Flow and return fro different places?

[doitall]

Nice drawing Dextrous

Rip it all out and start again after the festivities are finished.

 

[1974stephen]

Nearly right, but not quite.

It's a combi, so no tank, and no MV apart from the one I've already put in, to control just one radiator on its own programable room stat.

The other rads are all plumbed as 15mm T's of a 22mm F&R run that goes round the middle of both floor after initially T'ing just after the boiler.

Does this calrify the situation or would you still like a drawing?

 

[twgas]

drawing please.

If there's only your new MV it will never work as you want it to.

 

[dextrous]

Op, is it like this

Untitled

• dextrous
• 27 Dec 2009
• 1

 

[1974stephen]

In a very simple form, yes. Except the new MV is on the third rad from the boiler rather than the first in your example (as is plumbed now)

It's a Ferroli Maxima 30C boiler which it seems (and I don't know why I think this, as I have no evidence, and don't know how the boiler works) but it seems like once the return water is not much cooler than the flow, the pump slows down, and only slowly moves the water round the system rather than at 'full speed' as it would when it's just started. If this is the case then it could explain why I have my problem.

As this rad is T'd off from the 22mm quite a way from the boiler, it's as though the path of least resistance is not through my rad, even though I've closed down the lockshields on all downstairs rads. (the new rad is also downstairs). Once all other rads are warm, and the heating's been on for say one hour, even though the new rad is hot immediately after the heating started, it then doesn't stay hot for the dursation of the heating bing on. It just goes to being warm.

Because the new room is so needy of heat (it's a conservatory) I've come to the conclusion that it would be better to feed it from the boiler independantly from the rest of the system so it can be on when the rest of the house is not needed. In short I only need to know whether I need to extend the flow pipe for the new rad all the way back to the boiler or both.

 

[dextrous]

OK, starting to get the picture now. First thing to note is that having the valve where it is serves no practical purpose other than to close the rad off when the system is running, which is contrary to what you want anyway.

Have you tried removing the TRV head on the radiator?
Have you tried closing ALL radiators, including those upstairs?
Also, all this playing with the lockshields will not really help with balancing the system.

If this brings no joy and you want to have an independent heating circuit for the conservatory (which I believe is desirable as conservatories are meant to have this as part of the regs - others will comment on this no doubt), then one solution would be

Untitled

• dextrous
• 27 Dec 2009
• 1

Using honeywell 2 channel programmer. One room stat is wired and the other is RF
All wires run back to the wiring centre which is situated near the boiler, as are the zone valves
Note that the return pipe returns close to the boiler as well - if you use hep2o then it will save time and installation costs

There may be alternatives, but I know that this will work, since it's what I installed at home for an independent bathrooms heating system (We like warm towels in the summer)

 

[1974stephen]

Thanks dextrous.

The MV is situated where it is, because I originally planned for the programmable room stat that controlled it, to do exactly that. Isolate that radiator when the rest of the system was running, and not be able to fire the boiler. This was done like that so that the conservatory was not heated on the days when we didn't use it (wife works part time), and it's mainly used as play room at the moment, and the little man is a nursery sometimes and will never go in there. It’s controlled by a programmable room stat, and as such doesn’t have a TRV.

Now were using it (only really finished it a few weeks ago) I realize that it needs more heat, for longer, than the rest of the house, hence the change of plan of getting it to fire the boiler, and isolating it from the rest of the system.

I haven't tried closing all the other lock shield valves, as the occupants of the house will no doubt kick off if I let them freeze whilst I check the temp and flow in the conservatory!

I agree that what you suggest is preferable and what we really need.

With regard to your latest drawing, I note that the return is close to the boiler, but if you imagine the return was not plumbed back to the boiler, but onto the return of the existing circuit, a few rads away from the boiler, as long as the existing circuit MV was on the flow rather than the return, the there would still be a path for flow when just the conservatory rad was calling for heat, all be it a slightly longer one. Is that right, if not necessarily the 'proper' way?

I have issues with getting two pipes to the boiler with regard to space and aesthetics as the house is practically renovated now, but could mange one much easier, hence trying to short cut!

 

[dextrous]

I admit that I don't really know - others will no doubt comment. My gut feeling is that it shouldn't matter on a closed system, hence my earlier (and possibly wrong ) statement, but I wouldn't rely on it.

Sorry if I had subsequently raised your hopes through my ignorance

 

[doitall]

The returns should be common back to the boiler with no other connections.

The reason being you are introducing two circuits, and you need to try and balance them.

Other than that you will get reverse circulation which is probably not important, and you may find the lesser circuit stops the existing.

Fitting a lockshield valve on both returns will give you some control.

 

[twgas]

I'm pretty sure if you don't connect your cons' rad return after all the others join together you will get reverse circulation.

Dex; it's just like a HW circuit on a conventional system.