Thermostatic mixing valve recommendation - 180 degrees

[LucMan]

It's not my system, but if it was, I'd have put all 10 panels on the roof in one spot, up the flowrate with a different series/parallel arrangement and perhaps increase eff. a bit, set the elevation at optimum winter tilt and cover some of the panels as needed in the summer. Seems like less plumbing and perhaps fewer/easier controls.

The manufacturers specify the flow rate range for their panels.
Covering and uncovering panels on roofs is usually not an option for clients.

[J.P.M.]

You are correct in your assumptions about excessive time spent under stagnation conditions.
The sks4 panels operate at a very low flow rate normally and they utilize steam back when the load is satisfied, so yes they can be under stagnation conditions frequently during the summer month's. All systems need to be designed properly to minimize stagnation temps.
I would not recommend installing 10 sks4 on a roof in direct sunlight for solar thermal heating or any non drainback system for that matter with out a way to handle the excess production during the summer month's. A dump zone would be required, or as is the case in the simulation that I posted 3 panels were to be mounted on the roof for domestic hot water year round. The remaining 7 panels were to be mounted under a 3 ft existing overhang on the south wall of the barn at a 75 degree inclination. The panels would be shaded during the summer month's.

It's not my system, but if it was, I'd have put all 10 panels on the roof in one spot, up the flowrate with a different series/parallel arrangement and perhaps increase eff. a bit, set the elevation at optimum winter tilt and cover some of the panels as needed in the summer. Seems like less plumbing and perhaps fewer/easier controls.

[LucMan]

I checked out the website and the OG-100 cert. prior to my first post to this thread. It seems like a fine product. I would comment however, that given the published, certified efficiency curves, which are quite similar to other very similar designs but without inert gas, I'd continue to question the benefit of such design features, i.e., the inert gas.

My question was about the very high collector temps. shown in your graph.

1.) I assume those are stagnation or VERY low flow rate fluid temps. or absorber plate temps. at zero or no flow. ? The efficiency curves for either of the Buderus collectors (selective or semi/higher emissivity selective surface treatments) do not allow for a fluid outlet temp. that high unless the flowrate < ~ 20-30 lbm/hr. or so - essentially stagnation. Where is the temp. sensor located, and of what type is it ?

2.) While they are a robust looking product, cooking in the sun for several months under zero or low flow conditions probably won't increase their efficiency or service life. Because the Argon is sealed, which I'm sure it is, without some accommodation for gas expansion, the elevated temps. will increase the gas pressure, perhaps causing the gas to exchange with/leak into the environment sooner than it does anyway.

3.) Those elevated summer temps may be a problem for any working fluid (water/glycol ?) in the collector loop.

4.) FWIW, I'd cover all of the collectors once the heating season is over, or at least some of them if the system also provides DHW, and/or change the control logic to avoid prolonged +300 deg. F. temps. Repeated and short thermal cycling over say, a 200 deg. F temp. swing on a regular basis (if DHW summer service is involved), probably isn't a collector's best friend either.

You are correct in your assumptions about excessive time spent under stagnation conditions.
The sks4 panels operate at a very low flow rate normally and they utilize steam back when the load is satisfied, so yes they can be under stagnation conditions frequently during the summer month's. All systems need to be designed properly to minimize stagnation temps.
I would not recommend installing 10 sks4 on a roof in direct sunlight for solar thermal heating or any non drainback system for that matter with out a way to handle the excess production during the summer month's. A dump zone would be required, or as is the case in the simulation that I posted 3 panels were to be mounted on the roof for domestic hot water year round. The remaining 7 panels were to be mounted under a 3 ft existing overhang on the south wall of the barn at a 75 degree inclination. The panels would be shaded during the summer month's.

[J.P.M.]

Hi J.P.M. - great diplomacy You don't always get accused of that!

Yea, on this forum, I can only recall one other instance. Good thing it's about communication and information exchange and not a popularity contest.

While I try to mix being straight with people and, at the same time not bruising over fragile egos and thereby lowering the effective communication quotient, some posters probably do the same as some of my former associates and former co workers, who every so often seemed to confuse me with Oedipus the King.

At least that's what I surmised from what they'd called me at the close of a disagreement. But most of that wasn't a popularity contest either.

Without writing/thinking for him, I get the sense Jr. Spyder and I share some of the same, probably anachronistic sensibilities, opinions and manners with respect to communication.

[J.P.M.]

The flat plate panels are sealed and filled with inert gas. Buderus makes some really interesting solar products including their 200 gallon combi tank. All engineered and manufactured in Germany.

http://www.buderus.us/products/solar_energy/solarcollector/logasol-sks-4.html

http://www.buderus.us/products/tanks.../pl750-25.html

I checked out the website and the OG-100 cert. prior to my first post to this thread. It seems like a fine product. I would comment however, that given the published, certified efficiency curves, which are quite similar to other very similar designs but without inert gas, I'd continue to question the benefit of such design features, i.e., the inert gas.

My question was about the very high collector temps. shown in your graph.

1.) I assume those are stagnation or VERY low flow rate fluid temps. or absorber plate temps. at zero or no flow. ? The efficiency curves for either of the Buderus collectors (selective or semi/higher emissivity selective surface treatments) do not allow for a fluid outlet temp. that high unless the flowrate < ~ 20-30 lbm/hr. or so - essentially stagnation. Where is the temp. sensor located, and of what type is it ?

2.) While they are a robust looking product, cooking in the sun for several months under zero or low flow conditions probably won't increase their efficiency or service life. Because the Argon is sealed, which I'm sure it is, without some accommodation for gas expansion, the elevated temps. will increase the gas pressure, perhaps causing the gas to exchange with/leak into the environment sooner than it does anyway.

3.) Those elevated summer temps may be a problem for any working fluid (water/glycol ?) in the collector loop.

4.) FWIW, I'd cover all of the collectors once the heating season is over, or at least some of them if the system also provides DHW, and/or change the control logic to avoid prolonged +300 deg. F. temps. Repeated and short thermal cycling over say, a 200 deg. F temp. swing on a regular basis (if DHW summer service is involved), probably isn't a collector's best friend either.

[LucMan]

Kind of high on the daily max. temp. for a flat plate. Why is it designated hybrid ?

The flat plate panels are sealed and filled with inert gas. Buderus makes some really interesting solar products including their 200 gallon combi tank. All engineered and manufactured in Germany.

http://www.buderus.us/products/solar_energy/solarcollector/logasol-sks-4.html

http://www.buderus.us/products/tanksforboilers/pl750-25.html

[J.P.M.]

Here is the simulation for Newburgh NY.
This was for a barn horse washing area, kitchen, bath,storage area & apartment. Total square footage 1600 sq ft. Designed for radiant and low temp radiators ( max 140 degrees)
10 Buderus hybrid flat plat panels, a 300 gallon Buderus triple solar tank with oil backup.

Kind of high on the daily max. temp. for a flat plate. Why is it designated hybrid ?

[LucMan]

Here is the simulation for Newburgh NY.
This was for a barn horse washing area, kitchen, bath,storage area & apartment. Total square footage 1600 sq ft. Designed for radiant and low temp radiators ( max 140 degrees)
10 Buderus hybrid flat plat panels, a 300 gallon Buderus triple solar tank with oil backup.

[russ]

You're most welcome. Holler back or PM me as your needs dictate.

Your Ob. Serv.,

J.P.M.

Hi J.P.M. - great diplomacy You don't always get accused of that!

[J.P.M.]

J.P.M.

Thanks for your sincere care and great diplomacy on how you said it. I'm definitely being cautious and seeking a lot of advice, especially on keeping the system safe. I know there's a lot I don't know yet. A couple things make me comfortable. One is that I've worked closely with a HVAC engineering firm (total professionals) who have drawn the exact schematics and specified every component of the system as if there was a boiler on my roof. They are not solar experts specifically but I trust their heat system expertise and had a great experience with them in the past. I wouldn't consider this scale of a project without help from a pro. Second, for better or worse my engineering degree is in Aeronautical/Astronautical engineering - in other words Rocket Science. So fluid dynamics, thermodynamics, structural dynamics and control systems are all in my past. And of course all of those operate at much higher pressures and temps than residential solar heat. That being said if I had to take a test on any one of those subjects today I'd probably fail - but I know enough to feel comfortable building and operating this system. In actuality I'm really just the plumber now as virtually every part of the plan has been vetted by a pro. That doesn't stop my thirst to keep questioning and learning. That's why I'm here, and loving all the feedback.

Please keep the warnings coming and don't be afraid to tell me I'm nuts. You won't be the first.

JR

You're most welcome. Holler back or PM me as your needs dictate.

Your Ob. Serv.,

J.P.M.

[jr_spyder]

I honestly and sincerely do not want to rain on your parade. I encourage you to continue reading/studying/asking questions. Your life/choice/time/money/blood/treasure. But respectfully, I get the feeling you may not be considering or be aware of the technical and engineering issues involved in what you have described up to this point. I'd just as respectfully suggest you look more before you leap, then look some more.

Best Regards,

J.P.M.

J.P.M.

Thanks for your sincere care and great diplomacy on how you said it. I'm definitely being cautious and seeking a lot of advice, especially on keeping the system safe. I know there's a lot I don't know yet. A couple things make me comfortable. One is that I've worked closely with a HVAC engineering firm (total professionals) who have drawn the exact schematics and specified every component of the system as if there was a boiler on my roof. They are not solar experts specifically but I trust their heat system expertise and had a great experience with them in the past. I wouldn't consider this scale of a project without help from a pro. Second, for better or worse my engineering degree is in Aeronautical/Astronautical engineering - in other words Rocket Science. So fluid dynamics, thermodynamics, structural dynamics and control systems are all in my past. And of course all of those operate at much higher pressures and temps than residential solar heat. That being said if I had to take a test on any one of those subjects today I'd probably fail - but I know enough to feel comfortable building and operating this system. In actuality I'm really just the plumber now as virtually every part of the plan has been vetted by a pro. That doesn't stop my thirst to keep questioning and learning. That's why I'm here, and loving all the feedback.

Please keep the warnings coming and don't be afraid to tell me I'm nuts. You won't be the first.

JR

[J.P.M.]

Good one!

Thank you. I take my engineering very seriously. Myself not so much.

[russ]

Talk to people who know me now and they'll probably say I'm more eccentric and have no more common sense now than then, but I'd like to think I'm a bit more circumspect in my engineering.

Good one!

[J.P.M.]

If this as hot as your panels can get in in SoCal than I don't think I have to worry too much about overly high temps in my panels in the North East. Thanks.

You may and, IMO, probably will as you become more versed in the peculiarities of what your have in mind. The location and ambient temp. are not always major inputs to instantaneous collector outlet temps.

The outlet temp. of a liquid solar thermal system is a function of many variables. A few: panel area, flow arrangement, flow rate, fluid transport properties, solar irradiance and collector characteristics to name a few. Your liquid outlet temps., even in a quasi - steady state can easily exceed your 180 F. target depending on the design (or lack of it).

I got to + 180 F. or so in Buffalo back in the day with a small, home made water cooled collector and it wasn't anywhere near as efficient as available these days.

I stagnated another home made air cooled collector at about +300 F. (pinned the thermometer). The box was made of particle board surrounded by insulation and had become dried out by then, probably reducing the kindling temp. Anyway, it started on fire. No damage except to my self image and a charred collector box. A humbling, but valuable experience and ONE hint of many I got that I was in over my head. I returned to school that fall, entering an engineering curriculum.

Talk to people who know me now and they'll probably say I'm more eccentric and have no more common sense now than then, but I'd like to think I'm a bit more circumspect in my engineering.

I honestly and sincerely do not want to rain on your parade. I encourage you to continue reading/studying/asking questions. Your life/choice/time/money/blood/treasure. But respectfully, I get the feeling you may not be considering or be aware of the technical and engineering issues involved in what you have described up to this point. I'd just as respectfully suggest you look more before you leap, then look some more.

Best Regards,

J.P.M.

[jr_spyder]

I can, but I'm not sure it will be representative of New England or of much use. FWIW, my highest collector outlet temp. occurred on 06/15/2008 at 1520 hrs., P.D.T. That water outlet temp. was 203.7 deg. F. I was testing the max. capabilities of the system located on my roof. I'm actually more interested in the day/day, yearly performance and serviceability/reliability of the system. So far, so good. On an annual basis, the solar fraction for the DHW thermal collector system is above .90 and probably closer to .95. After 6+ yrs. I've replaced 1 flex/expansion joint gasket. All else is nominal. Claiming solar fractions much higher than that are hard to justify for several reasons.

If this as hot as your panels can get in in SoCal than I don't think I have to worry too much about overly high temps in my panels in the North East. Thanks.