Tankless ele. water heater.

[dmccarty]

Charolais,

A big issue with instant water heaters is that they can only raise the temperature of the water N number degrees for X amount of GPM. Gas instant heaters can raise the temperature more than electric for a given GPM. You need to figure out the temperature of the water supply to your house and then look at the specs on the water heater to see if it will raise the temp to what you need.

I know at my city house the water supply temp varies during the year. With our well I think the water is going to be 50-60 degrees year round. So to get 120 degrees I need an instant water heater to provide at least 60 degrees of heat. It was tough to do this with some instant electric heaters at decent GPM.

I *** THINK *** that dishwasers are supposed to run water at 140 degrees to kill the bad bugs. If the washer does not have a water temp booster the water won't be really cleaning the dishes.

Check the specs on the instant water heaters. They show this information. What we thought about doing was to use an instant water heater and if the water temps where not high enough we would put in a solar water heating system to boost the supply temps. Hopefully the electric heater would not be needed....

Instant water heaters seemed to be 700-800 dollars. Twice what an 80 gallon water heater costs. The water heater we bought cost the same to run as the 40 or 60 gallon heaters.... To put in solar water heating was about 2500-3500 dollars. I can buy lots of electric power for 2000-3000 dollars....

Later,
Dan

 

[Boondox]

Dan, so you're saying we'd be in serious trouble trying to take hot showers with an instant water heater...since our incoming water is only 34F!

Jeez, another good idea bites the dust! /forums/images/graemlins/confused.gif

Pete

 

[slowzuki]

Boondox, they do make models that will do showers. With a lo-flow head you should have trouble finding a model that would work.

Ken

 

[dmccarty]

Pete,

It depends. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

If you are running electric it might be iffy. Gas has the "power" to really heat up the water more than electric and at higher GPM.

I have not looked into this in a few years so maybe they have improved the models. We where going to put one in but the issue with the water temps and as well as the extra dollars we just decided to put in an 80g high efficient water heater. Right now we are fine with two small daughters and us with a 40g water heater. In a few years that might change so we splurged on an 80g heater. The cost was higher to buy over a 40/60g but the operating costs where the same so we went with 80g.

One option on the electric water heater is to have one for each water value. Course that gets expensive. /forums/images/graemlins/grin.gif

Later,
Dan

 

[slowrev]

Good point Dmccarty,
If one heater does not heat enough, you have to add another one downstream to boost the water temp on up. About 1,000 or better to get water hot enough for a dishwasher. Take a long time of efficiency gains to pay that back. Also you will have to run 2 runs of wire to the location and have 2 more breakers in your panel.

Ben

 

[KennyV]

If you were concerned with hot water quantity, would not having a pair of 40 gallon heaters produce more hot water than an 80 gallon tank??? Seems you would have twice the recovery rate, for about the same initial price. What is the recovery rate of the 80? KennyV.

 

[slowrev]

It would cost twice as much to operate, however a larger single tank costs almost no more to operate.

Ben

 

[OkeeDon]

OK. I find the idea of a tankless water heater intriguing. If I were to include one in my new house, it would be LP gas, because I'm not going though another couple of weeks without hot water when the next storm hits.

But, let me throw a curve into this discussion. I'm also intrigued by the idea of installing the hot water plumbing in a loop with a low volume pump, so there is always hot water moving through the lines. While this journey obviously cools the water, which must be reheated when it returns to the water heater, it is also the epitome of luxury -- instant hot water at any tap at any time.

Anyone have any ideas about how such a loop would affect or be affected by a tankless water heater? The water returning to the water heater would only be a few degrees cooler than the water entering the loop, so the effort to reheat it would be a lot less than "new" water.

 

[KennyV]

Don,
I’m familiar with a few systems like that … insulate both runs, supply and return. You will like it… If you plan ahead the additional plumbing is not a big expense, your return path, and pump can be ‘very’ small.

As to tankless. A commercial applications where a steady ‘quantity’ of high BTU input works well, domestic use it not that common, dose not work out as well… KennyV.

 

[v8dave]

Don, I agree with Kenny. The recirculating pump would be triggering the "tankless" water heater to come on too often.

There is a down side to these high efficiency gas heaters. Since they don't send a lot of waste heat out the flue, on cool down they condense water out on the flue system (the high efficency "pulse" heating units have to have a water drain because of this). This can corrode the vent systems. And, on a system that cycles on and off a lot (like with a recirculating water system) there will be more water produced in the flue eating away the lifetime of the unit.

Recirculating hot water systems are how Hotels manage to have hot water quickly on tap in the rooms. So, it is a fairly common system, just not used in houses much.