Tankless WH installation: in series?
The plumbing supplier where I am getting my tankless WH (Takagi) has suggested putting my tankless WH in series and use both to supply the entire house (w/d, kitchen, 4 1/2 bath); with a recirc unit down and up. They say this will prevent running out of hot water, or temp drop when one heater is over burdened. I think this will use one tankless all the time and the other will only turn on occasionally, and will put undue wear on the 1st unit.
The way the house is layed out has the kitchen and master on one end, and the other 3 bathrooms at the other end. I’d rather have one tankless for left side of the house and one for the right with short runs from each unit to the taps; this would eliminate $1000 in recirc lines and utilize both units.
My wife is concerned that we will run out of hot water if have one unit and use the shower (2 heads), tub, w/d, dishwasher and downstairs
bath all at the same time (I agree, but don’t think we should plan for the most hot water we could need, just the common usage).
Any suggestions out there?
Thanks.
Replies
Tanless units provide X amout of hot water at a set temp, depending on the size of the unit, if the flow of water is more than they are rated for, the temp falls. I they are set up in series the first unit should only bring the water part way to he required temp. the second unit will bring it the rest of the way up. After they are up and running the first unit can be adjusted so it does roughly half the work.
I love re-circ lines, & recommend them for most everyone, BUT tankless WH & re-circs do not mix.
First you have to have enough flow for the tankless to kick on, or you just end up circulating cold water.
Second the main purpose of a tankless over a tank is to save money in energy costs so your only burning gas when you need too.
As McPlumb says if you set ip right one does the initial heat & the second finishes it off.
But in series may not be necessary. What size are the units---- how many GPM are they rated for? If you want to split the two count how many GPM's on each system will be used, & see if you are still under the tankless units recommended rating.
Most common problem with tankless I hear about is roman tub fillers, they allow so much water through them the tankless unit can't keep up.
"Why do you hurt me when I do bad things to you?" My youngest son to his older brother
Recently I was looking at a website that sold tankless.They sold a twining cable for tying several units together. Did not get the manualls to see what they did or where they where used.Don't remember the brand, but it might have been for Bosch..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I have seen electric ones that do that as an on demand type feature, as the demand increases it kicks in the next set of coils------ 3 phase ofcourse.
"Why do you hurt me when I do bad things to you?" My youngest son to his older brother
I think the low-end Seisco that one of my customers has does that too. It has (4) 60A breakers and (4) typical WH elements. It turns on the first 1 or 2 every time, then the rest as needed. It still only produces maybe 3-4 GPM usable, but it's enough for a single guy. I wonder if his new wife is going to 86 it but so far they haven't called.
If they do everything in series instead of parallel they should be fine, but your toast if you wash clothes or dishes the same time someone wants to take a shower.
"Why do you hurt me when I do bad things to you?" My youngest son to his older brother
I installed a Seisco last Spring for a friend's RFH system. Seisco advertises that is a "Power Sharing" technology so one chamber isn't always started first, and that they ramp up instead of being full-on or full-stop. It replaced an LP Rinnai (that had never worked properly), but it's never had a bit of trouble keeping up in the coldest weather.
Edited 12/10/2007 1:15 am by splintergroupie
I put in a tankless but left the previous electric 40 gallon hooked up before it. It at least gets the water coming in to room temp. before the tankless. The one bathroom that's about 50 feet away I installed a 2 gallon point of use right before all the fixtures so there's no waiting at the faucets and shower. Everything's working great so far, and utility bills are fine. I'd definitely do it again versus a re-circ. system.
Maybe they were thinking a conventional wh with a tankless "preheater"?
Beer was created so carpenters wouldn't rule the world.
A few added thoughts:
I would look at the larger heaters, the ones designed to run car washes, commercial kitchens, etc. They are big enough to be used alone in your house.
OR....
Run two units but use one upstairs and one downstairs, or something similar, rather than in series.