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The last 10 posts

Friday, June 18th 2004, 11:50am

by swegman

The irrigation company came back to the house and tried switching heads, without success. This weekend, I will try to design a circuit that turns off the HVAC systems when the irrigation system is running. I believe I can tap into the aux. pump control output on the irrigation controller. According to the irrigation company, this output is normally used to control a well pump relay, and it becomes active (on) when the irrigation system is operating. I can design a circuit that senses the signal at this output and disables the HVAC units. The irrigation company says the controller can have 4 different programs, so they can divide the zones, having 5 zones water on, for example, Mon., Wed. and Fri., and 6 zones on Tues., Thurs. and Sat. Then, they say it can be further divided so that, for example, zones 1-3 start at 2 am and operate for 1 hour, then the HVAC systems operate at 3 am to re-cool the house (in the event it warmed up), and the remaining zones start at 4 am.

We shall see how well this works.


Monday, June 7th 2004, 5:07am

by drpete3

I have tried to get info about boosters in the past but with little luck. One question I have is is hard on the first pump to have a second pump connected in line? I will be curious to hear what your company has to say. Keep us posted.

Saturday, June 5th 2004, 7:50am

by swegman

The irrigation company is coming back to the house on Monday to look at the system. Over the telephone, the guy suggested it may be necessary to install a booster pump. I suggested trying different heads first and possibly changing the zoning.

He indicated that the first choice for locating a booster pump would be in the basement, after the pressure tank. Since my basement is actually a lower level, complete with bedroom, I am concerned about the noise of such a pump. Just how noisy are booster pumps? Anything else I should be aware of with booster pumps?


Wednesday, June 2nd 2004, 5:07pm

by swegman

I do have a RPZ valve, along with an in-line filter. The valves are Irritol 2400TB. 1 inch pvc schedule 40 is used up to the various pipes. 1 inch Poly pipe is used from each valve to the heads. Flow rates, depending on the zone, vary from about 5 gpm to approx. 12 gpm (if I recall correctly).

Wednesday, June 2nd 2004, 6:59am

by HooKooDooKu

I doubt the bends in the lines is really a problem. Your real pressure stealers are backflow preventer (doesn't sound like there is a need in this system), valves (you'll lose around 5psi), elevation (another 5psi for that 10-18foot difference) and friction losses in the pipes (you have to know pipe size, length, and flow rate through the pipe). As an example, 10GPM through a 1" Sch 40 PVC will have a pressure loss of about 2.5 psi per 100ft (an elbow is usually equal to adding 1-2 extra feet of run length).

Tuesday, June 1st 2004, 5:38pm

by swegman

I checked with Grundfos today, the maker of the pump in the well. According to them, at 32 gpm, the pump will produce a pressure of 35 psi. As the flow rate decreases, the pressure increases. It is not possible to increase the pressure from the pump beyond the 35 psi at a flow rate of 32 gpm.

Unfortunately, the storage tank in the basement is approximately 10 to 18 feet lower than the heads. Thus, the water flow has to fight gravity. In addition, the supply lines to the heads have bends (the lines are not straight). This all serves to lower the pressure at the heads. As a result, I don't know what the actual pressure is at the heads. I wonder if this can be measured?

I looked over the original proposal, and note that the designer had spec'd Toro 4" inch pop-up heads (570 sprays), but that the installers used Rainbird 1812 and 5012 12 inch pop-up heads. Could this really make a difference? The installers said they were concerned that the 4 inch pop-up heads would not spray over the shrubs as they grew, and thus used 12 pop-up heads.


Tuesday, June 1st 2004, 11:49am

by drpete3

My opinion also is that your company should have seen this problem ahead of time. I you are designing a system and you have a 30 gpm pump but you know that 18 gpm will be needed at times for somthing else then you have a problem. The problem lies with do you design for 12 gpm or 30 gpm. in the case of 30 gpm then obviously you will be under supplied at times. With the 12 gpm as I stated earlier your pump will cycle on and off and theat will wear out your pump.

Tuesday, June 1st 2004, 9:53am

by drpete3

I dont know either but i am suspicious that a booster pump is the answer and I think it might cost another couple hundred dollars. I think it is possible to install a booster to come on when pressure drops below 40 and to turn off at 60 psi, which is what would happen when the hvac comes on and goes off while the irrigation system is running. The other option is to install smaller nozzles on your rotors which will decrease the demand for water from your irrigation system. The problem there is your pump will start cycling whenever the hvac system is off.

Tuesday, June 1st 2004, 6:35am

by HooKooDooKu

I don't think a change in heads is going to get it, and given that you already have 11 zones, breaking the existing system in to more zones doesn't sound too desirable either.

Because you say the system works fine with the HVAC off, I think you are right about the pressure problem. I suspect that where ever the 30gpm spec from the pump is coming from does not mean 30gpm @ 40-60 psi needed to run an irrigation system (i.e. you can get 40psi OR 30gpm but not both).

The only "simple" solution I can see to run both as the same time is installing another pump for the irrigation system. I don't know if it's possible, but perhaps all that is needed is a "booster" pump so that you can take the 12gpm (or less) that should be going to the irrigation system and increase it's pressure. The only question I have about that is weither or not the HVAC system still has all the pressure it needs when the existing pump is going at max for both.

The only other thing I can think of is your idea of shutting off of the HVAC. Can you solve your issue of the HVAC being shut off by irrigating just before day-break and only irrigating 2 zones per day?

Sunday, May 30th 2004, 6:50pm

by bobw

Boy, you've got an interesting situation. I don't think that you're going to get a whole bunch of relief by changing head manufacturers, especially at this point in time as the distance between heads is pretty much established. As you pointed out, the system seems to work fine when the HVAC system isn't pulling pressure from the system. The optimal solution would be some form of pressure tank after the HVAC and before the irrigation system to help maintain pressure. No matter what you do, you are going to have issues due to the wide fluctuations with pressure to the irrigation system. If you adjust for the low pressure, then when the HVAC isn't going, the water will spray too far, etc.

A couple of ideas....

I'm not really knowledgeable about pumps, but would it be possible to change your relay on the storage tanks to come on at a higher pressure (say 50 instead of 40?). At least you won't be starving the system for pressure when the HVAC is running, and this would give a narrower range of operating pressure. The downside would be that your pump will run more often to keep the pressure in the narrower range.

Another thought is that the Rainbird heads all come with a number of nozzles to adjust distance vs. pressure. Some judicious renozzling could give you some better results, but not much if the heads are only popping a few inches.

Other than that, you could try to get your contractor to create some more zones and move some heads off of the existing ones so that you don't need as much pressure to get them to pop....

Good luck...