Water Heaters

[coleman]

What size water heaters are being used in the 14x24 plans?  Thanks

[Redoverfarm]

Not being familiar with the plans I can say that any water heater size is based on the amount of hot water that you plan on using and the amount of space that you have to incorporate it into the mechanical area.  I do know that if you have a couple of teenagers (love to stay in the shower) and do a lot of laundry(teenagers clothes) that a 30 gal will probably not cut it.  I am not up on the new "tankless heaters" but they do take up a lot less space and only heat up what the demand is.  Maybe someone else on the board will shed some light.

[glenn kangiser]

The tankless are nice - a little touchy, but will provide continuous water.  A small one may only serve one fixture.  We have the Bosch HX125 - which has since been superseded.  It will do one major and one minor at one time.  It generates its own spark to light the pilot so saves about $100 per year by not wasting pilot fuel.  Pilot is off when not in use.  No standing pilot.

They are not interchangeable for LP or natural gas so be sure you get the right one from a dealer who knows what they are selling you.  Anybody want to buy a natural gas one with one small shipping dent? :-? :-/

[Preston]

I'm looking for the specs that I saw, but it seems that some of the smaller Electric Tankless that are meant for just one room such as a bathroom or laundry room, are more cost effective than that gas tankless.

[glenn kangiser]

The electrics pull a lot of juice though.  Check amps and wire sizes.

A whole house electric water heater could double your A/C requirements for the whole house.

[MountainDon]

Considering the relatively small floor area I would think tankless would be the way to go. Of course tankless also has the advantage of saving energy. As far as electric vs. nat. gas/propane that partly depends on what you have access to. You didn't note if you were grid tied or not.

First you need to decide on fuel type: electric, propane, natural gas.

If you choose electric, do the research and see what the electrical requirements are, voltage, current draw.... If you choose n.gas or propane look for a model with no pilot light. Some of the Bosch don't even need electrical hookups for the igniter.

Then you have to decide what flow rate you need. Tankless water heaters are rated on xyz gallons per minute at a certain temperature rise. If your water is colder at some times of the year, like my city utility water in winter, use that as the low temperature. Then pick what size heater you would need. I have seen some cottage sized, low flow, units that are not recommended for shower use.

Depending on your climate you may be able to mount a tankless on an exterior wall to save interior space. That's dependent upon your lowest anticipated temps.

One thing to look for with a tankless is how easy is it to drain the water in case you leave the building vacant in freezing weather. I heard, but can not confirm, that some are more difficult to winterize than others. If you find more info re that please post it here.

As for any kind of water heater with a holding tank, I believe the only thing they have going for them is initial purchase price.

OMMV

[John_C]

I spec'd an electric on demand water heater not long ago.  If memory serves me it would do 1-major and 2-minor outlets.  It needed Three 40A, 240V circuits.    If I was installing one I'd try to keep the run to the breaker box as short as practical.  That wire would add up pretty quick.  It made me go back to looking at propane water heaters.

[ScottA]

Tankless is the way to go if you can handle the up front cost. I'm going to go with propane and hang mine on the outside. Anyone building a cabin that needs to be winterized should install a port at the lowest point possible in the main waterline and rig it so you can blow all the water out of the system with compressed air by opening all the faucets one by one. I usually had to add this when I winterized houses for people. Compressed air is the only bullet proof way to be sure all the water is out of the system. BTW I'm a master plumber for over 25 years.

Scott

[glenn kangiser]

Good to have a plumbing pro here, Scott.  I just did enough to be dangerous.

[Redoverfarm]

Scott  I will need some advice later on exactly what I need to do to use compressed air to purge my water lines as my cabin will be drained in the winter.  Short of running the plumbing on a slight angle toward a downward flow (not always easy) that would be a sure fire way.  I have already situated a floor drain in the basement near the HWH and pressure tank for this purpose.

[MountainDon]

Anyone building a cabin that needs to be winterized should install a port at the lowest point possible in the main waterline and rig it so you can blow all the water out of the system with compressed air by opening all the faucets one by one. I usually had to add this when I winterized houses for people. Compressed air is the only bullet proof way to be sure all the water is out of the system. Scott

That's what I do with the RV... I have a small air compressor permanently mounted inside to make the blow out easy. Turn it on, open the air valve and open and close faucets one after the other, open and leave open the low point drain. Any tips you can think of to make it the easiest thing with a small cabin? How about waste lines... any ideas other than RV type anti-freeze?

For the cabin I'm thinking of going with PEX for supply lines.  ??

[ScottA]

Best I can offer for ease Don is to make it easy to get at. It really needs to be in the lowest possible location so you can leave it open like you said so any remaing water can drip out. I usually installed a boiler drain and then used a rig I made fom some fittings air valve stem and an adapter to screw on it like a water hose does. They do make traps with drains if you can find them and get at them but the best way I found to do it is to suck them dry with a shop vac. Wrap a wet rag around the end of the hose so you get a good seal and the water will come right out. Don't forget the toilet tank and trap.  If you are on a city sewer the anti freeze option is the only good way to keep the stink out.

Pex is fine just be sure to use the right fittings for the brand of pipe you get. Copper or brass fittings are best.

Scott

[MountainDon]

I never thought of the wet/dry shop vac.    I have a small "spare" one I won someplace.

[Preston]

Is the whole house drain needed for a place that won't need to be winterized?  It's never been necessary on the projects I've worked on in the past, we just let everything drain.

[peter nap]

Well Scott, since your here, might as well pick your brain. Mine gets a little scattered sometimes .

On my water system, I have put am electric irrigation valve on a timer, at the low point. When I leave for the weekend, start the timer and let it drain. The prototype system I made to test works great.

I plan on using a tankless hotwater system though. Propane and I haven't picked a model yet but am going to look hard at Glenn's Bosh.

My concern with it is twofold. First, it was mentioned that draining them was difficult sometimes and second, the igniter. How do I position the unit so it will drain by itself when the electric valve is opened. I had planned on mounting it under the house to be on the low side of everything. with a 45 degree slope from the unit to the drain location (which is in a covered pit)?
Second, is the ignitor going to try to fire even with the gas off and the water drained?

[ScottA]

Preston a drain is not required just suggested to save trouble later.

Peter that sounds like an interesting idea but how do you relive the vacum in the lines (open faucets)? The tankless needs to be blown out since it has a coil inside it might drain it might not and flow triggers a tankless to fire, no flow = no fire but I'd turn it off anyways.

Scott

[peter nap]

The idea until you posted was to open the faucets. Since the coils on the HW side need to be blown out, I think I'll put fittings on the air chambers and connect a small compressor to run on the timer also. I'll have to put a check valve at the top of the chambers to keep the water from flowing up during normal operation, but I have a couple dozen somewhere.

[fritz]

I've glanced through the archives..but need some help with this.  I'm looking at LP and I'm running into price/ size issues.  What I *think* I understand is that the Bosch 1600 and 125 (for example) rely on internal air for combustion (not a separate air intake).  Since the 14 x 24 little house with a 12/12 pitch foor is roughly less than 4,700 cubic feet, this ends up being an installation in a confined space (or did I miss something?)  The Bosch 125 requires 6500 cubic feet based on the manual: 50 cubic feet per BTU hour

So with that, is there a reasonable way to vent bring in combustion air for this?  Or is not not a real concern?  Or do I need to step up to a larger unit with both intake and exhaust flues?  A straight air vent would just bring our frigid Iowa winter into the cabin

ANy thoughts anyone?

[MountainDon]

The 1600 series manual seems to be quite explicit in stating the combustion air requirements. Unless you're going to build an air leaky version of the 14x24 that could be a problem.

I noticed that a while back as I'm planning a 14x26 version of the little house. I haven't decided upon my final course of action. I dislike the idea of spending more money for the larger 2400 unit just to get the external combustion air feature. One of the hazards that could arise is the downdrafting of air through a wood stove chimney (to replace the air the water heater used).

The Vermont Casting Aspen stove I've selected has it's own air feed. However, there's the possibility of the 1600 water heater drawing enough air on a burn to cause a downdraft anyways. 

I have not yet looked into other brands of supply on demand water heaters to see if anyone else has a smallish unit with an external air supply. Maybe someone else has and can fill us in.

If I come up with something I'll post here.

[fritz]

Thanks, I'll do the same.  I thought I was probably in familiar territory for someone.  I'd like to buy before year end and take advantage of a $300 tax credit this year.  But no need to rush and buy the wrong thing.  I'm also looking at a direct vent gas stove, the small Garnet from Quadrafire.

[MountainDon]

Rinnai has a small gas water heater, the model R53i that has a sealed combustion unit and uses no interior air. $1003 MSRP. It uses an electric igniter unlike those Bosch.    It requires 120VAC for operation.  It does have what appears to be separate air intake and exhaust vents.

[glenn kangiser]

You could just do as John mentioned in another post - give it a little room on the side insulated with it's own little exterior door - sided to match the house if you want - intake air vent through the door.  5" roof vent on the 125 as I recall -- I'm running mine on an outside wall with no vent but in the uphill patio - under the greenhouse.  The local hardware guy put his in the attic -- no vent -- and he is a fireman.

[Dustin]

Make sure that you put a couple of the large sediment filters at your incoming water source line. Gunk in your water will clog up your demand water heater very quickly-  the heat exchanger precipitates the gunk out, causing your system to fail.
I'm talking from experience here.
You can buy the big heavy duty filters at home depot. I saw some unit there the other day that backwashes itself, but it costs $300, so I didn't bite. But it may ultimately be chaper after replacing enough filters.
   

[glenn kangiser]

Some stuff I have read says a lot of that can be eliminated by running the heater only as hot as you need it and not extra hot as more problems occur with higher heat. 

We set ours fairly low - not scalding as it will make all the water at that temp that you want to use. 

[fritz]

I found this Rheem RTG 53 DV (as in direct vent) that looks like it might be a good option, too

This is one of several sites
http://www.cporheem.com/residential/1-2_bathroom_homes/direct_vent_tankless_water_heater/rtg-53dvn.html