Pex Solar Water Preheat Project

[menaus2]

Originally Posted by Daox

Never used them and haven't heard feedback on them. They seem like nice little packages and a good list of features for the price as long as you don't care about having it all packaged in a fancy plastic box.

For only $7 extra you can! All the fancy plastic box you could ever dream of right here.

[menaus2]

Update:

Folding and securing the EPDM liner



Putting on the composite decking boards over the liner.





Assembling the tank lid. It's in 2 2ft by 4ft sections. I didn't have enough extra EPDM, so I used 4 mil plastic folded over itself in multiple layers and stapled down. It shouldn't reach the plastic's melting temp, and will see how it holds up over the years.



Lids in place, the nearest decking board isn't attached yet at pipping for the 2 pex Heat exchangers and 2 pump lines are yet to be put in.





I also ordered 2 300ft rolls of pex from pexuniverse and they're on the way. The next step will be integrating the storage tank into the existing plumbing

[Mobile Master Tech]

Stop the presses!! Before you buy any "traditional" circulators, be sure to check out the electronically commutated pumps built by ITT/Laing and sold under Laing, Bell & Gossett and others.

Their E10 composite housing pumps, often used as replacements for hottubs, have a similar max head as the Taco 014-21/22ft. They flow the same amount as the 014 to a little over 6gpm before falling off in max flow capability. The E10, however draws 50w at 2gpm/20ft of head and a max of 60w, at which it flows 6gpm at 20ft head. The 014 draws 178W! The E10's can be found on ebay for $130-180 depending on voltage and plumbing connections.

The E5 draws 39w max, and produces 14ft of head. It flows 6.6 gpm at 9ft of head. The taco 008 produces 15ft of head and draws 91w!

For lower head requirements, the e3-6 circulators are brass/potable water rated, have a max head of nearly 10 ft, outflow a Taco 007 to 3.5gpm while drawing max 28w. I'm using these in my open loop radiant floor system and love them. The 007 draws 82w!

You could use 1 E10 pumping to both panels with an actuator valve and an inline ball valve for each, allowing you to finetune flowrates. You would then have 60w max draw instead of around 91w. Or, use 2 E5's for around 78w instead of around 182w.

Corrosion of cast iron pumps is almost always what causes them to fail and also causes an insulating layer of rust deposits on your HX and collector surfaces, dropping efficiency. These Laing pumps are made of non-corrodable materials and are jamproof due to a single, pivoting spherical bearing:



They also offer other models that may serve the need better than the examples I gave here. Grundfos has their ECM controlled Alpha pumps, but they are pretty expensive in stainless steel.

Here is a pic of my SR728C controller ($135 shipped on aliexpress.com), an e3-4 circulator on the bottom right, and an e5 circulator on the top right:



The SR728C has 5 temp inputs, 2 separate pump controls for multiple arrays, a 1500w additional output control, etc etc. My money is on these!

Craig
The MMT

ps: LOVE the tank decals, menaus2!!!! You wanna sell some?

[Daox]

Very interesting. I'm also working on selecting pumps for my solar hot water system. I'll definitely look into these other manufacturers. Thanks.

[Mobile Master Tech]

Originally Posted by Mobile Master Tech

I am also shamelessly soliciting compliments on Charmaine's beautiful table runner (she makes these by hand!) on which I took these pics so I will be allowed to continue spending so much time with all the wonderful resources Ecorenovator has to offer!!

[GaryGary]

Hi,
Here are the brochure and specs on the Laing E10:

http://completewatersystems.com/wp-c...04/LTBR-21.pdf

http://completewatersystems.com/wp-c...4/LTSS-301.pdf

Looks like a lot of good features.
One not so good thing is that the max temperature is listed as 140F.

I've used the several of the Grundfos 15-58 three speed pumps with good results. Very reasonable price -- $70ish I think? The three speeds provide a lot of flexibility.
I've not had any problem with using the cast iron case pumps -- have one that has been operating since 1996 and is still working fine -- this may be a function of water pH etc that the pump is running in.

Gary

[Mobile Master Tech]

The brass housing e1/e3, etc. use similar innards and are rated to 203F. The composite material used in the E5's and E10's is the same stuff car radiator tanks are made of. Those regularly see 230F temps on the inlet nipples and go many years before failure-I suspect Laing is just being cautious.

In any case, since pumps are typically on the supply/upstream side of the heat collector and stratification in the tank makes for lower supply temps to the pump, I think it is unlikely the pumps would ever see sustained temps much above the 140F rating.

Even if used in a radiant heating setup where the pump sees the hottest water, not many are running hotter than 140F supply water.

Many setups do fine with cast iron, but if there is a problem, once you realize it you already have that insulating coating of crud on inner surfaces.

Addding together the benefits of quiet running (you can drown out the sound of my e1'S and e3's with a whisper), the power saving, and the avoidance of corrosion possibility, it was a no-brainer for me.

Craig

[menaus2]

Originally Posted by Mobile Master Tech

ps: LOVE the tank decals, menaus2!!!! You wanna sell some?

Nah... Opensource it! Just shoot me a pm with your email, and I'll send you the high resolution source image.

I also was thinking about the possibility of using a single pump with a 3 way actuator, but I think the valve could prevent proper drainback. Programming some kind of delay between the two sounds over complicated, and an extra pump cant be much more than the actuating valve anyways. Instead maybe an E10 for the 13.5ft head panel and an E5 for the 11.5? I like the idea of using a couple inline ball valves to adjust the flow rates.

[Mobile Master Tech]

Forgot yours was a drainback system-easier to just use 2 pumps and 1 each of the e5's and e10's should work great. Ball valves are the easiest way to throttle flowrate. If you are using separate pumps anyway, unless you can take advantage of stratification (difficult in a shallow tank), you may as well just let them run full bore and get better efficiency out of the collectors.

Another thought-some of these Laing designs are also available in variable speed like the potable e1/e3's like I have. This would allow you to finetune flowrates by dropping power consumption, saving energy. You may want to kick around and see if they offer other variants suiting your needs that come with a speed control.

The only downside (a small one compared against the benefits) to these pumps is since they are electronically commutated, they probably won't work on a PWM variable speed control. My SR728C can control 2 arrays simultaneously and one of the pump outputs can be set normally or vary pump pulsewidth to maintain a specific deltaT across the collector array as solar energy waxes and wanes.

[GaryGary]

Hi,
It looks like your collector area is 166 sf and your vertical distance from tank water level to top of collector is 16 ft?

If so, I'll make the case for something like a Grundfos 15-58, and you can compare it to the Laing pumps.

The Grundfos 15-58 looks like a good match for your startup head requirement of (16 ft)(1.2) = 19 ft.
And if you go with about 0.04 gpm per sf of collector, you need 6.6 gpm. At 6.6 gpm, the 15-58 delivers about 13 ft of head, which is probably enough to overcome pipe friction (which is all you need to do after startup).
You can work through this sizing procedure to make sure: Pump and Pipe Sizing for a Solar Water or Space Heating System
This is something you want to do for any pump you are considering.
The pump curve for the 15-58 is on this page:
New Page 1

The 15-58 may actually do more than the 0.04 gpm/sf, which will give you somewhat greater efficiency -- all good.

The 15-58 is $75 depending on where you buy it.

On high speed power consumption is 85 watts.

The pump is very quiet -- I have to touch mine to see if its running.

Its good up to 230F.

These cast iron circulators are built like tanks and have the reputation for very long lives.

I don't mean to sound like a salesman for Grundfos -- Taco and others make similar pumps that would likely work as well.

I have trouble with the argument for varying pump speed to save pump power under lower sun conditions for these reasons:

When your 166 sf of collector is in full sun and assuming it achieves a standard sort of efficiency, it will be producing about 24000 BTU/hr or about 7035 watts.
This is from: Solar Collector Efficiency Calculator

If you look at this page:
Determining Solar Water Heating Collector Flow Rate
The drop in collector output in going from 0.04 gpm/sf down to (say) 0.02 gpm/sf is about 3%, or 210 watts. So, to me, one message is that you want to be very careful in dropping pump flow rate on the idea that you will end up saving pumping power -- the drop in collector output for such a change is likely to be a lot more than the saving in pump power.

Granted, the example above is done with full sun, and the drop in collector output would be less than 210 watts in part sun, but is it really going to be less than the 20 watts or so that you save by ramping the pump speed back?

To me it, the variable speed pumps seem like a lot of complication and expense to maybe end up not saving anything? I'd be glad to be wrong about this if someone has good numbers to show a real saving under real operating conditions.

The one advantage I do see to variable speed pumps for drain backs is that they can prevent the kind of short cycling that sometimes occurs under low sun conditions when the collector can get hot enough to trigger the controller to start the pump, but cannot collect enough heat to keep the controller from turning the pump off as the collector cools when the flow starts. But, this is not normally a problem worth worrying about much, and a simple 2 speed pump would be plenty to handle this.

I'm not saying this is as slam dunk decision for either Laing or the Grundfos (or similar) pumps -- I can see pluses and minuses to both.
To me it comes down to is the power saving worth the extra cost and the risk associated with the low 140F operating temperature limit?

---
Very nice job on the tank!


Gary