DIY Doctor UK DIY Forums

I'm sure the answers to this are well known but can't find them. Please tell me if I'm wrong to believe that:

1. in a simple basic domestic modern central heating system, the radiators are connected 'in series' ('daisy-chained'), saving much copper.

2. therefore the Individual radiator thermostats and, I think, balancing cocks must operate by routing only a proportion of the total hot water flow through the radiator into the radiator's 'radiating/(convecting)' part. ( I realise that needs a complicated cock design).

I notice that with the CH on, all thermostats set to max and all balance cocks screwed down, the radiators' feed and exit pipes are cold. Perhaps I've got the wrong picture of system operation. I'd be very glad for any further explanation. Thanks.

For it to work, the ballance cocks must be all fully open & the TRV turned to full. The only time you turn down the ballance valves is when you find one of the rads not getting so warm. You then go to the rads that feel are the hotest & turn down the ballance valve buy about a 1/4 "So if its 8 full turns to shut the valve off, turn it 2 full turns off" to help push the water to the rads that are not so hot. This is only done after you have blead all the rads, starting with the highest on the system 1st, which is quite often the bathroom towel rail if fitted.

Thanks very much for your reply, collectors, but I need to understand how it is possible to regulate or balance individual radiators which are connected as a chain, by simple valves only able to restrict the flow. Maybe I don't understand something about the valve actions - I'm wondering whether perhaps the valve designs allow some of the flow to 'bypass' the radiator?

Not a clever stopcock, rather each radiator has a bypass pipe. I have one or two radiators which are quite high above the wall, and each has a pipe running from one end to the other and the radiator is attached to it by T-pieces. As such, when the TRV, or the lockshield valve is closed, the preferred route for the hot water is the pipe. This explains why your inlet and outlet pipes don't warm up if the radiator is off.
This works on the principle that the water prefers to flow through the radiator. Although, I'm surprised, since the radiator inlet is the same size as the bypass pipe and the radiator presents a more torturous path.

Of course, this assumes the radiators are in "series". My old house had microbore pipes running from the boiler to each radiator, making them effectively "parallel." This type of setup might also answer your query.

Thank you, KDM, for your reply which I unfortunately missed in 2008. It turned out that my radiators were actually connected in parrallel so I no longer found the valve actions hard to understand. I seem to have a way of wrongly expecting complication (such as radiators being in series) when matters are actually simple! That said, I did see series-connected radiators in an old steel-piped system.

surd100 wrote:Thank you, KDM, for your reply which I unfortunately missed in 2008.

2018, I think. I completely missed the date!!