Heat pump flow control setup

pethys

Running a Midea 16kw monoblock with 100lt buffer and multi zone wavin manifolds. 200lt DHW tank. This system can be set up with room thermostats to trigger the floor heating or temp differential to trigger the heating.  Mine uses flow temp differential. Wavin manifolds are connected to the room thermostats.

Of course the circulation pump runs constantly when in heating mode. When the manifolds demand heat the heat pump starts, depending on demand from the buffer tank.

Currently running a rgn 32-80 circulation pump, simple three speed setting. Contract calls for a 32-10fx pump, variable speed. 

The wavin manifolds deadend, ie there is no bypass valve that let's the water flow through the system. Water only completes the loop when a zone valve opens. 

System operates, zones work, DHW works. DHW  is independant of the floor heating circuit via a valve controlled by the heat pump. DHW is currently priority commanded. I will request the variable speed circulation pump be installed.

Question: Will configuring a bypass valve at the manifolds make any appreciable difference in the efficiency of my system? Is it necessary given that these are centrifugal pumps? What else am I missing here?

Background: living in a country where details, research, critical thinking, following manufacturers recommendations, etc. are non existent.

Jamie Hall

I doubt that a bypass will make much difference in efficiency -- not sure, in fact, since you are running of a bugger tank what it would accomplish.

I honestly don't think I've ever seen anything except a centrifugal pump in a modern heating application. There were, a century or so ago, a few steam systems which used steam ejectors to induce a vacuum, and of course in some power applications steam ejectors were used on the feedwater lines. Their efficiency is none to good -- and, of course, without steam, they are not an option. So called Jet pumps are used in some water supply applications. They have much better suction characteristics than straight centrifugals, but their efficiency is horrible -- and there's no point to them if you don't need a big suction lift. There is no form of positive displacement pump which would be appropriate.

What did you have in mind instead of a centrifugal pump, and why?

hot_rod

Are you going to use a ∆p, variable speed type of circulator? That will adjust to the changing flow rates and respond to a closed zone by ramping down. Should be no need for a pressure bypass valve.
Got a pic or drawing on the the buffer is piped?

Do you mean a 32-100 Grundfos circulator?°

pethys

Thanks, not changing from a centrifugal pump, just going to request the variable speed pump that's in the contract. 

I guess my main concern is that the pump is operating constantly against a dead-end. It would seem that a bypass valve allowing water to circulate back to the unit when in standby and close when a zone valve is commanded would put less strain on the pump.

Might not be worth my concern, however.

hot_rod

A 32-80 is a fixed speed, the 32-100 is a Magna variable speed circulator with a lot of different delta P adjustments. Multi zoned systems benefit, as will efficiency from an ECM variable speed circulator.

pethys

Ok, thanks for confirming the variable speed pump will get my closer to optimal operation. Pumps that are accessible here are regen brand. 

I will disregard my dead-end concerns, especially with the variable speed pump.

There is little to no lift. Pump is coming right off the buffer outlet and all components are at living floor level.