New hydronic install

ScottWoh

Currently this house has a forced air system with miles of un-insulated duct work running through the crawlspace under much of the house. It’s serviced by a 40 year old Magic Chief furnace. We are in the process of a major renovation that will remove about 1/3 of the house and rebuild it. In the process I would like to move to a hydronic heating system. I have run the heat loss calcs using Hydronic Explorer and have for the most part decided on a Buderus 115WS boiler with Logamatic control. Our propane fired water heater will also be replaced with a indirect fired unit. One hydronic heating system currently exists in the form of a thin-crete radiant slab in the kitchen, this is currenty run through a plate heat exchanger/mixing valve tied to the water heater. With the heat loss calcs and the floor plan finished we have chosen Myson select radiators. One other radiant floor zone will be added into the mix. I have drawn in Flopro designer one possible diagram that I think would work. I have left off many of the details, such as differential bypass valves, check valves, purge stations, drains etc. I don’t know FloPro well enough to correctly set up the mix temp on the mixing valves on the radiant loops.



From a physical piping installation, the attached drawing would work well. I could install it and keep the piping and pumps serviceable and neat. I would really like some feedback to see if I’m on the right track. If it looks like this is a viable design then I was planning on doing the math to calculate the pipe size etc. I don’t know some of the flow characteristics such as head on the Myson units yet.



I would appreciate any feedback and input. Thanks.

ScottWoh

Attachment

Forgot the attachment

Mark Eatherton

Caution......

What you've drawn is an old/early concept of primary secondary. It works, but, each time the water flows through a circuit, it lowers the entering water temperature for the next set up. This creates two problems. One is that if all loops are calling at the same time, you could realize a LARGE differential in temperature around the primary loop, resulting in a condensation production situation that the Logomatic will see, and attempt to abate by shutting down loads.



The other inherent problem, as I already stated, is the continually decreasing supply temperature to the down stream circuits. So long as you take the decreased entering water temperature into consideration, it should work fine.



The alternate solution would be to have one set of secondary take offs coming from the primary loop, and put your individual secondary pumps on a manifold so that all zones see the same temperature of water going to the load.



You could also consider one variable speed pump, with zone valves on the returns and lower your parasitic wattage consumption.



TImes, they are a changing, and so does our designs.



ME

Steve Ebels_3

Quick observatiion

You would be well served to take a good look at reconfiguring your piping to utilize a VFD circ like a Wilo Stratos or Grundfos Alpha. Use zone valves rather than circs as your loads are very small and have tiny temp drops. Speaking from experience, the Buderus will take some mighty low water temps and keep right on truckin'.



Take a look at the delta T shown on some of the zones. ..........they are around 5 degrees. You want to shoot for 20+ and that means more emitter capacity and/or less flow. Even a small circ on some of those loads would be a waste of energy. Definitely not a Euro approved type design.

CMadatMe

I also didn't see

Any mixing or injection. I ask because I didn't get a sense that the rads were being sized to adjust for correction factors. I did see LP in the orginal post. How come no Mod/Con? Radiant, panel rads, it's a no brainer.

ScottWoh

Rev 2

My initial thought was to go with two sets of secondary take offs coming from the primary loop and putting the two lower temp radiant floor loads on the down stream take off. Thinking that I had three different load temps: indirect water heater, Panel Radiators and radiant loops at the end, I thought this arraignment would also work. The bypass on the primary loop is a ESBE, and with the DHW on priority I kind of thought I’d be ok.



One variable speed pump with zone valves would be a very attractive alternative. I assume the pump runs at a constant head pressure and is driven from a sensor placed at some point on the loop essentially in closed loop control mode? We do this in our CIP systems, however each piping path is sequentially operated and the pressure is set per path to maintain turbulent flow. I’m a bit confused on how a single pump system would operate through the thermostatic mixing valves on the radiant floor loops. The Myson radiators would all have TRV thermostatic valves so regulating via a closed loop pressure sensing system would I assume take care of the need for differential bypass valves in the zones.



So marking up the drawing again with the suggestions leads me in this direction, although far from the primary secondary system I had thought.

Mark Eatherton

That's better....

But you will have to have a means of mixing down for the low temp zones with its own circulator...



I must admit, I didn't scrutinize your numbers as closely as Steve E did. From the stand point of providing the hottest water to all calling zones, it is better to do it the second way.



If you do go the variable speed route, you do not want a pressure activated bypass in the circuit. The pump will continually try to fill the "hole" in the system.



ME