using an electric tankless water for heating small apt???

Question

Has any one tried using an electric tankless water heater for heating ????

I have 1bd 600sqf unit the heat calculation calls for 25k btu, NO boiler is made below 50k, I have radiant pex in floor heating, so my temp can be set to 120-130.

I hear that electric tankless water heaters are designed to take cold water and bring it up to 120 or whatever your setting is max 140

but with radiant after awhile my return will be 110 and going back out 130 using very very few amps to heat those 20 degrees but how long will that last ?????

or are they capable of taking on hot water and heat it even more ???

Johann Jells · Answer

Mike, you keep quoting btu's vs watts. Means nothing to me without my looking it up. But the reason I said use a heat exchanger is because you have radiant installed, and a water heater installed. The water heater should be run at 140 (you know that right?) and have a temp mixer for domestic water. So were you to use that water heater to heat the unit you need a unit like I linked to provide radiant temp water. If electric really is cheaper ditch the gas unit and install an electric one. Why have 2 devices when one will do?

Mike Row · Answer

Why do people jump to conclusions faster than they could blink with their own eyes????

Lets just focus on the main question I asked: " the use of an ELECTRIC tankless water heater as a source of heat"

lets read that very slow.... pause,,,,,, process,,, think...... then respond.

I am not interested in baseboards,boilers, heat exchangers, 180 degree temp, heat pumps, mixers etc......

Process the information Small APT 600 sqf why should I have a (lowest 50k btu boiler to heat the unit) when only 25k needed????

Why would I put a heat exchanger??? in a small unit burn 50k to reduce temp???? those are only good if you have a LARGE house and you want to have a driveway melt or something you would heat exchange antifreeze from main heating unit.

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I have propane currant rate $2.20

if you have natural gas its twise less around $1.50 per 1 mill of btus or whatever the calculation is

electric .12 cents per watt

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Small APT 600 sqf not a penthouse over 3k sqf

looking for EFFICIENCY in heating cost effective way

Johann Jells · Answer

Sorry, I couldn't follow your cost analysis as to why electric is cheaper. But if you already have a water heater why not just put a heat exchanger on it and be done? The unit below is all you'd need.

http://www.tacocomfort.com/products/systems/radiant_systems/radiant_mixing_block_rmb-1/index.html

Roger Garnett · Answer

A tankless water heater isn't designed for continuous duty cycle, or recycling the water, but for quick heatups. A guess without looking at the specs, but they probably wouldn't do well in that environment. Water heaters are also designed for lower operating temperatures than a boiler. Plus they don't include re-circulation pumps.

Plus - if you are using electric to heat it, for that small of a space, you might as well heat the air directly with an electric heater unit or baseboard, and not suffer the energy loss heating the water.  Another electric heat option  - an heat pump stye air conditioner  with a heating mode. (be sure it's rated for 20 below +, some quit at like -10 or so.). A win-win - tenant gets AC, pays for heat & A/C themselves.

Mike Row · Answer

sorry I coudnt help it myself the formula is 150k divide by 90k = 1.6 times $2.20 = $3.66 an hour

Mike Row · Answer

1. domestic hot water comes from a tankless GAS water heater

2. Yes I have gas, propane

3. I think youre missing the point here.

I asked about heating small APT with an ELECTRIC tankless water heater since it uses less energy to heat WARMER water, in other words if incoming water was 120 and return was 130 only 10 degrees not much energy needed to bring water to additional 10 degree.

propane is expensive todays rate 2.20$ a gal summer was 1.80$ gal using a tankless GAS water heater min 150k btu propane uses 90k per 1 galon so that 150k boiler costing you $1.60 an hour of operation . (im just rounding numbers out of my head not actual calculations if any one wondering)

etc....

Johann Jells · Answer

Where's your domestic hot water coming from? Do you not have gas? Electric for an Ithaca winter sounds expensive. I have several units heated by standard tank water heaters running through baseboard radiators. They also provide the hot water. For radiant it would be simple to add a heat exchanger. I've been told I should do that anyway for health safety.

Peter B. · Answer

Great question! I looked into this when I was considering building a new complex.. After a lot of reading and research they really wouldn't keep up in wisco winters. I did read the reviews of one builder who built a large complex in missouri,they had no issues and it was an easy and cost/space effective way to heat there units. .. It seemed to work there...