Towel rail- which return?

[MikeR]

Hi Guys, hope you can help with this..

I am fitting a heated towel rail located between the boiler and the pump.

I have identified available pipes as 22mm flow from boiler (to pump and 3 port valve), 22mm CH return, and 15mm HW return.

If I connect into 22mm flow the towel rail should be warm whenever the boiler is on, but where should the return connect, to the 22mm CH return or the 15mm HW return? Or even to 22mm flow?

Thanks for any advice

-- MikeR

[PeTe33]

22mm CH return.

Then adjust the valve on the return side of the towel rail to about a

1/4 of a turn off closed is a good place to start. If it doesn't get warm at all open it a little more. It will only need to be opened a very small amout though.

[Christian McArdle]

Assuming this is a standard fully pumped system,

The return should be connected to the 22mm return to the boiler. Don't connect to the 15mm, as 15mm is already a bit undersized for a modern HWC. An entire zone (i.e. the towel rad, HWC or all the radiators) should join the trunk return at one time. Interleaving the returns can lead to types of parasitic circulation.

The flow should be connected between the pump and the input to the zone valve(s).

You will need to fit a balancing valve on the towel rad. Preferably rebalance the entire system. In lieu of this, ensure that the towel rad valve is almost closed, or it will starve the other rads and hot water cylinder. Basically only open it a fraction at a time until it just goes warm.

+------+ pump +-------------------+ | F----->>-----+-----## | |boiler| | +--------+ | | | towel rad HWC radiators | | | | | | R------------+---------------+----------+ +------+

## = 3 way zone valve (or two 2 way valves) HWC = hot water cylinder

Christian.

[MikeR]

Thanks guys, so it wouldn't work then sited before the pump?

[Set Square]

Presumably the idea is that it should get warm whenever either (or both) HW and CH are on - including in the summer when only the HW is on?

In that case, the feed needs to come from a point *after* the pump but

*before* the 3-port valve - otherwise it won't work. [This could present a bit of a challenge if the valve sits right on top of the pump, like mine does.]

Connect the return into the CH return pipe. As others have said, you'll need to have the lockshield valve only just open in order not to starve the other rads and HW coil of flow.

[Christian McArdle]

Not unless you could guarantee effective gravity flow.

Alternatively, you would need to plumb it in series with the boiler output, but this would be frowned upon in a modern system.

Christian.