I've read lots of useful information on this group about hot water UFH,
but has anyone any thoughts about how to control it? This is for a GF
extension that is going to be the kitchen. Concrete floor with the
usual insulation underneath. Combi boiler driving the existing central
heating.

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

Thanks

On 21 Mar 2006 07:45:29 -0800 someone who may be "Nigel Frost"
wrote this:-

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

It needs to be on a separate zone, ideally with a lower flow
temperature. Both are easily arranged, look on the web for how to do
it with the aid of controls and valves.

An ideal solution is a thermal store, which can provide water for
radiators and underfloor heating at separate temperatures and
domestic hot water at useful flow rates. However, these are not as
cheap as some alternatives. http://www.consolar.co.uk/ is an
example.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Nigel Frost wrote:
I've read lots of useful information on this group about hot water UFH,
but has anyone any thoughts about how to control it? This is for a GF
extension that is going to be the kitchen. Concrete floor with the
usual insulation underneath. Combi boiler driving the existing central
heating.

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

Convert to S-plan system if you're not already. ie. seperate motorised
valves for CH and HW. Add a third motorised valve for the UFH system.
Replace the existing controller for one with three zones or add a new
controller for the UFH and add it in so it switches the boiler on too.
The Honeywell CM67 is popular and works well. Reply again if you need
more info on how to modify the wiring - it's not too difficult though.

The UFH control would run the pump for the UFH system. I have wired in
an over-temp cut-off too that ensures the pump will cut out if the
water temp goes above 50degC. (Otherwise the screed turns to dust
apparently!)

As regards the UFH water temperature, as someone else said I guess the
best way is to use a lower-temperature boiler or thermal store. I've
used a thermostatic mixing valve which works very well so far. Just set
and forget!

Jon.

Nigel Frost wrote:
I've read lots of useful information on this group about hot water UFH,
but has anyone any thoughts about how to control it? This is for a GF
extension that is going to be the kitchen. Concrete floor with the
usual insulation underneath. Combi boiler driving the existing central
heating.

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

Thanks

First of all, get a three way time switch. I did. It works. Only bugger
was having to add a relay so that firing up the main boir for e.g HW
didn't cayuse the secondary UFH pump to come on.


Secondly, think long and hard about independent zones and thermostat
placements. I didn't :-) I have to do a fair bit of manual
adjustments..fortunately the main UFH area is all one big space where
we tend to leave doors open, so temperature equalises over the area
fairly well.

The message .com
from "Nigel Frost" contains these words:

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

You may well find you don't need to. The thermal mass of 3" of concrete
will keep it warm for quite a considerable time after the heating's gone
off.

The system I've installed (but not yet connected) in the conservatory
has a thermostat in the return path. That in effect sets the temperature
of the floor.

--
Skipweasel
Pay no attention to the man behind the curtain.

Guy King wrote:
The message .com
from "Nigel Frost" contains these words:

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

You may well find you don't need to. The thermal mass of 3" of concrete
will keep it warm for quite a considerable time after the heating's gone
off.

But sadly keep it cool a long time after it has come on.
I reckon a 1-3hr lag.



The system I've installed (but not yet connected) in the conservatory
has a thermostat in the return path. That in effect sets the temperature
of the floor.

On Tue, 21 Mar 2006 19:48:03 GMT someone who may be Guy King
wrote this:-

I'm wondering how to enable the UFH to be kept on (perhaps timed, or
perhaps just thermostat) independently of the main heating
thermostat/controller.

You may well find you don't need to. The thermal mass of 3" of concrete
will keep it warm for quite a considerable time after the heating's gone
off.

That is a good reason for having it on a separate zone. It can then
be turned off before the radiators (and turned on before them, for
example in the morning).


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Thanks for all your help - very useful indeed.
It seems that a separate zone, with it's own controller, is the way to
go.
I'm a bit wary of the systems with only a thermostat on the return
path, as the water entering the UFH pipe will be hot!
Other systems I've seen advertised on the web have a CW blending valve,
room thermostat, and a pump. I'm curious as to why the UFH needs its
own pump, when the boiler has a perfectly good one.

Nigel Frost

Nigel Frost wrote:
Thanks for all your help - very useful indeed.
It seems that a separate zone, with it's own controller, is the way to
go.
I'm a bit wary of the systems with only a thermostat on the return
path, as the water entering the UFH pipe will be hot!
Other systems I've seen advertised on the web have a CW blending valve,
room thermostat, and a pump. I'm curious as to why the UFH needs its
own pump, when the boiler has a perfectly good one.

Thats because of the temp reduction thing. You want to be still pumping
hot water around even when the boiler has cut off...and the blending
valve may have more or less isolated you from the CH main circuit.

Also the CH pump will not work efficiently when the blending valve has
almost shut off the flow and is in 'recirculate' mode.

The ideal for UFH is moderately warm water flowing fairly fast through
so that there is little temp differential between flow and return,
otherwise you get uneven floor heating and possible cracking.

Whereas normal CH is piping hot flow, and cold return.

I can't see the point of a a thermo on the return path either. Its the
forward path that needs to be prevented from getting to hot,and a
packaged pump/manifold/blending valve/motorised valve like wot polyplumb
do is a really good way to go.

It made installation for mine a complete snap. And the little flow
meters on the manifold are a boon when setting up and balancing.


Nigel Frost

The message
from The Natural Philosopher contains these words:

I can't see the point of a a thermo on the return path either.

It effectively sets the temperature of the slab. Regulating the inlet
will not control the temperature of the room as well.

--
Skipweasel
Pay no attention to the man behind the curtain.

Nigel Frost wrote:
Thanks for all your help - very useful indeed.
It seems that a separate zone, with it's own controller, is the way to
go.
I'm a bit wary of the systems with only a thermostat on the return
path, as the water entering the UFH pipe will be hot!
Other systems I've seen advertised on the web have a CW blending valve,
room thermostat, and a pump. I'm curious as to why the UFH needs its
own pump, when the boiler has a perfectly good one.

Only things I have seen is as ours, the thermostat head/valve is on the
return, but operated by a remote sensor strapped to the inlet manifold
thereby allowing cool return to recirculate without further heat pumped in.


--
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Guy King wrote:
The message
from The Natural Philosopher contains these words:

I can't see the point of a a thermo on the return path either.

It effectively sets the temperature of the slab. Regulating the inlet
will not control the temperature of the room as well.


It does not set the temperature of the slab.It sets the temperature of
the return water. Under conditions of slow flow and hot water the slab
takes on many different temperatures. The function of the thermo mixing
is to make sure none of these are excessive.