Just for my interest re ufh manifold

[saveasteading]

This is all working fine, ticking over with 20° feed to make it a pleasant building site.

I'm just wondering what the cross pipe at the top is for, short circuiting the system.

As it appears, the pump would circulate the water round and round the manifold, with no feed of heating water.

So I'm guessing another pump somewhere forces the heating supply.

But what is the function of that link?

[ProDave]

It's a sort of automatic bypass.  I assume this is on a heat pump which are usually very picky about a minimum flow rate so it has unhindered flow from the heat pump, and when the manifold pump wants some heat, the pump will suck it out of the flow pipe.

[JohnMo]

Your UFH (pump and manifold) is effectively on a close coupled tee.  The heat source just circulates around a loop, which is the cross piece and the piping above it on either side, the UFH pump pulls from the circulation loop and deposits back to the loop from the UFH returns, without affecting the duty of the heat source circulation pump.  It provides a means of hydraulic separation as you have no mixer valve in the system.

Edited February 13 by JohnMo

[saveasteading]

8 hours ago, JohnMo said:

The heat source just circulates around a loop,

Gotcher. So the primary loop gets the hot water to the location, in a comfortably sized pipe  with its own pump. Then the manifold and ufh pipes,  with lots of resistance, draws the hot water from the loop with its own pump.

Presumably both circuits turn off when there is no demand from any ufh loop. 

 

It's the first time I have poked at this in action. It surprised me how little difference there is in temperature between the feed and return pipes from each slab loop. But it makes every sense on reflection. There was even less difference in the feed loop but that is now explained too.

The plasterboard jointers love the unusual luxury of a warm building and very warm floor.

[Lofty718]

Do you have a radiator circuit too or is it fully UFH?

Edited February 14 by Lofty718

[John Carroll]

8 hours ago, saveasteading said:

Gotcher. So the primary loop gets the hot water to the location, in a comfortably sized pipe  with its own pump. Then the manifold and ufh pipes,  with lots of resistance, draws the hot water from the loop with its own pump.

Presumably both circuits turn off when there is no demand from any ufh loop. 

 

It's the first time I have poked at this in action. It surprised me how little difference there is in temperature between the feed and return pipes from each slab loop. But it makes every sense on reflection. There was even less difference in the feed loop but that is now explained too.

The plasterboard jointers love the unusual luxury of a warm building and very warm floor.

Looks like a very crude form of manifold temprtature control to me, normally, a TMV (mixing valve is used) which mixes some of the manifold return with the hot incoming boiler water to give the required manifold temperature, if its supplied from a ASHP at say 35/45C then neither a TMV or the above required.

Edited February 14 by John Carroll

[Temp]

If you assume the UFH loop pump and ashp pump have same flow rate then no water flows through the short circuit. 

 

If there is any difference in flow rate it will go through the short. 

 

[saveasteading]

8 hours ago, Lofty718 said:

or is it fully UFH

Fully ufh. There are 2 manifolds and this one is a long way from the heat pump and plant room.

That would explain why this one has the 'short circuit' or figure of 8 principle and the other doesn't need it.

[John Carroll]

I suppose it acts like a LLH or CCTs, if the manifold pump is circulating more than the supply then one would think that the manifold supply will be diluted, if the supply flow is greater then the the manifold supply will be at the same temperature as the supply temp (ASHP?) but the return temperature will be higher than the manifold return which may affect the HP COP?

How does the manifold temp compare to the supply temperature?.

Edited February 14 by John Carroll

[saveasteading]

2 minutes ago, John Carroll said:

a LLH or CCTs,

In full please?

[saveasteading]

3 minutes ago, John Carroll said:

the manifold pump is circulating more than the supply then..

The manifold circuit is a smaller diameter, and I'm presuming this indicates a smaller volume of circulation. 

I'm so glad now that we fitted insulation to the feed side of this circuit. Most of it is now boxed in the wall, in the service void.

Question for the plumber may be whether the feeder and manifold pumps are linked and both turn off when there is no demand.

[marshian]

18 minutes ago, saveasteading said:

In full please?

LLH = Low Loss Header

CCT = Close Coupled T's

[John Carroll]

48 minutes ago, saveasteading said:

In full please?

LLH is a low loss header and CCTs are close coupled tees which achieve the same, or different flow rates in the primary or secondary circuits, typical example might be a system with  high resistance due to number of rads, pipe runs/sizing etc, a LLH or CCTs allows the boiler circ pump to deal with the boiler heat exchanger head loss only, the secondary pump deals with the system losses.

Edited February 14 by John Carroll