topic Re: Piping system flow going in multiple directions in Revit MEP Forum

Piping system flow going in multiple directions

jtZDMNU — Tue, 20 Jun 2023 20:18:43 GMT

Hi,

I am trying to work with the piping system tool and I don't seem to get it right. I made a simple system loop with a pump and a water heater.

Two things:

I want to be able to see the values of the flow I'd specified for a pump and see the calculated pressure loss along the system and in the system browser. Right now, I have "not calculated" and "not available" values showing.
When I analyse my system, the flow seems to go in every directions and I dont understand why. I made a supply system and a return system and made sure that the connectors were bringing the flow in the right direction.

There must be things that I dont understand. After many hours of reading and trying, I'm asking your help XD.

Thanks,

Joel

Re: Piping system flow going in multiple directions

RobDraw — Tue, 20 Jun 2023 20:45:29 GMT

You don't have a complete system. Have you tried adding a few devices?

What are the connector settings on the ? While your at get the settings for the connectors in the water heater.

Re: Piping system flow going in multiple directions

jtZDMNU — Tue, 20 Jun 2023 21:00:05 GMT

Hydraulic return inside the connector at the top of the pump.

Hydraulic supply outside the connector at the bottom of the pump.

Hydraulic return outside the connector at the top of the heater.

Hydraulic supply inside the connector at the bottom of the heater.

And is there any documentation on what is considered a complete system for Revit ? I wanted to make the simplest one so I can play with it and try to understand how the calulations work.

Thanks,

Joel

Re: Piping system flow going in multiple directions

RobDraw — Tue, 20 Jun 2023 21:21:37 GMT

Yeah, technically, you've got a closed loop system but I would make a system more like one that actually functions like real life. Your pump should not have a supply and a return. It's either going to be on the supply side or the return side.

Fix the pump and add a couple devices. If you still can't get it to work, share the model for a quick analysis.

Re: Piping system flow going in multiple directions

iainsavage — Wed, 21 Jun 2023 09:00:26 GMT

The pump should not generate the flow rate values.

Flowrates should normally be generated by terminal equipment such as radiators, fan coils etc but in your case it could be generated by the heater instead.

So on your heater you would have a Hydronic Supply, Out, Preset and with a flow value parameter associated to the connector. You would also have a Hydronic Return, In, Preset with the same associated flow parameter. The flow parameter will assign the required flowrate and push it into the pipe network.

The connectors on the pump should normally be Global, Bidirectional, Calculated so that the pump acts as an in-line component. Associate a flow parameter to the connectors (the one you've already got works okay for this) - this parameter will read the flowrate from the connected pipe.

I tested this and it works.

In a normal system with terminal equipment, each terminal would have a Hydronic Supply, In, Preset and with a flow value parameter (Instance) associated to the connector. You would also have a Hydronic Return, Out, Preset with the same associated flow parameter. The flow parameter will assign the required flowrate and push it into the pipe network and the values will totalise through the network. In this case the heat generator connectors would be Calculated rather than Preset and the pump and heat generator would read the totalised flow from the connected pipes.

The attached document should help you.

Re: Piping system flow going in multiple directions

jtZDMNU — Wed, 21 Jun 2023 16:40:52 GMT

Ok, so based on the logic that the terminal elements define the flow for the system, I set the connectors for the heater to preset and I specified a flow value at the connectors. For the pump, I set the connectors to act like a component (Global, Bidirectional, Calculated). I also created a parameter for the pressure loss on the heater so Revit doesn't set the calculated value to 0 and everything seams to work. Revit reconnected automaticaly what I tought was two systems (supply, return) into one hydonic system.

To summarize what I understand :

the preset flow values of terminal elements

are calculated by components

and the flow can be modulated by the flow configuration set to system with a flow factor if desired.

Thanks,

Joel

Re: Piping system flow going in multiple directions

RLY_15 — Wed, 21 Jun 2023 20:04:40 GMT

You've got it.

This is a link to a (fairly old) primer on how to set up connectors for proper calculations. It echoes what's already been talked about in this thread, but is useful to hold onto in the office.

https://forums.autodesk.com/autodesk/attachments/autodesk/188/9128/1/Understanding%20Connectors%20in%20Revit%C2%AE%20MEP%20Content.pdf

Re: Piping system flow going in multiple directions

iainsavage — Wed, 21 Jun 2023 21:09:51 GMT

Same document as the one which I uploaded earlier.

Re: Piping system flow going in multiple directions

RLY_15 — Wed, 21 Jun 2023 21:13:11 GMT

True, disregard my utter blindness.

Re: Piping system flow going in multiple directions

iainsavage — Thu, 22 Jun 2023 08:45:59 GMT

No trouble, its well worth repeating!