tankless water heaters and dishwashers
hi folks..
just wondering if there are any issues using a tankless water heater, and the newer energy efficient dishwashers..
do the lower flowing dishwashers pull enough GPM to get the water to 120+ degrees?
i would hate to put in a tankless only to find that i also need a smaller point of use tank under the sink to work the dishwasher..
let me know if you guys and gals have expereinced any issues with this..
thanks
oak
Replies
A decent dishwasher will have it's own water heater built in. Got to in order to hit the 160 to 180 degree sanitizing cycle.
Which makes the tankless issue a moot point - for the dishwasher.
When using the sink for other purposes, remember the tankless has a certain flow rate before the heater kicks in. For some models this flow rate is surprisingly high. Trying to shave with a slow hot water flow becomes impossible with a tankless. You have to change your behaviors when dealing with this issue, or add a point of use heater.
Most DWs have a heater, but most are designed to only keep the water warm, not heat it above the supply temp. Ya gotta read the fine print.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I qualified my post as, " Most DECENT Dw's..."
Which means if the OP is planning on spending the $ for a tankless, I would expect him to also pony up the cash for a decent DW.
Otherwise, you're right. The lesser models probably only depend on the incoming water temp. gotta read the fine print.
Well, DWs have lots of different features. Most are set up for 120V, 20A circuits, and the heaters are only a few hundred watts. If they can even heat the water hot enough, it may take 15 minutes, and then they need a thermostat to stop the timer while heating. Generally a unit with a "sanitize" cycle should have the right stuff, but it's not a given -- may just wait a fixed time to heat on the sanitize cycle and may not wait for water to heat on other cycles.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Well, what features should our OP be looking for in a DW?
My Kitchen Aid has the high temp sanitize (160 degrees) and high temp heavy wash cycle. It is almost silent and has a SS interior. I really like the rack designs and it's ability to handle many sized items.
Well, the OP was worried about the tankless heater coming on, IIRC, so that's mostly a different issue. But if you're faced with a situation of cold or unreliably heated water coming in you'd need to check the DW specs for minimum water temp. Most will say 110-120F, I suspect. To handle cold water you're basically talking an input temp of 50F. If you have a tankless that's really sluggish firing, probably you can figure on about 90F average.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I noticed the same with our Takagi Jr. You need to go "full hot" and then temper with cold. Not the best answer if you are on septic or have high water costs, but we are on well with sewer so it is not a problem.
Used to shut of the shower to soap up, but if you do that with a tankless you will get a shocking shot of cold. Mainly did it because the shower was too small. New shower is big enough that I can re-direct.
To your DW question - see if it has an integral heater. If not, you may want to select another.
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thanks for the responses guys...oak
Not sure if this is up you alley -- we have a conventional HW Heater -- but it took too long to get HW to the kitchen sink -- maybe 3-4 minutes -- installed a circulating pump from grunflos (?) and we have HW in less than 2 seconds -- costs a buck a month to run -- we could cu t down on the cost by minmizing the time we what this convinence to say 6 special hours instead of all day but not the night 9 to 5 AM -- all the best
It does not cost a buck a month to run.
The electric will be 5-10 $ per month depending on the size of the pump and utility rates. The cost of the heat loss in the line will vary widely depending on the fuel source, length of circ line, r-value of circ line insulation, and efficiency of the heater. The cost to maintain the heat in the circ line can easily surpass that of the cost to run the pump. It is easy to end up closer to a dollar a day. A timer is a great idea.
Circ systems in conjunction with a tankless heater can overcome the low flow ignition issues but will introduce a new set of issues.
Circ pumps are an energy wasting convenience. I love mine. It probably only runs for about 3 hours a day. It is on a timer but we usually just turn it on and off. The switch and timer are very conveniently located.
Good analysis. I've often thought that a short-term recirc control would be a good seller, i.e. I know I'm hopping in the shower in ten minutes, or washing the dishes, so I push the button now and the lines heat up, and stay on for 30-45 minutes. I have had clients ask for recirc that runs 24/7, but relent when they understand that this is essentially radiant heating for their crawl space.
My plain-vanilla Frigidaire DW pulls enough water to cause the Aquastar to come on immediately.
You still have to hook up the DW inlet to your hot water supply line. If you first hook it up to the cold side by mistake, as i did, the DW heater won't be able to boost the temp enough and your dishes won't come clean.
Edited 9/1/2006 8:05 pm ET by splintergroupie