Harris hydro field adjustment

[joe8120]

I have been running a Harris hydro turbine for several years and it works very well. Head - 45 ft., Flow - max 30gpm in winter and spring, minimal/no flow in summer, about 210 ft. of 2 in. pvc penstock. The turbine is the permanent magnet version, wired for 24V, and I usually get about 120 watts during max flows. A few questions:

1. I have read the manual on the field adjustment and don't understand the purpose of the adjustment or the instructions in the manual on how to adjust. Under what conditions would you adjust the field? I have a key which looks like a chuck for a drill and I know you insert it somehow into the turbine probably when it isn't spinning. Other than that I'm at a loss. If possible, keep the comments simple as I am not an electrician.
   
2. The turbine is single nozzle. How difficult is it to add another nozzle? I can get another nozzle tube and it would seem that I would have to drill out the blank where the tube is placed. There also are several screws and what appears to be caulking material in the existing nozzle tube to keep it in place. Or perhaps I should send it somewhere to get another nozzle tube installed. Another nozzle would be helpful in adjusting the flow into the turbine as well as increasing the flow during high volume times of the year.
   
   

Thank you. Great forum.

Joe

[Flux]

I don't know your machine well enough to tell you how to adjust the field. If it is wound field then it would have a rheostat. Some of those are permanent magnet and if you have a key it is probably used to alter the air gap or a magnetic shunt.

The idea of altering the field is to get the turbine running at optimum speed where it produced maximum power out. This would mean setting the field so that it runs on load at something like half its no load speed. You could just tweak it for maximum current.

I would imagine that fitting a second nozzle would be fairly straightforward. You would just copy the mounting of the original one and aim it as for the original. You may have to f drill the casing as you suggest. You will need a manifold to feed both nozzles with the full flow available, the restriction ( and speed increase) must come from the nozzle itself.

I would expect someone here to know about how your key changes the field but if you can give a link to the details you have I may be able to sort it out.

Flux

[hydrosun]

The turbine has to be shut off to adjust the magnet strength. The chuck key is inserted in the large hole on top to engage the gear teeth on the inside top of the rotor.  You turn it one direction, turn the water back on and see if the power output increased. If so, shut it off again and see if moving it more in that direction will increase the output more. If the output goes down, then move the key in the other direction. So it is a matter of trial and error to find the point where the output is the highest. If you change the size of the nozzle or number of nozzles you may have to adjust again. Sometimes the difference is so slight that I don't bother to change the magnet setting.  You must be sure that the three set screws on top of the rotor is loosened before attempting to move the gearing. Looking through the top you should be able to see these set screws and then insert an allen wrench through the three small holes in the top cover to loosen them. If you still can't move the gearing you may have to take off the top cover and oil up the gearing. Sometimes when they haven't moved for awhile they get rusted.

 Yes you can add extra nozzles to your turbine. I've seen an unit that was so modified. Aiming correctly was always a problem.  It would probably be easier to send it to Don Harris to have him add them for you. He has the parts and can drill and tap for the set screws to accurately aim the tubes and nozzles. I can get you the phone number if you want it. He's semi retired now so he has someone else do most of the new manufacturing of turbines, but will work on old units.

Chris

[joe8120]

Thanks. The manual was not very clear as to the process of the adjustment. Using a calculator that I located, it seems like I may be getting as much power as possible from the turbine and 1 nozzle but I don't mind trying to experiment to see if more is possible. I know that during high water flows, there is quite a bit of excess water flowing off of the intake but the turbine only has 1 nozzle available. In hindsight, I should have ordered it with 2. Despite this, its amazing how much power can be generated over 24 hours.

I knew that Don Harris has gone into retirement but didn't know that he would still work on units. He would do a much better job than me in adding a nozzle. I would appreciate his number. What is the best way to get it from you?

Joe

[hydrosun]

Since Don used to advertise his number in HomePower magazine and is in all the old magazines I feel OK with putting his number here. Don Harris phone number is 831-425-7652.  I need to get in touch with him about some nozzle tubes that are corroding, but I heard on the news that a forest fire is in his neighborhood so I'm waiting a few weeks. He's always very helpful and low key about anything I've needed in the past.

Chris

[joe8120]

Thanks, I'll wait a little while and give him a call. I'm assuming that you have the same turbine as mine. I'm curious how long you have had the turbine and the life of items like nozzles and nozzle tubes. I've mounted mine in a plastic olive barrel and it seems to be holding up well but I've only had it installed for about 3 years. It is used 3 or 4 times per year depending on how many times we visit and stay there.

Joe

[hydrosun]

I've installed over a dozen Harris hydro systems over the past 10 years. I've only had to replace a few bearings so far. The baffles on the shaft keeps out the water from the bearing better than the old systems and the bearings seem to last longer. Some systems over 5 years without replacing. I tell people to see if they can wiggle the pelton wheel. If not leave it alone for another year.  Did have a few problems with some of the earlier bridge diodes. The nozzles haven't been any problems. The nozzle tubes that have been showing problems are the older aluminum tubes. The newer Harris units are made with brass. I think it might be the ph of the water in this one area that might be accelerating the corrosion. I'm guessing the pelton wheel itself will eventually wear out, but I have one over 15 years old and still seems fine. Of course higher pressure and grit in the water will wear them out faster. But all the parts are available for replacement. I'm glad Don found someone to take over making the turbines so we can keep the old ones working too.

Chris

[joe8120]

I was wondering about the availability of parts but have found several on-line sources that sell them. I have been thinking about purchasing a spare wheel as a replacement when the time comes. Since they last so long, I would be afraid that they may not be available in the future. The same would go for the nozzles. My turbine seems like new however I only use it 4 times per year. I've tried smaller nozzles during the summer when the creek is a trickle but have not been able to produce any real power. I'm thinking that an adjustment to the field might make it possible to produce some power during that time. Can you explain what exactly happens when you insert the key to move the rotor and its effect on power production? I'm assuming that this helps to produce power with very little flow or more power with lots of water flow.

During high flows in the winter and spring, I have been using the 1/2" nozzle (the largest I could find). By going with a 2 nozzle set-up, I'm hoping to capture a little more power. Would the turbine operate well with the 1/2" nozzle and then turn on another nozzle with say a 1/4" size when water flow is higher? What is the effect on the turbine/wheel with different size nozzles operating at the same time? Or should both nozzles be the same size?

Joe

[hydrosun]

Moving the gearing moves the magnets in relation to the iron backing, in effect making the strength of the magnet weaker. The idea is to match the strength of the magnet with the amount of power available in  the water to only slow the wheel down to half the speed of the water to make the most efficient transfer of energy from the water to the pelton wheel.

 You can use different sizes of nozzles from different sides. I usually put in four jet systems, with 4 different sizes of nozzles, so it it easier to get a wide variety of water flow without having to unscrew nozzles. Changing the strength of the magnets allow you to match the changing water flow. So you can use a very small nozzle in the summer and still run efficient. There is some residual losses internally so there is an absolute lower limit. I've run at 2 gpm at 115 feet head and produced 12 watts. I got a blank nozzle and drilled it out with a 3/32 drill bit.  Those numbers are from memory and could be slightly off.

I just call up Don Harris and get parts directly from him. If he isn't available I guess I'd get parts from Denis Ledbetter who is now making the turbines. He can be reached at 707-986-7771. I haven't worked directly with him yet so I don't know what his prices and policies are.

Chris

[hydrosun]

I forgot to add that I find that the 1/2 inch nozzles are a bit less efficient than the smaller nozzles. I think that there is a bit of splash and some of the energy is lost. I prefer to use  two smaller nozzles to equal what the 1/2 nozzle will let out. Gives me more flexibilty also. The only time I'd use a 1/2 nozzle is in lower head systems and I need to put all the water I can on the system.  Higher head systems run into the limit of power that the generator will produce before the largest nozzles are needed. So the largest nozzle I use is the 7/16th. A 1/4 and 7/16th will put out more power with about the same amount of water as the 1/2 inch nozzle.

And the smallest (1/8th) are a bit less efficient also. So I tend to use the middle sizes. I think that has to do with aiming directly at the center of the nozzles, a bigger percentage of the water hits the divider and bouncing away before giving up all its energy. Don once said it would be better to use only half the pelton on those smallest nozzles. Aiming the nozzle just off of center. All these tweeks to get the highest efficiency aren't absolutely needed. He also talks about changing the wiring from star to delta at the extremes of flow also. I've never found it worthwhile to make the change. When I set up my first system I tried all the different combinations of wiring and magnet strength to see if I could get a bit more power. Now I just look at a frequency on my volt meter to adjust to the highest output. The frequency is 1/10th of the rpm. So at 100 feet head I should be around 2000 rpm or 200 hertz.  Once you find one maximum output with the ampmeter, you can check the frequency and then when you change flow you adjust the magnet strength to that frequency. It makes the adjustment quicker when you know which direction the magnet strength needs to go.

Chris