Need a future control strategy for to much emitter ME

Gordy

 As you know my 50's home has a combination of all ceiling radiant with rooms that have both RFH, and ceiling radiant. Some of the RFH was existing, and where it was not I'm slowly along the way sleeper RFH. Some of the reason for adding the RFH is just in case the ceiling system fails, which I have my doubts there is a back up plan in place.



For now all the emitters are running together to satisfy the load. What my future thinking on control is, and this is when I switch to a mod/con, and update control. Is to have the RFH carry the load for the shoulder temps which seems to be when outside temps are in the 30 ish range, and above. This is when the boiler runs very little so floors seem a bit cool to neutral, could be I have to much emitter going on average water temps are 105*. So anyway RFH carries the load at shoulder temps, and then ceiling, and RFH comes on line together when temps get cooler at some unknown point yet to be determined.





 All in all the hope is that once the whole emitter system is on line when it gets colder that I will be running really low average supply temps, and when its warmer out I will get a little warmer in the floor department with a higher average water temp when shoulder temps are around. So how would you control this type of strategy?



Gordy 

CMadatMe

IWorx

Simple and cost effective. You could go as far as boiler and dhw control. Boiler choice could be a simple Vitodens 100 and let the IWorx control it via 0-10vdc.



http://www.taco-hvac.com/products.html?current_category=384

Mark Eatherton

Tricky question...

I prefer to keep things as simple as possible so that anyone can work on the system (I pity whomever inherits my system in the mountains :-))



One possible way would be to use 2 different zone valves for both the ceilings and the floors, and then use a 2 stage thermostat in each zone. 1st stage (assuming placement of a Lochinvar Knight with 3 different temperature reset schedules) could make a 1st stage call to one given outdoor reset curve. The second stage would bring on the 2nd stage zone vale which would then call on the boilers 2nd ODR, at a lower ODR schedule. You could actually "nest" them. In other words have some overlap in the ODR logic.



What makes you think the ceiling might have issues?



ME

Gordy

All for Keeping it Simple

 That was one strategy in my head using the boilers logic, and yes it will be a fire tube Knight some day.



 The ceilings have no issues, and I don't think they ever will from all the tubing I have seen that was embedded in plaster in some recon work.  But In some reading around here people do come across failed aged copper mostly in concrete though. IT is 60 years old.  Time will tell so I'm covering my but while redoing floors.



   Adding the RFH it will end up being a space suit, or replacement emitter for the ceiling. That all depends on how a potential ceiling failure happens. If it starts getting leakers all over I will shut loops down as needed. If the ceiling caves in ( act of God or outside forces) I will definitely replace it with a modern ceiling radiant set up. For now its a space suit with low water temp potential.



Thanks Mark







Gordy

Mark Eatherton

Radiant sandwich..

I LOVE my radiant sandwiches :-)



If it weren't for simplicities sake, and I REALLY wanted finite control, I'd configure an ENV control logic with algorthyms capable of controlling the MRT to the nth degree.



You are only limited by your minds eye, and the ability of a given control device to accurately control flows.



In my mountain home, I have installed a non electric TRV system due to their extreme accuracy at set point, and am using the ENV logic to control things below that set point (cold idle conditions) as well as its monitoring/data logging abilities and the capability to send me an email if something is amiss.



It works like a champ, but as I said, I can only think of one person on the face of this planet that could figure it out after my demise.



You could incorporate non electric TRV;s into your design, but I am thinking you'd have to have two TRV's per zone. One for the RFH, and one for the RCH. That is the only way I can see that you'd be able to schedule the 2 stage operation. You could have one TRV that monitored each room/zone, with electric zone valves down stream of that to decide wether you were using the floor, or the ceiling, or both, but it would not be a simple system. But I guarantee it would deliver excellent comfort ;-)



Lots of flexibility...



ME

Jean-David Beyer

I can only think of one person on the face of this planet that could figure it out after my demise.

I imagine some of the smarter people who post here could figure my system out after my demise. But my former contractor could not. I do not know about my present one -- his company have not needed to figure anything out, just follow the I&M manual. They can do that pretty well. But I run two separate reset curves on this boiler, one for each zone, and that sure confused the former contractor. I also run those resets very tight in an effort to get the circulators to run as long as possible.  So my downstairs zone runs 75 F water until it gets down to 50F outside. They think that is crazy, but the waste heat from my computers, etc., is enough that 75F water in the slab will keep the house at the setpoint on the thermostat for that zone (69F). I thought of lowering it slightly more, but that is as low as the boiler will  go with outside temperature.



Now if the new owner wants to raise that temperature more than a degree or so, it will act as though the boiler is too small (actually it is about twice the size it needs to be). So they are going to have to diddle the reset curve a little bit, and neither of my contractors seem to understand how to do that very well. Actually, one of the techies at the new contractor could probably do it, but he is usually sent out on more complex jobs, and he is in the union, so they send him to jobs that allow only union workers (they do not do only residential work).