Solar DHW Panel Replacement-PGP

Paul Pollets

already planned on disconnecting the CW feeder.

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Paul Pollets

Panel Replacement

Here are some pics of the replacement we're involved with where 16 panels froze due to failure of the RPZ device, allowing all the antifreeze to be drained. The Heliodyne panels did not fail due to any manufacturing defect.

Our biggest site problem is the replacement panels are a different size, as the manufacturer reduced the copper outlet stubouts by 21/2". We've ordered "union extensions" overnight to make the piping changes.

We rigged up a platform to make the work a little easier.

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scott markle_2

RPZ

what's does RPZ stand for? If the system had glycol why did draining it out cause a freeze problem? Any summer aplication for all that capacity?

Paul Pollets

RPZ=

"Reduced Pressure Zone"; this double check valve prevents the non-potable system water from contaminating the potable supply. The RPZ had debris under the seats which allowed the glycol to leave the piping via the dripcup. No glycol, freeze conditions...piping bursts. The RPZ's are suposed to be serviced yearly, which would have discovered the problem...but....A special license is also required to be a "certified backflow specialist" to repair the devices.

RPZ's are required in our state for ALL boiler installations, or in this case, the solar DHW system, which uses a closed loop glycol system. Glycol can be toxic, and must never be able to "go backwards" into the potable water system. Even soda machines require an RPZ before the water connection to the device.

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Paul Pollets

Capacity

The 16 panels are supposed to supplement the dorm DHW system which needs 350gph at 120 degrees at peak load. I have no way of knowing it's BTU production without some control modifications.

We've put forth a proposal for a 4-30 VitoSol vaccuum tube array (120 tubes total) that will generate 70% of the existing DHW demand for the new dorm, which is being built next month.

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[Deleted User]

SIllyness...

Paul, I do hope you have enough common sense to NOT put the make up back on the solar system.

Everytime I see a snowmelt system with an automatic make up on it, the hair stands up on the back of my neck. If it hasn't already frozen and broke, it will. Its just a matter of time.

Throw a PIG on it if nothing else.

ME

[Deleted User]

Good man....

Most would leave it there because they thought it was mandatory. In reality, I've seen NO WHERE that a make up is required (steam excepted).

One of THE largest annual insurance losses in the world today is from water damage...

I know OUR insurance company DEMANDS that we NOT make a solid connection to the heating system from the potable water lines. Hence, the PIG, or Fail Safe as our office manager prefers to call it.

See you in less than a month!

ME

Metro Man

BTU output

Paul,

In good sun and angle .... 16 collectors (look like 4 x 8's) should generate around 40 MBTU's ea/day or 640 MBTU's per day.

Too bad someone installed incorrectly. If the system is loosing pressure an alarm or shut off could have been installed. Usually this is a non-issue. I have had clients add water to they're systems to boost pressure only to find out too late to much water .... oopps!

Looks like lots of capacity for DHW production....

Metro Man

Dan Foley

Solar

Interesting project, Paul. We're getting into solar as well and have a few projects in the pipeline. Looking forward to catching up with you in Denver. -DF

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singh

Look

forward to seeing the finish pictures.

Is there any type of dump zone?

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Paul Pollets

Dump zones

There are no dump zones. I'll post pics of the existing pumping station and controls when we get there. This project uses technology that's quite dated.

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hot_rod

Use it or lose it

if there is no DHW load during the summer month on the building, you may need to find a place to lose some of that thermal energy.

I saw some large hydronic unit heaters on an apartment building to shed excessive summer solar harvest a while back.

Watch the maximun temperature rating of the solar tanks you are considering. Some of the solar tanks have max temperature listings that that system could easily exceed.

And be sure the tempering valves can handle the temperature.

Viessmann should be able to predict the output of that system. They have some pretty impressive output graphs for those tubes??

hr

Paul Pollets

Capacity

The existing solar has a 350g ASME storage tank. The dorm is always occupied and the primary DHW source is a commercial 120g propane heater. The DHW has tempering valves.

I already have the Viessmann output reports for the new dorm system. 120 tubes = 16 4x8' flat panels. The system will be supplemented by a dedicated GS1-72 staged boiler for DHW and a dedicated Vitodens 6/24 for RF heating only.

I'm hoping the facility will approve newer controls for the existing setup.

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Metro Man

solar/dhw capacity

So Paul if I'm looking at this right.... you had 512 sq ft of collector area which should be able to heat 512 to 768 gallons of DHW storage. Snce this was only going to a 350 gallon storage tank @ probably max temp of 150*F system probably shut down alot.

Seems like not matter what glycol system you'll be using (flat plate or evacs) over-temping will be a continuing problem. Maybe over sizing x - tank(s) to be safe.

Too bad system wasn't set up for drain-back.

Metro Man

hot_rod

Dave may be onto

the reason it dumped glycol, and took on water via the fill system? Max temperature reached and the panels stagnanted. Over temped and over pressurized to pop the relief.

Even at a mild one gallon to one square foot of collector, Wouldn't those 16 panels need 480 gallons of storage?

hr

Metro Man

Rule 'O thumb

For flate plate solar collectors..... 1 sq ft collector area (close to optimum angle and south) mult. by 1.5 for storage size to heat storage to approx. 120*F.

512 sq ft collector area X 1.5 = 768 gallons storage. You can take that down to 1 to 1 if conditions are not optimum.

Metro Man

scott markle_2

Is it possible that the glycol became diluted from make up water that was drawn as a result of stagnation and blow off?

Seems like because of the location of the back-flow preventer it would, if leaking, be draining mostly fresh makeup water.

If the storage was undersized this seems like an alternate explanation . Is the propane fired tank connected to the storage tank by a circ. in a way that permits some use of this water volume for storage as well?

How is it that a college instals a system like this and does no monitoring and maintenance? When a system fails like this it it also fails in it's primary objective to provide economically viable alternative energy. It's fortunate that this institution is forgiving of this, and can see the value in continuing with solar investments.

Metro Man

Die-looted

Scott,

I am sure that is what happened on this system. Fill a glycol system with 50-50 mix then start adding water....... no more 50-50

If P/R leaked then it's leaking the mix.

When storage systems are undersized on closed loop glycol systems stagnation and high limits happen more frequently. Although these systems should be sized for worst case for expansion issues.

Why does any homeowner, institution, gov't, or etc.. not perform regular maintenance? Pay me now or pay me more later.

Metro Man

Paul Pollets

More Pics- Update

Here are some pics from yesterday, including a shot of the mechanicals with tube & shell HX. There is 700g of storage capacity with (2) ASME tanks. The other pics detail the issue of the replacement panels having a shorter union make-up dimension and all the "union extension" pieces we're installing to be able to reassemble the panels. We expect to finish the assembly by tomorrow, clean and commission the system within 2 weeks.

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Metro Man

Young HE

Paul,

Looks like an old Young H.E. If you have in budget flush DHW side too. Worked on many of those. If it goes south we've gone stainless.

Not a big fan of unions. Seems like they all weep a bit. We just sweat slips and go. Are you using unions with Viton seals?

Are your tanks in series or parallel?

Have fun in the sun......be glad it's not the middle of summer!

Metro Man

hot_rod

Who gets the old ones?

You'd be surprised the market for used thermal panels, even leakers! I've sold a bunch via e-bay.

Don't be tempted to scrap them until you try at least an ad in the local papers.

hr

Paul Pollets

Panels

I'll ask the facilities manager what he's going to do with the old ones. The new unions were supplied by Heliodyne. Since the system has a primitive delta-T controller, I'm trying to sell an upgrade for the control with a pumping module.

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