Help with setting Grundfos pumps.Single Pipe CH heating system.

[Jonnyh88]

I'm trying to get to grips with a system I have inherited as a new home owner. I know that single pipe systems are crap and should be replaced, but that's not an option right now so I have to make sure what I do have is set up correctly.

My bills are astronomical - £6-700 a month right now, and it's not been that cold.

Boiler: Worcster Greenstar 8000, 48k Regular Boiler

Feeds into cellar, where there are three Grundfos pumps. One on the boiler output, to the right of the LLH, and then two pumps to the left of the LLH. The top pump is the return CCH, and the bottom is the return HW tank.

Hot water tank and Central heating are both controlled by Honeywell Total Connect via the motorised valves shown in the pic.

The central heating is a single pipe system, feeding 17 radiators across two floors of the house. About 10 of those have smart Honeywell TRVs, and the communal areas are regular rads that are not controlled.

I am noticing that some of the Radiators do not seem to have good flow, as they are only getting hot at the very top and are staying cool at the bottom and at the lockshield return valve.

The main thing I can see to configure are the Grundfos Pumps. What settings should they be on?

 

[Jonnyh88]

@John.g
Thanks John, appreciate your help, as as the cost of running this system vs the heat I actually get is a concern.

All 3 are UPS3 pumps, yes.

Right now I have the boiler output pump set to Constant Speed Two.

The CH return is set to Constant Pressure 1.

The Hotwater is set to Constant Speed Two. The HW only runs twice a day and is independent from the CH controls.

 

[tamzbackforalook]

Ist thing,
Whoever recommended or supplied your "fancy" trv's is a clown.
Too much restriction for a 1 pipe come back when you have the correct valves fitted (and they won't be smart)

 

[Jonnyh88]

Ist thing,
Whoever recommended or supplied your "fancy" trv's is a clown.
Too much restriction for a 1 pipe come back when you have the correct valves fitted (and they won't be smart)

Can you help me understand why this would be the case? I was under the impression that the valves the Honeywell TRV sits on were correct. What difference does it being smart controlled make?

I've provided a pic of the valve and the TRV too.

 

[ShaunCorbs]

@John.g
Thanks John, appreciate your help, as as the cost of running this system vs the heat I actually get is a concern.

All 3 are UPS3 pumps, yes.

Right now I have the boiler output pump set to Constant Speed Two.

The CH return is set to Constant Pressure 1.

The Hotwater is set to Constant Speed Two. The HW only runs twice a day and is independent from the CH controls.

Try cp3 on the heating pump see what you get / heats up

 

[SimonG]

Pumps not the issue its restricted flow through the trv's. That's why only warm at the top, not getting the volume of water through the radiator.

 

[gpbeck]

Flow into rad in a One pipe is by gravity only, ie warm water rising up nearest vertical into rad. Any flow restriction has a great effect. So you need wide open valves at least.
The hotter the flow temperature the better, but boiler will not then condense so inefficient. Only decent answer is to repipe the system.

 

[Sparkgap]

Flow into rad in a One pipe is by gravity only, ie warm water rising up nearest vertical into rad. Any flow restriction has a great effect. So you need wide open valves at least.
The hotter the flow temperature the better, but boiler will not then condense so inefficient. Only decent answer is to repipe the system.

What he said. Looks like 15mm copper conns? YUK! Don't know how your system is arranged but sometimes it's easier to run a new pipe from the return end and repipe the whole thing as reverse return, especially if the flow and return drop under the floor. Armstrong diverter tees used to be the answer but not sure if they do them now.