Second water heater install

[MTy]

In the process of redoing my master bath and need to add a second water heater because of the new tub. I was going to hire it out but with the confidence I have from doing the bathroom plumbing (it all works perfectly thanks to the help I got here), don't think there is any reason I couldn't save a bunch and do the water heater as well.

House is 2.5 baths. One has a standard tub shower combo. Master has 60 gallon soaker tub and walk in shower with 2 2.5gpm heads. It's only me right now but plan to be here a while so that could change. House currently has a 50 gallon 8 year old electric heater in the attic. It's enough during the summer but during the winter I can barely fill a standard tub. If the shower or anything else has run or needs to run I'm outta luck.

1. Plan is to add a 40 or 50 gallon in series. Then replace the old 50 gallon in a few years with another 40 or 50 gallon. Any issues with that sizing plan?

2. Wondering if I would benefit from a hybrid heater. I'm located in west TN so we do get below freezing but for most of the year we are in the ideal range. But we also have some of the lowest electric rates in the country.

2. My house pressure is about 90psi with 100psi spikes when a fixture is turned on. due to uponor pex in the master reno I want to reduce the water pressure which means a PRV and expansion tank. Will the prv be as effective if installed on the cold input line in the attic near the water heater? That would be easiest for access reasons.

3. Any other considerations? Any reason I couldn't diy this having done the bath plumbing, including copper soldering?

 

[Fitter30]

With adding a second water heater it has to be piped reverse return. First in last out. Look up reverse return, heater will be piped in parallel even flow through both of them. The PRV needs to piped in in cold water line before all indoor faucets and water heaters with a expansion tank before heaters.

 

[Sponsor]

 

[MTy]

With adding a second water heater it has to be piped reverse return. First in last out. Look up reverse return, heater will be piped in parallel even flow through both of them. The PRV needs to piped in in cold water line before all indoor faucets and water heaters with a expansion tank before heaters.

Correct me if I am wrong but it's my understanding that would only be needed if I was piping the heaters in parallel ( which would also mean buying two heaters that are exactly the same) but I plan to do them in series.

 

[Fitter30]

Series doesn't give you twice the hot water the first heater will fail first most of the lime will end up here. Piping reverse return will give you even pressure drop across both heaters even if they are different.

 

[MTy]

My thread was not meant to be a rehash of the series vs. parallel argument. It's clear from hours of research that is one of those things where there are pro and cons to each way and every plumber has their preferred method. I have decided based on the pros and cons I will be plumbing via series if I use two tanks.

That being said I have decided a heat pump heater will probably be most efficient over the long run. The question is now do I go with the 65 gallon from Rheem at HD, the 80 or a 50 or 40? If I go the 50 or 40 I'll plumb it in series with the current 50. When the old one dies I'll add either add another 40 or 50 heat pump heater.

Please see my water needs in the OP.

 

[Fitter30]

Here is a hot water to cold calculator just change settings to gpm, Fahrenheit
https://www.spiraxsarco.com/resources- and-design-tools/calculators/water-mixing/water-mixing

 

[WorthFlorida]

BTW, hybrid water heaters are extremely low cost in annual energy cost compared to a conventional WH. Just look at the energy tag. Why your current water heater cannot keep up with the tub fill may have to do with the oncoming water temperature. An eight year old WH was built after the new energy requirements were enacted. Increasing the thickness of the foam insulation was about the only improvement and lost of heat into the space is very small.

If you plan for a hybrid unit, they are very tall and may not fit in an attic space. 40 and 50 gallon water heaters come in two or three different heights so be sure to get one that will fit.
If your attic space requires a latter to access it, do a get a buddy or two to help with replacing the WH. Thought when empty WH are not too heavy, they are bulky.

It may just be easier and faster to install a thermostatic mixing valve on the existing WH. Set the WH temp to 140 degrees and set the temp at the mixing valve for 120 degree output.

https://www.google.com/aclk?sa=l&ai...=2ahUKEwjAu_mE6NHxAhWCgFMKHXpmDJQQwg96BAgBEFA

 

[MTy]

Thanks for the help. I think I figured out what part of the issue with my current heater was. It seemed to have a very slow recovery time which was part of the capacity issue before the new tub install. Looks like it's on a 120v line. Not surprising given other stuff from the previous owner I've run into. Thankfully I had my electrician run a 240v line in prep for a second heater.

Given that my new plan is to get a single 65 gallon heat pump heater from Rheem. With an actual capacity of 59 gallons and first hour rate of 75. I should be able to at least fill the 60 gallon tub (apprx 40 gallons of water from the tank), run the HE dishwasher and a shower all at the same time. Factoring in the mixing of cold water. Am I off base on this?

I'll be setting the tank to 140 and using a mixing valve as well.

 

[Fitter30]

spiraxsarco.com/resources-and-design-tools/calculators/water-mixing/water-mixing
calculator for mixed water just change setting to us gpm and to f temp
120* hot/ 45* cold/ 105* mix= 80% hot @ 10 gpm

 

[MTy]

1. I see the Rheem 65 gallon HP heater requires at least 700 sq ft of space or venting. It's therefore my understanding that in a 700+ square foot attic space it should need no venting?

2. Condensate line. Any reason I couldn't tie into the drain pan line that runs to the outside of the house? Assuming it has proper slope.

3. Is the condensate going to be a constant stream or occasional? The pan drain terminates just outside the siding and I'd rather not have a steady stream running down the side of my house. Could run the pipe over and down into a flower bed though. Or tie into a gutter.

 

[MTy]

Bump on my above questions. Plan to order the water heater soon.

 

[Reach4]

1. I see the Rheem 65 gallon HP heater requires at least 700 sq ft of space or venting. It's therefore my understanding that in a 700+ square foot attic space it should need no venting?

No venting. I am not a plumber. I would worry about freezing. In most attics the attic is outside of the insulation envelope.

2. Condensate line. Any reason I couldn't tie into the drain pan line that runs to the outside of the house? Assuming it has proper slope.

Freezing?

3. Is the condensate going to be a constant stream or occasional? The pan drain terminates just outside the siding and I'd rather not have a steady stream running down the side of my house. Could run the pipe over and down into a flower bed though. Or tie into a gutter.

Intermittent. More when you use hot water.

 

[Jeff H Young]

A water heater can go in a closet. why it would need 700 sq ft attic I don't know? usually spaces are described in cubic feet also. Its your water heater heater and specs Id follow them.
On the Condensate issue , I think the drain pan is meant for emergency and generally the pan and drainline are independent of other uses. I wouldn't want my heater sitting in a wet pan anyway. the T and P can't go in the pan either

 

[MTy]

Attic is the only place to install the heater and that where the current one is. Installing anywhere else would require massive repiping. But that brings up another question. Can a heat pump heater be installed in an attic? We don't get bad freezes, usually, but it can happen. Worse comes to worse I could set it on all electric mode for those few times we get into the 20s or less.

That might solve the freezing condensate issue too. The only other option if I don't run it outside is to put in a pump and run it to the furnace condensate line a few feet away. A pump is required because otherwise the line would block the attic walkway or create a tripping hazard. Can I tie into the furnace condensate line?

I meant draining connecting to the same line as the drain pan further down past the pan itself.

 

[Jeff H Young]

Condensate pump sounds ok .
Point I was making on the attic install why can a heater go in a 9 sq ft closet , yet need a 700 sq ft if in a attic?. You'll have to read your specs if it says no attics then no attics, I install in attic infrequently

 

[Reach4]

A water heater can go in a closet. why it would need 700 sq ft attic I don't know?

This is a hybrid WH, which means it has a heatpump. This needs to draw heat from ambient air.

 

[MTy]

This is a hybrid WH, which means it has a heatpump. This needs to draw heat from ambient air.

This. Specs say it requires 700sq. ft. Or needs venting. Nothing about no attic install. The only reason I asked about the attic is Reach's point regarding condensate freezing. However, assuming condensate has some warmth to it and I insulate in pipes in the attic the condensate wouldn't freeze until it left the attic. If it froze just outside I doubt there would be enough condensate to back things up and cause issues. If we are lucky ( I like winter) we might get 1-2 days a year where daytime temps stay below freezing. But 99 percent of the time any frozen condensate would melt during the day. That side of the house is also SW facing.

Of course my assumptions could be off. I think I'll look into the feasibility of a pump and connecting to the furnace condensate drain. Definitely not ideal though.

 

[Reach4]

This. Specs say it requires 700sq. ft. Or needs venting. Nothing about no attic install. The only reason I asked about the attic is Reach's point regarding condensate freezing. However, assuming condensate has some warmth to it and I insulate in pipes in the attic the condensate wouldn't freeze until it left the attic. If it froze just outside I doubt there would be enough condensate to back things up and cause issues. If we are lucky ( I like winter) we might get 1-2 days a year where daytime temps stay below freezing. But 99 percent of the time any frozen condensate would melt during the day. That side of the house is also SW facing.

Of course my assumptions could be off. I think I'll look into the feasibility of a pump and connecting to the furnace condensate drain. Definitely not ideal though.

So you would want to avoid bellys in the line.

Why would you need a pump to get to the furnace drain line? Is the furnace in the attic?

 

[MTy]

So you would want to avoid bellys in the line.

Why would you need a pump to get to the furnace drain line? Is the furnace in the attic?

Yes, and only about 3 feet away. But unfortunately the only walking path to the upstairs furnace and rest of the attic is between the WH and downstairs furnace. So, to keep the walkway unobstructed I'd either have to run the drain right up against the floor and then up to the furnace drain or up against the rafters and then back down.

I'll snap a picture when I get home. Might make this discussion easier.

 

[Dana]

This. Specs say it requires 700sq. ft.

No they don't say that at all. The specs say it requires a minimum of 700 CUBIC feet (, say, 10' x 10' x 7'), preferably in a semi-conditioned space.

Or needs venting.

The "venting" and volumetric requirements are about giving it access to the source of the bulk of it's heat, namely the room air. It's basically an air source heat pump taking heat (and moisture) out of the surrounding (or ducted-in) and putting that heat into the water in an insulated tank. It WILL lower the temperature of the room/attic where it's located. Take a close look at the specs, which usually indicate a minimum and maximum ambient operating temperature.

A typical ambient temperature operating spec for operating in heat pump mode would be between 45F and 110F- so when it's 120F in the attic on a hot summer day it's no more efficient than a plain old tank, and when it's in the low 40s or cooler, same story. The is a spec you need to pay attention to. Most will automatically switch from heat pump to resistance heating mode when the ambient temperature is out of range, but read the spec carefully to verify that it does. Some of the newer Rheem units rated for use in northern climates have heat pumps with a working range of 37F-145F, which would probably work OK in a Tennessee attic.

Nothing about no attic install. The only reason I asked about the attic is Reach's point regarding condensate freezing. However, assuming condensate has some warmth to it and I insulate in pipes in the attic the condensate wouldn't freeze until it left the attic.

The condensate is going to be <40F (colder than the incoming wintertime water temps in your area) when it's only 45F in the attic, not much warm to it at all. Condensate freeze up during a Polar Vortex disturbance cold snap is a real issue if the cold snap comes right after a warm-ish period with high attic dew point temperatures (= lots of condensate). When it's near or below freezing it won't be running in heat pump mode to self-protect against icing up the coils, and even when it's 50F up there the volume of condensate will be low compared to in the shoulder seasons when outdoor (and vented attic) air dew points are in the 60s or higher.

As long as the condensate disposal is operating strictly from gravity using flexible tubing, and running inside the house rather than on the outside (where it could develop a freeze plug) it's probably not going to be a problem. If the condensate is handled by one of those little AC type condensate pumps that can have a pint or two of water in it just prior to pumping, there is a chance that a freeze-up could break the casing on the pump unit. (I've personally never tested an air conditioner type condensate pump in a freezer to see what happens, but I would if I was counting on it to work in an attic that could freeze. A pump housing that breaks in the freezer test is a lot cheaper to replace than fixing the the water damage from letting the condensate drip in the attic.)

Typical air conditioning air handlers don't need special treatment on their condensate disposal setup for freeze protection, since they don't generally run when it's cold enough out to freeze even overnight, (let alone for days.)