120v gas tankless water heater

[Coppersmith]

If you're running a normal-flow shower, the (gas) tankless will easily keep up,

My shower has three normal flow (not low flow) heads, left, right, and overhead. I normally only use the left and right. This sprays both sides of my body simultaneously so I'm not cold on one side. All three on make me feel like I'm drowning.

If you are mixing your shower water to over 105°, you are a lobster.

My shower has a (verified) temperature dial rather than just a hot/cold mixer. I start off at 100F and gradually raise it to 108F. I exit when I start to overheat which usually takes 15 minutes. I should note that I normally feel cold and the shower helps me warm up. I also wear sweaters since my wife likes to keep the house at arctic temps.

 

[winnie]

If you are running 3 shower heads, each 5 gallons per minute, and are in a cold climate with 40F incoming water, and like to cook yourself at 120F, then you need 576K BTU per hour to keep up...and yes, you would need 3 large tankless heaters.

On the other hand if you normally only use 2 of the 3 heads, each 2.5 gallons per minute (normal flow, not reduced flow), water comes in at 50F and you use 108F, then that works out to 139K BTU. I have a 160 K BTU gas tankless unit and _love_ it. I've had some health issues and sometimes need to be in the shower a long time. I've never run out of hot water, never have problems with multiple devices (1 low flow shower head, dishwasher and washing machine, running at the same time). Never a problem with the kid using up all the hot water before I need the shower. Love it.

-Jon

 

[rnatalie]

Very clever. Did you nod this up yourself, or have a really smart contractor?

A little of both. When I bought the first heat pump (it's a geothermal unit) I noticed the thing had the capability and asked if they'd hook it up but they begged off. Ten years later I was expanding my house and I put in a second heat pump (and a second Rinnai) and the contractor was all set to hook it up. He had all the parts but we sat down and puzzled out how it needed to be plumbed.

What scared me was earlier on I find that the electrical contractor is wiring up a 240 disconnect and has smaller tank hot water heater that he's hooking up to it. After some phone calls to the Heat Pump guy and the Plumber, I finally figured it out. You want to collect the heat from the desuperheater into a storage tank. Now you can buy storage tanks that are made for that (I've got one on the other side for the hydronic floor heat), but they're expensive because they're not mass produced like hot water heaters, so the thing is just sitting there playing storage tank with a note to not turn the disconnect on. I guess if the Rinnai ever dies, I could turn into.

If you are mixing your shower water to over 105°, you are a lobster.

I resemble that remark. My Kohler digital shower controller is set for 112 degrees.

 

[kwired]

It wastes a little energy, but it still is a win over tanked heaters. The thing circulates the water and only comes on briefly to reheat the water when it gets too cold. The Rinnai controller has a timer so you can set the hours you want to have the recirculator run.

In my case, in the summer time,it also has the effect of running the water through the heat pump's desuperheater scavenging some waste energy.

That seems pretty useless if you don't have a tank to collect some that waste energy into.

I do have heat pump with desuperheater, it will warm a tank up pretty well, not super warm but significant enough it can be warm enough to shower with. No way it puts out enough heat to warm the cold incoming water "on demand" to an acceptable user level, but give it a tank to store the energy in and some non usage time and it makes a significant difference. If anything a non powered electric storage water heater tank makes a great "preheat" tank on such a system, then run from there to either conventional storage tank heater or an instantaneous heater, but input power only needs to be enough to raise water to desired output temp and much less than if you would be entering with straight cold water.

 

[kwired]

A little of both. When I bought the first heat pump (it's a geothermal unit) I noticed the thing had the capability and asked if they'd hook it up but they begged off. Ten years later I was expanding my house and I put in a second heat pump (and a second Rinnai) and the contractor was all set to hook it up. He had all the parts but we sat down and puzzled out how it needed to be plumbed.

What scared me was earlier on I find that the electrical contractor is wiring up a 240 disconnect and has smaller tank hot water heater that he's hooking up to it. After some phone calls to the Heat Pump guy and the Plumber, I finally figured it out. You want to collect the heat from the desuperheater into a storage tank. Now you can buy storage tanks that are made for that (I've got one on the other side for the hydronic floor heat), but they're expensive because they're not mass produced like hot water heaters, so the thing is just sitting there playing storage tank with a note to not turn the disconnect on. I guess if the Rinnai ever dies, I could turn into.


I resemble that remark. My Kohler digital shower controller is set for 112 degrees.

Should have read remaining posts before replying - looks like you did end up with a storage tank.