Anyone familiar with solar/pebble bed heat system?

[larryh86gt]

My sons home has solar panels and a pebble bed heating system. (In addition to forced air). In his furnace room there is a very confusing array of ductwork, actuators (I think 5 of them), motors, etc. There is no information from the previous owners on how this system operates thusly we do not know which on or off position things should be in. My son doesn't care all that much but just the thought of it not being utilized drives me nuts. I took a number of photos of the various gadgets in his furnace room and if someone wants perhaps I could email them to you for some advice or at least a starting point on how we can figure the system out.
Larry

[Beamer]

I suspect you checked the obvious like brand names or any tags or labels on anything?

I remember seeing manuals taped inside of the service areas of heaters and air conditioners - is there a panel anywhere you could open and maybe get lucky with a brand/model?

[TDHofstetter]

Email me them photos? I've done some solar, & worked on some solar. Tends to be the case that solar stuff is vastly overcomplicated.

That's a FHW system, true? By day, it pumps cold water to the collectors & gets hot water back; it pumps that through the pebble bed for heat storage, & the water coming back out of the pebble bed pipes is cold again. At night (or when the collected water ain't hot any more) it all shuts down till the next time the collector warms back up again.

Meanwhile, air (or water) can be pumped through the pebble bed to reclaim the heat stored there.

It'd be interesting to twig around with it.

[CajunRider]

Some photos would be useful.

[larryh86gt]

Emails with photos sent guys.
Larry

[CajunRider]

Let's check things out Larry.
1. There should be a loop from the solar collector to the top of your pebble bed and exit out the bottom and return back to the solar collector. That one brings heat from the collector to the bed. That should account for one actuator.
2. In the heating cycle, air will be drawn from the top of the pebble bed and sent to your house loop. The air return from the house loop will go to the bottom of the pebble bed. In this cycle the air is partially heated before going through your furnace.
3. In the cooling cycle, air will be drawn from the bottom of the pebble bed and and brought to the house loop, the return from the house loop will go to the top of the pebble bed. In this cycle the air will be partially cooled before going through your AC.

2&3 together should account for the other 4 actuators.
Since there is a big pressure drop across the pebble bed, the motors are usually booster blower to get the air to flow through the bed.

[larryh86gt]

Would these be the controls/timer for the solar system?



What is this?










Its quite an elaborate system.


Roof panels


Side panels


View of the back of the house.

Anybody familiar with a system like this?
Larry

[TDHofstetter]

Ok - top picture.

The top (grey) device is a thermostatic switch. From its top should be a copper-wire-looking thing going off into one of the plenums. That's actually a probe tube, sealed on the far end, and it reacts to minute changes in internal pressure. It'll have an adjustment inside that grey box so you can select the temperature at which it turns on/off.

The middle (black wheel) device is the timer that turns the system on by day & off by night. It'd be maybe better to replace that timer with an "electric eye" that prevents the system from running on dark cloudy days and also doesn't lose its mind when the power goes down for 13 hours.

The bottom device (cream color) is SOME sort of controller, although the specifics aren't very clear without a closer look at it. It's probably got all the logic for the whole system in it.

Second photo... that box is just a collection of relays to switch heavier loads than the controller can directly handle. Each of the eight or so little clear boxes appears to my distant eye to be a Potter & Brumfield KUP-series or KUMP-series relay plugged into a grey Potter & Brumfield socket. They're socketed for easy replacement - you can unplug 'em just like vacuum tubes - they just pull straight out & plug back in. Each will have either eight or eleven little contact tabs on the bottom; those tabs plug into matching slots on the grey sockets. In the bottom-right corner is a transformer for the (probably 24VAC) power for the relays.

Those relays will actuate fans, dampers, whatever else the system needs to function.

It really doesn't look like a very complicated system at all... and it's apparently complete. The only itching issue I can see is the gravel bed - it may be really dusty inside, so it might be a really good idea to filter the air coming out of it (whether in cool-down mode or heat-up mode). The best part of the sytem's simplicity is the fact that it can be made to work - one piece at a time, or all at once - for virtually the rest of forever. Even those relays are cheap to replace if one EVER dies (that's extremely seldom), and they're a VERY standard relay so they'll be readily available for the foreseeable future. Spares won't die on the shelf like solid-state electronic stuff, either.

[dicklaxt]

Whats the two black and white gizmos on the wall to the right of ductwork in pic#3,actually there may be three of them,I see a corner peeking out at me?

Just out of curiosity do you have a block/flow digram of how the system works?

dick

[larryh86gt]

Jan 4, 2010 2:12:58 GMT -6 dicklaxt said:

Whats the two black and white gizmos on the wall to the right of ductwork in pic#3,actually there may be three of them,I see a corner peeking out at me?

Just out of curiosity do you have a block/flow digram of how the system works?

dick

Three thermometers.
We do not have a system diagram. We have the original blueprints of the house and the pebble bed has 37 tons of pebbles indicated on the blueprint.

Jan 3, 2010 23:00:57 GMT -6 TDHofstetter said:

Those relays will actuate fans, dampers, whatever else the system needs to function.

Tim-Would the 5 actuators that show open and closed positions be manual actuators or are they electrically operated?

[TDHofstetter]

Yep, those are just indoor-outdoor double thermometers, used to visually keep tabs on temperatures in three portions of the plenum assembly.

A little more research turns up that bottom cream-colored device in the first pic - that's a differential thermostat, which switches on (or off) when one remote temperature is higher than another remote temperature. No brains in that one, so all the logic is actually hardwired in that bank of relays. Sure would be good if that relay box had a ladder diagram tucked inside, but it may not be at all hard to replicate that diagram from a closeup and a little digging to track wires.

The relay sockets are always connected thus ("NO" = Normally open; "NC" = Normally closed; "C" = Common):

Layout:
| | | |
| | |
| | | |

Connections:
NO - C - NC - coil
NO - C - NC
NO - C - NC - coil

Tim-Would the 5 actuators that show open and closed positions be manual actuators or are they electrically operated?

That'd be electrical; it looks from here like there's nearly nothing manual in the system - everything's fully automatic.

EDIT: I should clarify about those relays. The sockets are connected so as to bring the relay contacts out to screw terminals, and the simplest way for P&B to do that is to swap the NO and NC contacts on the socket. So... ON THE RELAY the connections are:
NC - C - NO - coil
NC - C - NO
NC - C - NO - coil

...while ON SOCKET, the connections are:
NO - C - NC - coil
NO - C - NC
NO - C - NC - coil

The coil connections (just two) are always located on one side of the socket (that would be the right side of all the relay sockets in that picture) and the NC-C-NO contact connections (three possible sets, but it looks like they only used one or two sets each) are always located on the other (left, in the photos) side of the socket. If we look at that same boxful of relays from a little different angle, you'll see only two screws to the right of each relay and nine on the left of each.

[larryh86gt]

What is the tan box unit in the upper right braced up with angle iron? (and there is a filter in it on the right side of it).The house has 2 furnaces, 2 a/c's but there is only one of this unit.


This is the tag on it.

Little by little the system makes some sense. No great epiphany believe me. But just looking at the whole system at once was too much to grasp.
I appreciate the input here guys.
Larry

[TDHofstetter]

Boy, that one's a mystery till we see it opened up. It looks a lot like just a big motor starter, but it might have a sail switch in the back to detect airflow. It could possibly be some sorta' HVAC-system controller scavenged from a small office building, too. Let's dig that cover off & see what it contains. Might just be an overall on-off switch for the whole solar system... in a big fat box.

By the way, my brain tickled at me after I wrote that last, about the relays. It tickled & itched something awful, pushing something at my forebrain. Nudge, nudge, nudge, it did. Tickle, scratch. Finally my forebrain looked at it... I had made an error, hadn't remembered the relay socket terminals correctly - NEARLY, but not quite. They SHOULD be:

C - NO - NC - coil
C - NO - NC
C - NO - NC - coil

My only excuse is that it's been a few years since I worked with those P&B relays. I believe I still have one or two out in the shop, but it's been a good long time since I spent my days tracing wiring through panelfuls of 'em. Fifteen years or more.

[CajunRider]

I wish I had your sharp eyes Tim. I'm good with basic theory and stuff. You are so much deeper into every thing. Me - I just plod.

[TDHofstetter]

I wish I had YOUR energy & endurance, Cage!

[CajunRider]

Jan 9, 2010 8:25:25 GMT -6 TDHofstetter said:

I wish I had YOUR energy & endurance, Cage!

In so many ways I'm like a RISC computer chip. Simple operation and do it real fast and do it a lot of times to get any thing done.

[larryh86gt]

Jan 4, 2010 13:36:52 GMT -6 TDHofstetter said:

Boy, that one's a mystery till we see it opened up. It looks a lot like just a big motor starter, but it might have a sail switch in the back to detect airflow. It could possibly be some sorta' HVAC-system controller scavenged from a small office building, too. Let's dig that cover off & see what it contains. Might just be an overall on-off switch for the whole solar system... in a big fat box.

I haven't opened it up yet Tim but on the label it appears to be 220 and it also says refrigerant 22 so I am guessing it is a type of a/c unit?

[TDHofstetter]

Hmmmmm... might POSSIBLY be a heat pump for cooling... we'll know once ya get the cover opened, from the compressor inside.