What Temperature Is Your Tap Hot Water?

[sudsmaster]

Well if you look at a 50 year old gas water heater, and then a new version, you'll notice the insulation is about twice a thick on the newer model. That translates directly into less heat loss and better energy efficiency. There are probably other advances regarding venting of exhaust gasses. And then there are the on demand models that only heat the water as it is being used.

I addressed the energy efficiency issue on the 40 year old 50 gallon water heater here by wrapping an extra inch of insulation around it.

There are lots of marketing ploys with regard to energy efficiency. For example, my new neighbor recently replaced all the windows on his house with double pane numbers. He said it set him back about $50k. Yikes. But he still says parts of the house are hard to heat.

I researched the whole home heating issue about 15 years ago. The materials I reviewed pointed out that windows comprise only a small fraction of the total living space envelope. So I made sure the aluminum slider windows all got new felts (they rattled in the wind!). And then I insulated the attic floor and under the living space floor with fibreglass, to about R-25. I also wrapped all the forced air heating ductwork, including the air return, with at least 1" insulation. I also made sure that any air leaks from the living space to the attic were sealed off. The end result is that it slashed my heating bills in half, at least.

 

[iej]

There’s no question but modern boilers are drastically more efficient. They’re far better insulated but the bigger impact is they can pull much more heat out of the flame with much better heat exchangers, which is why they are condensing. The exhaust gasses are cool enough to see the water vapour and it will condense in the boiler itself.
That indicates just how efficient they’ve become. In a lot of older boilers most of the heat just goes straight up the stack and is just lost to the atmosphere.

A lot of what’s possible now wasn’t back then. We’ve access to more advanced materials, complex manufacturing and control systems. In the past they often relied on just clunky cast iron.

Improving insulation is a big deal in a house, but you need to do it targeting the areas of greatest heat loss. Putting in just triple glazing, without dealing with insulation in walls, floors, attics and improving heat recovery is a bit like trying to keep soup warm in a thermos flask with the lid off. It’s but pointless.

Also improving heat losses from plumbing or ducting is important.

 

[kenmoreguy89]

My water gets out at 172F most of the times, not less than 145 when my sister or father living in the other parts of the mansion also use it and water in the tank is still heating. I have solar panels and a wood powered large furnace that burns a load for 2 days and LP gas for summer.
If I set it lower I wouldn't get water hot enough to do my whites.
Good thing about solar panels and wood furnace is that we have virtually "free" hot water, of course wood cutting and stashing is quite a job but we have much land and many trees and you do not need to pay for the gym! Triple win!

 

[kenmoreguy89]

Oh and of course the furnace also heats radiators.
Though I have a wood cooking stove at my place and that is all I used to cook in the winter time and it heats my whole place too that I need to turn on radiators very rarely.
Food cooked and baked on and in a wood stove just taste a thousand times better

 

[kenmoreguy89]

And it is so convenient to have a oven that is always hot 24/7 that there is always something in it whether it's bread or a cake pie or a frozen lasagna for those days I just don't feel like cooking.

 

[warmsecondrinse]

From the ~1880's to WWII-ish most 1-3 family homes (and frequently larger apartment buildings, esp until 1920's) were heated by low pressure (2-5psi) one-pipe steam systems. There was no hot water heater. Hot water was produced from a coil running off the boiler. AFAIK, 1-3 family homes did not have any kind of temp limiter or mixing mechanism. The water produced was literally spitting hot. However, it didn't take long to run out.

My grandparents' home had no shower until I was in college. You'd run a bath with just the hot water. By the time you'd drawn enough water the temps had cooled to ideal. It's something you got used to and only noticed when you messed up.

Most of these boilers were originally coal fired. As mentioned above they were converted to oil. How was this done? Simple: You removed one of the vents that was about the size of the burner nozzle and stuck the nozzle in its place. Seal up the openings as well as the other vents and you're done.

One of my grandparents' rentals had just such a conversion. A piece of debris got stuck in the nozzle, oil dribbled down and accumulated. Eventually it caught fire. Clouds of black smoke spewing out of the chimney yet form inside the house you'd never guess there was a problem. The firemen told us they'd seen this more than a few times over the years. Supposedly, this kind of fire isn't much of an issue if the pre-WWI boiler was well made.

#60 'Energy-saving' scams

A lot of those energy 'audits' of the 70-90's were mostly plots to separate you from your money. For most older homes in the northeast you got the most bang for the buck by insulating in the attic and plugging air leaks around the house. If you had an older boiler that was problem-free but throwing off a lot of 'waste' heat the second thing to do was to insulate the basement walls. Ideally it would be floor to ceiling but at least from the ceiling to 2 (4?) feet below ground level. The thing is, the 'waste' heat really isn't. It keeps the floor of the first floor warm, allowing for a lower thermostat setting.

My mom and her 2 brothers learned this the hard way. For reasons I'll probably never know my grandparents' oil-fired furnace had to be replaced by a more efficient gas one.... immediately! This was a Crisis... with all of them talking in Capital Letters. I asked how they were planning to dry laundry and keep pipes from freezing. When I explained that was what the 'waste' heat was allowing they thought I was crazy and ignored me... again. Plans went ahead and we had the entirely predictable results: Cold grandparents, cranked thermostats, frozen pipes, cold floors, drafts, etc. For the record, the was the second time they made heating decisions in defiance of the laws of physics..... not that I was counting.

 

[drhardee]

Hmmm...interesting. Our Rinnai tankless HWH is set to 108 F. I set it at that temperature as that's as hot as we like our showers (with the shower valve set to completely hot), with no "tempering" from cold water.

I don't see the need to have to temper too-hot water with cold when I'm showering, and 108 F will melt grease off of dishes when handwashing whatever doesn't get placed in the GE Profile DW, which will boost temps up to 130 or 140, with a 150 F final rinse, or higher, if "sanitizing" whatever.

As for the wash, the Miele takes care of temps up to 190 F, should such temps be necessary. Darks get washed at 105 F, colors at 140 F, sheets at 120 F.

 

[launderess]

Tempering Hot Water

Much depends upon source of hot water....

As shown in training videos above those getting hot water from a side arm or coil off a boiler that is making hot water or steam for heating likely will need some sort of tempering system. Otherwise there is a great risk of water at nearly or truly scalding temperatures coming out of the taps.

Tankless and even tanked (storage) water heaters are a different matter. There you have things a bit easier to control temp of water. Not long ago Ruud and other makers of tanked water heaters offered models with dual temps. High (180F) for automatic or semi automatic washing machines along with dishwashers, and low (about 130F) for bathing and other uses.

Recall growing up both in our house and many others children weren't allowed to touch hot water taps. Our baths and showers were adjusted by adults because water was just that hot out of taps.

Tempering hot water generated by boilers isn't new. Biltmore estate in NC as originally built had two huge coal fired boilers that also heated water. Hot water for domestic use was tempered. OTOH there was one pipe that gave straight hot water that went to laundry/utility area.

 

[launderess]

Heating water off the boiler

Is in the cross hairs of green movement, and may soon go way of Dodo in many areas.

Greens don't like fact that getting hot water via coil in or off the boiler means that thing must fire all year long. This even when heat isn't called for such as during warmer times of year. They see this as a waste of energy.... Their preferred method for hot water involves any sort of stand alone system ranging from solar to instant or any combination to exclusion of tank/storage heaters. Storage is fine if water is heated say by solar or some other green method, but just keeping a tank of water heated by gas, electric or oil isn't on...

OTOH keeping boilers fired all year long in many instances keeps corrosion down and extends life of same. Heated water has oxygen driven off, and that oxygen is what causes metals to corrode especially old cast iron boilers. Of course if one goes with a higher grade of stainless steel....

 

[warmsecondrinse]

LOL, that second paragraph is too complicated for most of the greens. And extending the life of a boiler makes carbon footprint calculation too abstract.....

 

[sudsmaster]

If the water is pressurized in a sealed system, where does the oxygen go? It must stay in the water.

OTOH, if a boiler is drained at the end of the heating season, then I could see more oxygen hitting the now exposed inner walls.

I guess it could depend on the design. A sealed system should have the same amount of oxygen inside it hot or cold.

And if anything, a hotter temperature means faster corrosion, all else being equal.

Out west here boilers and steam heat etc is fairly rare, at least in residential areas. We have generally milder winters in most of California, where natural gas/air heating is the norm. And, most residential hot water is provided by the tried and true tank method, although on-demand systems seem to be more energy efficient and increasing in popularity. If I ever add hot water to a separate workshop building here, it might well be an on-demand type. The only catch could be if there is insufficient gas flow to run anything but a small on-demand type unit.

 

[launderess]

See:

https://heatinghelp.com/systems-help-center/what-to-do-with-boilers-during-the-summer/

There are ways to remove air from steam boilers. Quite simply you drive oxygen out of water by heating it up. There are valves on any sort of boiler from steam locomotive to residential heating that allow initial gassing off when firing up a cold boiler. See video clip below.

Problem is no steam receives back 100% of water sent out to heat as a gas or vapor. Eventually water that is lost must be replaced. That fresh water contains oxygen so there you are.

 

[tomturbomatic]

Thank you, Launderess!!

Isn't it amazing how the engine is only brought to life when the steam starts circulating even though there is water in the boiler and fire below the boiler. That stoking of the fire reminds me of my grandparents' coal furnace and the way flames would lick out of the door when it was opened for stoking. It is no wonder that hell was described in terms of fire.  The subtitles sure explained things well. 

 

I have a hydronic system that was charged up with water almost 30 years ago and once the original charge of water had its oxygen combine with the copper and iron, there was no more oxygen to interact with the materials in the system.

 

Thank you again, Launderess  

 

[warmsecondrinse]

On the subject of coal, I'd like to add that a well-run system by someone who knows what he's doing is clean. For several years I unknowingly worked in a school heated by coal. I only discovered it by accident when i came upon the ash bins set out for pick up.

The school had a full time licensed fire man to take care of the boiler.

A few years after I left there was a big hue and cry about the "dirty coal boilers" that were "suddenly discovered" in the NYC school system.

Of the school that were (supposedly) a problem, not a single one had a full-time licensed fire man to take care of the boiler.

The response was typical NYC Board of Ed: Spend millions to replace EVERY coal fired boiler in the school system...

 

[thomasortega]

I would definitely love to have a way to have even more hot water.

Rental unit, tank isn't too big (only 50 gal).

During the winter, like now, its a PAIN.

I can fill only a couple of top loaders with hot water (usually one for towels and other for sheets, both are plain white) but then... I can't do a third load of whites)

During the summer, I can easily have 3 TL filling with FREAKING HOT and then open the cold valve partially to have warm for the other clothes, then I close the cold to use the rest of the tank water (lukewarm) for delicate items.

What I'd really love is a way to run ALL the washers with freaking hot water if needed.