Cheap way to reduce hot water heater draw.

[richwolf]

My Rheem 40 gallon water heater is around 6 years old and works great.
My dilemma is that we take showers when the electricity rates are the highest. Our 15kwh battery has enough capacity to run the hot water heater but we are limited on how many amps we can feed into our main panel.
We have a Solark 12 K that feeds into a sub panel for our garage and heat pump and then feeds into our main breaker.
I looked at hybrid water heaters but the price doesn’t seem to justify the cost and the location wouldn’t work since it would cool the upstairs in the winter.
I looked at lower wattage water heaters but those still run about $500 or so.
Not being one to replace units that work I did some research and found I could replace the 4500 watt heating elements with 3500 watt elements. I also ordered a new anode rod.
This 1000 watt reduction should keep us from drawing from the grid when rates are the highest.
Around $75 for all the parts.
We’ll let you know how this works out.

 

[BentleyJ]

Unless you need high wattage for faster hot water recovery time the lower wattage element makes a lot of sense. Does the same job just takes a little longer.
Regarding heat pump water heaters, they operate with a Coefficient of Performance of at least 2 and higher. Even if you didn't use the waste cold air for space conditioning year round you are still getting water heating for half as much electricity. You should seriously consider it when the convention WH needs to be replaced.

 

[Hedges]

Timer (and power relay if needed), so heater doesn't run during peak times.
lower wattage - use 120V to power 240V water heater, for 1/4 the wattage. Maybe wire both elements in series and use 240V for 1/2 the wattage. Current may be low enough for just the timer, although the plug-in electronic ones have wimpy relays. I have used those, in particular for a coffee maker, and had them fail. Now I used a pool/spa timer.

If storage capacity is insufficient, turn up thermostat and add a tempering valve.

 

[OzSolar]

Timer (and power relay if needed), so heater doesn't run during peak times.

That would be my first suggestion.

If storage capacity is insufficient, turn up thermostat and add a tempering valve.

One trick I've seen plumbers do to increase the capacity of stored hot water is to add a circ pump to the water heater. Typically the customer is told the to run the pump for ~1 hour before they want to fill up the thier jacuzzi tub, etc

Replace the tank drain with a T, reinstall the tank drain into the the new T. Then plumb a circ pump between the drain and the hot water inlet. Effectively doubles the amount of stored hot water.

Kind of clumsy I know but the OP could run the pump for a period time outside of peak rates and still have plenty of hot water when it was needed.

 

[Hedges]

I'm toying with related ideas for my new place.
It has forced air gas furnace for upstairs, no heating in the downstairs den.
Also gas water heater.

First plan, circulator pump and hot water baseboard radiators in den.

Another idea, add HPWH between cold water feed and gas water heater.
Plumb radiator loop from output of gas water heater to input of HPWH.
Set thermostats so HPWH is primary, gas only used if temperature drops too low.
Add another loop to radiator on air inlet to furnace (need to see if any electronics in airflow, think about operating temperature issues.)
Modify thermostat to enable circulator and air handler, only enable gas furnace if house temperature too low.

Purpose of HPWH (or other heatpump) is utilization of PV I plan to install, and expectation gas will (artificially?) keep going up in price.


For OP, I've read that batch pre-heater is simple and effective. Water tank in box with glass window.
I'm also attracted to evacuated tube collectors, which work in cold locations.

 

[efficientPV]

You could have also put the upper and lower heating elements in series to lower power.

 

[再生可能 エネルギー]

First plan, circulator pump and hot water baseboard radiators in den.

For a hot water heater only, not used for heating a home with radiators,
would you run the circulator pump all the time or only when the thermostat is activating the heating element?

 

[Rednecktek]

What about a solar water heater, either a tank-in-a-reflective-box or the simple coil-of-black-pipe? If the water can get pre-heated by the sun before it hits the tank, that'll reduce the wattage draw from the heater because it's just not needed to run as long.

 

[richwolf]

You could have also put the upper and lower heating elements in series to lower power.

No
Both elements run separately.

 

[richwolf]

Regarding heat pump water heaters, they operate with a Coefficient of Performance of at least 2 and higher. Even if you didn't use the waste cold air for space conditioning year round you are still getting water heating for half as much electricity. You should seriously consider it when the convention WH needs to be replaced.

from my research heat pump water heaters seem to have reliability issues and appear to not last any longer than a traditional water heater.
My problem is not the amount of energy used BUT the amp draw that it takes to power it thus causing grid draw at peak rates.
Also I would have to move water heater location if I went hybrid which I am totally opposed to.

 

[richwolf]

What about a solar water heater, either a tank-in-a-reflective-box or the simple coil-of-black-pipe? If the water can get pre-heated by the sun before it hits the tank, that'll reduce the wattage draw from the heater because it's just not needed to run as long.

I have enough power from my battery to not draw from the grid at expensive rates provided I reduce the amp draw which the lower wattage heating elements will do.
I’m not interested in rednecking it.
My conversion cost will only be $75

 

[richwolf]

I'm toying with related ideas for my new place.
It has forced air gas furnace for upstairs, no heating in the downstairs den.
Also gas water heater.

First plan, circulator pump and hot water baseboard radiators in den.

Another idea, add HPWH between cold water feed and gas water heater.
Plumb radiator loop from output of gas water heater to input of HPWH.
Set thermostats so HPWH is primary, gas only used if temperature drops too low.
Add another loop to radiator on air inlet to furnace (need to see if any electronics in airflow, think about operating temperature issues.)
Modify thermostat to enable circulator and air handler, only enable gas furnace if house temperature too low.

Purpose of HPWH (or other heatpump) is utilization of PV I plan to install, and expectation gas will (artificially?) keep going up in price.


For OP, I've read that batch pre-heater is simple and effective. Water tank in box with glass window.
I'm also attracted to evacuated tube collectors, which work in cold locations.

So where do I put this magic box?? On my roof where I would have to drill holes and protect against freezing??

 

[richwolf]

That would be my first suggestion.



One trick I've seen plumbers do to increase the capacity of stored hot water is to add a circ pump to the water heater. Typically the customer is told the to run the pump for ~hour before they want to fill up the thier jacuzzi tub.

Replace the tank drain with a T, reinstall the tank drain into the the new T. Then plumb a circ pump between the drain and the hot water inlet. Effectively doubles the amount of stored hot water.

Kind of clumsy I know but the OP could run the pump for a period time outside of peak rates and still have plenty of hot water when it was needed.

Don’t need to do this. My solution is $75. Once I do this my battery will cover my evening shower needs.

 

[Think About It]

I've worked on a few 4500W dual element hot water heaters. They only draw 4500W because the lower element/thermostat goes on first and heats the lower part of the tank. When the upper thermostat kicks in the upper element it cuts the power from the lower element. It's called a flip/flop system.

https://www.canton.edu/media/employee/elec141/Sequence_hot_water_heater.pdf

 

[richwolf]

That would be my first suggestion.



One trick I've seen plumbers do to increase the capacity of stored hot water is to add a circ pump to the water heater. Typically the customer is told the to run the pump for ~hour before they want to fill up the thier jacuzzi tub.

Replace the tank drain with a T, reinstall the tank drain into the the new T. Then plumb a circ pump between the drain and the hot water inlet. Effectively doubles the amount of stored hot water.

Kind of clumsy I know but the OP could run the pump for a period time outside of peak rates and still have plenty of hot water when it was needed.

I need the heat during peak rate times cause that’s when we shower ?. I just don’t want to draw from the grid during that period which lowering the watts hence the amp draw will accomplish . This will allow my battery to cover our hot ? water needs.

 

[Rednecktek]

I have enough power from my battery to not draw from the grid at expensive rates provided I reduce the amp draw which the lower wattage heating elements will do.
I’m not interested in rednecking it.
My conversion cost will only be $75

Hey, you asked for cheapest way. Besides, it'd be the funnest way too. ?

 

[richwolf]

Hey, you asked for cheapest way. Besides, it'd be the funnest way too. ?

So how much would your solution cost, how would it be plumbed and how would it reduce my amp draw? How would you address the freezing issue?
To me funnest is cheapest and easiest!
If I want to have fun ? I jump on my mountain bike ?‍!

 

[Rednecktek]

You found a $75 solution, can't really beat that if it does what you want.

I remember as a kid my dad did a solar water heater from an old free hot water tank sitting in a box in the yard. The mylar covered foam, a can of black spray paint, some lumber (ok, it was the 80's when you could say the word lumber for less than $50) and a sheet of thin plexi over the top. It worked well and was cheap, never had any freezing issues, and preheated 50gal at a time.

Knowing what I know now that was a pretty slick idea. ?

In your case I would never have thought you could accomplish that much difference with so little money. I'm impressed.

Still no fun though. ?

 

[Hedges]

For a hot water heater only, not used for heating a home with radiators,
would you run the circulator pump all the time or only when the thermostat is activating the heating element?

Only when room thermostat is active, requesting baseboard radiators heat the room.
HPWH acts as batch pre-heater for gas heater. Any time hot water is used in the house, HPWH gets cold water in and heats it, feeding hot to gas water heater.
Gas water heater only comes on if it has cooled of due to no flow, or if needed to keep up with high flow rate exceeding HPWH heating rate.

So where do I put this magic box?? On my roof where I would have to drill holes and protect against freezing??

I could put batch preheater on the ground at south side of home (different home from what I describe above). Cold water in, preheated however much, warm water out to feed water heater.
Freezing not so much of a problem in my area.

Evacuated tube system has sloped tubes and either a manifold or storage tank on top.
If manifold, it needs flow to collect the heat. Could be potable water in non-freezing locations, glycol if freezing. Advantage of evacuated tube is it works where there is freezing.
Maybe could have slope manifold and potable water convection loop. Insulation and circulation could be used for freeze protection.

Everything is cost, complexity, reliability. That's why I suggested batch preheater. Plumb in a bypass valve in case it fails.

As he describes:

You found a $75 solution, can't really beat that if it does what you want.

I remember as a kid my dad did a solar water heater from an old free hot water tank sitting in a box in the yard. The mylar covered foam, a can of black spray paint, some lumber (ok, it was the 80's when you could say the word lumber for less than $50) and a sheet of thin plexi over the top. It worked well and was cheap, never had any freezing issues, and preheated 50gal at a time.

Knowing what I know now that was a pretty slick idea. ?

In your case I would never have thought you could accomplish that much difference with so little money. I'm impressed.

Still no fun though. ?

I need the heat during peak rate times cause that’s when we shower ?. I just don’t want to draw from the grid during that period which lowering the watts hence the amp draw will accomplish . This will allow my battery to cover our hot ? water needs.

Big enough tank that you don't need to heat more water until the next window of low rates.

Alternatively, change when you shower. Morning? Evening? After midnight?

Best case is operate water heater with PV during low-rate times.

 

[richwolf]

Only when room thermostat is active, requesting baseboard radiators heat the room.
HPWH acts as batch pre-heater for gas heater. Any time hot water is used in the house, HPWH gets cold water in and heats it, feeding hot to gas water heater.
Gas water heater only comes on if it has cooled of due to no flow, or if needed to keep up with high flow rate exceeding HPWH heating rate.



I could put batch preheater on the ground at south side of home (different home from what I describe above). Cold water in, preheated however much, warm water out to feed water heater.
Freezing not so much of a problem in my area.

Evacuated tube system has sloped tubes and either a manifold or storage tank on top.
If manifold, it needs flow to collect the heat. Could be potable water in non-freezing locations, glycol if freezing. Advantage of evacuated tube is it works where there is freezing.
Maybe could have slope manifold and potable water convection loop. Insulation and circulation could be used for freeze protection.

Everything is cost, complexity, reliability. That's why I suggested batch preheater. Plumb in a bypass valve in case it fails.

As he describes:





Big enough tank that you don't need to heat more water until the next window of low rates.

Alternatively, change when you shower. Morning? Evening? After midnight?

Best case is operate water heater with PV during low-rate times.

Don’t need or want a bigger tank.
Don’t want to shower between midnight and 6 AM!
My plan is to eliminate all expensive TOU rates. We have some of the highest rates in the country.
My battery has enough capacity to heat our water but I need to reduce the wattage so we don’t tap into the expensive rates.