, again. Use the WAV formula and Ohms Law. The answer relates to the resistance of the heating element, which relates to the amperage. For a heating element designed to operate on both 120 and 240V which uses the entire element, the answer would be "yes" but when operating on 240V the current or amperage would be twice that on 120V, thus twice the watts and twice the BTU's, and also twice the cost for the electricity. I have a heater of that type in a bathroom. When wired for 120V the line connects to one end of the element and the neutral connects to the other. When wired for 240V, L1 connects to one end of the element and L2 connects to the other.

And the answer would be "no" for two heaters of the same wattage, that is the amperage for the 240V would be 1/2 that of the 120V, same watts, same BTU's, and same cost for electricity.

 

[woodgeek]

Kinda like sipping from a fire hose but thats why i love this place. I may just be over thinking this cuz my primary heat source is wood. The circa 1985ish heat pump rarely gets turned on. and i already have the electric wall heaters installed i think ill just vacuum them out a bit and try em to keep the chill at bay in the bathroom and one bedroom. Only gonna run two and they have thermostats so maybe they wont eat me alive.

I am assuming the heat pump is in good repair as you use it for central A/C in the summer, or does it underperform there too?

Your situation is actually complex. If your old HP is in good repair, I suspect that it can provide your heating much cheaper than the baseboards (probably 50 cents on the dollar per BTU). If your elec was cheap and you were buying wood, your savings on wood might be pretty small. If you are scrounging, and happy to put in the time, then you are (duh) ahead. The problem is that if the baseboards were doing more than just being a supplement, say they were carrying half of your total load, then your electric bill would be the same as if you just ran the heat pump (at 200% eff) to carry the whole house, and skipped the wood!

When it is time to replace the HP, a new unit will heat your house so cheap in your climate that wood will look unattractive from a $$ or scrounge time standpoint. Of course, you will fire up your stove on the cold days or when you feel like it....

If your ducting is inside the insulated envelope of the house, can you run the blower on circ for distribution? If no, a tech might be able to swap out your tstat for a newer model that will....and it would still be cheaper to run than a space heater.

In the end, we are lacking some info here on your setup, so its hard to say much more. Personally, I would track my costs running the baseboards for a few days by reading my meter, and then do the same running my heat pump, and compare.

Also...I don't believe all that stuff about pulsing and no overshoot giving higher eff. The pulsing gives proportional control and more comfortable and quieter operation than clicking on and off every few minutes. That's all.