Rads only heating at the top.

[JohnD]

Do you mean you closed ALL the hot rads and the cold ones did not heat up?

 

[sparer]

Do you mean you closed ALL the hot rads and the cold ones did not heat up?

No, I was asked to close 3 (post #4) but I knew that the 4 x TRVs on the 1st floor were closed already.

 

[JohnD]

If you close ALL the hot ones, I think you will find the cold ones heat up. In which case there is an easy fix.

 

[noddy997]

If you close ALL the hot ones, I think you will find the cold ones heat up. In which case there is an easy fix.

Perhaps a YouTube video will help him, written text is easily misinterpreted.

 

[Johntheo5]

The problem was the pump wasn't giving enough head in PP, proportional head, mode.

 

[sparer]

The problem was the pump wasn't giving enough head in PP, proportional head, mode.

Exactly. This is what I was surmising in the original question but thought I would need to change the pump rather than finding a different operating mode.

 

[sparer]

Perhaps a YouTube video will help him, written text is easily misinterpreted.

I'd already watched a couple of videos on Youtube about balancing the radiators and had already done this. If that's where JohnD was going, he didn't say so.

 

[MNW67]

We've got an old Georgian house that has a system operating rads on 4 floors. The LG is 2.6m from the GF where the boiler and pump is located. There are 2 more floors staggered over 4m (see attached).

I remember reading that it would pump up to 6m.

The rating of the pump in terms of head (e.g. 6m) is actually nothing to do with the height of your house. It's very confusing! Instead, it is a measure of the pump's capability to overcome the resistance in the central heating system i.e. it's ability to push the water through the boiler's heat exchanger and all the pipes, valves and radiators. The pump is not actually pushing water upwards, it is just circulating the water around the system.

 

[sparer]

The rating of the pump in terms of head (e.g. 6m) is actually nothing to do with the height of your house. It's very confusing! Instead, it is a measure of the pump's capability to overcome the resistance in the central heating system i.e. it's ability to push the water through the boiler's heat exchanger and all the pipes, valves and radiators. The pump is not actually pushing water upwards, it is just circulating the water around the system.

That's interesting

 

[MNW67]

That's interesting

You can have a large bungalow which needs a higher rated pump than a 4 storey house.

 

[Johntheo5]

The rating of the pump in terms of head (e.g. 6m) is actually nothing to do with the height of your house. It's very confusing! Instead, it is a measure of the pump's capability to overcome the resistance in the central heating system i.e. it's ability to push the water through the boiler's heat exchanger and all the pipes, valves and radiators. The pump is not actually pushing water upwards, it is just circulating the water around the system.

It's interesting alright, I have used a similar pump to fill my CWST in the attic from rain water butts on a few occasions where we had few days of mains outage, I was only pumping from the ground so a ~ head of 5M but any 6M pump should IMO pump to a height of say 10/12M once primed because of atmospheric pressure, the pump suction only requires a (NPSH) suction head of around 3M.

 

[Johntheo5]

Exactly. This is what I was surmising in the original question but thought I would need to change the pump rather than finding a different operating mode.

PP mode is interesting as well, if you ever have to replace that pump I would suggest that you get one that displays, at least, the power, watts, some now also display the flow rate in m3/hr, very useful for trouble shooting or whatever. Also, some, like mine, have a settable PP (and CP) mode which can be incrementally set in 0.1M steps to give almost any required head/flow so you can match the head/flow in PP mode to the CC head/flow with all rads open, the head/flow will then reduce as zone valves close or/and /TRVs throttle down.

Below shows what might be indicative of your head/flows in CC mode and PP(3) modes, even though the flowrate isn't greately reduced, the difference in head of 1.4M means that some rads just wont get their required flow without, at the very least, balancing, a pain.