Effect of changing to a flat panel radiator in a fin tube system

Schnelltdi

Hello all 
Somewhat new to hydronic systems, but fascinated by their efficiency and comfort. So I'm remodeling a bathroom in a duplex. Wanting to get the holes off the floor and have the pipes come out of the wall to more idiot proof the bathroom. Previously there was a 4 foot fin tube radiator and wanting to put a buderus 12 x 24 2.5" thick (model 21). My question is will this adversely affect the system? Looks as though this bathroom shares its circuit with 3 bedrooms and this is believedy to be the last in line to the Weil-Mclain CGI gold 85,000 btu boiler. Another circuit teed off from the supply is a circuit for the kitchen and living room.  Also there was a more gradual circuit with 45's, but I'm considering 3 90s on S and R. Lastly all piping is 3/4 copper, but this radiator steps down to 1/2". The radiator would be about a 1 to 2 feet higher . Might this be a problem?

EdTheHeaterMan

If the circuit or loop you are referring to is a series loop, then yes that may be a problem. 1/2” pipes will have a smaller Gallon Per Minute (GPM) flow. Less flow = less heating capacity. In a series loop, the loop can carry the amount of water (heat) of the smallest pipe in the loop.

You can have a bypass in 3/4” with 1/2” tee for the panel. Place a full port ball valve between the tee fittings in order to create some restriction to flow through the bypass to cause some water to take the path thru the panel radiator

To be clear, the tee fittings would be 3/4” straight through with 1/2” branch to the radiator

EdTheHeaterMan

Here is an example diagram. The Balancing Valve should be full open on commissioning.
After the baseboard radiators are up to temperature, gradually close the balancing valve to divert more heat into the panel radiator. When there is enough heat flowing into the panel, then tighten the packing nut and remove the handle. I usually hang the handle on a wire hook near the valve in case you need to make adjustments in the future.

Schnelltdi

Thanks so much for your thoughtful answer! I kind if had something similar in mind but not sure how effective it could be until I saw your reply. My idea was to put two 3-way ball valves in the wall behind the panel radiator and use those to balance the flow. These 3 way valves could also act as an isolation circuit to remove/ install the radiator as I complete the remodel. These would be accessed through the neighboring bedroom's closet in the same unit. I can't remember if the ones I have somewhere from "kitz" are full port or not. I say in the wall due to access, but what might the restriction do if not put under the floor as in your drawing? It would also be somewhat restrictive due to the elbows to make it up into the wall. I suppose if you think its vital for the balancing valve to be on the same horizontal plane for the circuit, I could fashion up some sort of access panel in the ceiling below however it would be in the lower apartment. How vital is it not to use 90 degree elbows instead of let's say 45's?
Thanks again!

EdTheHeaterMan

As long as the 3 way valves allow the full GPM flow (about 4 GPM for 3/4") to pass, then you should have no problem. The bypass need not go below the floor with access to the valve. Just use the 3 way valve to do the job and only one is needed. a regular reducing tee on the other side will work. As long as the 3 way valve is a type that can be adjusted to allow a portion of the water to flow strait thru and a portion to branch off. Some valves are not set up for that.


A valve with an "L" port ball will not work for you. A valve with a "T" port ball may work. The best valve will have expanded oval cuts in the ball to allow for a portion of the water to flow thru one port and a portion to flow thru the other, similar to the one at the bottom.

EdTheHeaterMan

To better understand the flow of heat thru pipes, you may want to read the first few pages of this text. I used it in my 1 day seminars. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf
After you read the explanation of the way water carries the heat thru the pipes, you can reference the "Rule of Thumb" charts in the back of the book.

Your 3/4" pipes and baseboard can handle up to 40,000 BTUh of heat but you may only have 20,000 or 30,000, so your GPM can be somewhat restricted. But if the loop you are working has a total near 40,000 BTUh of heat emitters, then you do not want to have any restriction on that 3/4" pipe.

hot_rod

It would be good to know what that loop actually needs for gpm. How many feet of fin tube total, that could get you an idea of required flow rate.

Possibly an adjustable H valve could be used. I've never tried one on a 3/4 loop, however.

The bypass can be adjusted to allow some flow to the rad, the rest passes by.

Schnelltdi

So I'm having some trouble finding the right 3-way or mixing valve for this issue. I have ordered and received a 3-way full port "T" configuration valve from Valworx and after looking at it, it appears the flow no matter what would be too restricted outside of letting it set at a completely open Tee. The ports on the ball are just 3/4" round. So you can have one or two ports with small arcs of opening and the other with only one arc of opening..... seemingly far more restrictive than a 3/4" port.  EdTheHeaterMan accurately indicated an oval port in a 3-way valve may be needed, but I didn't find such a valve. I did see some t-type regulating valves but don't have any idea if these would work. I have had some discussions with a friend in Germany and we talked about whether this system is in series or parallel. For me, this is difficult to say for sure as I don't have access to looking at all the piping. Last heating season I was trying to figure this out before removing the fin tube register and had an idea which side of the bathroom's register gets warm first. I also detected other registers would get warm before this one. Lastly I applied air pressure to the supply side near the boiler and to my surprise, both supply and return lines at the bathroom heater received air pressure,  but one was clearly more air pressure/flow than the other....this one was the one I had thought had gotten warm first in my previous test. I then realized the reason is the other circuit likely was taking some of its supply pressure and dumping it into the return that is joined somewhere going from its 3/4" copper to a 1"return back to the boiler. Their are two valves near the boiler that appear to be some sort of gate valves that isolate one circuit vs the other. Might these two valves act as a way to balance the supply or are these just meant for a way to isolate? They both appear to be stuck and likely not turned in a very long time. 
I'm not sure hot_rod on what GPM would be.....is that something I could get from the circulator pump or being there is two circuits, would I have to put some sort of in-line gauge? I could estimate the linear footage of the 3/4" copper lines, but that's all it would be......an estimate. I could get the fin tube total measurements....will do later today. Any help would greatly be appreciated!

Schnelltdi

Here is the valve I ordered

Schnelltdi

One more thought, what would be wrong with just putting 2 conventional ball valves in the "H" configuration to this radiator? One on the crossover between supply and return and the other on the supply before the radiator. The crossover would always be slightly open and the supply would be as open to allow the desired output at the radiator?

hot_rod

Schnelltdi said:

One more thought, what would be wrong with just putting 2 conventional ball valves in the "H" configuration to this radiator? One on the crossover between supply and return and the other on the supply before the radiator. The crossover would always be slightly open and the supply would be as open to allow the desired output at the radiator?

That was Eds original suggestion. The 3 way valve was just to help clean up the piping for you.