Supply Flow to System

[braden.bent]

Hello,

I created a test water supply system (Domestic Hot Water for tubs/showers, and Domestic Cold Water for tubs/showers and toilets). I have run the generate layout for my piping and auto sized it as well. My next step is to figure out how to get a water main added to the system to supply the cold water to the system as well as to my water heater that will in turn supply my hot water to the system. Is there any way that I can create a supply that can act as a main water supply or water meter and supply the system with however much the system is pulling from the main?

[iainsavage · Accepted solution]

Duplicate your domestic cold water system, rename it.

In your hot water tank family the hot outflow connector should be Calculated. Create a flow parameter and associate it to the connector.

For the cold inflow to the tank make the connector Preset and associate a second flow parameter to it. Use a formula to make the inflow parameter equal to the outflow parameter.

Do the same for your cold water tank family.

The outflow connectors should get their values automatically from the appliance fixture units and then pass the value to the inflow connectors.

[dyp4f]

I know from other engineering software pieces that, usually we are required to set a specific point as the start of a pipe network. This is called the "feeding" or "supply" point, and this point, or this connection with the Municipality Mains is required for the hydraulic calculations of the network.

However, in Revit no specific point of the domestic cold-water is required to be specified as “feeding point” from the Mains, or as the Start of the network.

Therefore, I am wondering how Revit calculation engine can make the required calculations to find a hydraulic solution of the domestic cold-water network inside a building.

[iainsavage]

It only calculates the pressure loss in the pipes, fittings and appliances based on the flow through each section.

WARNING: For open system it does NOT calculate pressure loss/gain due to height differences. This loss at circa a third to half a bar per storey is generally far more significant than frictional losses.

[fabiosato]

Hello,

You can create a placeholder family, just with the connector and some simple geometry to represent the point of connection, and you can set the connector properties as desired, leaving no open system.

[dyp4f]

Yes Fabio, something like that. It seems more logical to me, than having an open system, and a pipe with an open end just standing there unconnected.

[iainsavage]

Just to be clear, by “open” system I mean one in which water flows into and out of the system rather than being recirculated e.g. domestic water, open cooling towers etc.

In recirculating systems static height differences can be ignored because what goes up one side comes back down the other side and the static heights cancel each other out. In an open system that is not the case and the static height differences must be accounted for in the overall pressure drop but REVIT DOES NOT DO THAT, so beware when sizing pumps etc for this type of system if using Revit’s pressure drop calculator.

Hope that is of help to anyone reading this post.

[dyp4f]

Yes @iainsavage, that's a very important thing that we all sould always consider when calculating pressure drops or gains in open systems: the difference of water (or any fluid) static pressure due to the difference of level height.

[iainsavage]

The point that I was making is that Revit does not include this in the calculations and you have to add it yourself. Don’t just take the value from the pressure loss report, it is only for frictional losses.