Solar and radiant integraton

Rodney Summers

Hey Rod,

The Buderus system using the BFU indoor sensor and outdoor reset runs the radiant loop in constant circulation P4.

Do you see any reason why I couldn't consider that zone as a primary and put the loop to the heat exchanger off a pair of closeley spaced tees acting like a seondary? The diff controller would run the seconday pump when the floor called and the solar tank can meet the need.

Rodney Summers

Solar and radiant integraton

I'm installing a 700 gallon tank to provide assist to the radiant floor heat for the main living area. Using the Buderus outdoor reset, the BFU, the FM 241 card, motorized mixing valve, and constant circulation.

I want to integrate the water in the solar loop when it's hot enough. Can't quite figure out the schematic for how to make this work. Here's a rough drawing of what I think I need to do. Not sure what control to use that will pull water from the solar tank when it's hot enough but ignore the water from the solar tank when it's not hot enough. I don't want the boiler to be heating this mass in the tank when the sun isn't shining.

Rodney Summers

i also wanted to hook a solar hot-water setup to my buderus lt160 hot water tank that is now powered by my g115-28

i probably need a storage tank for the collectors to heat
then a control for the my buderus hot-water tank to tell the storage tank to provide heat

then i need to figure out how to pipe it because id like to still use oil as a back up if the storage tank cant provide heat

can someone tel me how i would pipe and control this

thanks
Jason

Josh_10

Thermomax has a ton of differential temperature controllers that you can use. I have been piping the supply from the tank right into the boiler return and any time the return temp is lower than the storage tank the control turns on the pump and injects the heat into the boiler loop.

Here is a link: http://www.thermomax.com/Delta T Index.htm

hr

Primary secondary

maybe a few PS loops. Check out this link for a good example.

http://www.pmmag.com/CDA/Archives/7df8232b040d7010VgnVCM100000f932a8c0____

hot rod

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Simply Rad_2

Overheating

Make sure when you are designing you system with heating as your primary use that you have an alternative heat sink in the summer. This is when you could find trouble without a place to use the heat. The system is not designed to stagnat day after day and will eventially shorten the life of your system. Plus this will add to your system performance because you are using its full potential winter and summer. Might want to inject the solar into the primary, a storage tank might produce 160 degrees+ on a good day and may be too hot to not mix.
Good Luck Jeffrey

Rodney Summers

Great link rod

Thanks. I've read a few of the articles there. I think I'm getting closer. I've taken one of his drawings and modified it since my DHW is coming off an existing set of panels and the new panels will only be used for space heating.

Help me understand a couple things in terms of the Buderus FM 241 card, mixing valve, and the drawing below.

Missing from the picture would be a differential controller that would sense the panel temp and the water temp and determine if the flow to the panels should be started, right?

With the radiant zone in constant circulation controlled by the FM card, mixing valve, and BFU unit, what controls whether the circulator from the solar tank or the boiler comes on? Do I need another controller in the mix?

hr

I'm not up to speed

with the features of the Butter Us controller.

Typically I do it with an assortment of differental controls. I know how to operate them

Actually Mike Miller, a royal knight of the tekmar clan, put together a nice schematic for a wood boiler buffer that would also work for this.

Did you do the math to assure you have enough solar panel horse power to warm 700 gallons to a use-able temperature?

And I agree with SR, you may need to cover some panels come summer to keep from boiling over that storage. Too much of a good thing make it problematic, sometimes

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Kevin_in_Denver_2

Solar Tank

Are you planning on using a pressurized tank? If so, who makes it? If you're planning on an atmospheric tank, the design might change a bit.

Rodney Summers

Done the sizing homework

My radiant floor is designed for 95F (using Wirsbo and Slantfin) at 0F outside temp. I'm giving up on the 0F and working the solar assist based on 20F.
I've used RETScreen software for sizing the panels and tank. Great tool!
8 AET MorningStar 40 panels at a 57 degree tilt on 3-3.5 hours of sun in January on Cape Cod will get 700 gallons of storage to 120F. The radiant floor uses ~12K/hr. I should get around 15 hours of usefull heat from the tank.
I've got a hole in my basement floor that's 8'x8'. I'm planning on digging this out and building a tank for 1000 gallons. I figure I can use the extra capacity in the summer as a heat dump.
The tank will probably be at atmospheric pressure. Any issues I might need to overcome in this approach? I don't want the added expense and trouble of trying to seal it.

cheftim

Well..

Rod,

In the picture above, the circulator going to the radiant is constant circ. So, what do you think about using a differential controller with a sensor on the solar tank and if it's above 95F, the floor design temp, then fire the solar tank circulator, otherwise the boiler one.

When making the primary loop, are there guidelines for building it? Should it be very small? Are there ratios between the pipe size and tee spacing and such?

hr

Your drawing

doesn't provide boiler return protection, a means to keep the boiler from flowing into the solar tank, and a few other things.

A primary secondary loop would allow the various circuits to work with each other, hydraulicly speaking.

A Caleffi HydroLink is another method I use to keep the various circuits working peacefully.

If you chose to tackle a home built P/S get a copy of Dan's book at the book store here. It will help you design flows and pipe sizes correctly.

It's always easiest to do it right the first time copper tube and fittings are getting expensive

hot rod

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cheftim

So let's say I used a Caleffi

With the primary as the radiant floor circuit and the two secondaries are the boiler and the solar loop. Kind of reversing the normal use of the manifold. Will that cut it?

Weezbo

Dry Earth has a lot of storage capacity,...

i have considered loading an insulated earth berm during intense summer solar gain off of a gravity air flow system by introducing pex out and back within the air piping, off the solar to redistribute the BTU.s me and the mouse in my pocket need to break out the calculator*~/:) the thing that sorta boggles me is not losing my solar array to extreme cold...any ideas? heard or seen anything along these lines of endeavour?

Rodney Summers

Not sure what you're asking Weezbo

I run a glycol mix in the panels I use now for DHW and haven't had any issues even in the cold winter we had a couple years back. I'll assume from your email address that you're in Alaska?

Jay_14

tekmar 363

Hello,

May I suggest consider using a tekmar 363. It has a storage tank feature that allows radiant floor heating through a storage tank. Should the storage tank not have sufficient heat capacity, a backup boiler is used to heat the radiant floor. The 363 when used with a Room Temperature Unit (RTU 062) will tend to operate the system on constant circulation. Please see page 7 of the attached A363 PDF.

Mixing is accomplished using a variable speed injection pump rather than a mixing valve.

The tekmar 363 can be used with any boiler including Buderus.

If you have any questions, call me at tekmar Control Systems.

Jay Vath
tekmar Control Systems
250-545-7749

ALH_4

Or

The tekmar 363 is an excellent choice, but also a mixing valve in combination with a diverting valve will work. You'll be hard pressed to find a control more solid than the 363, or any tekmar control for that matter.

-Andrew

Kevin_in_Denver_2

Storing heat in earth

Weezbo,

A guy named Brian is doing something like this and blogging it at ourcoolhouse.com

Kevin_in_Denver_2

Drainback, etc.

1. 300 extra gallons of storage cannot operate as a "heat dump". Those 300 just get too hot all summer as well.

2. You're showing a drainback collector loop. That's the best way to reject extra heat in the summer. At 160F, the collector pump turns off, and the collectors dry stagnate, which is OK.

3. Siggy's article describes a pressurized closed loop drainback storage tank. You're right, you can't accomplish that with a hole in the ground. The best way to build the tank is with an EPDM liner (no seams). It usually comes in 12' rolls, so keep that in mind when you excavate the tank.

4. The water in an atmospheric tank has a lot of oxygen in it. You'll need a heat exchanger between the solar tank and your boiler if it's cast iron.

5. You'll have to find a high temp. submersible pump for your collector loop.

Weezbo

That site shr has changed:)

Eric_6

re:solar/radiant interface

Hi all,

From the original post we would be using a cast iron boiler w/logamatic + Fm241 card and 3 or 4 way mix vlv, By moving the Logamatic's operating sensor out between a divert vlv and the mix vlv we would be able to utilize the existing equipment. A differential controller would control the divert valve. High delta tee on is needed.
We have found that the boiler may get hot but will stay off for long periods especially during shoulder seasons and we are not running solar in series w/boiler which may act as a radiator itself.
As for stagnation issues during summer (no pool or hottub) then maybe in new construction deeper tubing under outside slabs or European solar differential controllers w/vacation function or tank cooling function (a couple of them becoming ETL listed as we speak).

Solar thermal rocks, Most bang for the buck on solar DHW preheat!

Regards,

Eric

Rodney Summers

Yes it's drainback

I've been working over different designs on the solar portion of the system and keep mixing up discussions.

I am using drainback so the summer temps won't be a problem.

I'm thinking about the EPDM route. I'm also considering either putting in a wooden box and lining with EPDM or pouring concrete. I'd like to find an inexpensive flexible pre-made liner if possible.

My intention is to use a heat exchanger between the boiler and solar systems for the reasons you mention.

You mention a high temp submersible. Are you referencing the pump needed to go to the panels or to the heat exchanger?

Rodney Summers

I'm liking this approach

Eric,

Let me see if I have it right in this picture.

1. The diff controller is monitoring the input to the heat exchanger via sensor A and the floor temp via sensor B. If A is greater than floor design temp, 95F, and sensor B is showing less than 95F, turn on circulator D and open the diverter valve to the solar loop.

2. If the solar portion is maintaining the required floor temp then the Logamatic sensor C will not be calling for boiler water through the mixing valve.

3. If sensor A isn't seeing temp > 95F then turn of circulator D and close the diverter valve to the solar loop. Logamatic sensor C will initiate flow to radiant floor via boiler when needed.

I think I'd want to put the sensor A at the solar tank and also use it to control the circulator from the tank to the heat exchanger.

Kevin_in_Denver_2

If the tank is a hole in the ground=pumping problem

The collector loop drains completely every night. The only way a centrifugal collector pump can prime itself the next day is if the pump is submerged.

I guess you could extend the top portion of the tank above ground to ensure a wet collector pump.

hr

looks to me

like P3 and P4 will be running in series under some conditions? I still feel a PS would be a better piping to keep the various circs from interfering with one another.

I think I'd rather see an additional circ than the 3 way motorized valves.

hot rod

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Rodney Summers

Different zones

P3 is going to a baseboard loop and p4 is for the radiant loop. Do you still see something in series?

Otherwise, does this look like it will work?

ALH_4

I think

The diverter valve is on the wrong side of the mixing valve.

ALH_4

I think

The diverter valve is on the wrong side of the mixing valve. I would post a diagram, but the attachments do not seem to be working right now.

You want to be able to run the solar storage tank as hot as you can get it and use a heat delivery system that will utilize the coolest water possible to maximize the useful energy in the tank. The mixing valve can be thermostatic, or it could be a motorized 3-way or 4-way with an outdoor reset control, such as a Dekamatik HK1.

-Andrew

ALH_4

I think

The diverter valve is on the wrong side of the mixing valve. I would post a diagram, but the attachments do not seem to be working right now.

You want to be able to run the solar storage tank as hot as you can get it and use a heat delivery system that will utilize the coolest water possible to maximize the useful energy in the tank. The mixing valve can be thermostatic, or it could be a motorized 3-way or 4-way with an outdoor reset control, such as a Dekamatik HK1. Be sure to locate the diverting valve before the hot side of the mixing valve so that the mixing valve can control the temperature of the water supplied to the floor or radiators.

-Andrew

Rodney Summers

High delta tee

Eric,

What do you mean by high delta tee on?

So does my drawing a couple of posts down capture what's needed?

Rodney Summers

Fine Home Building had an article about dumping extra solar power down a geo thermal well. One of those Zero energy homes.I think it was in Oragon.

Rodney Summers

I'm not a plumber

but I'm fairly technically inclined. So if I ask a lot of questions it's to increase my knowledge.

The mixing valve in the diagram is being controlled by the Buderus fm241 card from the boiler loop. I don't think I want the diverter valve before it since would be interrupting flow from the boiler.

The drawing is from Buderus' application diagrams and recommended by Buderus tech support. I've merely added the diverter valve and solar heat exchange loop.

I think your comment about using the coolest water possible from the solar loop is something I have missed though. Would a mixing valve between the diverter and the circ for the solar loop with a return from the floor be the ticket?

cheftim

Modified drawing

I think this might get it closer. Does such a controller exist though or does this require multiple?

1. The diff controller is monitoring the temperature at the solar tank via sensor A and the floor temp via sensor B. If A is greater than floor design temp, 95F, and sensor B is showing less than 95F, turn on circulators C and D and open the diverter valve to the solar loop. The thermostatic mixing valve after the diverter is set to the floor design of 95F.

2. If the solar sensor A is greater than 95F and sensor B is showing sufficient floor temp, then turn off circulator C. The mixing valve and shutting off the circulator to the HX will maximize heat store in tank.

3. If the solar portion is maintaining the required floor temp then the Logamatic sensor C will not be calling for boiler water through the mixing valve.

3. If sensor A isn't seeing temp > 95F then turn of circulators C and D and close the diverter valve to the solar loop. Logamatic sensor C will initiate flow to radiant floor via boiler when needed.

Eric_6

re: motorized divert valve

Hi Cheftim,

Yeah, you want the motorized divert valve before the mix valve as solar could come in much higher than the radiant could withstand.

Are there high temperature zones also ? If so then may have to rethink the solar connection points as the Logamatic boiler sensor is to be located between divert and mix valves (FM241 mix supply sensor is located in normal location), We need to have 20 to 25 degree delta on (between solar storage and radiant system return) so we are not short cycling the divert valve or firing the boiler excessively. I'll post a diagram on Thur. or Friday.

We have used this with a Buderus G124x or G234x series in the past and they use the L8148E as secondary hi limit to Logamatic. You may need the L8148A w/G115.

Also, we have found the Tekmar 363 to be the best control to use when variable speed mixing is involved with cast iron boilers (you get two var. speed controlled circ w/solar storage priority and mixing reset . Of course if the boiler is a mod/con then controls and piping will be different.

Sunny Regards,

Eric

cheftim

Thanks Eric

I'll look for the diagram later this week. Much appreciated.

Yeah, there are three other zones. A IDHW loop to a MegaStor with 3-panels solar pre-heat tank, two baseboard zones, and then the radiant zone.

Rodney Summers

Dont' laugh

In the mean time, here's my latest stab at getting it right. (I know what you pros are thinking but, hey, I like doing this stuff)

1.) Floor design temp 95F

2.) If sensor A shows > 95F and sensor B < 95F open diverter to solar loop and turn on pump E

3.) Thermostatic mixing valve D is set for 98F. If feed to valve is > 98F then flow gets diverted away from HX and pump E needs to turn off.

4.) When sensor A see < 95F, close diverter to solar loop turn off pump E

5.) Logamatic sensor C sees need for heat in loop and mixing valve returns water to boiler. While floor is satisfied, mixing valve keeps boiler out of loop.

6.) Need to figure deltas so boiler and solar don't compete.

Rodney Summers

Don't Laugh

but here's my latest attempt.

Tekmar diff controller monitors tank temp A and floor temp B.

When solar is providing hot enough, open diverter valve to solar loop.

FM241 card can still monitor mixing valve but when solar loop is optional is controlling mix of floor and solar loop.

When solar loop has no more heat, diverter valve closes and boiler comes back on line.

Rodney Summers

and one last thing

put a NO contact in the line from the Tekmar to the diverter valve triggered from the P4 pump. That way there's no solar floor heating when P4 is shut down for warmer season. Pump E can be run off relay from same output of controller.

Rodney Summers

Buderus tells me this won't work

The goal is to mix the solar loop ONLY into the radiant floor loop and not the whole system.

They say if the mixing valve is open fully to the radian return loop, there'll be flow just through the floor. I'm good with that.

They say if the mixing valve is closed fully to the radiant return loop, there'll be flow through the radiant floor loo AND the heat exchanger. Good with that too.

They say the problem is when the mixing valve is between states, mixing. They say no water will flow through the heat exchanger.

Thoughts? Any way to overcome?

Brett O'Connor

Utilizing an electric boiler

We have utilized Thermomax and intigrated solar into numerous systems. From injecting the solar into the primary loop when the temperatures of the solar tank exceed the design of 130 degrees mixing the water down utilizing outdoor reset on the solar side. This is an example of a simple system utilizing an electric boiler. Controls are the key in these systems.

Rodney Summers

Hey Eric

Any chance I could get a peek at a diagram of how your hooking something like this up? I haven't found an answer yet that specifically fits with the G115, FM241, and solar loop assist only on the radiant loop.

Thanks.