I had many excellent recommendations in a recent thread for wall coverings for a cabin in the mountains that we are building.
Here are a couple of pictures if anyone is interested: in the snow last week from the outside, pre-insulation on the inside, mid-sheetrock (just about to finish up the mudding this month), and lastly the closet under the stairs where the Pex rough-in plumbing and wiring for the water heater should go.
Which brings me to my question as I have no experience with tankless (or really any) water heater. The cabin is small (20’x20’ interior) heated with the wood stove and 4 in-wall 1200 amp heaters. Two running for 20 minutes take the cabin from ~45degF to 65degF.
Water requirements are rather minimal with only one shower, two bathroom sinks, kitchen sink. In the long run of 5-10 years we may put in a dishwasher and a washing machine (both apartment sized). But the challenge is that the water supply is well under 40degF in the winter (34F currently) and even in the summer it doesn’t really get much above 50degF. The general contractor+electrician elected that a tankless electric water heater wouldn’t really do the job. But as we may go 1-8 weeks without being there during the winter and summer and we really cool it down when we aren’t there, we really like the idea of a tankless water heater to not waste energy but also to get the hot water in action quickly. We don’t anticipate many showers there but would like it as an option. So before everything is sealed up, I want to be confident one way or the other. I think the heaters will kick in quickly and be cycling off before the water heater is really in use, regardless. And the panel is a 150 Amp service anyway so there is “plenty” of power.
It would require running 6 gauge wires and a new 50 or 60Amp double breaker which I can do no problem. But if someone with more tankless or on-demand water heater experience knows more, I’d appreciate any thoughts. Or for such a dramatic temperature to heat, would we need a more powerful 24 kW heater.
Can we install something like the Rheem R-Tex11 or 13 and be happy with the water flow in the shower? Even in the winter? (I don’t need a gushing shower but need more than a trickle!)
A couple things:
Your set-up sounds exactly like my father-in-law’s except he is only there for 3 seasons now. He went with a small 20 or 25 gallon hot water tank and that’s plenty for his needs. It’s also easy to shut off and drain when he closes up for the winter (to Florida).
As far as the tankless go, I can’t comment on the specific models, but I can share some general advice I was given by a friend who was very senior in our local natural gas supply company and it does sound like you’re on the right track based on his advice:
Tankless only have a maximum amount of heat they can apply to the water in the time it flows through the heating pipes, so they can only raise the water temp by a finite number off degrees depending on the model. You need to look at the coldest your water will be and see if it will raise it from that temp to about 120F in the depth of winter. Some models may only raise the water temp by 50F, so if your winter water is coming in at 40F, you can then only get it to max 90F, which is cooler than normal hot water. Another model may heat the water by 75F and be perfect for you. Model X may be fine in Florida in the winter, model Y is needed for a frozen winter area, conversely Model X would be overkill in Florida.
Because they have limited flow and capacity to heat, they can only do one thing at a time. For example: you can’t shower and do clothes together. For a couple that’s fine, but for families that’s tough. Maybe a factor for you, maybe not.
The place I’m currently in has an on demand system and what he said is true about more than one thing. We just had guests staying and if anybody uses hot water (taps, dishwasher, clothes or another shower) while someone is showering warning beeps go off an the person in the shower gets cold water.
First of all, it looks beautiful, good job.
I want to interrupt things for a second and mention something GMANCANADA touched on.
What are your plans for draining the system in the winter? I don’t know which water heater is better for that.
I will add it is simple to shut off a standard water heater with a breaker.
I have a propane tankless with plenty of capacity to provide lots of hot water anywhere in the house at the same time. Input water is from a well and VERY cold.
I wouldn’t do tankless unless I had propane or natural gas. The electric ones are not adequate for whole house use.
I also have a gas tankless water heater and it works just fine. But for a place that small, perhaps point-of-use water heaters would work better. These operate on gas and are tankless. You install one at each use location, and they operate independently from each other. These are common in Europe.
Thank you for all comments so far. We have a valve just beside and outside the cabin to easily drain the whole thing whenever needed- all pipes are currently empty. And we also have the ability to use an air compressor to blow the other direction. Thus we figure we will drain everything for longer breaks (month?) but for shorter (1 week?) we will leave water in the system. We keep temp above 40 just to keep remaining water in the toilets and traps happy and keep condensation from becoming a problem.
No gas possibility. This is a 30 minute ski in in the winter. It is fairly remote- not quite as far as we’d like though.
This may not matter that much.
During the winter, that ‘waste’ energy ends up dissipating as heat into the cabin, thus keeping it warmer. So it isn’t really wasted. In fact, probably nearly as efficient as your electric heat.
(Of course, if you completely drain the plumbing & allow the cabin to match the outside temp during winter, this doesn’t apply.)
My tiny house uses a propane 140K BTU Takagi tankless water heater mounted inside the house with a vent to the outside. According to the Portland Water Bureau, winter water comes out of the tap at 38F and the heater will raise the temp by 77F at maximum capacity, which is, I think, 7gpm. My shower is limited at 1.5 gpm and since I live alone there is never water use at more than one point at a time. I assure you that even when there’s snow all over the place my shower is hotter than I can stand and should I be so inclined I could spend the day in there with the water running full out and never run out of hot water. I love my tankless, I’m NEVER going back. I once had a water heater rust out and flood the kitchen–that sucked and I never want to have to deal with a mess like that again, TYVM!
So 4800 amps total. That’s impressive - about what a serious industrial plant would might consume.
Right - I’m guessing this means the heaters are 1200 watts.
As for heating the water: I’d go the normal (non-tankless) route. The installed cost will be lower, the water will be hot less than 30 minutes from when you arrive, and by turning it off when you leave, energy costs will be modest. You’ll certainly want to make it easy to drain, but you’ve no doubt already planned that for the entire cabin’s plumbing.
As for rusting out: the way to avoid this is to check the zinc anode every couple of years, and replace it (for around $20) when it looks bad - maybe every 6 or 8 years. With this minimal maintenance, it will last a very long time.
@ Disheavel
I wouldn’t dismiss the propane idea out of hand. We have an off-grid cabin on an island and we operate propane fridges, bbqs etc through 3 seasons. We bring in a 100lb big propane tanks and it lasts (in our situation) for over a year.
It might be worth doing a quick calculation to see how the usage costs would compare to electric. Often time electric can be multiples more costly per BTU than gas.
@Chefguy
We rented a condo for a while that had point of use electric tankless, one for the kitchen & laundry area, one for the master bathroom and one for the each other bathroom.They were amazing! But it seems like overkill for the OP.