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A manifesto on shower temperature control

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Re: A manifesto on shower temperature control

#91

Post by shagie »

thrwawy74 wrote: post #48
gorgoiler wrote: post #45

As a friendly heads up to anyone exploring this space — temperature control is a complex dynamic between many components, chiefly the mixing valve, any local thermostatic dampers in the valve (rarer, but definitely a feature of high end mixers), and the source of hot water itself . Mixer taps are not simply mixing hot water at temperature H and cold water at temperature C. The temperature H which your hot water sourc…

So we need like a capacitor for hot water at the shower head.

How about a 13 kWh 2.5 GPM tankless heater - https://www.homedepot.com/p/Rheem-Performance-13-kW-Self-Mod...

For 2.5 GPM (typical shower) it can do 35°F heating. If you have a low flow shower head (1.75 GPM), you can do about a 55 °F heating.

You could also do a water heater booster - https://www.rheem.com/innovations/innovation_residential/wat...

Another approach is to go to the other end where you've got the tank running higher than is safe to safely touch (e.g. scalding) put put thermostatic valves on all sinks and showers. This way you can run the water heater at 140° then then use more cold water to reduce it to the proper temperature which is a slightly easier problem than running your water heater at 120° and then cooling it down to 105° which gets to "mostly hot water with cold water for pressure". Running a tank at 140° also inhibits bacterial growth (e.g. legionella)

Not enough for a shower, but for a sink you could look at an under sink water heater ( https://www.homedepot.com/p/Bosch-2-5-Gal-Electric-Point-of-... ) - but you're looking at 6.8 GPH recovery time rather than a 2.5 GPM flow rate. The main advantage there is that you don't have move the hot water from the water heater in the basement all the way to a sink (lots of hot water in the pipe that then gets wasted) and thus less water use to get hot water to the sink and less hot water use overall.

An under the sink tankless looks like https://www.homedepot.com/p/Rheem-Performance-6-kW-1-0-GPM-P... with 0.5 GPM for a 65°F raise (you wouldn't even need to run hot water to that sink - this is what I do for my upstairs bathroom since the water heater is so far away that you need to run the water for a very long time to get the sink up to 'wash with hot water' levels).

Re: A manifesto on shower temperature control

#92

Post by ars »

bluSCALE4 wrote: post #57

I'm actually installing a thermostatic valve today to go with a recirculating pump I have setup on an electric heat pump water heater. I'm going to be installing it exactly like this guy with an expansion tank. Does anyone see a problem with this layout? Apparently, his doesn't work. https://www.amazon.com/review/R3NQCKZCEQLLLC/ref=cm_cr_srp_d...

Get this and install by the heater: https://smile.amazon.com/dp/B08R1HKZ78/ or this: https://smile.amazon.com/gp/product/B09V7MDZHF under the sink.

There's a remote available also. By sure and carefully read the details - there is an "E" model, be sure and understand the difference and pick the right kind for your setup.

Re: A manifesto on shower temperature control

#93

Post by scottlamb »

avianlyric wrote: post #88
scottlamb wrote: post #66

Earlier quoted context omitted.

I have a Gröhe thermostatic valve which came with the house. It's somehow broken such that you can't get the water as hot as advertised unless the dishwasher is running (?). And it's installed behind tile, so we can't just get a plumber to come in and replace it; we have to also line up someone to re-tile the shower immediately afterward. We also have a pair of Gröhe sinks. We had to replace all four expensive, propr…

Sounds like an issue with your heater. Not sure why your dishwasher changes anything, they normally run off cold water and use their own heaters. Sounds more like you run your kitchen tap while filling the dishwasher, and flushes the cold water out of your pipes, and gives your heater enough time to get to temp. Have you tried see if you can set the output temperature of your heater higher? Could be the output temp o…

The water's hot enough everywhere else (this bathroom's sinks after the aforementioned delay, other bathroom, kitchen). The heater's set to ~130 deg F, which iirc is the upper limit of what's recommended and considerably above the ideal shower temp.

It really seems to be the dishwasher running that makes the difference. I rarely use the shower in question, but my wife does every evening, and it apparently doesn't help if I've done all the rinsing/hand-washing and loading of the dishwasher but not actually hit start. I don't understand the mechanism, but I believe her. I'm not sure if the dishwasher draws from the hot or cold tap.

Re: A manifesto on shower temperature control

#95

Post by cirrus3 »

kccqzy wrote: post #46
amluto wrote: post #25

Yikes, the max temp is 140F. That’s dangerous and has been a code violation for a long time, for good reason: https://www.pmengineer.com/articles/94780-upc-continues-to-e...

That's what I thought too. Why not take the first step to reduce the temperature setting on the water heater?

Yep, my first thought was why nothing was done at the water heater level if the full-hot is way too hot.

Re: A manifesto on shower temperature control

#96

Post by Macha »

gorgoiler wrote: post #45

As a friendly heads up to anyone exploring this space — temperature control is a complex dynamic between many components, chiefly the mixing valve, any local thermostatic dampers in the valve (rarer, but definitely a feature of high end mixers), and the source of hot water itself . Mixer taps are not simply mixing hot water at temperature H and cold water at temperature C. The temperature H which your hot water sourc…

This is also the case for electric showers though, where the shower itself contains the heating element and heats its own water, rather than taking arbitrary feeds of hot and cold water.

Re: A manifesto on shower temperature control

#97

Post by jxcl »

avianlyric wrote: post #88
scottlamb wrote: post #66

Earlier quoted context omitted.

I have a Gröhe thermostatic valve which came with the house. It's somehow broken such that you can't get the water as hot as advertised unless the dishwasher is running (?). And it's installed behind tile, so we can't just get a plumber to come in and replace it; we have to also line up someone to re-tile the shower immediately afterward. We also have a pair of Gröhe sinks. We had to replace all four expensive, propr…

Sounds like an issue with your heater. Not sure why your dishwasher changes anything, they normally run off cold water and use their own heaters. Sounds more like you run your kitchen tap while filling the dishwasher, and flushes the cold water out of your pipes, and gives your heater enough time to get to temp. Have you tried see if you can set the output temperature of your heater higher? Could be the output temp o…

> Not sure why your dishwasher changes anything, they normally run off cold water and use their own heaters.

For North America at least, this is not true. Dishwashers are hooked up to the hot water supply[1] (and it's a good idea to run your sink tap hot to "prime" the hot water for the dishwasher).

They _also_ use built in heating elements to keep the water hot, and to dry the dishes, though.

[1]: LG Dishwasher Installation instructions (as an example), page 8: https://www.lg.com/us/support/products/documents/Dishwasher%...

Re: A manifesto on shower temperature control

#98

Post by amluto »

Spivak wrote: post #44
amluto wrote: post #25

Yikes, the max temp is 140F. That’s dangerous and has been a code violation for a long time, for good reason: https://www.pmengineer.com/articles/94780-upc-continues-to-e...

It really shouldn’t be, at least for homes where the owner gets to choose. Being able to set you water temp extremely hot makes your hot water last longer because the comfortable water temperature is say like 70% cold, same applies for laundry. Also consumer dishwashers perform much much better with higher hot water temp.

There is nothing wrong with setting one’s water heater tank very hot (except potential inefficiencies — there would be more loss when not using hot water, and heat pump water heater can be less efficient heating to a higher temperature). Codes allow this.

What codes do not allow is excessively hot water coming out the fixture. IMO this is the most sensible kind of code: it disallows a specific unsafe outcome. You are not allowed to build a house that burns unsuspecting users of the sink of shower.

So you can apply technology! There are thermostatic mixing valves that can be installed near your tank to serve your whole house or at the individual fixtures. They’re not free, but they’re not terribly expensive, especially if just one is used for the whole house:

https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING...

Re: A manifesto on shower temperature control

#99

Post by morepork »

deathanatos wrote: post #89
waste_monk wrote: post #67

Earlier quoted context omitted.

>(And, apparently, as I learned, there's a mixing valve at the hot water heater: i.e., the hot to the shower is not direct from the water heater, like I had imagined. We raised the temp there, slightly.) When we changed from instant hot water to water tank + heat pump, the guy said the tempering valve was a safety thing (IIRC ours was set to 60 degrees Celsius by default, but could go up or down about 10 degree eithe…

"Safety" is also what my guy said. The problem is that in isolation the answer doesn't make any sense : why should I be heating water up to then re-mix cold water? Is that not a waste of energy? The fuller answer, I think, is that the "raw" hot line additionally goes towards uses that can take scalding water, one or more of the dishwasher and the laundry, depending on whether you have either or both of those in your…

Storing the water at a higher temperature effectively increases the capacity of the tank. Also the stored hot water has to be above a certain level (~60 degrees) at least some of the time otherwise it won't prevent any bugs growing in it.

Re: A manifesto on shower temperature control

#100

Post by rconti »

russellbeattie wrote: post #61

The amount of water wasted waiting for the water to warm up must be astronomical. In my place it can take three or four minutes of the water running to get warm - if not longer - and I don't think that's atypical. Multiply this by 7 days a week by everyone who showers in California alone and it seems like an issue that should get some serious attention.

It's particularly bad with my tankless hot water heater that apparently doesn't even turn on for 15 seconds, and then you wait for the hot water to get to the shower. I swear the whole thing takes 60-90 seconds, and I live in a tiny house. I can't fathom what the hot water is doing on its way to the faucet. (well, yeah, some of that time is also spent heating the cold uninsulated under-house pipes).
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