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 New Hot Tank Temperatures
Author: 06honda (Non-US)

I had a new natural gas direct power vent hot water tank installed to work with my infloor radiant heating system. On my old one it was hard to tell the temp due to it being a 18 year old tank with a dial type, so I just kept it on the triangle mark. This one is light controlled, I had it set a 120 but bumped it up to 125 this evening. My understanding is the floor temp for the system is around 110-115. My understanding is that this is achieved by some cold water being mixed into the hotter water from the tank but not 100%.Just wondering if the HWT temp should be around that or a little higher. No kids in the house so me and the wife are aware of being careful turning on showers etc. Very small house, one level 1080 sq feet. Thanks for any info.

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 Re: New Hot Tank Temperatures
Author: North Carolina Plumber (NC)

Usually cooler water from the returns are mixed with the hot water to the supply of the radiant to maintain the preset temperature the radiant requires. You may or may not have a mixing valve due to the fact that you're using a water heater instead of a boiler. There should be no problems of leaving the heater set at 125.

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

It is not uncommon to set the water heater as high as 135-140 when there are no kids and no seniors living in the home that might get scalded by accident. But keep in mind you could have visitors now and then so if they bathe you might want to warn them the water is extra hot in case they don't have it that hot at their home. Some people are concerned about bacteria that can grow in a water heater that is not hot enough so they set it higher. The water heater manufacturers all set the temp to about 125 at the factory due to lawsuits from people getting scalded after a new install, but it is customer adjustable. Also, if the water is not warm enough your dishwasher will have to heat it at the beginning of its cycle, that will use extra electricity and delay the dishwasher for a few minutes.

What happens in the summertime, do you shutoff the system by shutting a water valve or turn off the circulation pump maybe?



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 Re: New Hot Tank Temperatures
Author: packy (MA)

the temperature water you send to the floor is directly proportional to the outside temperature.
the colder it is outside the hotter the water wants to be.
you are looking for a floor temperature of 85 deg F.
when the outside temperature is say 45 deg you would want water about 100 deg but when it is below zero you will want at least 145..
the concept is simple but there are so many factors affecting the comfort level you achieve that it becomes quite complicated.
one simple example is that the water temperature under tile floors wants to be less than under hardwood floors.

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

packy, does the radiant floor heating have a control unit that measures the temperature and adjusts a mixing valve for you, or is this a manual thing that the homeowner has to adjust themselves? I've not been around something like this but have seen something maybe similar but simpler, piping under a driveway to melt snow and ice, the water was heated by solar.



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 Re: New Hot Tank Temperatures
Author: Paul48 (CT)

I don't agree with mixing heating and domestic hot water. That said....you can run 2 circuits off the tank set at 160*. One for domestic with a thermostatic mixing valve set for 120* and one with a Taco "I-series" mixing valve with outdoor reset.

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 Re: New Hot Tank Temperatures
Author: packy (MA)

yes, there are adjustable mixing valves controlled by outdoor sensors.
they also make a sensor that goes in the middle of the floor that knows when the floor is 85 deg F and adjusts the flow accordingly.
i have installed systems that were simple and were manually adjusted.
i have also installed systems that were big bucks and had more bells and whistles. these i let the engineers at viega design.
one thing that is common amoung all of them is the people are all very happy with the finish product. the comfort level far exceeds regular hydronic heat. (so does the price)..

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

Do the simpler manual systems you install have a separate boiler just for the floor radiant piping? Perhaps in smaller homes they are able to use the domestic water heater rather than have a separate water heating method. I'd think that in some areas of the country it would only be 3 or 4 months usage, or in summertime do they still want water to circulate to avoid problems?



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 Re: New Hot Tank Temperatures
Author: packy (MA)

i have never used seperate heat sources.
i installed a 75 gallon propane water heater last year for a 4.5 bath house i did.
they had a big whirlpool so the big tank was needed. the tank did have seperate tappings that were labeled for heat use.
[www.statewaterheaters.com]

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 Re: New Hot Tank Temperatures
Author: Paul48 (CT)

The installation is very labor intensive, and that drives the costs up. There's no reason a homeowner with good mechanical skills can't install a proper staple-up system themselves, if they do their homework. I was given this link by a radiant contractor, and he said he had been using these recently, with great success. They're not expensive and if you watch the installation video, you'll see they are not hard to install. [www.ultra-fin.com]

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 Re: New Hot Tank Temperatures
Author: 06honda (Non-US)

In the non heating system I just turn down the wall thermostats to a point where the heat will not turn on. Thermostats in the house are handy for keeping an eye on temps for the ductless ac unit use.

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 Re: New Hot Tank Temperatures
Author: 06honda (Non-US)

Here are some images of the basic layout of controls etc on the system.

















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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

Thanks for the photos and information, I've not seen this before.

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

06honda, what kind of maintenance problems or failures have you had to deal with, if any? How many years have you had the system?

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 Re: New Hot Tank Temperatures
Author: 06honda (Non-US)

The system was installed in 1999. The new hot water tank I just got was only the second one since the intial install. As for repairs: 1 x wall thermostat; 1 x WIRSBO Control Board, & one water value that leaked. Total for these parts approx $250 or so.

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

That seems pretty reliable for a 17+ year old system. The electronic control board may have gotten damaged by an electrical storm instead of an outright failure. I found their website, really interesting products.



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 Re: New Hot Tank Temperatures
Author: 06honda (Non-US)

After leaving it set to 125 for 24 hrs I ran the hot water tap in my bathroom for about a minute or so and filled a glass with hot water. The temp I got from a kitchen type thermometer aread around 135. Is it normal or common to have such a difference in temp as the tank is at 125? The hot water tank is only about 30 feet from the first tap, small house we have.

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

I'm not sure how accurate that temp readout on the water heater is, does your paperwork for the water heater say anything about it? The thermostats on a water heater have a built-in spread (hysteresis) of a few degrees so they won't quickly switch on and off when the water temp is at the desired setting. That means the water may get heated a few degrees above the setting, then cool down over time until the thermostat finally says it is time to heat the water again. So is your water heater displaying the desired temperature setting, or the actual temperature of the water in the tank? I suspect it is the temp setting you want but the actual water temp will vary some.

I'd check it again a few times, you may have caught it right after a heating cycle when the water was at it hottest. You can also check your kitchen thermometer to see how accurate it is. Stick it in a tall glass filled with ice and some water. Put the thermometer in the middle and not touching the bottom or sides of the glass, see if it reads 32 degrees.



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 Re: New Hot Tank Temperatures
Author: 06honda (Non-US)

Good explanation regarding temperatures varying, likely this is just what it is. I did find this in the manual:

"When hot water is drawn from the tank in frequent short bursts, a condition known as “stacking” is created.“Stacking” is the result of increased cycling of the burer and can produce very hot water temperatures
at the hot water outlet. "

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 Re: New Hot Tank Temperatures
Author: stuckinlodi (MO)

If you check the hot water a few times at the faucet and consistently get a temperature higher than what you'd like you can set the water heater setting to something lower and just know that "130 on the water heater = 140 at the faucet" or something similar. Kitchen ovens have this problem sometimes, you set the oven temp to 375 degrees but the oven actually gets to 400 degrees and affects the cooking time.

If curious you can contact the water heater manufacturer customer service dept online, it is easy nowadays to send them a question and ask if the digital readout on the water heater is showing the actual tank water temp or is it just the desired temp you select. We know the tank temp will vary as cold water comes in to replace hot water that leaves the tank. So after a long shower or bath that uses a lot of hot water you can check the digital display and see if it dropped when all the cold water came into the tank. If it did then perhaps it does display the actual tank water temp. But if the readout stays the same all the time then it is just displaying the desired temp that you selected and the actual tank water temp could be much different.

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 Thanks for the help. :)
Author: 06honda (Non-US)

Thanks for the help, have a good week.

Paul



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