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Reversing flow of single pipe loop

PwallPwall Member Posts: 13
I have a simple question but I will explain my situation first so everyone can see where I coming from.
I live in Maine, me and my wife purchased a house that was built in 1992, it has a 2 zone single loop fin tube baseboard heat that was common for the time. Hot water was provided by a Thermal Dynamics boiler listed at 85k. Upon inspection it was determined the boiler needed to go, it was 25 years old, had blown the DHW coil gasket and had pressure issues because the coil had pin holes in it.
At some point in 2004 they added a 20 x 20 foot addition to the house and just extended the first floor zone.
The thermostat for the 1st floor in in the living room.
No natural gas and only heating oil in my area so we went with a Utica Trifire boiler with a Utica indirect tank, kept the existing zones and added a third for the indirect. Zone valves are the original Taco 571's, the tank doesn't have a zone valve it only has a Taco 007e pump. The controller is a Taco Zone Control. The house heat is pumped by a Taco Viridian Delta T pump. Both pumps are pumping away from the boiler after the expansion tank.
The first problem we had was the boiler was short cycling and using a lot of oil. We reduced the nozzle from the stock .85 to the recomended by Utica .65. We also changed the Delta T from 20 to 15 in the pump settings per Taco. The short cycling stopped and the high fuel consumption stopped as well.
Last week twice the boiler shuddered like is was misfiring. Our tech came out and replaced the nozzle and double check ed all the settings and fittings and found the pump pressure was lower than it should have been and the feed line was loose. It hasn't shuddered since.
Our biggest problem which the old boiler suffered from as does the new one is the heat in the living room where the thermostat is doesn't really seem to heat like it should. The living room is the last radiator in the loop, the addition they added is basically in the middle of the loop and probably has 3 more feet of radiator than it should, it is also the hottest room in the house. When I put the thermo gauge on the radiators there is right about 20 diff between what is coming out of the addition radiator and the living room radiator. I also did a heat loss calculation using the Slantfin app and boiler size was right about 58k.
My question is can I flip the connections on the loop, make the living room the first on the loop? It's a pretty simple connection and not far apart. I can hook up what used to be the return for that zone to the supply from the boiler just after the ZV and then hook up the return to the boiler to what used to be the supply. The loop will just feed in reverse.

Sorry for the long post. Just trying to explain everything as best as I can so you can make an informed decision.


  • the_donutthe_donut Member Posts: 374
    Pictures and drawings speak volumes.
  • HVACNUTHVACNUT Member Posts: 1,734
    edited June 2018
    If the living room seems cold, but that's where the thermostat is, it should keep up, assuming the baseboard matches the heat loss. Is the thermostat near any baseboard, sunlight, heat from a TV or lighting?
    How is the thermostat itself?
    Is there Outdoor Reset?
  • hot rod_7hot rod_7 Member Posts: 9,138
    A room by room load calc, and an analysis of mow many feet of baseboard in all the rooms would be the best starting point.

    How long is the longest zone, what size tube, how many feet?

    Often times you can damper down rooms that are over radiated and do some room by room balancing balancing.

    Is the boiler running on outdoor rest control?

    Do you try running the cir on a fixed speed setting?

    Doesn't seem like tightening the ∆T 5° from 20- 15 would fix the short cycling and fuel consumption?

    He is some additional reading on what can happen with constrained, forced or limited ∆T function. In some applications it can save energy, depends on the entire system control logic, etc. In Idronics 23 will look at Heat Exchange more closely.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • PwallPwall Member Posts: 13
    I have run the circulator at a fixed speed and performance wise it's about the same.
    No outside reset but the boiler control does have an economy mode and that made the short cycling more apparent and the lack of heat in that room even more apparent.
    The thermostat is on the wall leading to the dining room. The first floor of the house is a partial open concept with no wall between the kitchen and ding room, no radiator in the kitchen but there is in the dining room. The living room is open on one end connecting to stairs to the second floor and the 3/4 open connecting to the dining room.
    I will try to upload pics tonight and get a good measure of the total run. The first floor I would say has at least twice as much radiation as the second.
    Sorry if I'm skewing some of the terms, my previous house was all cast iron rads with monoflow tees and worked like a champ.
  • hot rod_7hot rod_7 Member Posts: 9,138
    This link takes you to a fairly easy to use load program ap. It will also determine the amount of fin tube each room requires. Thanks to Slant Fin for making this tool available.

    Pic will help a little bit, but without some numbers or data any opinions you get will be guesstimates at best.

    Give it a try.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • PwallPwall Member Posts: 13
    These numbers are a real close approx and be off a few feet on the total run.
    Total length of everything on the first floor is 160 ft, from the boiler and back, 48 ft of that is fin tube radiator, 15 ft in the added on 15x15 room, living room is 9 ft.
    Second floor total run is 115 ft, that includes the up and down I estimated at 10 ft each way. Total amount of fin tube is 20 ft, master bedroom contains 10 ft.
    I did use the slant fin app and it looks like the total amount of baseboard is good just maybe the placement is bad.
    This is one of those house that always has a cold feel to it for some reason.
    We did over the winter close down some of the damper in the addition but other than cooling off the room it didn't really heat up the rest of the house.
    I probably need to put foam tube on everything, pull all the covers off the baseboards and clean them out again and straighten the fins. All we did so far was clean them out.
    Below is some pics of the boiler setup. The Zone control is above the tank on a board hanging from the floor joist.
    The big silver dryer tube is because this house is really tight and the dryer will cause the boiler to back draft if we don't provide make up air.

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 4,755
    If the baseboard on the first floor loop is 48'+15'+9' your pretty much maxed out on fin tube on that zone.

    If that is the case I would split the loop. You could easily split the loop using 2 zone valves and two thermostats. Two supplies and 1 common return. It will heat much better.

    But, do the heat loss, do the math first it won't lie and see whwer your at.
  • hot rod_7hot rod_7 Member Posts: 9,138
    The economy mode is off? Temperature modulation and delta T function circulators do't always get along so well. Shown in this graph. As the flow slows to try and maintain a fixed delta, with temperature modulation you fin tube output drops considerably.

    Tough to troubleshoot this time of year, delta T measurement and flow rate would tell exactly what the loop is transferring to the space.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • PwallPwall Member Posts: 13
    Total first floor fin tube is 48, 15 feet of that is in one room.
    I was thinking of zoning the addition. Would it work to put in a 3 way valve in the current line right before that room with the normally closed feeding the room and the normally open feeding into the return. I'm thinking I would probably need a back flow valve on the return from the room so I don't get any siphon.

    Economy mode is off because it caused a lot of short cycling. The heat loss calc shows we are right at the correct size for the boiler but some of the fins are oversized especially the addition.

    This is Maine we just had 2 days in a row of low 50's and today was a whole 64 I think. Tomorrow could be 80 or 40, you never know.
  • PwallPwall Member Posts: 13
    edited June 2018
    Below is 2 very basic and not to scale drawings of the first and second floor. The yellow dot is where I was thinking to put a 3 way zone valve with the thermostat in the addition. That valve would only hook to the thermostat so that it wouldn't trigger the boiler or pump and water would only circulate through that zone if the main first floor zone was calling for heat. The blue line would be where the bypass line would reconnect.
    Or should I tie in at the boiler with the other valves and run all new supply to that area with it's own return tying in with the return from the second floor. Remember each floor is a just a single pipe loop. And I'm of course trying to keep costs under control.
    first floor

    second floor

  • PwallPwall Member Posts: 13
    Since no one said it was a horrible thing to do I'm probably going to go with the above layout. I know running a completely separate supply with a ZV tied into the ZVC would be better and I might still do that I'm just looking at the cost of additional plumbing, a new ZV and a new ZVC because the current one is maxed.
  • hot rod_7hot rod_7 Member Posts: 9,138
    This is how most 3 way zone valves work. The port configuration may be different from brand to brand.

    You have an A, B and AB port. You want to flow either into or out of the AB port. Either A to AB is open, or B to AB. Used as a diverting valve it looks like this.

    So essentially when the addition zone with the thermostat is not calling, no flow is in that section of the loop. The main loop will continue to heat until the addition temperature drops. So really no temperature control in the main area?

    I'd split the zone, two t-stats, two zones.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot rod_7hot rod_7 Member Posts: 9,138
    Here are some flow reversing methods I have used. Mainly to help out long radiant loops.

    A motorized 4 way valve with a timer changes direction every 15 minutes or so.

    Or dual circulators, checks removed of course :)

    I think two zones with two thermostats would be the best way to get optimum control, however. Assuming you have enough fin tube in the area to cover the loads.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • PwallPwall Member Posts: 13
    Thankyou Hot Rod. I can see that if that addition zone is open I'm pretty much right back to where I am now with poor heat at the end of the loop. I will have to look harder at adding the 3rd ZV and a larger ZC. It's just going to take some reconfiguring of the distribution area and I might still have some 3/4 Oxygen Barrier PEX from another project around, just probably not enough.
    It's all about the $$$ in the end.
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