Thursday, December 17, 2009

Installing a Tankless Water Heater Part 1

I've been researching the Tankless Water Heater for a bit over a year as I have an old tanked unit - the current energy tax credit makes it very desirable - however being the conservative that I am, I'm waiting for the old unit to kick-the-bucket as it were. My current hot water heater is over ten years old so it should be getting close, right? In any case, I've been looking at this stuff for a while in preparation for my own install. It's interesting when you research products on the web - the first thing you find are all the things that people don't like about something. You also learn what people have done that incurred the wrath of the pros - mostly improper installs. I'll get into that later as it's all good information and stuff you'll want to know if you consider doing this yourself. All this came to a head when my neighbor Allen across the street told me that his old tank was leaking and that he was about to put one in - he was asking me questions about the install. I told him I hadn't done a tankless install yet (I have done the old-fashioned tank though) and was willing to help him put his in, as I'd like to get some practice in before tackling my own.

About my own experiences - I was a general contractor many years ago (over 10 years) before getting into software design. As such I worked with several other contractors that allowed me to practice plumbing, electrical, HVAC, building and other disciples that helped to increase my confidence level in tackling various building and/or remodeling tasks. Luckily the contractors I worked with were very good and up to and enforced the various building codes - they also instilled in me a desire to do good, neat work that both complied with codes and also incorporated the latest in best practices. Doing an install of this nature incorporates many disciplines so if you want to try part or all of this, I suggest you bone up on: electrical installation, plumbing installation and gas (in this case Natural Gas) piping installation. After reading this if you feel unconfortable with any part, HIRE A PROFESSIONAL! I can't stress this more - if you wish to proceed, read everything in the install manuals several times before and during the work. Also, if at any time you're not sure, stop and do some additional research. This isn't something for the weekender to attempt. More on this as we proceed.

First on the Tankless Water Heater:
The technology has been around for many decades - so there's been plenty of time to perfect the technology. One of the oldest producers that's availabe in the US is Bosch (most have heard of them as a tool manufacturer but they've been making and selling their tankless water heater in the US for many years). Most of Europe and a good bit of Asia have had tankless systems for a very long time - the US is way behind, mostly because cheap energy has been available here for so many years that the cheaper "big tank" units are simply easier to install and incur the least materials cost. This has all been changing with energy fuel costs all over the place.

There are basically a few considerations - first is the unit to be inside or outside? Second, what is the type of fuel or energy you're going to use to power it? In the Atlanta most will place the unit inside and in the Northcrest community, most will have the unit in the basement where all the house systems tend to congregate (most Northcrest homes have a single room in the basement that's home to the electrical panel, furnace, water heater and often the washer and dryer hook-ups). Natural Gas is plentiful and cheap in this region, it's also probably the most efficient and cost effective to use, so the focus will be on that install. The other options are LP/Propane and Electric. Solar doesn't generate enough amperage (I don't believe) so it's not an option (however if you're in Florida or one of the states that gets more than its share of sunlight, you might want to consider a solar water heater - but that's an entirely different animal). Outside tankless units are usually used on cabins or otherwise in installations where space is a premium.

Available Tankless Water Heater Options:
I read quite a bit about the various options, who to purchase from and where to source. There are a lot of opinions, and I'm sure the list will change by the time I eventually buy one for my own home. I had pretty much selected either the Bosch or Rheem units. Another manufacturer that is highly recommended is Rennai - however you have to be a certified Rennai installer to purchase one. In this case Allen purchased a Rheem unit at the Home Depot (Rheem EcoSense On Demand 6.6 GPM Natural Gas Indoor Direct Vent Tankless Water Heater Model # ECO-180DVN). With this kit he also purchased the venting kit (3 In. x 5 In. Concentric Direct Vent Kit for Rheem EcoSense Tankless Direct Vent Units Model # RTG20147-1) and the valve kit (Tankless Water Heater Installation Valves Model # TWH-FT-HCN).

What you need and a comparison of costs:
AT 6.6 GPM the unit is sufficient for most homes in the 3 bedroom, 2 bath range. You may want to consider something larger (7.4 GPM) if you often have two people bathing at the same time the dishwasher or washer is running - for both Allen and my own home,  this is not the case. The vent kit is necessary as you cannot use the existing B-vent. It's simply not rated for the bursts of heated air that the tankless produces - also the new kit is stainless steel and vents directly through the wall to the outside - you'll need to use the right kit for the manufacturer's warranties to apply. Finally the valve kit just makes the install a bit easier - it's not necessary but it does make things more efficient by providing the parts/pieces that you'll need for the required configuration. The extras add about $300 to the price of the heater. Along with all this we ended up buying about $300 worth of pipe fittings (water and gas), valves, electrical supplies and a water filter (more on that later). The unit was about $1k so a total of about $1600 in parts. Most installs of this type are going to cost in excess of $3000 with labor so you end up saving about half. To compare to a tanked unit - you can re-use most of the existing bits that currently hook up your tanked water heater, so  there's very little material cost with the exception of the tank. A 60 gallon GE unit is $678 (anything smaller makes it hard to fill the tub - if you have a jacuzzi you may need something even bigger). With the tax credit of about 30% on the tankless you'll get back about $480 (not sure if you can get a credit on all the bits/parts so this may vary). So it's about $700 for the tanked unit compared to about $1100 on the tankless, give or take. The $400 difference will probably be offset by the energy savings within 5 years or so (probably less, I'm being conservative but it depends on your hot water usage - if you have a family it will be more).

The Gotchas:
While doing research there are some very good posts on what went wrong - there's also a huge share of posts basically slamming the various units for one reason or another. For one, it can take 20-30 seconds longer for hot water to flow, depending on how far from the unit the tap is. There are also several posts by professional installers providing insight into the various units. The Bosch unit, for instance, is highly recommended, however it has a wear part that's about $300 compared to the comparable part for the Rheem that's about $80. Something to consider. Also, most who complain and have had to have a pro come in and fix and installation did one of the following:
  1. Improper plumbing installation. This usually involves the size of the pipe coming into the unit. A 3/4" supply line is requried - this doesn't mean you can connect to a 1/2" line with a larger 3/4" line and everything will be fine. This is all about capacity -when it's time for the water to be heated enough has to enter the unit to fulfill the units requirement - if there's a pressure drop the unit will red-flag and not produce enough hot water - it can cause the unit to be less efficient and certainly may reduce the life of the unit. There are many safety features in the tankless units to account for fluctuations so it may not shut down, however it could produce a condition that isn't conducive to producing the desired amount of hot water when needed.
  2. Improper gas installation. This unit requires a 3/4" line coming in with natural gas. As with the water line above, if the available gas line capacity is not great enough to power the unit, at minimum you wont get the hot water desired, and at worst it may cause the unit to fail. As I've stated previously, make sure you read the entire install manual and prepare to make any changes necessary for the unit install - if your pipes keep reducing until they come to where you need to place the unit, you'll need to tie-in earlier (closer to where the pipes come into the home) where larger piping is available. Another issue comes from re-using the flexible gas supply line commonly used on furnaces, appliances and water heater tanks - this line may have a 3/4" fitting on either end, but is usually 5/8" in actual tube diameter which may cause issues (most home flex is rated at about 110 BTUs - the tankless unit requires 160 BTUs or more so they aren't rated for this application). The best solution is to tie your piping directly to the bottom of the unit.
  3. Improper venting. These units produce short bursts of heat that far exceed the rating of the current B-vent that goes through your roof (what your old hot water heater and furnace tie-into). When you tie into the existing it produces a lot of heat and back-pressure at the unit, usually resulting in a shut down - the result is you don't get enough hot water. It can also kill the longevity of your unit as a worst case scenario and will void your warranty. Along those same lines, you must use venting that's rated for this application (stainless steel) and follow all the manufacturer's directions as to proper install.
  4. Electrical: These units have to be powered, so there needs to be an outlet available - at about 2 amps the needs aren't high, but don't tie the unit into a heavily used circuit where there are many peaks in amperage or this could affect the units ability to work effectively.

Starting the Project
So the first think we looked at was where Allen wanted to place the unit. A place on an outside wall opposite the furnace was proposed. As the washer and dryer are beneath we needed to make sure there was space with the vent kit above, and the valves and connections below. This required that the vent kit be loosely placed on the unit and the valve set below. When doing this, make sure that there aren't any obstructions on the outside (for instance there's a vent cover for the bathroom exhaust fan that made one location undesirable - it's better to not have the exhaust for the unit in direct line with anything above; on the other side of the panel the electrical meter is mounted on the outside wall, precluding that area from being available for the install). Another consideration is future planning - Allen wants to wall up the room holding the furnace, washer/dryer and tankless unit, so we tried to maximize space usage. This would require the removal of some legacy steel plumbing pipes (no longer in use) and the move of the washer/dryer supply lines. Note the image above - this was the initial placement - after reviewing that there's a vent above that location it was moved over to the right (which necessitated the move of the supply lines for the washer).

Another consideration on the placement was the availability of a circuit - currently there's a 15 amp single outlet for the washer - we decided to upgrade to 20 amps (there was already 12 gauge romex) and place a two gang box on the end of some shielded piping. While at it I suggested that the outlet for the dryer be moved up to make it more convenient. Next I took a look at where the best places for hooking up the water and gas would be and started loosely maping out the best routs to the new tankless unit. I drew up on a large piece of paper all the drops, changes of direction and connections needed - we choose to use Pex piping which I've recently done a bit of work with - since I felt really comfortable with it and also owned the crimping tools, we based all the fittings for water on Pex. After laying everything out we worked on an initial project plan. Whenever there are lots of dependencies it's good to make a list of the order for getting things done. It went something like this:
  1. Shut off power at panel
  2. Move electrical circuits, upgrade to 2 gang box, feed into new 20 amp breaker
  3. Power on panel and check new electrical fixtures for good grounds, etc.
  4. Locate hole for venting kit, break through and secure venting piping
  5. Prepare tankless unit for install
    1. Mount inlet valve set
    2. Mount outlet valve set
    3. Mount gas shut-off (supplied)
  6. Mount unit to wall
  7. Pipe water inlet backwards to a source pipe (we chose to pipe back to the supply lines for the original Water Heater - this would provide a convenient location for the in-filter).
  8. Pipe water outlet backwards to ti-in pipe (once again it was easier to tie-in back at the original Water Heater outlet point since we would have had to address the open line there anyway.
  9. Turn off gas
  10. Add a "T" style connection to the gas system, along with gate valves back to the unit.
  11. Turn on gas
  12. Check all Gas lines for leaks and correct if necessary
  13. Turn off water
  14. Do final connection to inlet filter and water supply
  15. Do final connection to outlet to supply home hot water lines.
  16. Turn on water and check for leaks
  17. Mount electrical control unit and plug in unit
  18. Turn on tankless unit
  19. Test
We made some modifications as we went along, however the above is what we came up with the first day. We both went on to further read and study the installation manual and met up the next day. At this point there was more than a small leak to his original tank so it was imperative that we get the job done. However we still didn't rush. The next day was set aside for the majority of the install. The goal was to get the unit hung and the water mostly plumbed. Day three would be for system tests and final hook-ups. More on the next post.

Continued in Part 2

-- John


Allen Mueller said...

This was a great install. Clean, efficient and well-planned. The essential difference between tank and tankless? Now I start the shower before I take my clothes off. I know - it's tough.

Allen Mueller said...

oh yeah, and KILLER write-up.

mrazekan said...


With galvanized pipe, an old house, and a long run to the old water heater, I also need run the hot water long before I jump in.


Thanks for the excellent writeup.


Anonymous said...

Did you need the adapter that came with the vent kit?

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