Repiping help

adam12

hey guys, new to the forum and I’ve learned a bunch reading posts. It sure is great to have a resource like this. Recently bought a house in the foothills of Northern California. This is my first experience with radiant heat, and I noticed some issues that got me looking into my system. My system is three zones, with circulators, and a coil in the AHU for my AC. The zone circulators are controlled by a Taco SR503, and the AHU coil is basically piped into the primary loop. I’ve attached a picture for reference.What started all this, is I was calling for heat in only one of the three zones, and noticed my boiler running more than I thought it should. I noticed when only calling for heat in one of the zones, I was getting flow at all four manifolds (3 zones as zone 3 has 2 pumps, 2 manifolds). After looking at the piping in the mechanical room, it looks to me like isn’t proper separation between primary and secondary loops. Perhaps the mixing valve creates a primary loop.?? But I’m not sure how the internals of that thing work. I do know that the knob is stuck. It won’t turn either way, I know water is flowing through it, but I don’t know what’s stuck in there, if anything. So seeing as I know that when I run one pump, water circulates throughout the whole house, and I can’t stand looking at the sloppy piping the way that it is, I thought I’d re-pipe the thing with proper primary/secondary loops, and get rid of three pumps and put zone valves in their place. A few rather large problems screamed out to me at first glance. Like where the uninsulated boiler return line ties into the insulated return from the radiant and AHU loops, it’s a big fat bullhead tee. The primary circulator is in the wrong orientation.(I found the burnt up motor and cartridge in a next to the AC unit. Guess whoever swapped it didn’t catch that it needs to rotate 90°). Also, the rubber plumbing coupling on the PVC exhaust is a nice touch. So I attached a drawing of how I might re-pipe the system and I have some questions on it. I’d really appreciate if someone could lend me some expertise on this.

1- is this a good idea? my system run comparable to what I have if I switch from zone to zone valves?

2- if I switched to zone valves, would I still be able to use 503, or would I need to buy a different controller?

3- most of the existing piping is 3/4”. I planned to stick with three-quarter for the secondary loop, but what size should I run the primary loop?

4- I drew a bypass in the U Loop. My thinking was without I may lose more heat in the primary loop. Does that bypass belong there, or should I just have that coil part of the primary loop?

5- do I need a DP valve on the secondary loop?

6- the connections to the boiler are 1 1/4”. Assuming the primary loop will either be 1” or 1 1/4”, will I be able to use one of my existing “00” series pumps even though it’s 3/4”?

I have a tendency to overthink things and do too much sometimes. I’m trying to avoid that here, but I think circulating the entire house when I’m only calling for heat in one zone is causing my propane tank to go on E more often than I’d like. Thanks so much for reading this and I would appreciate any guidance. I can get from you all. Take care.

adam12

auto correct got me more than a few times but when my post talks about the U loop, it’s supposed to say AHU loop. I think the rest can be deciphered.

hot_rod

A horeshoe loop or a Separator are options. The sep gives you 4 functions in one device. Saves time and money on the installation.

Delta P ECM circ with zone valves.

What size boiler? !" piping on all the loops will cover 80,000 BTU.

You need a ZVC zone valve controller if you go with zone valves, which for your application makes sense. You don't need zone pumps for such small zone loads. A delta P circ will help adjust and balance flows and use less electricity.

What temperature do you need for the AHU? The boiler will need to run to that temperature, you may need a mixing valve for the other zones depending on what temperature they need? If you can get required SWT with 15° of one another, a single temperature system would be easiest.

adam12

Ok my boiler is an MP-120. Couldn’t find it anywhere but I’m assuming 120k. At this point in time, I’ve got more time than money so I’m likely to stick with fittings to separate. And honestly I have no idea what temp water I need at the AHU. I just assumed I’d want it hotter than the radiant loops, which Im basically guessing at as well. Right no the system is circulating 100* water, and that seems low to me, but again Im just trying to figure all this out. Im thinking 120* to the AHU would be about as low as I’d want to go. Is 120* too hot for the radiant loops? I’d take suggestions kindly… is my boiler too big? Pipe too small?

When you mention a single temp system, is that referring to primary loop one temp and both secondary loops another temp? Or is it just referring to the system as a whole? Where basically Im just trying to send the same temp water to the load so no need for mixing. What is the CK over by the pump on the AHU loop? Thank you so much for your help Hot Rod. I really appreciate your time.

adam12

ok I just read that back and my question about the single temperature system reference was stupid. Don’t bother with it, please. Single temp means single temp….🤷🏻‍♂️