Need a control option that I can't find.

Harvey Ramer

So here's the deal.
I am in the design process of a dual fuel Woody Biomass system. Econoburn wood boiler with a thousand gallons of buffer tank. Piping running underground to house.
Already existing, An HTP low mass Mod Con piped P/S Moose Antler config. with 4 zone pumps. DHW is piped in as a zone.

The loop from the buffer tank will be tied into the boiler loop. Supply to supply and return to return. The circ. on the Buffer loop will be variable speed, "mixing in the boiler loop," controlled by ODR. "Here is the problem" I need an ODR controller that will cause this circ to go to max rpm upon a signal from DHW. My other option is a second, single speed circ. in parallel and a DP/DT relay that switches circs upon a call from DHW. I would prefer the former because it is simpler.
I checked Tekmar's offerings and didn't find anything to fit.

Lot of other control stuff going on here that I already have mapped out. This is the only stickler.

Harvey

SWEI

I could easily build that into an under $300 DDC controller, but remote support gets tricky.

How about an SPDT relay on the circ switching it between the mixing controller's TRIAC output and line voltage?

Harvey Ramer

SWEI said:

How about an SPDT relay on the circ switching it between the mixing controller's TRIAC output and line voltage?

I considered that, but wasn't sure that it would be acceptable to run the chopped current through the contacts of a relay. I'm game if it won't cause problems.

Harvey

Harvey Ramer

What is this DDC controller?

SWEI

DDC = Direct Digital Controls. Controller is a platform on which we can load software to do pretty much anything you can dream up.

Oh, and don't worry about switching the TRIAC output on a relay. At those currents (under 1A in most cases) even a small relay will have plenty of SOA margin.

Harvey Ramer

Do they have their own internal processor and able to operate in a standalone scenario? Do they need periodic debugging or anything of that sort? How easy or hard would it be to shift the ODR curves once installed?

SWEI

Harvey Ramer said:

Do they have their own internal processor and able to operate in a standalone scenario? Do they need periodic debugging or anything of that sort?

They run independently and do not depend on any connection to the outside world.

How easy or hard would it be to shift the ODR curves once installed?

Therein lies the challenge. The less expensive models (other than the SSC and MACH-Stat) do not have a user interface and would require some kind of BACnet workstation in order to change parameters. I'm actively looking at options for this, but don't (yet) have a simple solution.

Harvey Ramer

What about a computer software program to plug into the device to make changes? Are we dealing with some kind of language coding or ladder logic or something simpler and easier?

SWEI

Code is written in Control-BASIC, and you would need a copy of RC-Studio in order to modify that.

BACnet objects (variables, inputs, outputs, logs, alarms, schedules, and pretty much anything that is not actually code) can be read, written, and analyzed by any BACnet-compliant device or system.

Charlie from wmass

Why not the priority function of the Tekmar control you choose to run the pump during a call for domestic?

Mark Eatherton

The Ultimate control can be purchased through Rehau. It is completely programmable in simple If, Then language, is internet accessible (requires a $300 PC and internet connection to make it work) and it is limited only by your imagination. An advantage of having a PC in the job is that it allows you to do a significant amount of data logging, which then shows you any major deficiency in your control logic. It can also be programmed to send out an emergency email for whatever reason you deem important. Talk to Ollie Carman at Rehau's Leesburg Virginia office and he can quote you the skinny.

I have this logic at Hydronicahh, and it is fantastic. I started turning the heat up Wednesday, and the home is now nice and toasty warm awaiting my arrival.

Headed west to move some snow!

Merry Christmas and Happy Holidays!

ME

Harvey Ramer

Happy holidays to you as well, Mark.

Due to the desires of the home owner and other considerations, I opted to go with relay logic on this one. Granted, I could eek out a little more efficiency with a digital control.

I am definitely interested going digital in the future. I will investigate the Envy control further as time allows.

I will post the system and diagram in a new thread, for peer review.

Harvey

Zman

Harvey Ramer said:

SWEI said:

How about an SPDT relay on the circ switching it between the mixing controller's TRIAC output and line voltage?

I considered that, but wasn't sure that it would be acceptable to run the chopped current through the contacts of a relay. I'm game if it won't cause problems.

Harvey

I think this is the simple solution. I would be surprised if the contacts had any issues at all. As long as the coil has the correct voltage, you should be fine.

Harvey Ramer

Zman said:

Harvey Ramer said:

SWEI said:

How about an SPDT relay on the circ switching it between the mixing controller's TRIAC output and line voltage?

I considered that, but wasn't sure that it would be acceptable to run the chopped current through the contacts of a relay. I'm game if it won't cause problems.

Harvey

I think this is the simple solution. I would be surprised if the contacts had any issues at all. As long as the coil has the correct voltage, you should be fine.

I am going to try it. I guess i'll find out if it causes any problems.