Prioritising DHW hot demand from specific ports on a manifold

[RichJ]

Hi

 

I'm trying to work out what I need to implement a DHW manifold setup. I have a query re the hot water aspect.

 

I'm planning to run a 22mm cold mains feed from the main stop tap down to a Viessmann 100 combi, tee'ing off just before the boiler (in 22mm) to a cold DHW loop like shown in the photo (photo obviously lifted from another post on here). The DHW loop will be made up of 22mm copper and Wavin Hep2o manifolds.

 

The hot DHW will come from the 15mm output from the boiler and run in 15mm to a hot DHW loop. In contrast to the cold DHW, the hot DWH loop will be made up of 15mm copper and Help2o manifolds.

 

My question is, if I just feed the hot DHW from the boiler straight into a manifold with no loop in the pipework so the water can only flow into the manifold from one direction, will this prioritise hot water to the ports closest to the inlet? Is this a means of say prioritising the feed to the shower?

 

Edited December 4, 2023 by RichJ

[Kelvasco]

Hello,

 

Few things. The cold loop should come off the control group on the boiler so that you don't have pressure issues. This will likely mean 15mm for both cold + hot, or if your boiler can, then do 22mm for everything.

 

My understanding (happy for the proper experts of this forum to correct it) was the only way to "prioritize" was just fitting the specific application to the first point as the cold/hot feeds in. Also, match those across the manifolds. However, if you do the feeds in 22mm and then come out the Hep's in 15mm it won't make much difference as the feed rate will be greater than the 15mm output. That's what happens in our application (only for a bathroom though, not the whole house). 

 

We feed the manifold with 22mm's and then 15mm's to shower/bath/sink/toilet. Seems to be working as people can use the sink without the shower having issues.

 

Hope that helps.