Towel rail off primaries

[hudster]

We have an unvented system which has one big primary circuit with 3 zone values (DHW, CH and a separate underfloor heating loop).

In an ideal world, I'd like the new towel rail to be gently warm when ANY of the 3 valves are active (lots in winter, just DHW in summer).

Can I therefore tap the towel rail into the primaries before the values, so it gets heated when any of them call for heat?

That would mean tapping off the big 28mm primaries which run up to the 3 values. What's the best way to limit the flow so the towel rail doesn't end up being the shortest loop and taking all flow away before it gets to the values?

If that doesn't make sense I might need to do a diagram!

 

[holty]

Yes sounds like an awsome plan.

 

[oldbuffer]

Provided your system works by any one or more of the existing motorised valves firing the boiler, then you can tap into the flow after the pump and before the motorised valves, and into the return in such a way the hot water return connection remains the last one before the boiler.

If you have a Vaillant VR65 / 66 type system, which doesn't depend on the motorised valve to fire the boiler, it wouldn't work.

I'd suggest putting a gate valve on the feed to the towel rail (near the teeing in point) and having it almost closed. Bit belt and braces, but you could also put a TRV on the towel rail.

 

[rules&rulers]

Personally if it was my system then an electric towel rail would be my first choice. Reason it will always be the same temperature and why alter an already working system.

 

[muggles]

It'll work well but you might find that you need to put a check valve in somewhere to prevent reverse circulation around the radiators when the cylinder is calling for heat

 

[hudster]

Provided your system works by any one or more of the existing motorised valves firing the boiler, then you can tap into the flow after the pump and before the motorised valves, and into the return in such a way the hot water return connection remains the last one before the boiler.

If you have a Vaillant VR65 / 66 type system, which doesn't depend on the motorised valve to fire the boiler, it wouldn't work.

I'd suggest putting a gate valve on the feed to the towel rail (near the teeing in point) and having it almost closed. Bit belt and braces, but you could also put a TRV on the towel rail.

Funny thing is, I can't find a pump anywhere. The UFH has one but that just circulates water through the flooring coils.

The boiler is a Viessmann VITODENS 100-W (link). Looking at the brochure I think I'm safe to say the pump is within the boiler, and therefore I can take the feed off anywhere before the motorised valves?

 

[rules&rulers]

Just adding,your system has been installed and commissioned to run safely and efficiently by a competent,experienced person (i hope) and any alteration would have to match or improve at what has been installed already.
As your system is more than basic that is why i have mentioned an electric towel rail,they have advantages over plumbed in units as they emit the same temperature all the time and dont rely on the boiler firing up to supply intermittent heat to a cylinder or heating system.

If you had a basic system then a diy alteration would be ok.