Series Loop vs 2 Pipe Direct Return for Boiler

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Stupidhomeowner

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Hello to all, Im Gary from Chicago, just looking for some help with my radiator issue. I have a hot water boiler with 3 zones and a pump for each zone and a Taco switching relay. 1 zone goes to my 1 story addition on the back of the house with a crawl space underneath.

To make a long story short, I replaced the cast iron baseboard radiators that were in that room and added 2 walls of slant fin copper radiators (approximately 20' total). The problem is when the temp drops below 25f outside, the thermostat in this backroom won't go above 65f. We do have a little electric oil radiator that we plug in and that gives off enough added btus to allow the thermostat to reach whatever desired temp.

I have 10' of extra radiators I am getting ready to install in that room on another wall. My main question is how would you guys run the piping. Currently I have it in what I understand is a 2 pipe direct system. I eliminated all the old galvanized piping that was in the crawlspace and changed it to 3/4" copper.

I am wondering if I should keep the piping the same way when I add this extra 10' or run it in a series loop. The extra 10' of radiator will bring me to about 30' total. The crawlspace is not below grade and is only insulated with very thin fiberglass insulation between the floor joists. I did insulate all the copper with 1" fiberglass( 1" or 1/2", cant remember).

Here is a diagram of the piping that I currently have.
 

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Fitter30

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Fin tube 1 & 2 & 3 will be in the same room? First problem f tube has more pressure drop than f tube piping is coming off the bull of the tees ( side outlet of tees). There is so much info needed to design a system that throwing more heat emitters in a cold room. From is the f tube under windows to offset the cold coming in, pipe sizes, pumps ,boiler size, water temp and heat load calculation. What water temp are u running? What is the return water temp per zone? Per zone 20° f should be design less to much flow more not enough flow. Need pics of boiler and piping around it and pumps.
 

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Hey there, thanks for the reply, the boiler runs at 180F. and yes, all 3 radiators will be in the same room.
 

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Fitter30

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Easy to check zone supply and return temps. Each fin tube needs to check in and out. Use a electronic thermometer with probes ( under $30 ) can hold the probe with a rag and not a non contact. Air scoop is piped wrong needs 18" of straight pipe minimum on inlet and one zone doesn't go through it. Cast and copper fin tube put out about heat per foot accept cast takes longer to get to temp and is quieter. Can air get to all the f tube or is it blocked? Think your going to find differences in water temps across each emitter. Why did u change out the cast f tube for copper?
 

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Or a one pipe system with a bypass at each emmiter and atrv at the first emitter.
 

Stupidhomeowner

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Or a one pipe system with a bypass at each emmiter and atrv at the first emitter.
hey there, thanks for your input. couple questions. do you think the heat loss would be greater with the more piping i have in the crawlspace doing the 2 pipe system compared to running series loop(which looks like i would have less pipes in the crawl). running series loop would mean the last radiator in the chain would maybe not be as hot as the first, but its only a total of about 30'.

Also, what is the bypass and atrv?
 
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Stupidhomeowner

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Easy to check zone supply and return temps. Each fin tube needs to check in and out. Use a electronic thermometer with probes ( under $30 ) can hold the probe with a rag and not a non contact. Air scoop is piped wrong needs 18" of straight pipe minimum on inlet and one zone doesn't go through it. Cast and copper fin tube put out about heat per foot accept cast takes longer to get to temp and is quieter. Can air get to all the f tube or is it blocked? Think your going to find differences in water temps across each emitter. Why did u change out the cast f tube for copper?

I do want to get the probe you are talking about. as my name suggests, im just a stupid home owner with limited knowledge so some of what you are saying doesn't register with me. i will look into the air scoop you are talking about (im not even sure what that is lol)

i got rid of the cast iron because i had to drop my floor in that room to match the other part of the house. the radiators got broken upon removal and i figured it was easier to install the slant fin. stupid mistake but nothing i can do now.
 

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hey there, thanks for your input. couple questions. do you think the heat loss would be greater with the more piping i have in the crawlspace doing the 2 pipe system compared to running series loop(which looks like i would have less pipes in the crawl). running series loop would mean the last radiator in the chain would maybe not be as hot as the first, but its only a total of about 30'.

Also, what are the emitters your talking about?
Emitter is something that is designed to emmit heat. If you do the piping above the floor in series you'd put a bypass with a trv on the first emmiter. The valve will close automatically when it reaches temp and will send the water through the bypass to the next emmiter.

Your heat loss is what it is unless you change the insulation. Your going to loose the heat through the floor or under the floor. The reverse return gets the same temp to ever emmiter. If you want to do a single series lopp build the bypass one pipe size smaller.
 

Stupidhomeowner

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Emitter is something that is designed to emmit heat. If you do the piping above the floor in series you'd put a bypass with a trv on the first emmiter. The valve will close automatically when it reaches temp and will send the water through the bypass to the next emmiter.

Your heat loss is what it is unless you change the insulation. Your going to loose the heat through the floor or under the floor. The reverse return gets the same temp to ever emmiter. If you want to do a single series lopp build the bypass one pipe size smaller.
So if I do the series loop I would still have the piping in the crawl, I would just come up through the floor at each end of the radiators. I think I might have a professional come out and take a look because I’m a little lost with the bypass your talking about and I’m sure you don’t want to hold my hand through all of this lol. Thanks for your input though.

I guess I will ask if I run it in a series loop without any bypass, what would I be losing out on?
 

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So if I do the series loop I would still have the piping in the crawl, I would just come up through the floor at each end of the radiators. I think I might have a professional come out and take a look because I’m a little lost with the bypass your talking about and I’m sure you don’t want to hold my hand through all of this lol. Thanks for your input though.

I guess I will ask if I run it in a series loop without any bypass, what would I be losing out on?
You'd be losing even temperature distribution.
 

Stupidhomeowner

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Thank you very much

I was looking at the trv valves and I’m not sure I will be able to fit those on my slant fin radiators. With the end caps I have it doesn’t seems there’s enough room to put them in.

I’m thinking I have to run the 2 pipe reverse return. I wouldn’t need any valves installed with it correct?
 

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Technically 67' or less of 3/4" finned tube radiator in one zone should be trouble free. You just don't have enough currently to keep your room up to temp. Piping 10 more feet of finned tube shouldn't cause issues, it's just making sure you get flow with the piping method. Your drawing is pretty rough. Try to make sure the length of pipe to and from each radiator is close to equal and you should be able to get enough flow to get the new one to heat. I assumed you were redoing the piping and then would want to optimize your setup. But if you just want a quick and dirty add on you should just be able to cut a tee into the supply and return and be on your way.
 

Stupidhomeowner

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Technically 67' or less of 3/4" finned tube radiator in one zone should be trouble free. You just don't have enough currently to keep your room up to temp. Piping 10 more feet of finned tube shouldn't cause issues, it's just making sure you get flow with the piping method. Your drawing is pretty rough. Try to make sure the length of pipe to and from each radiator is close to equal and you should be able to get enough flow to get the new one to heat. I assumed you were redoing the piping and then would want to optimize your setup. But if you just want a quick and dirty add on you should just be able to cut a tee into the supply and return and be on your way.

So I have no problem starting from scratch with the piping. I just wanna make sure I’m optimizing my flow and heat as you said. This will be the 2nd time I’m tearing into it and I really don’t want there to be a third, my crawl space sucks, all work is done from your stomach or back lol.

My only issue is adding a bypass on every element and the trv (for the series loop). I googled those valves and I don’t see how they will fit within the space of my end caps.

So I’m guessing the 2 pipe reverse method you posted would be best?
 
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