solar collectors plus munchkin T80

lolo

Hi,
I would like to hear any ideas and recommendation for installing thermomax solar collectors in combination with munchkin T80, and an indirect water heater.
Should I use an IWH with two coils inside? one to be heated by the munchkin, the second to be heated by solar.
Can I connect the solar tubes some how to the munchkin loop? maybe in series with the munchkin? what if the water-glycol runs through the solar first and then through the munchkin? and from there goes to the radiant floor and indirect water heater.
Pros and cons for different suggestions will be greatly apreciated.
thanks

Unknown

Call HTP

They have all of that, and the know-how to put it all together, and will caution you if you do anything that would endanger your warranty.

They're good people.

Noel

jerry scharf_2

my $.02

Lolo,

I am building a systen with a solar collector and a bioler/indirect. It wouldn't make any sense to have them both in the same tank, once the Munchkin heats the water to target temp, there's no place to store the BTUs coming from the solar collector. I'm doing a pair of tanks, first the solar and then the boiler. The bigger the solar tank, the more BTUs you can store.

You also have to think about what to do with the excess heat in the summer when the collector output exceeds the DHW heating demand. Mine's going to the hot tub. It's a long run with a commesurate heat loss, but I'm dealing with free BTUs, so I'm not concerned.

jerry

Kevin_in_Denver

Solar Info

In another life, I used to do these interfaces. Radiant makes it very viable.

The best info. on the net for DHW is at http://www.ecs-solar.com/ Tom Lane seems quite experienced, perhaps he can recommend someone to help you with the space heat portion. Try to find a designer or installer who can show you ten systems that have been operating successfully for several years. "Do not try this at home"

By the time solar died out in 1985, all the smart people were doing drainback, so the glycol is generally unnecessary.

In the meantime, good luck, and I think solar is at the start of a permanent comeback. Anyone who starts learning ASAP should have success soon.

This is the best forum I've found for solar, does anyone know of any others?

lolo

Hi Jerry,
could you elaborate a bit more on the pair of tanks?
are you talking about one to store solar heat, and the other as an standar indirect? or are you using both as thermal storage and running the intake to the boiler from the tanks?
thanks

hr

A primary loop

with plenty of storage as a secondary. Sounds like you want DHW and radiant from the solar? Large pressurize-able buffers are the hardest piece to find inexpensively. Find or build one with a HX so you just need to glycol the panels and HX not the buffer tank capacity. Flat plate HX's are nice for this.

Lochinvar has a line of nice insulated storage tanks from 250 gallon up. 250- 500 LP tanks are rated for this, about $1 per gallon used around here. But you need to insulate them.

I enjoy tinkering with solar, by far your best returen is solar DHW. It is a year around load and only takes a panel or two and 65 gallon indirect tank. I'll bet I get 90% solar DHW in June and July.

Solar heating will require more panel and storage, of course. Have fun.

hot rod

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Larry Weingarten

Home Power

Hello Kevin: You likely know about Home Power magazine, homepower.com , but just in case... It is a reliable source, for solar electric and more recently, thermal info. It's written from an "in the field" point of view. A drawback, their discussions are in print.

jerry scharf_2

I'll try to explain some more

Lolo,

I'm hoping you understood why I said you can't have just one tank mith multiple coils. If not, say so and I'll go through that in more detail.

If you've got that, then the T80/indirect works just like there was no solar hot water. The goal is now to heat the water coming into the indirect as much as possible, and only use the T80 in case the solar can't keep up.

To heat that incoming water, you need something to capture and store the heat from the solar collector and some form of heat exchanger to heat the potable water. You can look at three ways of doing this. One is to have a second indirect where you run a solar collector fluid through the coil and heat the potable water in the tank. The second way is to run the potable water through the coil and keep the solar collector fluid in the tank. The thind is to have a tank with solar collector fluid and you have an external heat exchanger to heat the potable water.

From what I understand, the first way is the least effective at capturing the solar energy but will guarantee that you never run the boiler in the summer. The second way is more costly than the third, and the third requires another circulator pump and control.

I'm waffling between #2 and #3.

I hadn't thought of the old propane tank idea from Hot Rod, but that now has me thinking I may go that route. 3 inches of Corbond on the outside should do the insulation.

jerry

Brad_9

I would strongly recommend that any of you go to www.ecs-solar.com and get Tom's book "lessons learned" before proceeding with any solar heating system. It will save you many hours of re-doing your system and potenital dangerous situations, frozen collectors, and leaking fluid.

For domestic water heating, it is possible to use a single tank system with two heat exchangers, if you have the correct layout and sizing. Solar coil on bottom, indirect coil on top. Size as though your lower half of the tank is the solar tank. So for an 80 gallon tank it would work as a 40 gal solar tank. Use 2 gallons of storage per sq ft of collector unless you use lots of hot water. But, there are no really good dual coil tanks that I've found that aren't way too expensive. Mine is fine, but inadequately insulated and my utility room is too hot. I'll fix that soon, but will never match a good foam insulated tank.

#1 works great, #2 and #3 will do next to nothing unless you reverse solar/dw.

Kevin_in_Denver

Solar Magazines

Solar Today is another good magazine. Just no online discussions.

lolo

solar and boiler in parallel, or series?

Hi,
I will explain a litle bit better.

I want a solar collector system that will do DHW but will also help heating the house (radiant staple-up 140 F).

I know that a lot of thermal storage is needed (thanks for the lp gas hint).
The solar collector loop will be filled with antifreeze (north-east US).
And I am thinking about a T80 and a superstor for a boiler-indirect.

Let's say that I already have the solar system running, and I have 2000 gallons of thermal storage.
Do I want to feed this hot water through the boiler (in series).

Or conect the thermal storage in parallel to the boiler on the primary loop (own circulator), in the same way as when you install multiple munchkin boilers together?

I could heat the DHW with one of those tanks with two loops. But as mentioned, they are not cheap, and if I also want to do space heating (radiant) wouldn't it make more sense to use the solar heated water to feed the boiler, and that way the solar stored energy could go either towards DHW or the radiant floor,with one single system?

I like the idea of connecting them in series because that way there are no extra controls, the water coming from the solar storage tank into the boiler will be heated by the munchkin more or less depending on its temperature, but it will always come out at the desired temp for either heat or DHW prioriy.

If you would go with the in series option, where would you put the 2000 gallon solar heated tank?
in the primary piping return? before the circulator?
or in the return of the secondary piping?
any thoughts?
thanks everybody.

lolo

thanks

thanks hot rod,
I guess I didn't read the subject of your posting, and I couldn't really understand the first part.
I have just posted another question (at bottom) where I basically asked what you have already answered.
thanks again

jerry scharf_2

enough BTUs???

Hi,

Are you really going to have enough BTUs out of the solar collectors to do both DHW and radiant in the winter? People generally size the collectors for just a bit more than their DHW demand in the summer, so you don't have too much trouble with overheating. Once you do that, you can almost guarantee that you won't have enough collector to produce the DHW in the winter, not to mention the radiant.

If you're doing it so that you have excess winter BTUs beyond DHW demand, what are you doing with the system the rest of the year?

jerry

Paul Pollets

Solar w Thermomax

I've used several Thermomax vacuum tube DHW panel systems with the SMT400 control. Nothing better in the market, in my opinion. I use a Viessmann B tank with (2) coils....one for the solar connection, and one for the boiler backup.

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David Woycio

solar/dhw/radiant

The systems we install in Colorado are all drain back water systems. When installed correctly (ALL plumbing a collectors are sloped min. 1/4"/ft.) these system outperform any glycol system. There is virtually no maintenance other than keeping the solar storage tank full. The solar collectors that we have used since 1982 are the flat plate type. We use custom built stainless steel storage tanks that we insulate with 4" of foil-faced polyisocynurate insulation. I have installed on occation a tank that we would build out of 2 x 6's, plywood, and then lined with an EPDM bladder. They work fine but are more labor instensive. The domestic water load is simply a series of coils (4, 1/2" x 50' refer tube works great if don't have to have double wall) submersed and supported in the top 1/3 of the solar storage tank.

There are lots of ways to tie into the radiant heating system. We usually drop another coil(s) in the solar strorage tank and treat as another injection loop just as you would when plumbing the boiler. Tekmar's 363 works very well in this application as the controller. If your interested, our web site (metro-solar.com) has an animation and some pics. that may interest you. They site is still in the early stages of developement but may help.

Good luck and have fun with the sun.

Stevo

Solar w Thermomax

I'm with Paul. We have had good luck with the thermomax collectors on the foggy coast of Northern California. Used A Butler Solar wand heat exchanger on a conventional Electric water heater that gets back up power from a 2500 watt Solar PV aray. (clients already purchased the water heater and roughed in for a flat plate. If more Btu's are needed for domestic Hot water the System can pull from the grid. Net metered here in California. The Grid is a big batery when the meter spins backward:-)

Bob Gagnon plumbing and heating

Metro man

I am making 4 heat exchanger coils for my solar storage tank like you describe. can you tell me how you support the coils? I hung mine on a length of 1 1/2" L copper and 3/8" brass threaded rod. do you use reverse returns to hookup the coils. are 4- 1/2" coils enough heat transfer for domestic hot water? thanks for your help, Bob Gagnon

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David Woycio

DHW Coils

Where are you hanging you're coils from? Yes, plumb reverse return and make the feed manifold 3/4" and return 1/2". Also braze the connections. Are you using 1/2" refrigeration tubing? The last set we tested, @ 4gpm and 55deg inlet temp. with 135deg. solar storage tank, the outlet temp was 134deg after running for 5 min. Pretty awsome heat exchanger. Like I mentioned before, this NOT a double walled heat exchanger that may be required in your area.

If you want to go a step further, install a 3gpm flow restrictor on the outlet of the coil.

Bob Gagnon plumbing and heating

dhw coil

I'm hanging the coils from my floor joists. why do you restrict the flow on the outlet? it seems like you have plenty of heat transfer. do you need a mixing valve for the summer months? do you have any problems with mineral buildup on the inside of the coils? I am using 5- 1/2" X 60' coils, would you go 1" on the feed and 3/4" on the return? I'm using plumbers tubing 1/2" inside diameter. thanks for your help, Bob Gagnon

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Kevin_in_Denver

solar tank

How are you going to put a lid on the tank?

hr

The only issue

is keeping a lid on the tank. I tried an open to atmosphere tank in my shop and ended up with some sort of smelly film (bacteria possibly) growing in the tank. I just had a loose fitting foam cover on mine. Maybe a better fitting cover would address the potential for something growing in there. Or possibly some chemical treatment?

Has this been a problem Dave?

hot rod

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Bob Gagnon plumbing and heating

for the lid

I used 2- 4'x8' sheets of 1 1/2" styrofoam insulation, foil faced. it went a couple of years like that and seemed o.k. I'm hoping that adding some thermomax tubes will raise the temp. of the tank to where it's not an issue. bob

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David Woycio

DHW Coils

Floor joists? What type of tank is this? We restrict on the output just to make sure all the coils stay balanced. Depending on what type of water heater your dumping into will depend where to put the mix valve (we like sparco). If it is stainless install on the hot out of the water heater. If glass lined install on cold in.

If the cold is already 1" go with it, if not 3/4 should be fine. The 1/2" on the oulet just needs to run the lenght of the manifold then back to 3/4". Mineral build up has never been a problem with an on demand coil like this. I have had problem with recirc. coils and ALWAYS plumb a purge valve on the outlet.

I've never run 60' coils, but I think you should be fine. We used to run with just three 50' coils and where getting a 8 - 10 deg delta T but the cost of the additional coil wasn't much and worked great.

We spin our coils over an old spa filter (about 15" dia) then plumb them up. pressure test b4 install and you're ready to rock and roll. You can also support the coils from below with a copper stand. Ours look like an inverted "T" with a bar between.

Let me know how things work out