solar hot water problems

[machmeter62]

In our main solar closet are two tanks, each with a 100 gal capacity or more? Recently our pilot lite failed on the propane heated tank, and no possible re-light was successful! We assumed with this Northern Calif. climate, the solar system would be able to handle the hot water situation? However, we were also told that the "propane hot water tank" must have hot water greater than 100 degrees before allowing the solar system to function? Is this activated inside the tank thermostat, or else where?

If this is true can a plumber bypass or re-route the system without heating the propane water tank first to that minimum temp? We have a solar monitor in the home that monitors the water temp, but at this stage, a 170 degrees on the roof, and more than 110 at the propane water tank, but no hot water in the pipes leading to the propane water tank?

Thanx in advance for your help.

 

[MtHam]

"However, we were also told that the "propane hot water tank" must have hot water greater than 100 degrees before allowing the solar system to function? Is this activated inside the tank thermostat, or else where?" NEVER HEARD OF THIS!

I too have a similar system, the water from the panels circulates through the 1st tank which feeds the standard hot water heater (HWH). If the water coming from the 1st tank is cooler than the thermostat setting on the HWH, then the propane burner kicks on.

Sounds like you might simply need a new HWH. Otherwise, more details of your system layout are needed.

 

[MikeD74T]

mach, You're missing several factors to get a good answer. Does your solar directly heat water or is it a closed loop system. Does your solar tank serve as a preheat tank to the gas fired tank? Are there circulator pumps involved?
I had a close loop solar setup that heated a preheat tank so my propane gaw HW heater was fed with 180 degree water when there was enough sun. The solar instrumentation only controlled the first tank/circulator pump. Depending on how you are plumbed you should get 100% solar in the California sun in summer & at least 50% spring & fall. Can you post some pics? MikeD74T

 

[Egon]

Does the propane heater have a thermocouple on the pilot light? If so this may need changing or cleaning.

 

[machmeter62]

Thank you gentlemen for the replies. The blankets are about 6" thick around the two tanks, and difficult to un-clutter. I think the system is a closed loop? A couple of years ago a freeze valve failed and was dumping a constant small flow of water off the roof; we had no loss of water pressure anywhere....closed loop system? There is a jungle of plumbing on top of the tanks with many valves and no labels. Part of this problem is we use this system for a indoor spa also, but the spa system was added during construction of the home. This system creates several valve movements.

This entire project was installed in a new home in '85 by "Creative Energy," and they left the solar system business, I think?

I would like to send photos, but haven't made that transition to digital cameras yet!
I will try to post a mental picture of the plumbing, but again that maybe be difficult, because of a adjacent furnace located next to the propane tank. I may have to go under the home to find the in-coming water line to the propane water tank. To replace that propane hot water tank will require removing the furnace out first....it's that confining!

 

[machmeter62]

Mike,
I will start un-covering the tanks soon, sofar the only clues for the routing is the two pipes to the roof for the solar panels cold up/hot down with temp gauges and levers too, and adjacent levers for the the spa if wanted. Then the water heads to the large storage tank that has an independent 3/4" GRUNDFOS pump to recirculate the water there. This is located midway down the side of that tank, but the pump has failed. A recent solar service man looked at the situation, and said it's not needed? But no thoughts on how to by pass that 100 degree "fictious" (start-up) problem?

Today with temps in the 60's we had 143 degrees at peak coming from the roof panels. If this is a closed system, how is water ever added after a freeze plug/valve failure, or is that connected to the domestic water line to the home somewhere? Maybe the solar system needs filling to solve some issues?

I was away from home alot when this project was under construction, and regret not having any diagrams or manuals explaining problem solving.

 

[machmeter62]

EGON,
I only recall one successful lighting of that propane water heater. It takes a long special match, or long narrow pliers with a lighted match to reach into that slim cone area for ignition. It has no visible thermocouple, but that is a good point for replacement?

Everything designed or built in this century is passed through a "legal/eagle" office first, to avoid lawsuits?

 

[machmeter62]

MtHam,
We live on the Eastside of "Big Rock Ridge" and our propane server is/was until today when we were going to order more propane. I don't know if this is a new threat, but after my wife talked to McPhails, our server, they now charge in addition to the fuel purchase.....$85 dollars to re-light the propane tank!!

 

[MikeD74T]

mach, As you uncover, look for wire following the pipes. pumped systems usually have a controller with temperature differential sensors (thermistors ??) that sense & compare temperatures at different locations so hot water is not pumped in the wrong direction. You may merely have a bad thermistor. Sometimes you can test thermistors by reversing them & pump will run all the time, depending on your setup.
As for the gas HW tank with a pilot flame, there's a good chance that you just need a new thermocouple. Available at hardware stores , easily changed, & relight should only take a couple of minutes. $85 seems like a lot for the task but it can kill a couple hours for a technician including travel time. MikeD74T

 

[machmeter62]

Mike,
I checked the control panel at exactly mid-night Sunday after a 'mid-sixties" temp. spring-like day here. The panel displayed 110 degrees at the collector, and 110 at the storage tank also. I will get a new thermocouple and report back....it may take awhile....I am always behind the "power curve!" We tried to get hot water, and still locked out, and a new thermocouple with a lighted pilot light will solve the problem.

 

[machmeter62]

Since there is no propane getting to/near the thermocouple...it's now a gas valve failure. This is the original 25 yr. old gas control valve too. All of the procedures were followed for lighting, and a very-very faint smell of propane only, after holding the start button for several minutes.

 

[MikeD74T]

I've cleaned propane valves on occasion. There's orifices & sometimes strainers that get clogged with a flaked silvery material (like graphite ?) that can be easily be blown out with air. Just pay attention to relative part locations & orientations as you take apart/reassemble. Also take some pics as you disassemble. There may be simply a plugged inlet strainer where the tubing enters the valve body. MikeD74T

 

[grsthegreat]

are you saying the tanks are 25 years old????

i didn't think a water heater ever lasted that long. I replaced both of my propane high efficiency water heaters 3 years ago. been working on them ever since. The new electronic ones are soooo sensitive, if they sense an odor like gas, they shut off. problem is, the units are in garage, and cars smell like gas when starting. The water heaters are constantly needing to be reset. Gets real old at times.

I miss my old trusty pilot light units. tried and true, and nearly trouble free (cept for yours)

 

[Raspy]

Thank you gentlemen for the replies. The blankets are about 6" thick around the two tanks, and difficult to un-clutter. I think the system is a closed loop? A couple of years ago a freeze valve failed and was dumping a constant small flow of water off the roof; we had no loss of water pressure anywhere....closed loop system? There is a jungle of plumbing on top of the tanks with many valves and no labels.

Since you have a freeze valve on the roof, and since you are in California, with mild climate, and since the system was installed in '85, I'd say it has recirc freeze protection. This means the water in the solar tank circulates directly in the panels and then also recirculates if there is a chance of freezing.

In your case, until you get the propane tank fixed, just bypass it and run directly on solar. The valves you mentioned on top of the tank are for that purpose and were required for the tax credit during the '80s and will probably allow you to bypass the propane tank and run solar tank water straight to the house. Just follow the flow from your source to the cold on the solar tank. Then from the hot on the solar tank directly to the house instead of into the cold side of the backup heater. There is probably an anti-scald valve there to, so don't let that confuse you.

Then fix or replace the propane tank.

I have never seen or heard of a system that required a minimum at the backup heater as you describe. Forget that and look for a bypass.

Next thing is to look at the freeze protection system. You probably have recirculation freeze protection supplemented by a Dole freeze valve on the roof. Recirculation freeze protection is unreliable, inefficient and likely to cause a serious freeze up and damage to the collectors. In your case the freeze valve you mentioned is also not very reliable and is generally used to supplement the recirc system, or used on it's own.

It's not possible to say how much you should be getting from the system without much more information about it and your environment, but it probably will give you adequate hot water in good weather until you can get the backup fixed.

 

[Raspy]

As far as re-lighting the propane tank is concerned, you mentioned a faint smell of gas after a few minutes of holding the button down. It sounds like the pilot orifice is clogged or a spider has moved in or something. Not too uncommon and pretty easy to fix by taking the burner apart and carefully cleaning the orifice and pilot burner assembly. The thermocouple won't prevent you from lighting the pilot and it won't control the size of the flame. It only senses the existing flame and generates a current to keep it on after lit. The pilot flame must be big enough to adequately heat the thermocouple, and in turn, cause it to send a potential to the gas valve which will then hold open the pilot circuit. If the thermocouple looks burned up on the tip, replace it with one from the hardware store for a few dollars. Easy to do and cheap.

 

[nike]

Propane as with any fuel is dangerous to work on if you do not know what your doing...
HIRE A PRO.
If the tank is 25 years old have it changed out.
or/ have a pro look at it $85.oo is cheap compared to replacing the house...
or your life.

 

[handirifle]

The OP said he lives in northern CA, their climates can be anything BUT mild, depending on where he lives. Mountainous areas are as cold as many northern states. I live in the central coast region of CA, about 10 miles n of San Luis Obispo, and I got 1/2" of snow/sleet Friday. The ski mountains near Fresno, have a 15ft base of snow. everyone thinks the weather in CA is all beach weather.

As for the freeze protection, I was here for many solar installs in the 80's and most I saw used the "drain back" or drain down systems. The systems had a vacuum break on top and the collectors would drain completely when temps got below 40 deg.

Does the system in question, have a line from one of the valves that leads to a drain? If so that is what you have, most likely. I cannot imagine a solar system that "doesn't need" the circ pump, unless it's a batch system, with the tank on the roof.

The gas valve system is no big deal to remove and repair. I got my associates deg (many years ago) in heating/ Airconditioning and refirgeration, and then worked as a service repairman in the field for the next 5years, before getting hired on as an air traffic controller, in 1982.

You should be able to remove the valve/burner assembly as a whole unit. It's easy to see the pilot opening and look into it with a flashlight. To clean it, it's best to disassemble it from the aluminum or steel (they used either one) pilot line, and then remove the orifice. Use wrenches to back up the nuts when loosening, to prevent from twisting the pilot line. The orifice may or may not be threaded in. When cleaning, use a soft bristle brush, like a tooth brush, NEVER a wire brush. Also use compressed air. never insert anything into the opening in the orifice. If it gets enlarged, it can overheat the thermocouple or worse.

Reassemble, and relight.

If all that sounds like too much, then as mentioned above, call a pro. in the 80's all systems, I ever saw, the gas hot water tank was really an independent system, in that it simply would only turn on the gas burner, when incoming water temp was BELOW the min setting for the gas tank valves design. In other words, if the gas valve was designed to open at 100 deg, and turn off at 130, the gas valve would not activate, ever, as long as incoming water never dropped below 100 deg. The quote you gave above, sounds just the opposite, of normal design, and I suspect you either misread or misquoted.

If the storage solar water tank temp is 110, then I doubt your gas hot water heater will activate, even once the pilot is relit.

As mentioned before, after 25 years, it might be time for a system upgrade/overhaul.

 

[Raspy]

The most important clues to his type of system are these two statements: A freeze valve failed and was dumping a constant flow off the roof. And, at midnight the collector temp and the storage temp were both 110 degrees.

This usually indicates a recirculation freeze protection system that is still working, and a freeze valve that worked and then could not shut off.

Typical for that era system.

These are not the kind of systems that are put in a severe area, like Lake Tahoe for instance, but more at lower elevations. They are cheap to install and, with a bit of luck and maintenance, can go on for a long while with low overall efficiency. The drain down systems had many problems with the draindown valves. The drainback systems can't pour water off the roof from a freeze valve and they have a third tank or a non pressurized tank. Closed loop antifreeze systems also cannot pour water off the roof because they have a limited supply of antifreeze in the collectors.

He does have a circulation pump because the tank is below the collectors and he can read the two temps on a controller. The "recirc" I was referring to is a freeze protection system that recirculates solar hot water to the collectors to keep them from freezing. This is why they are prone to failure and less efficient.