adding mixing valve and expansion tank to conventional electric water heater

[Twowaxhack]

I thought you were just talking about water that hot being dangerous.

corrosive, mineral fall out and scalds.

 

[RustyShackleford]

He is ,he wants you to know how quickly water scalds

Yeah, I'm pretty clear on that. But again, Honeywell-Residio is really touting "anti scald" and they suggest nursing homes as an application. I gotta think they're pretty confident in the technology to be saying that. I'm gonna research it more, but open to turning the water heater no higher than 140, which still gives roughly 1/3 more hot water, than set at 120.

I though @Twowaxhat was saying fouling with minerals is more likely at higher temps.

 

[Twowaxhack]

Nursing homes are also required to have thermostatic shower valves, something you don’t have most likely. It’s a step up from pressure balanced with hot water limiter.

 

[RustyShackleford]

Nursing homes are also required to have thermostatic shower valves, something you don’t have most likely. It’s a step up from pressure balanced with hot water limiter.

The Honeywell-Residio one I'm using (and linked above) claims to be "thermostatic". Is this wrong ?

 

[MicEd69]

I though @Twowaxhat was saying fouling with minerals is more likely at higher temps.

He was and it is. Listen to the experts.

 

[RustyShackleford]

Ok, I'll listen to the experts ... what do you think I should to do ? Ditch this idea altogether (in which case, who IS a good candidate for such a mixing valve) ? Don't turn the water heater above 140, and live with only an approximate 33% increase in available hot water ?

 

[Twowaxhack]

The Honeywell-Residio one I'm using (and linked above) claims to be "thermostatic". Is this wrong ?

Nursing homes have thermostatic mixing valves at the individual showers also.

Two valves that offer protection.

Add another water heater, low flow shower heads, tankless gas water heater, Rheem hot water extender are choices.

 

[molson]

Maybe overkill for a residence, but the Caleffi digital mixing valve excercises nightly to wipe away any scale attempting to accumulate.
If not for mineral buildup, most makes of thermostatic mixing valves would probably outlast all of us.

 

[arctic bill]

Are you not getting enough hot water why do you think you need an expansion tank????

you need an expansion tank due to the check valve .

 

[MicEd69]

Ok, I'll listen to the experts ... what do you think I should to do ? Ditch this idea altogether (in which case, who IS a good candidate for such a mixing valve) ? Don't turn the water heater above 140, and live with only an approximate 33% increase in available hot water ?

I'm not one of the experts on this issue, but one fact is that 125-degree water can cause immediate burns to a person. So, a 160-degree setting would be extremely dangerous if you are relying on a single device that may fail and allow that high temperature water to flow to a fixture. Another fact is that the higher the temperature the water is heated, the fall out of any minerals (aka scaling) increases significantly.

You asked, "who IS a good candidate for such a mixing valve". Limiting the inlet temperature of the hot water to 140-degrees would be less risk.

And as Twowaxhack says above, who is an expert, "Nursing homes have thermostatic mixing valves at the individual showers also. Two valves that offer protection." So, his suggestion is dual devices to protect the user. He goes on to say, "Add another water heater, low flow shower heads, tankless gas water heater, Rheem hot water extender are choices."

To me, the tankless water heater option would be my choice. As a vacation home, using dual water heaters would work, but you would have twice the volume of water that needs to be maintained at temperature. But I assume you turn the water heater temperature down when the house is unoccupied. The issue with that is possible bacteria buildup in the lukewarm water when you are away.

 

[RustyShackleford]

You asked, "who IS a good candidate for such a mixing valve". Limiting the inlet temperature of the hot water to 140-degrees would be less risk.

And as Twowaxhack says above, who is an expert, "Nursing homes have thermostatic mixing valves at the individual showers also.

Ok, I think the answer is to turn the water heater up no higher than 140 degrees until I can confirm (or upgrade) all the shower valves to be of the anti-scald type; it looks like that's fairly standard with new ones these days, but I think the ones in this house date from its construction 20 years ago, so likely would need to be upgraded.

 

[Mitchell-DIY-Guy]

Whoa.

Hot water at a FAUCET (be it a shower or lavatory or kitchen faucet; point of use where hands get in) really should NOT be more than 120 or 125 degrees. Beyond that you run the risk of scalding and even 3rd degree burns in children or elderly. You indicated "renters", and if you had your water set to 140 degrees, which is higher than expected in any normal condition, you are setting yourself up for a potential liability, and causing permanent damage accidentally to your renters.

If anyone other than your own immediate family is using your home, you need to do whatever it takes at each point of use (washing machines and dishwashers aside) to limit the hot water to that 120 degrees or so. Whether you do it with anti-scald valves, mixing valves, tempering valves or whatever, you really ought to consider it for safety's sake.

It may be just easier to get that tankless since you said you do exhaust the water in a 50 gallon tank style.

I'm a home inspector, and if I found 140 degree water at a faucet that would be a huge red flag.

FWIW I had showers built in 1990 and 1992, and both had anti-scald valves, pressure balanced.

 

[MicEd69]

Whoa.

Hot water at a FAUCET (be it a shower or lavatory or kitchen faucet; point of use where hands get in) really should NOT be more than 120 or 125 degrees. Beyond that you run the risk of scalding and even 3rd degree burns in children or elderly. You indicated "renters", and if you had your water set to 140 degrees, which is higher than expected in any normal condition, you are setting yourself up for a potential liability, and causing permanent damage accidentally to your renters.

If anyone other than your own immediate family is using your home, you need to do whatever it takes at each point of use (washing machines and dishwashers aside) to limit the hot water to that 120 degrees or so. Whether you do it with anti-scald valves, mixing valves, tempering valves or whatever, you really ought to consider it for safety's sake.

It may be just easier to get that tankless since you said you do exhaust the water in a 50 gallon tank style.

I'm a home inspector, and if I found 140 degree water at a faucet that would be a huge red flag.

FWIW I had showers built in 1990 and 1992, and both had anti-scald valves, pressure balanced.

RustyShackleford said he has purchased a mixing valve and was going to turn up his water heater to 160 and use the mixing valve to control the water to 120 going to his fixtures. So, I'm assuming he is still going to install that mixing valve when he increases the water heater temperature to 140 and limit the water to his fixtures to 120.

So just to be clear RustyShackleford, and so I don't make an ASS out of U ad ME (aka assume), ABSOLUTELY install your mixing valve to limit your water to fixtures at 120.

I'm sure you have replaced your water heater in the 20 years of the house, and probably more than once. Depending on the age of the one you have now, you may want to go ahead and replace it with a tankless water heater and use that technology which would resolve your issue without multiple devices.

 

[RustyShackleford]

RustyShackleford said he has purchased a mixing valve and was going to turn up his water heater to 160 and use the mixing valve to control the water to 120 going to his fixtures. So, I'm assuming he is still going to install that mixing valve when he increases the water heater temperature to 140 and limit the water to his fixtures to 120.

Correct. Install mixing valve, turn water heater up to 140, set mixing valve to output water to 120 (or perhaps slightly lower, whatever the hottest shower a person could possibly desire is).

Once I've upgraded (or confirmed) all the 3 showers have modern valves (pressure-balanced or the like) consider turning water heater up to 150 or 160.

Supposed licensed plumber (in another forum) states "As far as faucets [not including showers], in residential settings, the additional protection is not legally required and virtually never done."

I'm sure you have replaced your water heater in the 20 years of the house, and probably more than once. Depending on the age of the one you have now, you may want to go ahead and replace it with a tankless water heater and use that technology which would resolve your issue without multiple devices.

A big part of my rationale is that there are 3 bathrooms. So that'd be one honking tankless. Also, there's no natural gas, just propane, so pretty expensive (of course electric is a non-starter for one this powerful).

 

[MicEd69]

{Supposed licensed plumber (in another forum) states "As far as faucets [not including showers], in residential settings, the additional protection is not legally required and virtually never done."}

Two things in that statement:
1. "the additional protection is not legally required". Not legally required, but maybe common sense should apply.
2. "in residential settings". OK, one can do what they want in their own house. But you state, "as many as 8 people in the vacation house (renters...). I would be slightly concerned about a liability issue for renters.

{that'd be one honking tankless.}

Really?




This is the cheapest propane water heater at Home Depot.



Showers, by code, are to be limited to 2.5 GPM. I think a tankless with a throughput of 9.8 GPM would be more than adequate for your conditions. Oh, the 7.5 GPM model is only $832.37, or $13.36 more than the cheapest propane 50-gallon water heater at Home Depot and would probably be more than adequate as well. The 6.5 GPM tankless is only $757.48, or $61.53 less than the cheapest propane 50-gallon water heater at Home Depot. That too would likely be just fine, but for $61.53, I'd get the 7.5 GPM unit.

Something to think about, especially if your existing water heater is 5-6 years old or older.

 

[Mitchell-DIY-Guy]

Forget the tankless GPM ratings. Look at two things: BTU/hr, and efficiency. If you don’t like the cost of propane (join the crowd, and don’t have a home in an area not served by NG) you’ll only want the most efficient condensing models, with modulating burners.

For “whole house” look for a 199,900 BTU model. That’s the only size I’ve seen installed as a whole house unit in anything other than a small home. They don’t come any larger else the Feds would call them “boilers”. That’s a whole different kettle o’fish.

So the choice set is narrowed considerably. Not cheap, but if you don’t supply your family—or tenants— with enough hot water you’ll hear about it!

 

[RustyShackleford]

I'm not a fan of tankless. First, the need to use propane (at this particular house). The need for routine maintenance. The difficulty of repairing and obtaining repair parts. And I think the energy savings are over-stated; they do nothing to reduce the actual hot water used (probably increase it, since you never run out), nothing to reduce the water "stranded" in the hot water lines when you turn off a faucet, and the losses from a tank-style are very low with modern insulation standards.

I thought there was a standard size tank style of 80 gallons. But I think I'm wrong about that.

 

[Mitchell-DIY-Guy]

You can buy 75 gallon gas water heaters at Lowes or Home Depot. They start at about $1600 and go up past $2000.. they are gas burners are 76,000 BTU hours, which is close to twice the size of most of their water heaters in the 50 gallon size. While Lowe’s does not list it with propane, it is available...

https://www.hotwater.com/water-heaters/residential/gas/?f=122,144&s=0&v=15&p=1&st=0

 

[RustyShackleford]

You can buy 75 gallon gas water heaters at Lowes or Home Depot. They start at about $1600 and go up past $2000.. they are gas burners are 76,000 BTU hours, which is close to twice the size of most of their water heaters in the 50 gallon size. While Lowe’s does not list it with propane, it is available...

I really would like to stay away from propane - not only is it more expensive per unit of energy, they are necessarily less efficient due to the need for a flue of some kind.

Here's an existence proof of a much larger (than 50 gallon) conventional electric unit for a sane price:

https://www.supplyhouse.com/AO-Smit...L85ZAs7Y5N-ozFQ0Pmp7pXY2StDKKqvxoCNfAQAvD_BwE
... not sure what are the implications of "commercial"; it would require an upgraded electrical feed (simple in this house) or being ordered with non-standard electricals (simple, with Bradford-White at least).

Here's a residential one, but says it needs to work in conjunction with a solar system to give specified output. Not sure why that is, although a 4500-watt heater is going to take a long time to heat 80 gallons.

https://www.supplyhouse.com/AO-Smit...e8yEjrhQCCEo2TpMvuYB7bub-9IkRL0xoCxr8QAvD_BwE

 

[Twowaxhack]

Use two 40 electrics or two 50 electrics in series.

Each heater would need 30 amp double pole breaker with 10ga two conductor with ground wire.