Water heater(s) for 140+ ft wide house?

12 years ago

Hello. We're currently in the process of planning a custom build in Texas. The home estimate included one 50 gallon water heater but our concerns are the size of house (141 ft wide split bedroom design 5000 sq ft living), number of baths (5 bathrooms) and space. The electric water heater is planned in the garage but we are considering adding a second on the opposite side of the house for the master and another bathroom.

Questions:

Should I consider tankless on the unit not in the garage or opt for a smaller tank in attic or other area?

I've read several negative articals on tankless but I am skeptical of their bias. What are your thoughts on tankless heaters?

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Comments (6)

david_cary
12 years ago
Tankless electric aren't generally worth the cost.

50 gallon electric is pretty small for your size house. My builder usually would do 2 50 gallon units with a recirc pump with a house your size. Alternatively, you can put the tanks at different points of the house.

Most people cringe at the idea of a hot water heater in the attic because of leaks.

If you only have electric (not NG), you should really consider an alternative to electric strips for heating hot water - it costs an average of $600 a year for electric and if you have 2 tanks or a loop, it will be more. Heat pump hot water heater is an option but it does make noise but it might be nice in the garage (would help keep it cool in the summer). Solar is another option but payback depends a lot on local incentives. Here, for straight electric, it is about 5 years. Even with just the federal credit, payback is about 10 years. Heat pump pays back in about 2 years if the noise is not an issue for you.
User
12 years ago
141 feet? What are you building? A mini storage unit?

Gas tankless has it's place, and that place is a new build when you can specify the larger than normal gas service from the beginning. Electric tankless is pretty iffy no matter what or when because of the huge electrical draws it will have. You'd need to plan for a 400 amp service minimum, and maybe even 600 amp.

Tankless is no panacea for siting the water needs with some good sense and an intelligently designed plumbing run.
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Starfish We went through the same decision process earlier this year - we had fewer baths but needed a single HWH to, additionally, provide space heating for the whole house. With the whirlpool tub, multiple shower heads and 5 bathrooms, you will potentially need a lot of flow. I thought our main concern was to have high recovery and respectable flow; my solution was the AOS Vertex unit with 50 gallon, 75,000BTU/hr and 127 First Hour Delivery Gallons all with a power exhaust that hooks to a 2" pvc pipe - claims 90% efficiency. I've been pleased with the Vertex - it meets our needs and is quiet and efficient. Since then, AOS has released a Vertex 100 model with 100,000BTU/hr and 164 First Hour Delivery Gallons. John
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You can certainly do a hybrid or combination system. Doing your proposed L/R lay-out, is the only way to go in my opinion, I would still suggest a pipe tying the two sides together. I would put and accessible ball valve in that cross connection pipe so, if for any reason one system went down you could open the valve to have one side support the other, at least temporarily. Do you have a basement under this home or only a crawl space? If you need hot water quickly and not shower volumes in the downstairs rt lav, perhaps a small undercounter electric would do the trick. I hate to suggest that, but you are dealing with geography here. Time, distance & flow rate . The Master Bath will be best serviced by tankless. Your hi flow shower head needs to have a specific flow rate attached to it. A standard shower head will provide 2.5 gpm. In my new shower that means 2.1gpm of 120f water mixing with .4gpm of cold to arrive at my nice comfortable shower temp. I have also seen 20 gpm shower heads. Put a number on the flow of the single shower head please. What is the volume of the tub. What faucet set are you putting on it and is the tub valve going to be a 1/2" or 3/4" connection. With 1/2" pipe you will not get much over 5 gpm. With 3/4" you can get 10-12 gpm. Some tub faucets, the waterfall type, require 3/4". Otherwise the visual effect is not as good. Get the tub volume and compare the flows to the time you are willing to wait for the tub to fill. Yes, you can put tankless in the attic, but understand that you need a pan below them to prevent water damage from any possible future leakage. That is just good sense. Tankless water heaters are compact. As a result people tend to install them in really small spaces. Please keep in mind that this is a mechanical system and must be accessible for inspection and service. I long ago coined the term, "Just because it fits, doesn't mean that is where it goes." You would not believe the places people have installed these. It is a good idea for you to have the "service space" discussion with all of your subs. A lot of duct work gets destroyed by the technician the first time he has to service the heat pump, furnace or air handler. Build all your system to perform well, but make sure everything is positioned for accessiibility. These types of agreements tend to be forgotten when the equipment arrives on the job and the contractor wants to "get it done". So the question to your General and each of the subs is, "How are you going to build and position the equipment so it can be easily serviced". That is a good discussion to have with your architect too. Make your expectations clear and let them know you will be following up to monitor this "agreement". Sorry to get off topic there, but you have what, as I look at the floorplan is going to be a really lovely home. I just want to make sure the cardiovascular systems work well for you too. Another thing, the gas line will have to be sufficiently sized not only for what you are planning for the initial job, but you want capacity for future expansion. I have seen so many places that get undersized gas lines and the owner is blocked from any possible future expansion. This is a big project and even with great care, things pop up.
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So kiniyagirl: To summarize here are some points that I would emphasize in order of priority: If you go tankless: 1. Work with a plumber who is familiar with tankless water heaters if you go that route. 2. Look at relocating the heater closer to the bathrooms. Often in older houses the heater was put near the chimney (which was shared with the fireplace) and not near where water was being used. 3. You want to use a condensing tankless (92% efficient or better). This will allow you to vent using PVC pipe out a sidewall. You cannot vent any of these in an existing vent (such as the masonry flue the old one used). 4. You want to use a 200k btu/hour unit. Nothing smaller. 5. You must evaluate the gas service before deciding to go this way. These use A LOT of gas at one time. Plan on a new gas line from where the gas enters the home to the heater. This can be done in CSST to make it easier. 6. A recirculating pump can keep the water in the lines to the 3rd floor warm and reduce wait times. A return line for that (using PEX) is advisable but there are ways to do it without a dedicated return line. The trade off is that the water returns in the "cold" water line - so you turn on the cold water and it's warm. 7. This all starts getting pricey fast. A new gas tank heater should be kept on your list as an alternative. A 75 gal gas with 75kbtu /hour input will do a lot to solve the issues you have and would not require new gas line or redoing the vent.
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momto3kiddos
12 years ago
Slightly off topic, but I would like to see your plans. We are planning to build a 5000 sq ft one story home with split bedrooms as well. Ours is only around 100 ft wide - more like an H layout. We are still working with our architect and would like to see your plan out of curiosity to see what ideas we may be able to use in ours. I will send you a private message, so you can respond that way if you wish. Thanks!
BAVE
Original Author
12 years ago
Thanks for the replys. Turns out the contract states 2 50 gallon heaters (located in garage) but we have the option of dual NG tankless for $2500 more.

Momto3kiddos: we opted for a very wide build because we have a shallow acre cul-de-sac lot. Here's the elevation.

http://farm8.staticflickr.com/7185/6780445252_36e38f44a3_b.jpg

Here is a link that might be useful:
sniffdog
12 years ago
bave

my house is over 100 feet wide and I ran into this exact issue. When I did the calculations of how much water is in a 100 foor long run (with the pipe sizes I had) it was over 5 gallons of water. Look at the gallon per minute ratings on the faucets and you can calculate how long it will take hot water to get to the sink (a long time).

I used gas tankless but it really doesn't matter what the hot water plant is. What does matter is how close (in pipe run) that hot water source is to the sink that or tub it is feeding.

If your houses is like mine where you have master suite on one end of the house and kitchen sinks on the other end, you might think about putting one hot water source near each end. I thought about a compromise (the middle of the house - in the basement) but then everyone suffers. I ended up with tankless under the master suite (our house - we get hot water first) and use a recirculating system for the kitchen. One day I will add a hot water tankless on the other end so I can remove the recirculating system. I have a basement which makes this much easier. If you do end up going with something in the attic (not recommended), make sure you have a pan and drain beneath the hot water plant in case there is a leak and put a water alarm on it which will sound off if there is a leak.

A good buddy of mine built his house in Florida where there are no basements (similar to texas I understand). He put his hot water tanks in the garage - and they were a long way from his tub. On top of that, the water pipes ran underground where the hot water would cool off before it reached his tub. He absoutely hated it because he has to run his tank at a very high temperature do get decent hot water temp at the tub faucet. And there is not much he could do about it. I helped him design a hot water recirculation system which helps get hot water to the tub faster but he pays for it in the monthly gas bill.

Plan carefully.
BAVE
Original Author
12 years ago
Sniffdog, thanks for the reply. Looks like we're going to opt to have one NG WH in the garage (near bedrooms, etc) and a tankless NG WH in the attic above the master bath (master bath and one additional bathroom. We have a split plan so the master bath will be approx 100 ft from the garage.

Water heater(s) for 140+ ft wide house?

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Water heater(s) for 140+ ft wide house?

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