Central heating Flow and Returns seem to be mixed up

[old duffer]

water flows....how and where is always the unknown on CH systems. Water takes the route of least resistance and this easy route will vary
As suggested, air is the most likely cause (pressure/volume not being able to overcome the resistance of the air, (TRV's sticking, blocked rads) and the results is a circuit not being able to function properly.
Pressure differential has to exist (even the smallest amount) so as to create a circuit flow across a rad. No differential, no flow.
I tried everything to get this rad moving until I pressure tested F/R and found they were the same.

 

[Philpee]

Hi all,

Thank you for all of your help. I've tried to do as many f your suggestions as I can.

I can't take a useful picture of the loop pipe as it joins the system under the only par of the downstairs that is still carpeted, and all our furniture is in that room.

However, today I checked the system, and the Flow pipe (marked by the builder), was cold, whilst the Return pipe, (again marked by the builder), was very hot.

I drained the system and re-joined the loop pipes, then refilled the system. With all the radiators off except the previously cold one, that rad started to get warm. After some time, and some bleeding, it got relatively warm, so I opened the other rads one by one. There is a huge amount of air in the system, and the pump struggles to get up to speed.

There is still air in the system, that I am struggling to clear, but at least the rads are getting hot. I know that new valves etc can fail, but the rads and valves downstairs are brand new the year, and the ones upstairs are old, but have not been a problem since the builder started work.

I do think, and my thoughts are not based on knowledge or experience in the trade, that if the flows and returns are fighting against each other, it is a recipe for disaster. Perhaps someone could tell me if I am talking nonsense? I have read that it doesn't matter these days what side a TRV goes, but, for example, the 22mm Return pipe upstairs has feeds going off it, where the pipe marked Flow is 15mm. I'll see what the builder says about it when he comes back from his holiday next week.

Thanks again for all your help. At least the temperature downstairs has got up to a balmy 13.8 C

 

[old duffer]

Hi all,

Thank you for all of your help. I've tried to do as many f your suggestions as I can.

I can't take a useful picture of the loop pipe as it joins the system under the only par of the downstairs that is still carpeted, and all our furniture is in that room.

However, today I checked the system, and the Flow pipe (marked by the builder), was cold, whilst the Return pipe, (again marked by the builder), was very hot.

I drained the system and re-joined the loop pipes, then refilled the system. With all the radiators off except the previously cold one, that rad started to get warm. After some time, and some bleeding, it got relatively warm, so I opened the other rads one by one. There is a huge amount of air in the system, and the pump struggles to get up to speed.

There is still air in the system, that I am struggling to clear, but at least the rads are getting hot. I know that new valves etc can fail, but the rads and valves downstairs are brand new the year, and the ones upstairs are old, but have not been a problem since the builder started work.

I do think, and my thoughts are not based on knowledge or experience in the trade, that if the flows and returns are fighting against each other, it is a recipe for disaster. Perhaps someone could tell me if I am talking nonsense? I have read that it doesn't matter these days what side a TRV goes, but, for example, the 22mm Return pipe upstairs has feeds going off it, where the pipe marked Flow is 15mm. I'll see what the builder says about it when he comes back from his holiday next week.

Thanks again for all your help. At least the temperature downstairs has got up to a balmy 13.8 C

a cross over of the F/R would create this so its very possible the orginal installer got it wrong then hid his mistake by switching at another location..or maybe he messed up a few places. The good thing is that he's a compenent person and as such can never make a mistake or have his work challenged...he pays a private company to protect his incompetence

 

[oldbutnotdead]

Some types of radiators (posh vertical ones) don't run well backwards, some TRVs are noisy if they run backwards. Open vent system may start sucking air in from the vent if it's running backwards.
System design- it's sensible to keep flow and return the same size (usual is both in 22mm or larger distribution from the boiler dropping to 15mm or smaller for individual radiators).

 

[ericmark]

I have read that it doesn't matter these days what side a TRV goes

I found my mothers TRV's take time to detect the heat and adjust, with the TRV on the supply side it gets warm quicker and starts adjusting flow faster, so the setting of the lock shield valve was not as critical as when the TRV is on the return.

So yes can work either flow or return, but easier to set up when on the supply side.

I am told one sets up the lock shield with a differential thermometer, I do actually have one, but unfortunately don't have the sensors at the moment to use it. So the 15°C sound good across the radiator, but in practice simply can't measure it.

The TRV reports to the PC,

so if the current exceeds target I close the lock shield a tad, and in mothers house with a modulating boiler, after a little time trimming the lock shields, the rooms were spot on.

However my house uses oil, which is on/off, it does not modulate, I have tried to adjust the lock shields, and to be frank it has not worked, I have opened the lock shields far more than I think they should be, and with 9 programmable TRV's I am not really getting the control I want, I think the micro bore is putting enough resistance on flow so all radiators work, and no need to guess what 20°C is, it is actually written on the TRV in °C not silly *123456, but I can hear the boiler cycling, but rooms not up to temperature, and the wall thermostat in the hall is a bit useless, as hall is slowest room in the house to cool.

The biggest improvement to the central heating, was to replace the laminate flooring with carpet, we are told fit the wall thermostat in a room with no door to outside, and no alternative heating, and on lower floor, only room would be shower room/toilet, and that room is so well insulated it would never work.

Three rooms down stairs, and hall, all have doors to outside, kitchen clearly has alternative heating, and a wood burning fire in living room, and dinning room only used in summer so heating turned down to 10°C.

What I need is some thing like Hive with linked TRV heads, but that's a lot of money, considering already have Nest Gen 3, so I will just muddle on.

 

[ericmark]

As @oldbutnotdead has said, running backwards can cause problems, when I moved in here it would run backwards, some one it seems thought if they fitted two pumps, one for flat, and one for main house, they could select either or both and heat either or both, it simply did not work, which every pump was not selected, the flow would reverse in that pump.

So if flat called for heat, some radiators in house would warm up in reverse direction, I got motorised valves fitted so I can turn off flat or house if not required. But the way the radiators heated up when flow reversed was nothing like how they heated up in correct direction.