tankless water heaters

[ohm]

I once installed one for a customer with a 125 amp service. Darn thing required three 40 amp circuits for it's three stages. No matter what I did, the kitchen lights would flicker when the thing came on. I was able to adjust it so that the bathroom and bedroom lights would not flicker, unless there was demand from 2 places (like 2 sinks, or 1 sink and washing machine).

Folks decided to live with the flicker rather than upgrade the service.

Looks like you squeezed every bit out of that 125A service. They say the electric tankless is close to 90% efficient compared to the gas units which are closer to 70% due to the venting req.

 

[sub3marathonman]

I think that the tankless is a good option but I would have it set up per bathroom not for whole house. Lot of money spent that way. It would be cheaper I believe for the bathrooms individually.

Individual units would not be cost efficient and would require at least twice the power additions to the service--instead of a 300 amp service it might take a 400 amp service.

I am still thinking that the tankless for each place is still potentially a good option. I know I wish I would have gone with a small unit for the kitchen sink too instead of just the master bathroom. A 30kw for the enitre house or two or three small ones for each outlet seems to work out the same to me. And, from what it looks like to me, the whole house ones are just two or three smaller units combined in one box.

One thing not factored too is the amount of water wasted because people have to wait for hot water. I know it isn't much, but over time it does add up.

 

[dumbcluck]

solved

solved

thank you all for the feedback. the customer has seen the light and agreed to let me upgrade his service to 200a. now i just need pg&e to play along and all should be good.

 

[charlietuna]

Individual units has two major problems 1) cost, 2) service sizing ! Even the smallest unit is going to cost about $1400.00 X 3 = $4200.00 and then add a 2 pole 30 amp circuit and a second 2 pole 20 amp circuit to EACH unit. Now when figuring service sizing these units along with the normal house loads are going to require over a 300 amp service. The payback will be well over ten years. The two units that i have installed have the ability to recirculate water thru the system. They have a very tiny pump that causes a differential pressure across the pump that can be programed to run. The last station in the line gets a needle valve that bypasses a very small amount of water and keeps the entire hot water system's water "hot" ! This cuts it's efficiency down if running. But is used mainly in institutional installs. My unit has a payback of about 4 1/2 years over the tank type heater. It does take some time to get used to--I do not use the bypass option, i am on a spring fed well so water is never a problem, only the cost of pumping it into my pressure tank. The cost of heating the water is of little concern too since not storing it saves about 45 per cent of normal heating costs.... On a new installation it is a good investment--but remodels usually have service size problems on electric units!

 

[LarryFine]

The biggest one I didn't install was a 28Kw 4-section unit, requiring four 30a circuits, or two 70a as an alternative. The existing 200a service was a completely-full 40-sp CH panel supplying, among other things, two 100a sub-panels. The seller of the heaters had contacted me about being an installer for them, and this was the first one.

The first was for a large basement improvement, complete with HVAC and a kitchenette, and the second fed a 4-car garage with an apartment above it. The customer was surprised at my mention of a service increase, mainly because the energy-saving expert people who sold it to them insisted that any existing service should be more than adequate.

I offered the choice of performing an upgrade to 400a now, or wait to see if they tripped the main breaker and upgrade later, at an obviously-higher total cost later. They weren't happy with either choice, ended up returning the heater, and I never heard from the heater sellers again. I agree that a fossil-fuel-fired tankless heater is the only way to go.


Sometimes, it feels like I have a tankless job.

 

[Pierre C Belarge]

Sometimes, it feels like I have a tankless job.

That must leave you with such an empty feeling. :grin:

 

[carlos cainas]

Glad to hear

Glad to hear

I was just about to give a Quote on one of these 70amp Tankless I wont even waist my time.

 

[Full Spool]

I have installed 3 of these titan units and so far the customers have been happy with them. The electric ones have a problem when the incoming temperature is below 40 degrees running more then one fixture at a time.

I recently did a test when water was 38 degrees coming into at 80 psi: the best I could get this unit to perform running 2 fixture wide open was 98 degrees and 120 w/one. The way you can heat the water more efficient is to install a ball valve on the output side of the water heater and adjust it accordingly until you get the best temperature rise. If you do a little research you will notice that these electrics are recommend for warming climates.

Rated at 2 baths: I tested this with 2 fixtures running simultaneously and it handled it with no problem, it will do 3 but pressure falls This was in the summer time and water would do 120 plus degrees easily with 2 fixtures.

Electric requirements:
60 amp breaker
disconnect
6/2 w/g wire

Plumbing:
If your home has cpvc plumbing and not copper lines you must run 36" of 3/4" copper line on both the hot and cold side.

Cost:
$220 buys the unit

Pros:
Very cheap unit compare to competitors
Heats up very fast and hot(temperature adjustable up to 140 degrees)
10 year warranty

Cons:
I have noticed that on a 100amp service your lights will flicker when both stages of heating elements are on and your heating and cooling system(electric units) are running. 200 amp service you will be fine, if you are running more then one unit make sure you load calcs are in check.

I agree with the statements about the electric needs to be design around these thing, they draw a lot of amps and no one likes flickering lights. The rinnai gas units are some of the best in the market and if the house required a high demand of hot water this is your best bet. The gas units will heat the water in the exchangers until desire temp is reach, and you don't notice a huge fall out in temperature on long runs. Also the rinnai requires you to run 120v to the unit, it doesn't have a pilot light that stays on all the time which makes it more efficient: the unit will only be on when the demand is there.

 

[Rampage_Rick]

I'd be interested to see a BTU / kW comparison between gas and electric units. I've been thinking about getting one of these things when it's time, and I feel that the time is drawing near on my electric tank.

I'm intrigued with the system having remotes in each bathroom, but what happens if I'm having a shower at say 120? and someone else dials their controller to a different setting?

 

[Full Spool]

I'd be interested to see a BTU / kW comparison between gas and electric units. I've been thinking about getting one of these things when it's time, and I feel that the time is drawing near on my electric tank.

I'm intrigued with the system having remotes in each bathroom, but what happens if I'm having a shower at say 120? and someone else dials their controller to a different setting?

I have never seen a unit that has individual operating thermostats, the gas units I have dealt with only have one centralize unit. Such as a thermostat for a HVAC system: you set your temp and that's what comes out of the unit.

 

[brian john]

I plan on installing an electric one at my pool for showering only, a single point of use. I figured on a medium size unit (I have the model numbr at work). Seemed like a decent option for this use. MOw the grass take a shower and then chill out.

 

[ohm]

I plan on installing an electric one at my pool for showering only, a single point of use. I figured on a medium size unit (I have the model numbr at work). Seemed like a decent option for this use. MOw the grass take a shower and then chill out.

If it's just for one shower you could get by with a 2 GPM unit, one of the smallest 240V units (40A).

 

[dereckbc]

I'd be interested to see a BTU / kW comparison between gas and electric units. I've been thinking about getting one of these things when it's time, and I feel that the time is drawing near on my electric tank.

And there is the key issue. Using 58 degree water at 3.5 gpm th eminimum DOE requirement requires 110,000 BTU/hr. To do that with electric is 240 VAC at 140 amps. 110,000 btu/hr for gas is a small unit. My main unit is a 9 GPM at 70 degree rise.

I wouldn't even consider electric in the north with inlet temps approaching 40 degrees, even a 60 degree rise is still a cold shower IMO

 

[charlietuna]

The setup i have (NORITZ) is gas, hangs on an outside wall and vents directly overhead via a stainless steel vent. I have a 15 amp GFI receptacle under it for control power for the unit(not a dedicated circuit). The control wire is 5 conductor stat wire and goes to the master bath(in my case) and then branches out to the other two bathrooms. These other two bathrooms can select the desired temp for their bathroom and it will remain at that temp until the hot water is not used for 15 minutes and then the unit will return to the default temp originally set at the master bath stat. I have found that 130 degrees seems to be fine for my family and the stats are never used--a waste of money in my opinion! The master stat does all kinds of things--measures gallons of usage--time of usage-etc...

 

[dreamsville]

I tell everybody to just replace their existing tank with a very good, (and not just the cheapest thing you can find), insulated 50 gallon, (or larger if needed), electric tank, and a mechanical timer. I've had mine installed for 25 years. I heat the water 3 hours in the morning and 4 hours in the evening. Plenty of hot water for showers and dishwasher. You can always install more trips to customize the settings to satisfy individual tastes. Or if you want to get fancy install an a multi-day programmable timer.

I did replace my original tank about 7 years ago with a good "Marathon" brand non-metallic tank. Has a lifetime warranty. Don't have to worry about rust.

I think this is the easiest most economical way to go all the way around. :smile:

 

[ohm]

And there is the key issue. Using 58 degree water at 3.5 gpm th eminimum DOE requirement requires 110,000 BTU/hr. To do that with electric is 240 VAC at 140 amps. 110,000 btu/hr for gas is a small unit. My main unit is a 9 GPM at 70 degree rise.

I wouldn't even consider electric in the north with inlet temps approaching 40 degrees, even a 60 degree rise is still a cold shower IMO

Since electric units run 99% efficient compared to 70% for gas the ideal set-up is to have the heater real close to a 400A SE panel and be an electrician who can do a little plumbing. Also, if there is just one person in the house you can use a 40A unit for the whole house as long as no user draws over 2 GPM.

Also, if you have a good conventional water heater in a conditioned space, hook your tankless heater inlet to the conventional heater outlet, but don't power-up the conventional unit, unless the tankless fails.

The conventional unit will eventually allow well water to rise to room temperature so the tankless unit only has to heat from 70 deg to 130 deg.

I did this for an 80 year old lady and her power bill dropped by half.

Be sure the tankless unit can handle the higher inlet temperature..some can't.

 

[dereckbc]

Ohm you must not have a wife or daughters?

Not sure where you are getting your efficiency numbers from but all the quality gas tankless models run aroun high 80 to low 90% efficiency. Othersie not sure who has a 400 amp SE to be able to compete with gas output?

 

[ohm]

Ohm you must not have a wife or daughters?

Yea a small unit used for the whole house is a SPECIAL application.

 

[LarryFine]

I heat the water 3 hours in the morning and 4 hours in the evening.

I've never been fully convinced that timing water heating saves that much. When the timer energizes, you have to heat that water back up again.

I feel the same way about setback T-stats. I know that, in the hottest part of summer, it can take a couple of hours to cool our house back down.

Remember, it's not just the air we heat or cool; it's the furniture, appliances, people, and the house itself: floors, walls, and ceilings. And wire! :smile:



Added: And no, the AC isn't too small for the house. Once desired temperature is reached, it does cycle, and it does dehumidify.

 

[ohm]

I've never been fully convinced that timing water heating saves that much. When the timer energizes, you have to heat that water back up again.

I feel the same way about setback T-stats. I know that, in the hottest part of summer, it can take a couple of hours to cool our house back down.

Remember, it's not just the air we heat or cool; it's the furniture, appliances, people, and the house itself: floors, walls, and ceilings. And wire! :smile:



Added: And no, the AC isn't too small for the house. Once desired temperature is reached, it does cycle, and it does dehumidify.

I agree Larry, timers are good if you have off-peak billing and a large attrium to store energy, like Embasy Suites. Set-back T-stats may be good if your system is oversized and can quickly get your home back to tolerable levels when you get home or wake up.