Question about heating your home:

I have often wondered which way would be better in our home heating system, which is heated by natural gas heating water in a boiler which then gets pumped to hot water radiators around the house (three stories). So what would be more efficient, to have the heat setting of the boiler at 140 degrees (F) or so, which we do in the summer, or to put it at 190 or 195 degrees in the winter or leave it at 140 for winter also. I can see arguments for both sides, higher temps gives better efficiency in terms of heat transfer from the radiators to the room but lower temp means the furnace runs less to get to 140 vs 195 but maybe longer. Not sure which technique uses less fuel. Any ideas?

Originally posted by sonhouse
. Any ideas?

The lower temp is definitely more efficient for a number of reasons - though all of them have to do with heat loss. Less heat is lost from any part of the system that is vulnerable to heat loss including both the heating system and the house as a whole.

I do not understand your claim regarding radiator efficiency. If the heat does not come out of the radiators into the room then where does it go?

Or am I mistaken about the way it works? Do you run the boiler at one of the two temps until the house reaches a given fixed temperature then turn off the boiler?

Make sure you insulate your boiler and pipes and your house.

And where do you live that requires heating in summer?

Originally posted by sonhouse
I have often wondered which way would be better in our home heating system, which is heated by natural gas heating water in a boiler which then gets pumped to hot water radiators around the house (three stories). So what would be more efficient, to have the heat setting of the boiler at 140 degrees (F) or so, which we do in the summer, or to put it at 190 o ...[text shortened]... less to get to 140 vs 195 but maybe longer. Not sure which technique uses less fuel. Any ideas?

can you consider, for a moment my idea, for my home. at present we have same system as you, natural gas which heats a combination boiler and provides heating and hot water. My plan consists of this, in our lower floor we have a large solid fuel inset stove. it is a requirement for convection and heat dissipation as well as cooling that there is an air gap which surrounds the stove. It is rated at 14 KW/H and sits within the chimney breast where an open fire once was. My idea is that i had hoped to utilise the flow of air around the stove and channel it, through air ducts powered be a thermoelectric fan to other areas in my home. These babies require no electricity and work from some type of thermoelectric module which acts as a generator from the heat of the stove. the warmer the stove gets, the faster the fan goes. i have surveyed the areas and can easily fit ducts to the kitchen and a bedrom upstairs via the secondary chimney breast. if i could make it work i think it would be awesome as well as carbon neutral! what do you think? is it viable or just a waste of time and resources?

Originally posted by twhitehead
The lower temp is definitely more efficient for a number of reasons - though all of them have to do with heat loss. Less heat is lost from any part of the system that is vulnerable to heat loss including both the heating system and the house as a whole.

I do not understand your claim regarding radiator efficiency. If the heat does not come out of the r ...[text shortened]... your boiler and pipes and your house.

And where do you live that requires heating in summer?

The boiler heats water for showers and such also. The efficiency I am talking about is the fact that you get more heat transfer if the temp difference is higher, say 200 degree water and a 60 degree room, a dif of 140 degrees will put more heat into the room than a 120 degree water temp and 60 degree room, only 60 degree dif.
The colder water temp of 140 degrees which I use means you don't have to use as much energy to initially heat the water but it would also not put as much heat into the house, so trying to figure out if that is better or to run it as hot as possible, say 200 degrees or so.

Robbie, I don't have a chimney, this house was built 125 years ago and it had coal heat with convection flow to radiators which worked ok but was a pain in the butt to clean up and made coal dust outside. It was considered the latest and greatest back then so they designed the house without much in the way of chimney, just enough for a coal fired furnace. We use pretty much the same thing, same chimney but with a more modern boiler run by natural gas, so much cleaner.

Originally posted by sonhouse
The boiler heats water for showers and such also. The efficiency I am talking about is the fact that you get more heat transfer if the temp difference is higher, say 200 degree water and a 60 degree room, a dif of 140 degrees will put more heat into the room than a 120 degree water temp and 60 degree room, only 60 degree dif.
The colder water temp of 140 ...[text shortened]... trying to figure out if that is better or to run it as hot as possible, say 200 degrees or so.

I am still not clear as to whether you turn the boiler on and off etc. If it is continually on like a geyser then the lower temp is definitely more efficient.

I am also not clear as to whether you end up with the room temperature the same or not.

The heat transfer efficiency of the radiators is almost irrelevant. The heat has nowhere else to go. It may take longer to heat up the house from cold, but that is a net heat saving. The only way it could save you heat is if the boiler has to be on longer and thus looses heat to its own environment due to poor insulation.

There is a similar situation with hot water. If you set an electric geyser to a lower temperature you will save a significant amount of electricity.

Originally posted by twhitehead
I am still not clear as to whether you turn the boiler on and off etc. If it is continually on like a geyser then the lower temp is definitely more efficient.

I am also not clear as to whether you end up with the room temperature the same or not.

The heat transfer efficiency of the radiators is almost irrelevant. The heat has nowhere else to go. It ...[text shortened]... set an electric geyser to a lower temperature you will save a significant amount of electricity.

The boiler has two controllers. One keeps the water at the minimum of 140 degrees F or so. That allows us to have hot water on demand for sinks, tubs, showers, etc.
The other is the thermostat in the living room, we only have a single area system so it controls the heat when it is turned on. So there are three controls, the overall power switch, which shuts the whole thing down or on, the min. temp control which runs 24/7 all year round and the thermostat which when in the off position, reverts to just min temp for hot water, the summer setting. Then if you turn the thermostat on, the temp in the living room controls how long the boiler is burning fuel, that is the setting that keeps the house warm. The only way to control heat in individual rooms in our house is to turn the water valves on each radiator down or up, no other thermostats but the one.
So under those conditions, is it more efficient to have the min water temp and max at say, 140 and 160 or should it be at 140 and 190 or so.

Originally posted by sonhouse
The boiler has two controllers. One keeps the water at the minimum of 140 degrees F or so. That allows us to have hot water on demand for sinks, tubs, showers, etc.
The other is the thermostat in the living room, we only have a single area system so it controls the heat when it is turned on. So there are three controls, the overall power switch, which shu ...[text shortened]... ent to have the min water temp and max at say, 140 and 160 or should it be at 140 and 190 or so.

If I understand you correctly (and I am not certain that I do) then the relevant parts of the system are:
1. A boiler that is always on at either a low temperature or a high temperature.
2. Radiators in the house that can be turned on or off to allow heat to get from the boiler to the rooms.

If that is correct, then the lower temperature is definitely more efficient because there is less heat lost to the environment at the site of the boiler and any pipes between it and the radiators.
How efficiently the radiators pass the heat to the rooms is irrelevant.

If the heater was electric then you could help the environment by putting a timer on it to use electricity in off peak hours.

Originally posted by twhitehead
If I understand you correctly (and I am not certain that I do) then the relevant parts of the system are:
1. A boiler that is always on at either a low temperature or a high temperature.
2. Radiators in the house that can be turned on or off to allow heat to get from the boiler to the rooms.

If that is correct, then the lower temperature is definite ...[text shortened]... en you could help the environment by putting a timer on it to use electricity in off peak hours.

I thought of a way I can have the best of both worlds, if I can find a controller to do what I want: a low temp setting just for hot water, the best thing would be a separate tankless water heater, I lived in Jerusalem for years and that is what everyone uses there, no hot water demand, no fuel used, electronic ignition so no gas has to burn at all when the system is on zero demand. Then the house heat would just be at the most efficient setting, the lowest that heats the house.
The only thing about the tankless system is they cost about a thousand bucks.
The alternative to that is a regular gas hot water heater, maybe there are units with electronic ignition and no fuel flow when hot water is not called for.
My system as it is can be set to any reasonable temp min and max, there are two temp controls on the furnace box, where you set the difference to 10 degrees apart minimum. Example would be what we normally do: Winter, set it to 190 degrees max and 160 degrees min but like you say, the pipes would lose heat that way but the pipes are in the basement so the heat rises anyway, not sure if that is a big loss.

In summer, no house heat is needed so we set the temp to 140 max and 120 min, that way we have hot water on demand.

In winter the thermostat calls for heat till it reaches the room temp we preset in on the box and we can vary that daily in a 7 day pattern, say turn on heat at 5 AM and go till 9 AM then turn off, then come back on at 5 PM till 9 PM, something like that.

In a case like that, do you lose heat to inertial losses, like the heat it takes to heat up walls and so forth? Would the walls absorb enough heat to even things out?

Originally posted by sonhouse
In a case like that, do you lose heat to inertial losses, like the heat it takes to heat up walls and so forth? Would the walls absorb enough heat to even things out?

I am not sure what the question is here.
In general, you were correct that higher temp differences results in more efficient (faster) heat transfer, but in no way does that ever save heat. All it means is that in the places where the heat transfer is to an undesirable place (basement or outside) you are loosing more.
You of course loose heat to the walls (and from there to outside the house) which is why it is good to insulate the house well - if you don't have double glazing or have open windows then that is where most heat will be lost. Also the ceiling may be a big heat looser if it is not insulated.

What I don't understand is your 'even things out' piece. I am guessing you are asking a question similar to the age old 'if I turn my geyser off at night will I save power'. The answer is, yes you will save power, but how much depends on how bad your insulation is.

Here in SA we are a bit short of electricity due to not enough power stations and the occasional break down / maintenance of power stations. The result has been lots of discussions regarding geysers as they are one of the biggest consumers of domestic power. There has also been lots of confusion and misinformation.
In general, to lower you electricity bill, lower the max temp on your geyser and turn it off as much as possible.
However, to help the power company and the environment, it is more important to turn off your geyser during peak usage. Some countries have in the past had a way for power companies to automatically turn domestic geysers off and on remotely depending on demand. I think we should implement either that or plain old timers here in SA.

Originally posted by twhitehead
I am not sure what the question is here.
In general, you were correct that higher temp differences results in more efficient (faster) heat transfer, but in no way does that ever save heat. All it means is that in the places where the heat transfer is to an undesirable place (basement or outside) you are loosing more.
You of course loose heat to the wall ...[text shortened]... pending on demand. I think we should implement either that or plain old timers here in SA.

By Geysers I presume you mean the gas burner? What is the weather like in SA? It seems like it might be pretty cold in winter, maybe like here in Pennsylvania (fairly central, about 100 Km north of Philadelphia in the Pocono mountain area). Do you have snow, do you have to insulate the walls and ceiling yourself or can you get away with Southern California style heating, basically a floor gas heater that is seldom used and insulation is not such a big deal. That's where I was born and grew up, lived in Venice Beach for years and it hardly ever gets cold, snows about once in ten years. I remember a time when it snowed, I was about 8 years old or younger and gathered snow from the entire lawn to make a snowman about a half meter high! I think it snowed maybe a Cm!🙂

Originally posted by sonhouse
By Geysers I presume you mean the gas burner? What is the weather like in SA? It seems like it might be pretty cold in winter, maybe like here in Pennsylvania (fairly central, about 100 Km north of Philadelphia in the Pocono mountain area). Do you have snow, do you have to insulate the walls and ceiling yourself or can you get away with Southern California ...[text shortened]... from the entire lawn to make a snowman about a half meter high! I think it snowed maybe a Cm!🙂

By 'geyser' I mean 'a domestic appliance for heating water rapidly' in South Africa they are generally powered by electricity and supply the bath and kitchen with hot water.

I live in Cape Town and as far as I know it never snows (certainly not while I've been here).
I use an electric radiator type heater in the winter and have no real insulation at all.
The winter doubles my electricity usage because of the heater and the extra heating requirement for hot water (geyser).

Originally posted by twhitehead
By 'geyser' I mean 'a domestic appliance for heating water rapidly' in South Africa they are generally powered by electricity and supply the bath and kitchen with hot water.

I live in Cape Town and as far as I know it never snows (certainly not while I've been here).
I use an electric radiator type heater in the winter and have no real insulation at a ...[text shortened]... icity usage because of the heater and the extra heating requirement for hot water (geyser).

Ah, those are called 'tankless" hot water heaters here. When I was in Jerusalem they all had rooftop solar panels to heat the water but it ran out fairly quickly and was supplemented by the tankless 'geyser' as you call it. That was a pretty good system, you only had to use the gas heater a couple of times a week, and short showers were in order, get in, clean off, rinse, get out.
The situation here is a bit different, winters get very cold, way below zero degrees C, like -10 or so, sometimes worse. I have some insulation in the house but not complete. It's a large victorian, 7 bedroom, so it takes a lot of heat in the winter so any help is appreciated. I have cut the temp down to 140 F, 55 degrees lower than last year, I'll keep track to see if that helps. Just starting winter here, not officially yet, still fall but it's starting to get on the cold side, maybe 5 degrees C, 40 degrees F about. Today I was going to work on grounds for my ham shack and a nice dipole but it is a cold rain today, miserable to work outside. I have an 8 foot ground rod and a nice chunk of fat ground wire but it is to wet to work today. I am building a ham antenna that will be about 135 feet long, up in the air about 50 feet, which is a bit low for ham use but that's all the taller the trees on my property are. Ah well, have to wait till tomorrow, supposed to dry out again.

Originally posted by sonhouse
Ah, those are called 'tankless" hot water heaters here.

No, actually, I am talking about an insulated tank that has a large electric heating element in it like a kettle. However it remains on all the time and the element is turned on and off by thermostat and there is hot water readily available at all times. However some heat is lost to the environment so keeping the temperature at the minimum required is more efficient than having it hotter than required then mixing it with cold at the tap (faucet).
I know my definition was a bit misleading - I just pulled it out of the nearest dictionary.

I have some insulation in the house but not complete. It's a large victorian, 7 bedroom, so it takes a lot of heat in the winter so any help is appreciated.
It is my understanding that insulation is the first thing to look at when trying to improve energy efficiency. Its obviously harder when the house is not designed for it. If you really want to do your bit for the environment, consider pressuring the government to enforce more energy conscious building codes. It is cheaper in the long term to build a house with energy efficiency in mind, however it is not always cheaper for the builder, so it doesn't always happen on its own, it needs a bit of government intervention.

Originally posted by twhitehead
No, actually, I am talking about an insulated tank that has a large electric heating element in it like a kettle. However it remains on all the time and the element is turned on and off by thermostat and there is hot water readily available at all times. However some heat is lost to the environment so keeping the temperature at the minimum required is mor ...[text shortened]... he builder, so it doesn't always happen on its own, it needs a bit of government intervention.

I think it is already code that new houses have to be built with insulation. Of course that lets the contractor use the cheapest least effective insulation he can buy legally. So that means insulation codes must come with effective insulation rating minimums that local conditions reasonably require.
Insulation saves energy in low and high temp times so it does double duty summer and winter.

Originally posted by sonhouse
I think it is already code that new houses have to be built with insulation. Of course that lets the contractor use the cheapest least effective insulation he can buy legally. So that means insulation codes must come with effective insulation rating minimums that local conditions reasonably require.
Insulation saves energy in low and high temp times so it does double duty summer and winter.

In Livingstone you can save a fortune on cooling simply by planting a few trees.
We had a good laugh about one guy who bought a house, chopped down all the trees, then a month later installed air conditioners.