topic Fin Tube misery in Revit MEP Forum

Fin Tube misery

revitworkbench — Fri, 31 Mar 2017 15:58:09 GMT

Hi guys, I am trying to create a fin tube family that can be chain-linnked together on the supply piping but I cant get the flow to work. I set both connectors to biDirectional and Hydronic supply and tried to link them together, but it failed miserably. Please see below, anyone have any ideas on how I can create this effect with multiple fin tubes that are Preset designation? Any advise would be appreciated.

Re: Fin Tube misery

RobDraw — Fri, 31 Mar 2017 16:17:31 GMT

Correct me if I'm wrong but I don't think that won't work in series. You need to have separate takeoffs for each FTR element in order to maintain the 7 GPM in the supply pipe.

Re: Fin Tube misery

revitworkbench — Fri, 31 Mar 2017 16:36:55 GMT

@RobDraw

Yeah, thats the problem I am trying to deal with. I know itll work with separate takeoffs but thats not how the piping schematics show that these things work in practice. Which would result in excessive pipe and fittings in the schedule, and also extra pressure drop in the system.

Re: Fin Tube misery

RobDraw — Fri, 31 Mar 2017 18:10:04 GMT

If you go in series, you are going to need 7 GPM going through each of them.

Re: Fin Tube misery

revitworkbench — Fri, 31 Mar 2017 18:54:37 GMT

Noted. But is that even possible from a revit systems standpoint?

Re: Fin Tube misery

RobDraw — Fri, 31 Mar 2017 19:06:18 GMT

I don't know as I haven't delved into Revit that far, yet. If it doesn't, then Revit is severely flawed as we are talking about the laws of physics. The question you should be asking is if that FTR will work at that flow rate.

Re: Fin Tube misery

Anonymous — Sat, 01 Apr 2017 02:02:15 GMT

If it doesn't, then Revit is severely flawed as we are talking about the laws of physics.

What does Revit's flaws have to do with improper calculations of flow? I don't use Revit to do any flow calculations and I wouldn't bother spending time trying to get Revit flow calculations to work. If you connect the 2 finned tubes in series, the 2nd will get a lower entering water temperature than the 1st, but the flow is 7 GPM through both. I worry more about coordination and system working as intended rather than Revit understanding that 7 GPM goes through 2 finned tubes in series.

Re: Fin Tube misery

RobDraw — Sat, 01 Apr 2017 09:00:18 GMT

That's great Sandleaz, but the flow is the topic of this discussion. Revithero asked how changing the flow to the proper values would affect the system. I was merely saying that if Revit didn't handle this simple situation correctly, then something is really wrong. Come on back when you catch up.

Re: Fin Tube misery

fabiosato — Sun, 02 Apr 2017 17:34:25 GMT

Hello,

If you set the connector to system, and place the fins in parallel, you can set the amount of flow for each fin.

Re: Fin Tube misery

revitworkbench — Mon, 03 Apr 2017 13:34:25 GMT

thanks @fabiosato, but the schematic shows it in series:

Re: Fin Tube misery

RobDraw — Mon, 03 Apr 2017 13:43:44 GMT

Do you still have a question?

In order to limit the flow through each FTR element to the assigned flow, you need to pipe in parallel. If you pipe in series, you need to make the flow through each of the FTR in the group, the total GPM of each individual element.

Re: Fin Tube misery

revitworkbench — Mon, 03 Apr 2017 20:17:21 GMT

Hi all,

So I was able to get the system to populate in such a way that it is somewhat usable. However the system browser doesnt update properly. Even though the fin tubes are showing that their system name says they belong to the system, they dont show up under that system in the actual system browser. Why is that? see below. I did this by setting the connectors on the end fin tube to Preset, IN/OUT, Hydronic Supply/Return and the connectors on the chain link tubes to Calculated, IN/OUT, Global with connectors linked. Anyone know how I can make them show up under the right system with out double counting the GPM in the system browser? Thanks!

Re: Fin Tube misery

RobDraw — Mon, 03 Apr 2017 20:44:50 GMT

Sorry, I haven't been able to play with system classification and names much, but have you tried changing the connectors to something other than global?

(I'm also away from Revit, so I can't even play with my theory. I'm way overdue for getting it on my home machine.)

Re: Fin Tube misery

fabiosato — Tue, 04 Apr 2017 23:37:28 GMT

Hello Revithero,

In this setting I believe using hydronic supply/return connector type is better.

When I use global type, I use the same type on both ends, so both will belong to the same system.

Re: Fin Tube misery

Scott_D_ — Wed, 05 Apr 2017 21:59:18 GMT

Why not use a single circular extrusion between two reference planes to represent a pipe with connectors on either end and then use an Array of the fin tubes so that its just one preset IN Hydraulic Flow connector, one preset OUT Hydraulic Return connector and the rest is just pretty graphics.

Each family Type will be '1x 1200mm fin tube' or '2x 1600mm fin tube' etc with instance parameters for the flow value and loss.

If you need to schedule the flow through each fin tube separately you could nest a fin tube family as an array in the whole assembly family and use the same flow parameter for each fin tube connector as you do for the assembly flow value. All the flow values for that instance of the assembly would then show the same flow for all the fin tubes and you could quantify them separately as well as have the flow work correctly for system sizing and schedules.