3-port valve location

[Creaky Hinge]

I have a pumped & vented CH system, with indirect HW cylinder. At present the only control consists of 2 gates valves (HW and CH) and a single timer connected to the boiler and pump. All rather quaint and in need of updating! I want to fit a 3-port valve, room stat, cylinder stat, and timer system. So here's the question:

Can I fit the 3-port on the return pipework?

The relevant cupboard is a bit of a squeeze in certain areas, and my life would be much simpler if I could do this. I would have thought the lower temperature might help the valve last a bit longer... maybe not! However, I'm not sure if it would muck up the flow somehow.

FWIW, the running order on the send side is: boiler, vent, F/E, pump, then tee to cylinder and rads. The only pipework on the return is the tee from cylinder and rads, then to the boiler.

Cheers,

Creaky

[Christian McArdle]

Yes you can, although I prefer 2 port valves when possible. It may not be possible in your case either for space reasons, or because of bypass concerns with a boiler without safety lockouts.

Christian.

[Creaky Hinge]

Thanks for the quick reply.

Yes, I would need a bypass valve if I went for the 2x2 approach, which is added pipework misery (in this case). So I'm going to take my chances with a 3 port :-)

Cheers,

Creaky

[Christian McArdle]

Indeed. And yes, no problems putting on the return. Just make sure you don't mix up the flow connections, or you can get parasitic circulation. All flows from each zone should be combined together before hitting the main return line. Interleaving radiator flows with the hot water flow can cause radiators to warm up even with the zone valve on water only.

Christian.

[Set Square]

I suppose you *could* put it in the return - but the default position would be in place of the tee where the circuits split after the pump.

Where are the existing manual valves? Have you considered replacing each of these with a 2-port valve, thus having an S-Plan system? [You may also need a by-pass with this arrangement if the boiler needs a pump over-run]. In my view, S-Plan systems are superior to Y-Plan because they don't have a 3-port valve - which is a frequent point of failure - and because they lend themselves to further sub-zoning should you wish to do this.

[<me9]

I would certainly recommend using 2 port valves. I find the micro switches in

3 port (mid position) valves unreliable. I don't know why this should be, as the same microswitches in 2 port valves seem much more reliable.

[Creaky Hinge]

Thank you both for your replies.

Having lurked here for a while, I'm aware of the whole 2/3 port debate. Opinion certainly seems to favour S-plan, but IMHO it's just more hassle than it's worth. I would indeed need a bypass, and space is so tight I would need to completely redo *all* the pipework, including moving the cylinder around a bit, re-siting the pump, etc, just to get it all in. I've no plans or need for zoning, either. A 3 port on the returns is going to be much easier & quicker. Maybe I'll live to regret my decision, maybe not... time will tell! :-)

All the best,

Creaky