Tankless Water Heater for Workshop Bathroom
I have read through many of the posts regarding tanked vs. tankless water heaters. I noticed that many were somewhat dated and I did not see any that quite captured my conditions. So bare with me as I ask my version of this common thread.
I am building a separate workshop building. It has a bathroom – sink, toilet, shower – as well as a clothes washer and a slop / laundry type sink. The bathroom is a convenience item, not a daily life item. The usage will be intermittent; sink perhaps daily to wash hands; shower perhaps once or twice a week, but not every week; clothes washer to run a load of dirty work clothes or shop rags maybe once per month.
The water supply is from a utility with incredible water pressure and volume. I don’t have a figure, but it makes the end of the garden hose whip around. The building is located in the desert southwest (Phoenix metro area) so incoming cold temperatures might be in the high 60s / low 70s in the summer and in the mid 50s winter time.
Gas is not available to the site. The building will have a new 200 amp service with room for breakers. The water heater will be in the same mechanical room as the service panel so power runs would be around 10 feet. The water heater is on an adjacent wall to the bathroom with the longest piping feed around 10 feet.
The idea of the tankless appeals to me not so much for the continuous hot water, but for the elimination of the idle time losses from a traditional tank heater. I can see two-week time spans with no requirement for hot water and even then it may only be to wash my hands.
Since I am running a shower and a clothes washer (not at the same time) I need a unit adequate for those tasks. A point of use heater seems not enough.
The downside to the tankless for me is the initial cost and the lifespan. I saw some nice deals on ebay for Titans and Bosch PowerStar units. Then I read some reviews on Amazon for both of those units and it scared me away. They both carry a common theme of poor customer support, and 2-3 year lifespans. Perhaps my expected occasional usage would extend that life span. Scaling also sounds like it could be an issue and I had not intended to treat the water in this workshop (except an inline filter perhaps).
A traditional 5 or 10 gallon tank seems a good alternative in this case except for the extended idle times. Will the 5-gallon unit support a clothes washer?
An alternative could be a hybrid system of sorts; point of use at the sink and a tanked heater for the larger loads that is switched. If I switch the tank unit on when I need it, what should I expect as a delay time to bring it up to temp? Any thoughts on switching it with a timer instead of a toggle? Any pros / cons to installing the heater in an insulated enclosure to reduce losses? The down side to this is the purchase of the multiple parts of the system and with a bathroom sink and a slop sink I would probably need two point of use heaters or a complicated plumbing scheme.
I really don’t want to have to wait for hot water at the sinks. But how would the idle time losses of an always-on tank unit compare to the installation cost of the additional point of use unit(s).
If anyone can throw some objective data my way I would appreciate it.
Thanks in advance.
Daen
Replies
Your idea of a hybrid system sounds most practical for the intended use.
A small under-sink electric tankless for day-to-day use, and a large tank-type electric for the times when you'll shower or wash clothers, which could be operated by a switch.
The cost for both should be less than $800, and the energy standby loss would be minimal.
If you have 4500-watt elements (they work non-simultaneously) in the tank, that translates to about 15,000 BTU's per hour, or over 1/3 as fast as a gas water heater (40,000 BTU). You would get useable hot water in about 1 or 2 hrs.
The water in the tank would gradually heat up just sitting in the room during times when it's shut off, so the temperature rise needed would not be much--maybe 40 or 50 degrees.
One caution: unheated water sitting a long time in a tank might start to grow bacteria unless the chlorine content of your water is high enough.
Check out the Eemax units. You can purchase one of adequate size for about $250. I haven't any experience with these but am considering one for myself. I'd appreciate all opinions after looking at the literature.
I am wiring an Eemax today.
One caution about any electric tankless water heaters.
Check the power requirements, min. &max flow rates, and temperature rise very carefully.
Units designed for nore than one fixture may require two circuits. Bosch requires two 30 amp/240 volt circuits. Same for Eemax. I think the minnimum flow for both is 0.7 gal./min. and have a max flow rate of from 2 to 3 gal./min. You also need to know what your coldest incoming water temperature is durring the winter months. A 45 or 50 degree temp. rise with incoming water temps in the 40's will not get it.
Both require a valve on the outlet side of the heater to adjust the flow rate.
Bosch does offer a map with zones and models recommended for them on thier web site. Eemax has all of the technical information on thier web site as well as a good customer service dept. that will research and answer your questions.
I have used Eemax storage WH for years, and am well satisfied with them and thecustomer service. They have honored thier warrenties completely. No second guessing or finger pointing. If a unit fails within thier warrenty period, they replace it.
I'll let you know how the Eemax performs this afternoon.
We finished wiring the tankless wh and turned it on.
Good instructions but the flow rate adjsutment took some carefull tweeking. We ended up with a hw temp of 140 degrees F. This is for a commercial kitchen sink and hand wash sink, thus the high temps needed.
The Eemax is a two circuit 277V/40A system.
They have several 240V models with lower current draws that are likely canidates for residental use.
Based on what we did today. I would say the Eemax is going to live up to thier normal standards.
Did you install one of the models that has the high temperature limit thermostat?
Yes.
We installed the EX200 model.
We will probably turn down the T-stat a littel today. 140 degree water is to hot for a sink IMO. there is a very real possibility of scalding at that temperature.
This all started after a health department inspector (newbie) made a semi-annual inspect on our small cafe'. The facility was originally built and approved as a limited service food vending operation. It was primarily cold (prepackaged) items and fresh coffee. They were also allowed to sale hot soups (canned) from a warming pots. All food service utensils were collected each eveing and sent off site for cleaning. The little old lady that operates the cafe' never did dishes, so all we were required to have was a hand wash sink with a small 5 gal. wh for it.
Apparently the health code has recently changed with respect to the hot food part, and either the new inspector did no know about "grandfathering" or there is no grandfather clause in the new code. We had to install a three compartment untensil washing sink in addition to the hand wash sink. The little 5 gallon wh wasn't big enough for the new set up, and we didn't have floor space for a larger storage tank model.
Thus came the tankless model.
This is the second electric tankless model we have installed. the first was a Bosch to serve two showers and two sink in restrooms that were once used by small crews in our electric service dept. The crews have been gone for years, but the restrooms are locate in the cafe' area and a lot by the general building population. the Bosch worked ok as far as we knew untill the water temps dropped this winter. thats when we started learning about choosing the correct size unit for the number of fixtures, etc. Our management team kind of got egg on the face with that one, so we, the maintenance crew got drawn into the loop on the cafe wh selection.
With one day of operation, it looks like we have a winner this time (hiding a gleefull smirk as I say that)
Since you're constrained to use electric anyway, just get the best-insulated unit you can find -- Marathon if you really want to do it up right. The standby losses will be negligible. You can add a switch to switch the unit off when you won't be needing it for several days. (Keep in mind that most electric units heat from the top down, so you have a decent amount of hand-washing water within 10-20 minutes of turning the unit on.)
If you go with tankless, it's going to eat up a big chunk of that 200A service.
My thumb suck is that you need at least a 10 gallon tank, maybe 20, to feed a washer. More still for a shower.