Towel Rail on Hot Water Feed Not Getting Hot

[ncdlloyd]

Hi,

We've recently moved into a property where the bathroom towel rail is connected to the hot water feed, rather than the central heating feed. I've been told that it should get hot when hot water is running in the bathroom, but this doesn't happen. If I run hot water in the bathroom the pipe that I think runs to the radiator heats up, but I can't see the exact pipe runs due to the tiling.

I've tried bleeding the radiator, no air comes out, I just get a trickle of cold water from the top. The small amount of pipe between the tile and the radiator doesn't get hot. Is there anything else I can do to troubleshoot?

Thanks,

Nick

 

[terryplumb]

Do you have a hot water cylinder that's heated by a gas boiler ?
If so it's likely that the gas boiler needs to be on ,set to heat the hot water cylinder, and your towel rail will heat at the same this is operating.

 

[Johntheo5]

Don't think anyone would connect a rad of any description to a DHW supply, the rad would rot away in no time.

 

[oldbuffer]

There are two main types of Domestic Hot Water (DHW) connected radiators:
1. Ordinary radiators / towel rail made of mild steel or aluminium (or copper / brass) connected to the primary coil inside the hot water cylinder. The primary coil contains hot water heated by the boiler, and transfers that heat into the main body of water in the cylinder. Considering most two zone systems, one zone is for hot water, the other for central heating. Such radiators are connected to the DHW zone, and as such will (should) have inhibitor in their water. Because the water recirculates, it doesn't matter that it isn't pure.
2. Special radiators made of copper, usually chromed, and phenomenally expensive. These can be connected to the actual DHW circuit, as they are effectively just additional lengths of copper pipe. Very rare to find newly installed ones, but quite common in 30's "mansion" blocks with communal boilers and hot water / central heating distribution.

 

[SandyLyon]

If the towel warmer is installed on the Secondary DHW system it would need to be manufactured from copper rather than mild steel and to be of any real use would need to be installed on a pumped / secondary circulation system.
Otherwise it would only circulate when a hot tap is opened.
Much better if installed on the Primary Circs to the cylinder, so it’s on when the cylinder calls for heat, winter and summer.

 

[stem]

It may be that your system is heated using solid fuel, or was at sometime in the past. With solid fuel there is no thermostat that can switch the heat source off completely once it's lit. So, to prevent the water in the hot water cylinder boiling a 'heat leak' in the form of a small radiator or towel rail was connected to the hot water cylinder flow and return from the boiler. So whenever the heat source was lit, it warmed up.

After conversion to gas / oil these systems were generally converted to have thermostatic control of the hot water heating. So, if when the hot water cylinder reached the set temperature and the boiler switched off the towel rail also went off.

The diagram below shows the general idea / concept. The towel rail will only be heated when the boiler is running and heating the hot water cylinder. It is not connected to the hot water tap circuit.

 

[ncdlloyd]

Thanks for the informative replies, much appreciated. This is an old house so chances are it was heated by solid fuel at one point. I know a new boiler was installed a couple of years ago, it sounds like they should have changed how this radiator works at the same time.

@terryplumb we have a hot water tank in the cellar, I assume this is the same as a hot water cylinder? Afaik all hot water in the house relies on the tank. The boiler kicks in whenever hot water is running, topping up the tank I presume. The towel rail never gets hot though.

Nick

 

[Johntheo5]

Maybe towel rad is piped in single pipe fashion on the HW primary.

 

[ncdlloyd]

@stem looking at your diagram some more it does correlate to what I think we have/had - there does seem to be a cold return from the radiator. Maybe nothing is pulling that cold through though, which is why it isn't in turn pulling the hot through.

Nick