A three temperature system with storage tank and 4 way valves

stoverdogs

We had originally planned to keep the tank at the highest temperature. At that time, there were (3) older cast iron boilers that cycled all the time. We wanted to run the boilers for a long time for efficiency, and then shut them off and run off the tank. The tank is partially insulated, and we plan to highly insulate it once final configuration is done. Your response is exactly what I am trying to get at...we need advice on how best to do this. In this forum there have been many methods suggested to make domestic hot water, some with injection pumping, etc. We are looking for advice on that also. Most of them use priority of some sort. I was thinking of using the Tekmar 361 to injection pump the domestic water. This sounds like a lot of stuff to buy, but some of these items were picked up almost for free. For example, the Landis & Staefa valve was bought new for $15 on EBAY. Yes, $15.

Since the 15-42 are all 220v, 3 speed. I am building my own relay panel using 2P3T relays. I have one up and running for a different system, and it works great.

We have to drain down this whole system in the middle of winter to do the re-piping, so I want to get this right. We thought about running the 2 Munchkins through the high temp loop (12 pumps) and then dump it into the tank., The question is where. At the 4 way? At a tank fitting? We need to put more temp gauges on the tank to see how the temp varies in that tank. Right now, on the medium temp loop (12) pumps, we have a delta t of 30 degrees. That will improve as we insulate the building.

I was advised originally to go with the closely spaced supply/return layout in order that we could circulate water rapidly though those 2" manifolds in a continuous loop with the tank, and the circulators loads would have less impact on the water temp in the loop. That seems to work pretty well, versus having the supplies and returns on separate manifolds. At this point, to separate all the returns would mean starting all over. That is not an option.

stoverdogs

piping 4 way valves, storage tank and three manifolds.

I have a fairly large system for a very large B&B. It uses a 275 gallon storage tank, (2) Munchkin 199m, a Tekmar 2" 4 way with actuator, and a Tekmar 1.5" 4 way with actuator. There are (3) 2" Wirsbo copper manifolds with closely spaced tees, set up as pump return, pump return, etc. Each manifold has (12) 15-42 circulators. We use Grundfos 43-75 to circulate water to the manifolds and from the 4 ways. I want water at 3 temps: 90 degree, for in slab and under floor, 120 degree for iron radiator zones that heat easily, and 150 degree for iron radiators zones that don't heat easily. We also need to make a whole bunch of hot water for guests, showers, jacuzzis. The tank is horizontal because there is not cceiling height to stand it up, as we would prefer. I also have a Tekmar 153 control, 360 and 361. Some of this is not yet hooked up. My question is how to pipe from the boilers to these 3 separate manifolds, to get the temp ranges we want, yet still be able to use the mass of the tank to be able to run the boilers at max efficiency, and shut them down when the tank can meet the heating load. We are in the process of starting to spray foam the building to cut heat loss. Can you help?

stoverdogs

Large tank system additional details

Sorry, I forgot a couple of items. We have an indirect water heater brand new, the 50g version. We expect to buy more, or use plate to plate heat exchangers. The Munchkins both have the Vision system. We also have a Landis and Staefa 1.5" 3 way with actuator and immersion sensors sitting on the bench. Currently, the Tekmar 4 way and actuator is mounted on a 2" iron nipple coming of the center of the tank which is laying horizontally. The tank is a ASME rated air tank with lots of 1.5" and 2" nipples all over the place as delivered from the factory. That feeds the medium temp loop of (12) pumps running zones at 130 degrees, and is currently controlled by the Tekmar 153. The other stuff is mounted on Uni strut, and waiting for final piping. This is a building nearing completion of a 10 year restoration, and soon to open as a B&B. We chose to use so many circulators because the place is so big, and the loads vary considerably. After all of these years we have a decent feel for which rooms heat easily, and which ones don't. The supply lines going out to zones are 3/4"or 1" Wirsbo or in some cases Kitec aluminum.

hot_rod

depends

on how you want it to operate. Will the buffer always be maintained at the highest temperature? In series with the boiler? Or do you want the ability to have the boiler fire directly to the load(s) and only buffer when the system has light loads? Perhaps a P/S piping with either or ability.

You want to prioritize the DHW load no doubt?

The mix down temperatures on OD reset controls?

I'll bet tekmar has piping drawings already in their data base to get exactly, or real close to what you want.

Search the PMmag archives for some of Siggy's past article. He has done several on mod con piping options, commercial and residential.

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