on-demand hot water for seasonal home?
mmoogie
| Posted in Energy, Heating & Insulation on
I have a client whose 80-gal electric hot water heater needs replacing. She’s a seasonal user, single occupancy, with occasional couples for guests. She uses the place steadily for a month in the summer and maybe 30 percent of weekends the rest of the time, shutting it down completely from January through march or april.
I think it’s crazy to put in another 80-gal tank heater.At minumum I want to downsize it to 50 gals. Would on-demand make sense with this usage pattern? To do so it would require adding a propane tank as well. No natural gas available here, and electric rates are too high to consider electric for it.
Steve
Replies
I doubt she'll ever recover the high cost of such a unit. Even in normal usage the added cost of tankless does not save enough gas to pay for itself before the unit wears out.
Usually for slight use you go with low capital cost even though the operating cost may be higher.
Tankless are also not good for guests because of their quirky starting and flow characteristics. It's wearisome to explain to guests how to get water out of them.
I'd go with a small conventional water heater, with the temperature set around 140°F (about the highest safe temperature), and make sure the showers all have low flow but confortable shower heads.
If the WH stays on when the house is not being used...I would think you could save a lot of money
Propane storage would be outside. Knowing nothing of the code issue, I cannot imagine that 20lb portable tanks could be used inside. So you are looking at a larger outside tank - which is a major PITA. BTDT. A company has to be on call to fill it and it's always a concern over how much is left in it. And when it runs out ... no hot water.
Are there 50G elec tanks that have a programable thermostat? Worth a check - would be nice to reduce the temp when the client is away, ramp up for when she will arrive. Or at least a programable power inlet. My folks had the latter.
>> a larger outside tank ..... A company has to be on call to fill it .....<<
Around here that "on call company" will never let you run out of propane as they come by, read the gauge and top up the tank on a schedule.
However, during that period with no propane use -- you still get a monthly minimum bill. Mine used to be ~ $20 per month for zero consumption - NG was run into sub-division - propane service was cancelled. No minimum from NG supplier.
I vote for the electric tank type heater - shut off and drained during the prolonged non-use period. Just shut off (not drained) for shorter non-use periods.
Jim
Never underestimate the value of a sharp pencil or good light.
We switched to NG as well when it was run on our road. Our propane company would only come out when the computer had booked a visit - based on past usage, time of year, etc. We'd go through 1200 litres in a month and half in the dead of winter. Always checking the guage to see where it was at and was always having to call when it got to 5%.
Only once did we run out .... in December ..... the 25th .... that was fun waiting for a delivery so we'd have heat and hot water again. Good thing we have a wood stove.
For the OP, I found this:
http://cgi.ebay.co.uk/DANFOSS-RANDALL-PROGRAMMABLE-HOT-WATER-THERMOSTAT-WP75H_W0QQitemZ170344870855QQcmdZViewItemQQimsxZ20090616?IMSfp=TL090616213001r13403
I couldn't find any installation info, but if a programable thermostat would override the two manual ones in the tank, that would be a good solution. Low heat on weekdays, ramp up for weekends. When the client is there for a month, she sets it for a steady temp. I'd rather see the tank have a built-in programable thermostat - don't know if they exist.
Edited 6/19/2009 10:34 am ET by Varoom
>>which is a major PITA. BTDT<<It's a way of life in these parts. I've got a 250 lb tank, as most people around here do. No more trouble than fuel oil. They deliver on a schedule once they know your usage patterns. Every now and then one blows up a house though. And the tanks are unsightly.Steve
I think you're on the right track with a 50-gal electric. As others have accurately said, the payback for a demand heater just wouldn't happen. Partly due to the extra cost of the unit itself, and partly due to the high cost of installation combined with intermittent occupancy.
Since occupancy is intermittent and unpredictable, a timer probably would not work as well (or as cheaply and simply) as a simple switch on the power line to the WH. If guests turn it on as soon as they arrive, they will have usable hot water in about an hour, and a full tank in about 3 hours. Getting them to remember to shut it off would be a bigger problem, but most places like this are equipped with a list of do's and don't's for arriving and leaving.
Other control options are available--all it takes is money.
There are setups you can buy to turn stuff on/off in the house via telephone. Probably run several hundred dollars, though.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
a 50 gallon is a big water heater especially for a cabin, I think mine is a 30
Yeah, depends on your usage pattern. For 3-5 people (when couples are visiting) 50 gallons wouldn't be oversized, but one could do with less, if the visitors are a little judicious with their hot water usage.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
if the visitors are a little judicious
WOW, Ya got that one right!!
DIL lived with us for 3 month once when they were switching domiciles.
Lived for 25 years with a single 52 gal elec, me, DW, 2 boys.
DIL liked 40 minute showers, 52 gal didn't cut that till I turned the hot water shutoff valve for their bath down to only 1/2 gpm and sawed/broke off the shutoff valve stem <G>
"must be sumptin wrong with deh pipes, will have to look at it when i have a chance' <G>
BTW, that was 15 years ago, at DIL's house now they have just a 52 gal NG tank ( I put in a 53 gal vs. 80 gal for them when the old 80 gal had a bad weld), so better recovery than elec-- , big difference is they now have a teenage girl and 3 younger boys, so no time now for 40 min showers!!
Edited 7/5/2009 11:22 pm ET by junkhound
Thanks for all the input. I wound up just putting in a 50-gal. electric unit. Seems the most cost effective considering her usage patterns.Steve
Since I've had two houses with these things (I had both installed), I'm familar with the goods and bads of these beasts.
Normally, I'd say it won't be worthwhile.
However, in this case, properly set up and free from winter freezes, I'm thinking you may have better success than most.
Understand it gonna run betwixt 2 to 3 grand. Get a good unit like the Tagaki K-3.
How about winter freezes? I assume there's no heat in the house when it's "shut down completely". It would seem risky to have any water in tankless units during a freeze. Are they easy to completely drain?
Bruce,
Plumbed corectly, a tankless is very easy to drain.
A tankless won't let itself freeze if it has a gas supply and electric power. If freezing and power outages are likely, the WH can be plumbed to drain when power goes out.
To the OP - it sounds like lack of natural gas and the extra install cost would argue strongly against a tankless in this case.
Jim x 3
Hi mmoogie,
I have a client whose 80-gal electric hot water heater needs replacing. She's a seasonal user, single occupancy, with occasional couples for guests. She uses the place steadily for a month in the summer and maybe 30 percent of weekends the rest of the time, shutting it down completely from January through march or april
We've got a little mountain cabin that gets less use than that.....only have a shower, bath sink and kitchen sink....got the smallest paloma lp external tankless from http://www.designerplumbing.com and carry a 20 lb. tank back and forth.....dual hookup like a travel trailer.....never run out.....when one gets close to empty I open the valve on the fresh one then at the end of the weekend take the empty one home for refill. The little tanks easily last us several weekends including cooking and don't weigh much. Since I do about anything that needs doing myself; it's no trouble maintaining a couple of lp tanks as needed. I used to use a single 100 lb tank and we'd simply run it until it was empty which wasn't very convenient but it lasted the whole vacation year and is a little cheaper to run but the twin 20 lbs. are cheaper than a fill service for such small amounts. Shucks your client can swap 'em out at the big box stores if they don't want to save the $ at a small lp dealer.
You can get a shower sized one with all the parts you need for easy draining and most all of your plumbing, electrical and gas line for around $800. It'll take you longer to figure out how you're going to mount it, run the lines and remove the old one than it'll take to install it. Experienced DIY oughta take about 3 hours to remove the old, get all your materials and another 2 hours to actually install it and fire it up. Dag gone I'd rather do that than install tile backer board in July. Now if you're going to hire any of it out......that's another $ story.
Now as for explaining it's operation to guests....."We have an ondemand water heater. You won't run out of hot water during a long shower but every time you shut it off, you have to wait for the water to cycle back up to temparature which means you'll get a burst of luke warm water as the plumbing lines heat back up. Plain english.....when you're showering leave the hot water running until you are through. If you cut it off and on during the shower you're going to get a surprise."
Now if that's too much to explain, then two things......1. when are we going to quit using a tiny bit of our time as an excuse not to bring guests into the 21st century 2. Print out the last paragraph and tape it above the shower head and let them figure it out on their own. Personally I rarely remember to tell a guest and it's even rarer that it matters.
Pedro the Mule - Works for us, no regrets four years
Hi,
You might take a look at this tank:
http://sharedreviews.com/r/28773-whirlpool-40-gal-12yr-energy-smart
Its got a vacation mode and some other modes that are easy to set, and might make it easier for her to keep the power consumption down when not there. Basically its got 4 simple push buttons on the top to select the various mode -- they are clearly labeled and easy to use.
It does seem like 80 gallons is a big waste for this kind of usage.
Gary
80 gallons is more than most people should need for her situation -- 50 gallons should be fine. But the operational savings of 50 vs 80 isn't that great -- maybe 5-10%.
This may be a situation where a on-demand unit might be worthwhile, but as you've observed the high initial cost and higher maintenance could easily negate any savings.
Note that the real issue with electric on-demand isn't the rates (assuming you're already heating water with electric and the new unit will actually save some KWH). Rather, the tricky issue is whether the service can handle that high of a demand, since an on-demand unit draws much more current (when operating) than the equivalent tank.
She might be a candidate for a Marathon unit, but they're spendy, and not that much better than the top-of-the-line State or A.O.Smith or whatever.