Stick N Brick Demand Hot Water Heater

MEXICOWANDERER wrote:

• This would apply to stuff that has tires so I do not feel guilty asking
• First of all incoming water temp would average 45F at the coldest
• This would be an LPG unit
• Must demand water heaters be protected against "the elements"? The piezo ignitor being the issue
• No danger of freezing
• Need enough hot water for shower or dishwashing, not simultaneously
• I've seen several economy models. I am suspicious until proven otherwise
• Lime and scale buildup is a concern. Water harder than a whoopee lady's heart
• We have Bosch heaters
• What is your idea of the recommended Delta T of 70F?

70F Delta T might be obtainable provided the GPM is low enough.

Bosch Therm 830ES can be mounted outdoors provided you buy an outdoor mounting kit which is not included.

Bosch Therm830 specs

Has 35F rise for 8.3 GPM, 55F rise for 5.3 GPM, no spec on 70F rise and min draw required is .5 GPM.

Will need good propane supply, 175K BTU burner input will most likely require replumbing the gas line from 1/2" to 3/4 and upsizing your propane regulator and possibly tanks to handle that draw.

Efficiency, is a measly 82% so your not going to save much if any on propane costs.

This model does require 120V AC to operate, at one time they did have one that used drycells...

Weighs in at a whopping 67 lbs and about 18W x 32H x 11 deep..

At $1250 US, it isn't cheap and that does not include the option outdoor kit..

Therm830 at Amazon

We looked at demand water heaters a few years back and the Home Depot sales guy actually dissuaded us from considering them.. Too many potential issues..

#1 cost. They are insanely expensive compared to conventional tank systems.

#2 Variable water temps according to water flow

#3 Min water flow of .5 GPM just to start the burner.

#4 Re plumb 15 ft of gas line from 3/8" to 3/4"

#5 Scale/lime buildup (we have very hard well water and even with a softener faucets still get build up).

#6 Requires periodic Scale/Lime cleaning.

#7 multiple taps in use at one time requires upsizing unit which is costly.

#8 Hot/cold/hot/cold/hot/cold endless cycle if you are not drawing enough water and or using well or water pump setup.

#9 Repairs may be insanely expensive and or parts not available making replacement the only option in many cases..

#10 required upsizing our exhaust flue from 3" to 5", adding yet another huge expense in double wall vent pipe.

#11 Required yet another re-plumbing of the water supply lines.

We opted for another tank system instead.

Have been looking at those for some time. Nice concept, as long as it works. More things to fail than in old-school tank heater, water flow sensor has to be very accurate. Can't justify the cost, compared to regular heater @MXN 3000/ USD 150 that will likely work for more than 5 years.

Thanks for the tip with vinegar and baking soda.

As an aside a vinegar-only flush is next to useless. It's when dissolved baking soda is used after that, radical cleaning takes place. Try it. People who are not chemists come up with "Use vinegar OR baking soda then flush".

I have the bosch as well.
I live in Los Angeles, so I don't have the hard water problem other allude to.
Mine is exterior mounted; however, it's using the same flue path as the original water heater used before I replaced it.
As others have stated, you can't run the water slowly (from my own observation, the heated water exceeds the hi limit cut out and then turns off the burner until it's cooled back down sufficiently).
This problem applies to flow restricted shower head(s) as well.

I have seen demand Wh's that are designed to mount outside on an exterior wall, so no venting or exhaust piping required.
The mineral scale may be an issue, they sell "descaling kits" that consist of 3 way valves so you can thread on a hose and pour vinegar through it to dissolve the scale.

drsteve wrote:
We have had a Bosch Aquastar 125000 BTU LP on demand for ten years, and love it. We're on a well, WP is in the 45-60 psi range, roughly 4 gpm delivery. Your supply water is about the same as mine tempwise. No worries there, your tap water will be plenty hot. Don't use faucet flow restrictors, they cause problems with temp fluctuations--these things need a decent flow rate, or the burner throttles back or shuts off.

No idea about the elements, mine lives in the basement.

I use a water softener, and I'm convinced it's the only reason the Aquastar has lasted for over a decade. Lime and scale are the kiss of death.

He is right about the lime and scale. I've talked to several plumbers and plumbing supply owners about the pros/cons. If you have even slightly hard water, you need to add a softener unit ahead of the tankless WH. Otherwise the WH won't last long.

If you have a city water supply (anywhere it gets cold) the cold water temp will drop to near freezing, requiring a big WH to get the necessary heat rise. Well water is nearly constant temp, so that is less of a problem.

We have had a Bosch Aquastar 125000 BTU LP on demand for ten years, and love it. We're on a well, WP is in the 45-60 psi range, roughly 4 gpm delivery. Your supply water is about the same as mine tempwise. No worries there, your tap water will be plenty hot. Don't use faucet flow restrictors, they cause problems with temp fluctuations--these things need a decent flow rate, or the burner throttles back or shuts off.

No idea about the elements, mine lives in the basement.

I use a water softener, and I'm convinced it's the only reason the Aquastar has lasted for over a decade. Lime and scale are the kiss of death.