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Tankless hot water heating, weird home
Old 05-11-2010, 03:43 PM   #1
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Tankless hot water heating, weird home

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Installed a Paloma unit one year ago in a 1 bathroom house. ....
Biggest problem: Be aware that 0.9 gallons per minute water flow is needed to trigger boiler in unit to ignite at a water temp difference of 40 degrees between input and output. This is not so much a problem in the winter when the incoming water temp is lower. In the summer when the incoming water temp is 70 degrees sometimes you can't get the 0.9 gallon flow with one spigot open. You can't trickle the water at the hot faucet and expect the unit to stay on. ....
Not allowed to reply to a thread so old and crusty, so here's a new thread.

We recently looked at a place in Prescott AZ - a weird one that is really dated and has a number of issues, the water situation among them. It has a well which supplies a couple water tanks that feed the house. There is a 4x8 solar hot water panel on the roof that feeds a 80 gallon tank (may be heating elements in the tank, not sure) - from the tank water goes through an electric tankless hot water heater, thence to the bathrooms and kitchen. I'm wondering if the solar unit might raise the water temp too much to allow the instant heater unit to kick on - leaving the house with a shower that only puts out hot enough water with it's valve in full hot position. I like really screaming hot water if desired - if the supply water is pre-heated by solar to say 95 degrees and the tankless heats between 85 and 125 will the hot water taps mostly output tepid water? Know some of you have tankless - RIT - don't I remember you said you have to leave the hotwater running?

Place supposedly was on Extreme Homes back at some point before 2002 - earth sheltered dome home. Would love to see the tv show spot but haven't found a source or episode breakdown before 2002 for the show. Anyone able to point me at a source?
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Old 05-11-2010, 03:50 PM   #2
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don't I remember you said you have to leave the hotwater running?
I've mentioned that it takes longer for the water to get hot at the faucet with a tankless. With a tank heater, hot water normally diffuses into the pipes, so you don't have to wait as long.

I sure would expect that if you set the water temp to, say, 120 degrees, that if the water is any cooler than that, the tankless unit is going to heat it up.
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Old 05-11-2010, 04:01 PM   #3
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We have propane tankless. It does seem to take longer to warm, but ours kicks on at 0.5gpm I think. The length of time though is (I believe) more related to the distance from the heater to the output faucets. We have two of them because the house is so big, but still seems to take a while. One neighbor put in a recirculating system on a tanked WH for "always hot" water. This was supposed to deal with the distance issue. Instead he had to turn off the system because his floors got too hot in the summer from the recirculating hot water.

I have no experience with an under sink electric WH.

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Old 05-11-2010, 04:36 PM   #4
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The question is an interesting one, but in the grand scheme of things if you've got 3 sq feet of floor space it's not a big deal to replace the tankless heater with a conventional storage heater, especially since it is electric. Heck, if we get the "smart grid", a lot of folks who must heat water with electricity will probably do that so they can heat their water when it is cheapest. You could probably sell the tankless unit for enough money to buy a nice conventional (storage) model. Less parts to fail, and you'd get hot water faster. Not unlimited hot water--but how much do most folks really need?
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Old 05-11-2010, 04:53 PM   #5
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There are solutions to the long-wait-for-hot-water thing, recirculating pumps or something. I recall it has to do with how long a run you have from the unit to the faucet so I do it again I'd go with the standard installation and add that later if needed. We have propane - still inexpensive compared to electric.

Just a couple of weeks ago friends of hours had their conventional hot water tank rupture in their attic, then flood their second floor, then flood the lower level.
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Old 05-11-2010, 04:54 PM   #6
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True, and I expect that the holding tank is just a conventional WH - if it's fed by the solar unit and that is functional it should do just fine energy conservation-wise on its own. Don't know why the tankless is there...
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Old 05-12-2010, 01:22 AM   #7
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The solar should be enough to give you screaming hot water. The tankless is the backup in case it's really cold outside or you use a lot of hot water.

I've vacationed in an Earthship (that's what this is, right?). The solar tank and tankless backup worked fine for 2 people.
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Old 05-12-2010, 05:47 AM   #8
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Fairly common here in the UK to have no hot water tanks at all. We have a small storage unit with the new furnace we put in 3 years ago. It fills the bath up maybe half way before it runs totally off the furnace itself. We also have 2 showers that are just the simple wall mounted elec.showers...works fine for us. Not sure we will have a hot water tank when we move back to the States in another year.
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Old 05-12-2010, 06:12 AM   #9
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True, and I expect that the holding tank is just a conventional WH - if it's fed by the solar unit and that is functional it should do just fine energy conservation-wise on its own. Don't know why the tankless is there...
You can put an electric element in many solar heater tanks as a backup for the sun on cloudy days. Why not check out that option?

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Old 05-12-2010, 07:29 AM   #10
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True, and I expect that the holding tank is just a conventional WH - if it's fed by the solar unit and that is functional it should do just fine energy conservation-wise on its own. Don't know why the tankless is there...
My guess is that the system is set up to circulate water through the solar heater and store it in the tank. When the sunshine is inadequate to warm enough water, it is heated as it is routed through the tankless water heater on the way to the tap. This way if the water is already warm, the tankless heater doesn't need to add more heat, but if it senses that the water is not warm, it adds heat automatically.
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Old 05-12-2010, 08:45 AM   #11
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It doesn't look like an earthship (made with tires in the walls), but has some similar elements.

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Old 05-12-2010, 09:27 AM   #12
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The solar should be enough to give you screaming hot water. The tankless is the backup in case it's really cold outside or you use a lot of hot water.

I've vacationed in an Earthship (that's what this is, right?). The solar tank and tankless backup worked fine for 2 people.
Earth Systems on the house plans - think they are now DBA Formworks Building.
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Old 05-12-2010, 09:34 AM   #13
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It doesn't look like an earthship (made with tires in the walls), but has some similar elements.

Something tells me that these folks have never been to Texas in August.
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Old 05-12-2010, 03:35 PM   #14
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There is a 4x8 solar hot water panel on the roof that feeds a 80 gallon tank (may be heating elements in the tank, not sure) - from the tank water goes through an electric tankless hot water heater, thence to the bathrooms and kitchen. I'm wondering if the solar unit might raise the water temp too much to allow the instant heater unit to kick on - leaving the house with a shower that only puts out hot enough water with it's valve in full hot position. I like really screaming hot water if desired - if the supply water is pre-heated by solar to say 95 degrees and the tankless heats between 85 and 125 will the hot water taps mostly output tepid water? Know some of you have tankless - RIT - don't I remember you said you have to leave the hotwater running?
I think of Prescott as hot & sunny, is that right?

Most solar water heaters have both upper & lower heating elements for the few days each year of clouds/rain (or even snow). One 4'x8' panel sounds about right unless the family is using a lot of water or not getting much insolation.

On a sunny day our tank (also 80 gal but two 4'x8' panels) would quickly go to 180-190 degrees if we didn't have the controller cut off at 165. We also have a thermal-limit valve on the house hot-water pipe that attempts to limit the max temp to 125 degrees.

If the water piping is in attics and ceilings then it might heat up during the day. Some afternoons our "cold" water piping puts out 120-degree water.

Best way to troubleshoot might be to tweak the water heater's solar controller to a lower max temp (or even shut it off) and see how the tankless water heater performs.

Or you could tweak the solar controller to allow 130-140 degree water into the house piping and not have to use the tankless heater at all. But while you may enjoy a screaming-hot shower, your guests (and the housing codes) may be just screaming.
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Old 05-12-2010, 07:20 PM   #15
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I think of Prescott as hot & sunny, is that right?

Most solar water heaters have both upper & lower heating elements for the few days each year of clouds/rain (or even snow). One 4'x8' panel sounds about right unless the family is using a lot of water or not getting much insolation.

On a sunny day our tank (also 80 gal but two 4'x8' panels) would quickly go to 180-190 degrees if we didn't have the controller cut off at 165. We also have a thermal-limit valve on the house hot-water pipe that attempts to limit the max temp to 125 degrees.

If the water piping is in attics and ceilings then it might heat up during the day. Some afternoons our "cold" water piping puts out 120-degree water.

Best way to troubleshoot might be to tweak the water heater's solar controller to a lower max temp (or even shut it off) and see how the tankless water heater performs.

Or you could tweak the solar controller to allow 130-140 degree water into the house piping and not have to use the tankless heater at all. But while you may enjoy a screaming-hot shower, your guests (and the housing codes) may be just screaming.
One of the attractions is that it isn't Phoenix hot or Hawaii humid. About 50,000 people and a nearby Costco. Lots of sun compared to Independence Oregon. Lots of snow too, which is not a good thing, but with a well stocked larder it might be ok. Story is that it melts fast, which was the case back in February when we went through. Prescott, Arizona (AZ) profile: population, maps, real estate, averages, homes, statistics, relocation, travel, jobs, hospitals, schools, crime, moving, houses, sex offenders, news, sex offenders

I'm pretty sissy about really hot showers, but do like the sterilizing effects of burn-your-paws-hot water on dishes and clothes, which has resulted in my banishment from laundry duty. Something about Barbie sized wool sweaters that the girl used to fit in. Suspect that the solar hot water needs some attention - saw a missing wire nut and a bunch of corrosion at that point at a wire junction up by the panel, also missing insulation on the water lines going to & from in that area. Insta-heater may have been a "fix" for something that just needed PMS. Wonder about the effects of freezing nights on the solar unit & associated plumbing.

Found a picture of the place from better days: Hurricane proof, disaster proof, Earth sheltered homes that are environmentally friendly. Nice being able to walk up to the solar heater; no ladders involved.
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Old 05-12-2010, 07:48 PM   #16
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Prescott is a nice sized town with a decent climate: high of 88F in the summer, and low of 23F in the winter. It has grown quite a bit; the last time we visited was 20+ years ago. Just now look it up and see that the median house price is significantly higher than a similar AZ town, Payson, so Prescott is more upscale. And Prescott has a higher population too. I guess many Arizonans move there from the Phoenix metropolitan to retire.
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Old 05-13-2010, 12:56 AM   #17
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One of the attractions is that it isn't Phoenix hot or Hawaii humid. About 50,000 people and a nearby Costco. Lots of sun compared to Independence Oregon.
Do I understand that you are looking to pull up stakes and move to Arizona? Or would this be a winter home only?

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Old 05-13-2010, 09:21 AM   #18
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Unclear as yet. Thought was to get a winter home. Problems with that include maintaining two homes, two property taxes, two utility costs, two sets of everything, moving twice/year, security. Another problem was we like our home a lot - we did it to suit ourselves - while we could get a very nice second home in a place with plenty of winter sun pretty inexpensively it would probably be a tract home - very comfortable and trouble free, but not our style. Once we start getting into interesting places the prices start getting sturdy. I can imagine living in a place worth maybe 200, 250, but having 500 in housing just feels wrong to me. No Robin Leach caviar dreams here. We're more a catch your own sturgeon and harvest your own eggs couple. Considering a full time home allows us to look at places that have more potential.

Oregon is a great green place, but people are people anywhere. Haven't found any place that didn't have friendly folks. The last 5 weeks in motel rooms taught that we are fairly self sufficient. We are down to two cats, one pretty old. The guy I have managing the rentals is working out. Might be time for a move and a new project.

Health insurance is an issue - we have Kaiser Permanente at present and AZ doesn't. May be a huge sticking point.
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Old 05-13-2010, 11:01 AM   #19
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Suspect that the solar hot water needs some attention - saw a missing wire nut and a bunch of corrosion at that point at a wire junction up by the panel, also missing insulation on the water lines going to & from in that area. Insta-heater may have been a "fix" for something that just needed PMS. Wonder about the effects of freezing nights on the solar unit & associated plumbing.
Yeah, rusty wires are probably not helping. Insulation tends to lose its UV resistance after a year or two and then crumble, unless it's painted. Sometimes there's so much heat transfer that the insulation isn't mandatory, although it does reduce efficiency.

If there's a risk of freezing then the system should have been designed to drain back into the tank at night or it should use some sort of anti-freeze as its working fluid. If it's the latter then the water heater is actually a heat exchanger instead of just a fluid tank. Heat exchangers can eventually corrode and leak, especially if neglected, but I think the anti-freeze is required to be non-harmful to humans. As far as we can tell.

Hopefully nothing was damaged by freezing weather. You have the mechanical/electrical skills to figure out what's going but it might need professional repairs.
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Old 05-13-2010, 08:40 PM   #20
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Lots of sun compared to Independence Oregon...
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Unclear as yet. Thought was to get a winter home. Problems with that include maintaining two homes, two property taxes, two utility costs, two sets of everything, moving twice/year, security...
Yes, one thing about AZ is that even where our boonies home is, we often have sunny winter days. However, I looked up Independence, OR, and saw that the winter low is 33F, which is not as cold as Prescott's low of 23F. It would seem to me that for a winter home, one might want a warmer place at a lower elevation.

Or, perhaps all you need is an RV to drive around in these lower states in the winter. It can be less expensive than a house, and satisfy the urge to wander at the same time.
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