Small radiator connected to hot water tank

[giomach]

We have a sealed CH system with separate programming for ground-floor radiators, first-floor radiators, and domestic hot water.

We recently had a very small radiator fitted in our very small downstairs toilet, and — presumably because it was most convenient for him — the plumber connected it to the DHW. That is, the radiator is connected to the hot water tank by two quite short horizontal 15mm pipes.

The problem is that this radiator does not heat up, except when the tank thermostat has closed and triggered the DHW motorised valve, so that the pump and boiler come on. But as soon as the tank thermostat opens again, switching the pump and boiler off, the radiator rapidly cools down. The result is that it is warm only for a short period in the middle of the night! The rest of the time, we have a tank of hot water and a cold radiator, without any movement of water between the two.

People tell me that the radiator should be removed from the DHW pipe circuit and reconnected to one of the central heating pipe circuits. I'm looking for a simpler alternative, though.

To move water between the hot tank and the radiator, why not a separate pump, fitted in one of those short horizontal pipes? Electrically it could be driven by the live wire coming from the hot water programmer, via a wall thermostat to be installed in the small toilet. But what sort of pump? It should connect to 15mm piping, would be active for short periods only, would need to pump only the capacity of the radiator each time, through a short length of piping, with no gravity to overcome. Or is this a crazy idea (if so, why?)

Thanks for your thoughts on this suggestion.

 

[Tigercubrider]

I am not a plumber and don't understand what you want

But my upstairs heated towel rail is connected to the hot water sytem while all the radiators are on the ch system . Is this what's you wanted?

 

[ianmcd]

no you need to connect both pipes from the radiator into the CH pipework

 

[FlyingFish]

I dont think you realise that your system will be indirect, so the hot water that is in the cylinder is the water that comes out of the taps. You cant use that hot water to pump around a radiator, and even if you tried the radiator would do its job and 'suck' the heat out of your cylinder so your hot water would cool pretty quick. Let a lone the issue of warm water rusting the life out your radiator!

If for some reason you cannot plumb into the actual heating circuit, then I suppose you could Tee in between the pump and cylinder 2-port and add another 2-port and room stat just for the bathroom rad. You would need to understand S-Plan+ wiring though, as well as getting the plumbing right

 

[ianmcd]

I dont think you realise that your system will be indirect, so the hot water that is in the cylinder is the water that comes out of the taps. You cant use that hot water to pump around a radiator, and even if you tried the radiator would do its job and 'suck' the heat out of your cylinder so your hot water would cool pretty quick. Let a lone the issue of warm water rusting the life out your radiator!

If for some reason you cannot plumb into the actual heating circuit, then I suppose you could Tee in between the pump and cylinder 2-port and add another 2-port and room stat just for the bathroom rad. You would need to understand S-Plan+ wiring though, as well as getting the plumbing right

The radiator is connected to the indirect HW pipework and not the DHW pipework but will have to be routed to the CH pipework

 

[FlyingFish]

The radiator is connected to the indirect HW pipework and not the DHW pipework but will have to be routed to the CH pipework

I understand that But the OP seems to think he can pump the hot water out of the cylinder into a radiator, just by adding a pump on a stat.

Something maybe possible by adding a pump, but controlling it to not conflict with the existing pump/circulation would be interesting. Perhaps changing the dhw 2-port for a 6 wire 2-port and having the pump switch on once the dhw demand has been satisfied may work, but adding a stat and stopping the setup cycling back and forth maybe an issue. What sort of performance you would manage from the indirect coil effectively working in reverse is any ones guess, you'd probably get some heat, but whether it would be useable??

Why bother, might as well do it properly

 

[Agile]

It is a pretty simple plumbing problem.

Best connected after the boiler but before any motorised valves so the rad heats whenever the boiler is operating.

 

[giomach]

With the help of all your responses I'm getting a better understanding. The rad is indeed plumbed into two pipes emerging from the hot water tank, but I've now realised that these are NOT (as I previously thought) the pipes carrying the indirectly-heated tap water, but rather the pipes carrying the directly-heated water from the boiler to the heating coil. So that's a relief, and sorry for misleading you all The problem is still to be solved, the symptoms are as I said, the rad is still being controlled by the motorised valve for the HW, but I need time to rethink about this "new" situation.

 

[Terrywookfit]

FFS Typical.....create a cockup find a solution.
Sounds like a DIY job!!

 

[Madrab]

Only way to fix it is get the rad feeds off of the hw cylinder circuit, which only gets hot when the cylinder stat calls for heat to warm the water in the cylinder and get it onto the ch circuit so it heats up with the rest of the rads.