Why a seperate zone for UFH?

[vetinry]

Good morning everyone

I've got to the point of sorting the plumbing for the new UFH which has been installed in the kitchen.

The system is made by Continental and they state that it must be installed on a different zone to the rest of the heating.

I guess my question is why?

I understand that installing on a different zone will enable independent control of the UFH circuit but is there something more fundamental?

When I removed the radiators in the kitchen, dining room and utility room, I have extended the 22mm pipes which fed this part of the system and will use them to plumb in the UFH.

So, if I simply plumb in the UFH, it will then be part of the main circuit.

I'm sure I (or more likely a heating engineer) can put this on a seperate zone, but I'm just wondering the rationale

Thanks

Steve

 

[picasso]

ufh runs at a much lower temperature than your rads or supply to the hot water cylinder, if it wasnt zoned you would find your floor very uncomfortable to walk on.

 

[mysteryman]

An add-on UFH kit usually has its own circuit pump and mixing valve. It will draw heat from the central heating circuit. Otherwise, it can be supplied via a third 2 port valve if you have an S Plan. [Two 2 port valves]

 

[daneski88]

UFH also needs to come on at an earlier times than the other circuits since it takes longer for a room to reach the desired temperature due to the nature of how it operates, and may also require night-time bursts to prevent the room cooling down completely. This needs to be independent from the other radiators for the sake of economy and comfort.

 

[vetinry]

Sorry, I should have given more information.

The continental system I have does have its own pump and mixing valve which I assumed would therefore take the water from the central heating and down mix to the required floor temperature.

Therefore, is there any advantage of plumbing this to a seperate zone valve if I'm happy that the floor will only be on with the rest of the heating.

Incidentally, will the pump for the UFH always be working when the heating is on or will it be controlled by the thermostat?

Thanks

Steve

 

[vetinry]

Ah

Should have read that final response before posting again.

Unfortunately, I believe that my central heating is of Y plan design. Does this make it more complicated to add an additional valve to than an S plan type?

Steve

 

[daneski88]

Not sure about the wisdom of having the UFH system on only when the rest of the heating system is on - it takes longer to heat a room from cold using UFH, so all the radiators may come on at say 4am instead of 6am, which is a lot of excess/wasteful energy being used.

If you intend to go ahead with it anyway, it won't make any difference what plan you have since you're not controlling the heating zones separately.

 

[vetinry]

I was asking about the system design because from what you've said, it's fairly important to get this onto a seperate zone.

I'm hoping that the supply to the area of the house with the UFH was discreet from other feeds and therefore adding a zone valve hopefully won't cause too many problems

Thanks

Steve

 

[daneski88]

Have a look at this for a schematic. The valves connecting to the radiators and cylinder are probably actually one three port valve.

 

[Agile]

You seem to be missing ( or avoiding ) the point !

Its essential that the UFH is seperately zoned so that it can be powered at different times so that it can provide the right comfort when its needed and avoid wasting energy and causing discomfort by having heat in bedrooms when its not wanted.

UFH needs to be started about 2 hours before rads.

With a "Y" system you need to modify it to an "S" or pseudo "S" plan.

Tony

 

[daneski88]

With a "Y" system you need to modify it to an "S" or pseudo "S" plan.

I take it this could be done by installing another 3 port on on the heating circuit, linked to the original one?

 

[Agile]

In accordance with the correct use of a forum, all postings I make are in reply to the original poster ( unless specifically stated ).

A second three port would be the cheapest way to add the necessary valve function.

Tony

 

[daneski88]

oops

 

[vetinry]

Thanks Tony

I'm struggling to cope with 2 3 port valves next to each other and so think this needs to be handed over to an expert.

Interestingly, my house is close to 300sq m and I read somewhere that above 150 sq metres, S plan should be used in preference to Y plan

Is this purely to do with flow rates through a 3 way valve?

And therefore, would it be preferable to convert my system to S plan at the same time as plumbing in the new zone?

Steve

 

[daneski88]

S plans are preferable since they are easier to zone independently, and thus enable you to leave sections of the house unheated if they are not in use - relying on turning off radiators doesn't stop water being pumped around the pipework in these zones.