Energy Efficiency in Hydronics Part 2, Fuel Efficiency

John Ruhnke

I want to apologize for the lack of paragraphs. I put them in but it comes out all lumped together on the wall. I have broken down energy efficiency of a hydronic heating system into three parts and the first part is fuel efficiency. As Heating Designers we can't do much about the efficiency of the fuel we use. We have to take what is given to us. Below is a graph of the Co2 output of different fuels per unit of energy. This is based on a national average and will very at different parts of the country. I got this from a paper John Sigenthaler wrote. It might be a little hard to read. It shows that electricity gives off more then three times as much co2 as natural gas. Electricity also gives off twice as much co2 as fuel oil. If you are worried about the impact on our environment then natural gas would be the best choice to start with.

Here are some cost comparisons for the state of CT. 1 Therm equals 100,000 btu's. Electricity $6.025 per therm, Gas $1.57 per therm, Oil $1.79 per therm and Propane at $2.86 per therm. In Connecticut we pay 78% higher for electricity then the national average and 26% higher for gas then the national average. A unit of electric energy costs almost 4 times as much as gas in our area. What type of fuel is Geothermal? Geothermal would be considered to be electric. The extra energy is coming from the sun stored in our ground. It is free so we don't count that. 0 co2 and 0 costs in fuel.  Geothermal is measured in Coefficients. The Coefficients range from 2 to 5. That is the same as being 200% or 500% efficient. Considering that 500% is most likely only going to happen in perfect or unrealistic conditions lets give it 300%. The same thing with solar. A solar system that handles 50% of the energy for the heating system would be considered to be 200% efficient Now electric is mostly made from coal in our country. Electricity also loses a lot of energy over the transmission lines and at the power plant making it an inefficient use of energy in many cases. Electricity may end up at your house with only 33% of its energy. In the case of a Geothermal System 300% times 33% equals 100%. So a electric Geothermal System starts with the same costs and energy efficiency as natural gas. Gas starts out at 100% efficiency too. Yet you didn't have to dig all of those holes in the ground!!!!!!!!!!!! In Connecticut with the higher then average price we pay for electricity, gas is most likely going to be cheaper in price then Geothermal. Though for most other parts of the country GeoThermal makes sense. Down south where AC is more important then Heat Geothemal makes sense. Out West where electric costs are much cheaper then the North East Geothermal makes sense. Does Geothermal make sense in the North East? Most likely NOT!!!!!!!!!!!!!!!!!!!!!!! 

Jean-David Beyer

Environmental impact.

"If you are worried about the impact on our environment then natural gas would be the best choice to start with."



There is another reason to heat with natural gas if the environmental impact concerns you.



Natural gas is mostly methane. If we did not burn it, it would escape into the atmosphere from oil wells, landfills, etc. And methane causes something like 10x the environmental damage as does CO2. So in any case, methane should be burned, not allowed to escape. And if it is going to be burned, we might as well get some good from it, such as heating homes and other buildings, running power plants, etc.

John Ruhnke

RE:

JD,

That is a good way to look at things.

EricAune

Energy factor/efficiency

Always concerned when energy factor is directly equated as efficiency.  Efficiency is measured by input vs. output, energy factor is the measurement of the input vs. output over a standard amount of time. 



Equipment should not be selected by energy factor alone; this is not an efficiency rating. Fuel source should always be part of the decision along with the factor (as you have stated)



Coal power generation will not be going out anytime soon, although we have converted and are presently converting many generators to natural gas, the cost of these conversions and operating costs of coal plants vs. gas are what truly writes the legislation.  An emotional set of ideals, shared by many or not, are not what the (major) business players in the field of power generation are concerned about.  Bottom line is the only thing right now.



54% of our power in the U.S. is generated from coal gassification,  a much smaller number (something like 16-17% right now) is derived from burning natural gas.

Devan

JR

Thanks for your post.

I am happy to know that someone other than myself understands that ground source heat pumps "geothermal" units in the North East are not positive solutions to sustainabilty. As you stated a GSHP system energy input (electricity) goes through a convoluted process and on the receiving end if lucky after generation losses, transmission losses 35% may be left, at a realistic COP of 3 , you get back what was lossed, but producing more CO2 from power plants, than say a gas mod/con boiler at 95% direct in home.

Better yet, fuel cell and micro-CHP is here, direct electric generation and heat ouput. Capable of producing electric at efficiencies around 85% vs. the 35% from a utility.



But to honest I still favor the saying, "the most efficient heating/cooling system is one that does not run"



Conservation, conservation conservation .. we still could do much more to build better home using passive technology , and paying better attention to the thermal envelope.

John Ruhnke

Overall Efficiency

The most important type of efficiency is Overall Efficiency. It is the amount of btu's found in the fuel used to heat a conditioned space. All else is wasted energy. It is measured over a 6 month period in time and averaged out. As an example, if you are burning 80,000 btu's per hour of fuel durring a six month period and durring the same six months the heatloss of the conditioned spaces in your house used 20,000 btu's per hour then your heating system would be found to be 25% efficient. If your system has solar energy either through the ground (GeoThermal) or Through the Air (Solar Thermal) then the efficiencies can reach over 100%. The only energy that counts in the calculation is the energy found in our fuel such as oil, gas or electricity. We pay a price for those fuels. Solar energy is free all the way around both in cost and environmental impact. Below is the equation used to measure it.

Overall Efficiency is broken down into two parts. I will talk about that next.

Part 2) Boiler Side Efficiency

Part 3) System Side Efficiency

Part 1) which I just discussed is Fuel Efficiency. Fuel Efficiency is the first step but it is really not part of Overall Efficiency.

Jean-David Beyer

So I should be able to calculate this, in principle.

I have a little trouble with your formula.



Is the HEAT LOSS (BTU) term the total heat loss during the heating season? Or is it the heat loss per hour? I think the whole first term is the heat loss (in BTU/hour) per degree difference between the (desired) indoor temperature and the (actual) outside temperature, right? So the first term unit is BTU/(degree*hour), right?



Now for the second term. The denominator is a little off because it is in CCF, but you probably mean therms because the heating value of a cubic foot of gas varies with its composition and is typically 3% higher; i.e., 103,000 BTU/CCF. For the numerator, it is not clear that the data are available unless you have a suitable instrumentation to measure degree-hours. I surely do not have this. I sure wish the controller on my new boiler let me read it out with my computer, since my controller displays the outdoor temperature -- it needs that for outdoor reset.



Let us imagine that I calculated the heat loss of my house correctly, and that it is 35,000 BTU/hour on a 0F day when heated to 70F inside. (I know that the design temperature I should have used around here is 14F.) But I could recalculate that for 60F and estimate the first term. And after the winter is over, I could read the gas meter and see how much I used for the season, neglecting the 3CCF/month I use for hot water. So all I need is the number of degree-days to  calculate the efficiency, right?



I know my old boiler used about 410 gallons of #2 heating oil in the 2008 heating season to heat this house. That comes to 56,785,000 BTU for about 4320 hours, or 13,145 BTU/hr for the whole time. Now if I only knew the number of degree-days that year around here.

John Ruhnke

RE:

JD,

The CCf of gas was rounded off. You are right that it is closer to 103,000. It still varies from area to area. Yes you can calculate it at home. Both sides of the equation need to be done according to the same time. Such as Dec 13th 2007 to Feb 13th 2008. Remember that systems are more efficient in the winter and less efficient in the spring or fall. So if comparing two different houses you have make sure you compare similar climate times. The goal is the best result over a 6 month period from summer to mid winter. But you can compare smaller time, lines too. The biggest problem with this is that the way we measure heat-loss is very inaccurate. It can very widely from software to software. What Dr Tom Butcher and I want to do is install electric baseboard in the dead center of rooms. We would hook a meter to them and measure the usage in a house over a 3 week period. At the same time we would measure outside and inside temps. We would also data log things and compare day time to night time performance to subtract out for solar gain. Dr Tom Butcher sent me two papers on this. Its been done before to find heat-loss. Once we get an accurate heat-loss we then can use it to calculate overall efficiency and compare different houses. Another option is a much larger data set. The U.S. Green Building Council will be collecting heat-loss and fuel usage in the near future.  They do 20,000 or more projects a year. With a larger data set you can afford to be less accurate because everything kind of balances out in the larger numbers and you will see trends.

Mark Eatherton

How to get paragraphs...

John, hit the RETURN key twice at the end of your paragraphs, and you will get a space between paragraphs.



So, now that you have exposed the deficiencies of our world wide electrical grid system, let me ask your opinion on some things..



What's your opinion on Nuclear Electricity? What would you say the net net efficiency of THAT energy source would be? Personally, I think we are behind the ball as it pertains to nuclear power production.



What is your opinion on Bio-Mass (wood gasification) systems.



What is your opinion on embodied energy?



What is your opinion on waste heat recovery?



You of course know that you are preaching to the choir here, and I have no problem with it, but I think you need to break out your energy consumption into two different categories. One for existing energy hogs, and one for the new, ultra high efficiency super insulate, modulating condensing comfort systems. The boiler technology has made LEAPS and BOUNDS, just in the short time I've known you, and it still has a long way to go.



It has been my personal experience that when converting from existing "BANG BANG" systems to a modulating/condensing system, that there is an inherent MINIMUM reduction of 30%, and possibly as much as 60% reduction to be associated with the conversion. This has been echoed by numerous other contractors with similar experience's in the field. If this is the case, then WHY do we still offer boilers with seasonal efficiency ratings as low as 82%? I mean, with our new President and Congress so concerned with the environment, I would think that the first they they would do is follow the European markets, and BAN all appliances with an efficiency of less than 90%....



I'm being a "straw" here. I do not want to spark any controversial debates, just looking for answers.



Hit the return key twice :-)



ME

MIke_Jonas

Hey Mark, I'm the choir, too

I appreciate what you say about banning all appliances less than 90%...



That just means the knuckleheads in the business will be installing OVERSIZED 90% appliances.



Sit down, brace yourself....I am an RPA member that does load calcs!!! I tell people on the phone that I'll need a minimum of (1) hour for a basic load calc and not to be suprise if I need (2). Most all ask why, the other guys are there less than 15 minutes. I've had a rash of customers lately that want a price over the phone. Seems some of my colleagues don't even bother to go out to the job site anymore....whats' that data plate say??? We'll just quote a 200,000, they modulate down anyway...



I keep track from year to year of properly sized boilers. Keep in mind, I only do residential boilers, no scorched air, etc. So far, in 2009, I've found one boiler properly sized and (2) that were only one size bigger than needed. The rest were (2) or more sizes too large.



The City of Chicago and some of the nothern suburbs, PeoplesGas and North Shore Gas customers, get a $ 600.00 cash rebate direct from the utility for any high efficiency boiler....on top of the Fed tax credit. The utility will inspect these installations, but no where do they determine or require data that the appliance was properly sized.

Jean-David Beyer

Nuclear Electricity?

"What's your opinion on Nuclear Electricity? What would you say the net

net efficiency of THAT energy source would be? Personally, I think we

are behind the ball as it pertains to nuclear power production."



If you are considering the efficiency of THAT energy source, explain how a utility can make enough profit from it to cover the insurance risk and 250,000 years of waste storage in the 40 years or so the plant should operate? The cost, if those externalities are included, would prevent any nuclear plants from being built. Right now we are relying on the Price-Anderson Act to cover the damage these plants can cause, and are ignoring the cost of the waste storage. Someday these chickens will come home to roost.

Devan

nuclear

A few weeks ago my family and I went to Niagara Falls, both NY and Canadian sides.



I went on a hydro-electric plant tour, and found this poster very interesting. I suspect it is much,much more profitable with fewer nuclear plants putting out more megawatts than other methods..

John Ruhnke

RE: Mark

Mark,



Thanks for the tip on paragraphs.





Nuclear? It may be a necessary evil if we can't reduce CO2 fast enough. The Co2 output would be 0 but it comes with extra baggage though that I don't like. Waste that lasts for generations that could cause as bad a problem as co2.





Embodied Energy Waste Heat Recovery are all good things. It reminds me of a talk I heard from Dr. Birol Kilkis on Exergy. Birol wants to take everything into account when choosing his energy. Like where did the energy come from? How much gas did the train use? and What energy did it take to make the steel for the train that delivered the coal to the power plant. Its very valuable and useful stuff. I admit that I need to learn more about the subject. Birol is a great man with a great mind. We should fire those idiots in Washington and replace them with people like Birol but that will never happen.





Wood or Bio Mass. I don't like wood. You can't control the combustion of solid burning fuels very well and those boilers will always be less efficient then other means. Also the particulates are very high. Towns that had a lot of wood burning stoves ended up with bad pollution and had to ban wood burning appliances because of it. Dr. Tom Butcher doesn't like wood because of the dangerous particulates. He did some studies on it and was not pleased with the results.

Leo_G

interesting Devan

how 3 nuke plants produce more energy then 36 dams!



Also, if the next generation breeder nuke plants ever come on line, that will get rid of most of the waste problem.

Gordy

Fuel efficiency

 Sticking to the body of the topic the discussion can get quite complex.



The bottom line is what types of fuel are available to the end user, and what is the cheapest to use for the end user. Dollars out of the pocket are what the consumer understands, unfortunately its at the present time with not much vision on where the path of that cost could be in the future.



As you said John there is not much we can do about the efficiency of the fuels we use, but there are choices for appliances which burn those fuels as efficiently as possible with the technology the industry has made  available to the end user.



Beyond this we are beating a dead horse if you will on what the energy industry should be doing to make the most efficient, and environmentally cleanest energy possible. Change will only be forced by necessity....Sadly.



To me electricity is the best solution because there are many ways to produce it. Plus the fact that almost everything we use energy for can be done with electricity. The problem is producing it efficiently, environmentally friendly, and cheaply.



The end user can also produce there own electricity if their building site lends itself to PV,Wind, hydro, maybe even nuclear on a city size bases. But these still come with large price tags for the average consumer.



As far as the fossils are concerned we will never see 100% efficient, 100% environmentally friendly, or the cost go down.....until its gone.



 

If you want to see some interesting facts on energy produced, used, exported, imported, proven reserves. For electricity, oil, and NG. On a world wide, and by country basis. Go to  https://www.cia.gov/library/publications/the-world-factbook/. Click on guide to country comparisons tab, ITs an eye opener. Many other interesting pieces of data.

Gordy

ttekushan_3

efficiency

90% efficiency of what? Take of those foam core insulated new construction homes. I and a few friends can heat the place by lighting off the flatulence developed by consuming comfort calories during another losing Brown's game. What's the combustion E of that? And no, I won't bring the combustion analyzer to find out. I'd say its an efficient system. To what should we really be applying the 90% criterion to?



And yes, on/off firing with rare exceptions is maddening. It assures a mis-utilization of resources. A stopped clock is right twice a day, wrong the rest of the time. On/off firing to the load might be right twice a week, wrong the rest of the time. We should have improved on that in the '70s.



Yet maintaining comfort temperatures when no one is occupying the space is wrong until someone shows up. If we model that and then weight heat output per square foot per occupant when someone DOES show up and deduct any energy lost through ice melt systems then 86% and 90% combustion efficiency stalemates alone miss the big picture.



I just can't get around the idea that using less energy is the goal, and that insulation, square footage heated per occupant, unoccupied comfort temperature maintenance, and very high mass heating systems that make indoor comfort temperatures less responsive to occupancy are all far more important (in my little mind) than, say, breaking the barrier into condensing technology for combustion appliances.



I know, this gets into embodied energy and worse yet, it gets into addressing wasteful lifestyles. We want limitless square footage and free heat. Its dangerous territory to tread.



Terry



P.S. why do pipe heating losses in the occupied space constitute a waste? My pipes don't go outside for a trip around the block for some fresh air before they come back to release heat. Is this a construction method that I'm unaware of? Is there some secret federal law that prohibits applying a little more insulation to a pipe? I really need to know. I must have been doing something illegal all along! And then there's those mattress tags...

Jean-David Beyer

I think this is important...

"Yet maintaining comfort temperatures when no one is occupying the space

is wrong until someone shows up. If we model that and then weight heat

output per square foot per occupant when someone DOES show up and

deduct any energy lost through ice melt systems then 86% and 90%

combustion efficiency stalemates alone miss the big picture. "



I got a mod|con boiler rated at 93% efficiency and suspect it can run higher, though I doubt I can get it up to 98% efficiency, since I am not going to be doing any snow melting. Since it was installed this May, I do not know from actual experience what it is going to do in the winter. Back before I thought about it, when this was heated by a constantly-hot (or whatever the opposite of cold-start is) oil fired boiler, I bought a very fancy thermostat that allowed me to set four different temperatures for each of the 7 days of the week. In those days, my schedules were such that I needed more than those weekday-Saturday-Sunday thermostats. I thought I could set it to 67F when I got up, 66F during the day when I could wear a sweater, 67F in the evening, and 64F at night. It even had an anticipator or whatever it is called, where it would start the heat earlier so it would hit the desired temperature at the times set.



It did not work, though. And this was not the fault of the thermostat. The downstairs of my house is heated radiant with tube in the slab on grade whose thermal mass is considerable. I do not know the significant way to measure the mass in meaningful terms, but it took 3 to 4 hours after the thermostat called for heat for the slab to heat up, and even longer for it to cool down. And actually hitting the temperature set on the thermostat took even longer. So the temperature swings were considerable. I reduced the problem by lowering the temperature of the water delivered to the floor, but it was clear I was never going to get there. I could lower it just so much before I could not get enough heat on the coldest day. Furthermore, the upstairs was heated with undersized fin-tube radiators, and lowering the temperatures of the hot water meant the upstairs was always cold. There was only one zone at the time.



The new boiler has outdoor reset and this may help with the problem of wide temperature swings. Instead of putting (an estimated) 140F water into the floor during the heating season, in the spring and fall it can go all the way down to 70F (if I program it that way), so the floor should not get as hot, and the swings will not be so bad just because the thermostat is going on and off. But realistically, I have now set the setbacks to 1F, at least to start, and doubt this will save a lot of fuel. If that is the best that I can do, I might as well just get a simple bang-bang thermostat. The system now has a zone for upstairs, a zone for downstairs, and a zone for the indirect hot water heater, and the controller can supply a different temperature for each.





"I just can't get around the idea that using less energy is the goal,

and that insulation, square footage heated per occupant, unoccupied

comfort temperature maintenance, and very high mass heating systems

that make indoor comfort temperatures less responsive to occupancy are

all far more important (in my little mind) than, say, breaking the

barrier into condensing technology for combustion appliances."



When my house was originally designed (if it was designed), it had almost no insulation, the windows were crappy aluminum single pane ones, etc., and heating oil was only $0.40/gallon when I bought it in 1976. So temperatures did not overshoot as much because the excess heat leaked out without even opening the windows. Over the years, I had the walls filled with foam insulation, the ceiling upstairs got 6" more blown-in fiberglass insulation, the crappy windows replaced with thermopane type windows with argon gas between the panes and low-E coatings, leaky storm doors replaced, etc. So it got to the point when the boiler would quit on a Sunday afternoon, I would not even call for service until normal business hours. It would only drop a few degrees in 12 hours. I wish I had recorded measurements of indoor and outdoor temperatures during those times.

Mark Eatherton

Nuclear's Additional Costs....

JD,



Are you of the impression that the Nuclear industry is NOT paying those costs? The cost of decommissioning, maintenance and fuel rod disposal IS taken into consideration, and those costs ARE rolled into the cost of doing business and passed on to the end users. The incremental cost per KWH is small when you take into consideration the KW production over the life of these plants. The days of Chernobyl and Three Mile Island still linger in people's minds, and rightfully so, but if you want clean reliable energy, look to Nuclear.



France derived 75% of it's electrical production from Nuclear, and estimated its back end decommissioning costs at about 5% of it's overall costs. It is also selling electricity at $0.03/KWH, and at those rates, GSHP does make sense.



For more information, go to http://www.world-nuclear.org/info/inf40.html



No business in their right mind (excluding the U.S. Gov't...) would attempt to operate a business at a negative profit margin. It is economic suicide. This is why we have regulatory agencies.



As for waste heat recovery, I have installed GFX drain waste heat exchanger up at Hydronicahh, and it is going to reduce the energy consumption for DHW production by 50%. That means my solar and other thermal systems will be capable of providing an even greater fraction of my energy needs without generating carbon on site.



My opinion on woody biomass is that when properly applied and controlled, it does make sense. The wood will eventually break down and generate the same amount of carbon dioxide that it would if it were quickly oxidized. The days of the old smokey wood burning appliances are gone. The EPA has stepped up regulation of these devices, and they are now required to be at least 90% efficient and 33% more efficient with minimal particulate loads than the old stoke and coke models.



This means you need a large storage tank, and when you load the appliance with wood, it goes into a full, HOT, clean burn, and quickly converts the wood to thermal energy, which is stored in the tank, and used throughout the day. This requires more frequent loadings at design conditions, but the ash load is nearly ZERO. The appliance does such a good job of conversion that in most cases, less than 5% of the material burned results in ash.



Times (and equipment) they are a changing. And with the advent of onsite storage and conveyance systems, the "convenience" factor is also increasing. This ain't your grandpas pot belly stove any more, and we need to pay attention to this sustainable, renewable resource. Besides, it is a know fact that trees convert CO2 into Oxygen. Why not let mother nature clean up our (and her) own mess?



As for embodies energy, or Exergy as you called it, it might turn peoples heads if they knew how much energy a photovoltaic solar panel consumed, in the process of being manufactured, versus the amount of energy that it will deliver in it's life time. At a peak efficiency of 20%, this solar star is kind of dull compared to Solar thermal systems with thermal efficiencies in the high 60 percentile. Solar electric has come a long way in a short period of time, but in my opinion, it still has a long ways to go before it can stand on its own legs without government intervention, which in my opinion, is the true test of time.



Face it. People don't do solar because it makes economic sense. People do solar because environmentally, it's the RIGHT thing to do, economics be damned.



As for the Price Anderson act, it appears to be a typical government attempt at satisfying the NIMBY principle with red tape. More government intervention that indirectly is financed by the American tax and rate payer.



ME

Jean-David Beyer

paying those costs?

"Are you of the impression that the Nuclear industry is NOT paying those

costs? The cost of decommissioning, maintenance and fuel rod disposal

IS taken into consideration, and those costs ARE rolled into the cost

of doing business and passed on to the end users."



I am definately under the impression that the nuclear industry is not paying those costs. I see no way the industry can make enough profit in the 40 year lifespan of a nuclear reactor to cover the storage of the nuclear wastes for 250,000 years or so required for the danger to be reduced only 50%, much less to a reasonably low level, since most scientists concerned with such matters seem of the opinion that there is no safe level at all. Think about the problems of storing those wastes for that long. No civilization in history has lasted over 6000 years, and that assumes China is a single civilization, and not a bunch of 1000 year ones. Who is to say that a civilization 10,000 years from now would devote any resources at all to maintaining a nuclear waste dump and keep it from leaking? It strikes me the hight of moral irresponsibility to produce such toxic long lived waste and forcing future generations to guard it with their very lives. Consider this: near me are a bunch of forts, made of reinforced concrete, for the defense of the east coast of the US. They were designed to resist artillery attacks from hostile powers (often technically proficient nations such as Germany). They are crumbling to bits due to lack of maintenance. Now in the case of the forts, they are of little use, so there is no need to maintain them. But these are only about 100 years old. We have no technologies capable of lasting a quarter of a million years without maintenance.



Second, the Price-Anderson act nominally relieves the industry of responsability for accidents. True, the nuclear users pay into a fund to cover the potential accidents, but as a practical matter, it is grossly underfunded. Perhaps if a nuclear plant melted down there might be enough money available to pay for the loss of the plant and compensating the stock holders. But it would never pay for the environmental damage, and the environment in this case is global. Within two weeks, the effects of Chernobyl were detected in USA after having blown 3/4 of the way around the world. Face it, the US taxpayer will again have to pay for the costs of this, either in terms of higher taxes, and in increased disease from nuclear fallout.



"The incremental cost

per KWH is small when you take into consideration the KW production

over the life of these plants."



I do not agree. The costs is enormous and they only appear small because the US Government is self-insuring itself and the nuclear industry from the true costs.

Mark Eatherton

We can agree to disagree...

I will leave it at that. Not everyone agrees with my opinions, and that is fine. I don't always agree with others opinions either. That's what makes the Wall an interesting place.



Thanks for keeping the debate lively and civil.



ME

Mark Eatherton

Keep on a singing that tune....

I hear you. And if you are using it to your advantage in your marketing efforts, your customers are hearing you too....



ME

ttekushan_3

insulation, control

Now you've got control over the situation. With the great insulating job you did and breaking the system into functional zones there's control over heat loss and how/when heat is replenished. It almost seems worth setting back the fintube 2nd floor a bit and leaving the radiant alone. If recovery on the radiant requires higher supply temps I guess the boiler can slip far enough away from optimal return temps to lose condensing ability. Setback conservation is lost entirely.



It will be interesting to see how the accumulated benefits stack up per degree day this winter.

Jean-David Beyer

It will be interesting to see

I am inclined to agree with you about running the radiant downstairs with minimal set back (or none at all). Right now I have it set to run 67F from 3AM to 9AM, 66F from 9AM to 3PM, 67F from 3PM to 9PM, and 66F from 9PM to 3AM. I.e., almost none at all. I think all that will do is have a little warmth in the floor when I get into and out from the shower, and so I do not freeze when getting ready for bed. ;-)



Upstairs, I have a 14 foot piece of Slant/Fin in each of the two rooms, replacing a couple of fin-tube radiators with 3 feet of tube. That way, I hope to run 140F water in there on the design day, and let it slip down to 85F or so on warm days. So I should get condensing a lot of the time when heating the upstairs. It may be that 140F is not enough, but my heat loss calculation indicates it should be. At the moment, I have it set to 62F up there most of the time, and 65F for a 2-hour period each morning and evening. I cannot let it go below 62F because I have some photographic solutions up there that can freeze at that temperature. I do not use the upstairs all that much, but when I do, I usually know a day in advance, and can set the thermostat accordingly.



It is kind of funny the controls. The W-M Ultra 3 has a very clever control board, but not quite what I need. It takes three thermostat inputs and can control 3 circulators. But I need it to control 4 circulators. So I have a Honeywell relay box to control the last circulator. For each thermostat, a separate outdoor reset curve can be used. What that does is allow both the upstairs and the downstairs zones to work at once if they both want to. But downstairs should go only to 120F and upstairs should go to 140F. So what happens is if both zones want to work at the same time, they will both get 120F water. Not quite enough for upstairs, but better than nothing. An additional relay box could go in there to prevent the upstairs from running when the downstairs was active, but I need a relay box with a 120 volt coil on the relay, and neither I, nor the contractor, could find one. I could easily enough make one from parts, but I do not think I could get it past the electrical inspector, and I do not think it will be a problem as it is.



It will always condense when heating downstairs (1150 or so square feet), and will condense most of the time upstairs (about 450 square feet). I am somewhat amazed it even condenses a little when heating domestic hot water which I have supplied at 180F and returns about 166F. The reason for this is that the indirect hot water heater is set to 120F, so it recovers very fast and the boiler never gets up to 180F at all; so the boiler spends quite a bit of time in the condensing region even when heating the DHW. Recovery time in the summer is of the order of 5 minutes. I suppose it could be longer in the winter.



Setback will be almost useless downstairs, but it should be effective upstairs. Outdoor reset will be helpful for several reasons; upstairs to keep the return temperatures low in warmer weather, and downstairs to keep the supply temperatures low enough to reduce the wild (6 degrees or so) swings I get by putting design-day water temperature in there when it is undesired.



I am certainly interested in how it is going to work when all this is put to the test in cold weather. It is supposed to go down to the upper 50s Friday night, but I probably have too much insulation to get the system to come on. ;-)