Underfloor Heating - mixer valve

[M.Joshi]

We currently have underfloor heating split into 2 circuits in our kitchen.

At present there is no mixer valve in the installation. A thermostat controls a Grundfos pump to allow/stop the central heating radiator flow from the boiler, to both circuits simultaneously.

I was reading on a website that sells underfloor heating kits, that a mixer valve should be used to mix the flow and return.

Different plumbers/heating guys have looked at the installation. Some recommend a 2-port valve and some a 3-port valve. None have mentioned a mixer valve.

Could someone confirm whether a mixer valve is required and also if we need a 2-port or 3-port valve?

Thanks.

 

[dancinplumba]

do you have rads upstairs ? where is thermostat ? what is stat on boiler set to ?

 

[M.Joshi]

Yes, there are radiators elsewhere in the house (upstairs and downstairs). The thermostat that controls the Grundfos pump is in the kitchen on the wall. The stat on the boiler is set to 12 o'clock.

There is a separate wall thermostat for all the radiators.

A single programmer controls the whole installation (which has a MegaFlo tank).

 

[dancinplumba]

sorry dont understand what temp 12oclock is ??
the water that goes round u/floor circuits should be approx 55c, what comes out of boiler is probs higher than this, so mixer valve is used to control u/floor water temp.

 

[Gray0689]

Yes it should have a mixing valve and a 2 port will make it in to separate circuit as long as its plumbed in correct

 

[M.Joshi]

Yes it should have a mixing valve and a 2 port will make it in to separate circuit as long as its plumbed in correct

If the underfloor heating pump is controlled by the same programmer as the main system, is there any benefit in using a separate 2-port valve?

I was told by someone that the reason a 2-port valve is required is because water will still flow through the pump and heat the underfloor pipes even if the pump isn't on?

 

[P4ULT]

do you have a manifold for the UFH

 

[M.Joshi]

do you have a manifold for the UFH

I don't think so? It was all installed about 5 years ago by some 'dodgy' plumbers hence why I am trying to determine what is required to correct it!

The underfloor heating pipe is grey with speed fit connectors I believe. The rest of the plumbing is copper.

I don't even think there is a separate fill connection. It relies on the main system filling loop.

 

[P4ULT]

to work properly you will need a manifold. if you want to control it independently you will need a 2 port zone valve and stat. seperate fill is not neccessary.

 

[M.Joshi]

to work properly you will need a manifold. if you want to control it independently you will need a 2 port zone valve and stat. seperate fill is not neccessary.

Thanks P4ULT - could you tell me what a manifold does?

 

[Gray0689]

I don't think so? It was all installed about 5 years ago by some 'dodgy' plumbers hence why I am trying to determine what is required to correct it!

The underfloor heating pipe is grey with speed fit connectors I believe. The rest of the plumbing is copper.

I don't even think there is a separate fill connection. It relies on the main system filling loop.

Love to see some pics

 

[P4ULT]

The manifold is what the UFH pipe should connect to and this will mix the water to your required temperature the 55 c mentioned earlier. Pics would be useful.

 

[Gray0689]

These are manifolds