Tommorrow, I am lifting the floor, and planning on where to stick the pump
and maniifold, and other connection planning. I did a dry run this
evening, and connected all the bits I have up.

http://img88.imageshack.us/img88/5839/ufhpumplp2.jpg

The plumbiung is reasonably straightforward. However I have a couple
questions regarding the pump, actuators and mixer thermostat, and how they
connect up electrically and adjusted.

Obviously the actuators are wired into the thermostat somehow, is the
power to the pump also fed via the wireles thermostat control valve? Or
does is the pump powered continuously?

There is also the mixer valve, with the extended temp probe, does this
need any special considerations? It does not seem to have any electrical
connections. What do I set this to? It seems I have 2 thermostats here,
one measuring the heat going out, and then the room thermostat closing the
return when the room gets too hot.

Any help/advice gratefully received!!


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On 25 Feb, 22:15, "Mark Gillespie" wrote:
Tommorrow, I am lifting the floor, and planning on where to stick the pump *
and maniifold, and other connection planning. *I did a dry run this *
evening, and connected all the bits I have up.

http://img88.imageshack.us/img88/5839/ufhpumplp2.jpg

The plumbiung is reasonably straightforward. *However I have a couple *
questions regarding the pump, actuators and mixer thermostat, and how they *
connect up electrically and adjusted.

Obviously the actuators are wired into the thermostat somehow, is the *
power to the pump also fed via the wireles thermostat control valve? *Or *
does is the pump powered continuously?

There is also the mixer valve, with the extended temp probe, does this *
need any special considerations? *It does not seem to have any electrical *
connections. What do I set this to?

It's a self-acting 3-port mixing valve, very like a TRV. 2 inlets, one
mixed outlet, the common outlet port is always connected to the pump
suction port.
The sensor bulb is on the end of a capilliary tube, so it senses the
water flow temperature, not space/air temperature as a TRV would.
It doesn't seem to have any electrical connection to the pump, si I'd
guess that runs continuously, or whilst there is a demand from any one
(electric?) room/zone thermostat.

It's manually adjusted so you need to be able to reach it to tweak it
up or down as the weather changes.

There's probably a clamp-on manual reset thermostat on the flow
header, probably to shut off the pump if it overheats. Excess
temperature can cause huge damage to some floor finishes.

You should have got wiring/installation details from the supplier
which would probably be better than my guessing.

Whatever suits. ISTR the recommendation is to start very low and creep
it up gradually. Check the instruction on the Rehau site.

On 25 Feb, 22:15, "Mark Gillespie" wrote:

Oh, and BTW there should be negligible pressure difference between the
flow and return connections (your red and blue lines).

You'd usually do this by connecting it to a local low loss header (aka
cross-over header).
This is a bit of straight pipe with an isolating valve at one end and
a lock-shield regulating valve at the other, like a radiator. The tees
for the F&R to the mixing valve ar along the middle bit of the pipe.
I'd do it in 22mm. You need to restrict the flow with the regulating
valve because the LLH has negligible resistance & will be a roaring
short circuit if not regulated.

The water flows along the low-loss header at the same rate when the
primary pump is on, whether the UFH/secondary pump is on or off. The
UFH pump draws water from the LLH as the mixing valve requires it and
returns an equal volume of water to the LLH. Primary flow must
secondary flow or you get mixing by reverse flow in the LLH.

Connecting it like a radiator (flow to red, return to blue) is wrong,
'cos the primary pump would then exert a differential pressure across
the mixing valve ports and interfere with its operation by the
actuator.

You need the primary pump running all the time the UFH is in use. This
is a bit of a bummer if you don't want the rest of your radiator CH on
all the time but need your UFH on continuously; you then need zone
valves.

You can only avoid the need for the primary pump if the mixing valve
set is connected from/to a thermal store.

Mark Gillespie wrote:
Tommorrow, I am lifting the floor, and planning on where to stick the
pump and maniifold, and other connection planning. I did a dry run this
evening, and connected all the bits I have up.

http://img88.imageshack.us/img88/5839/ufhpumplp2.jpg

The plumbiung is reasonably straightforward. However I have a couple
questions regarding the pump, actuators and mixer thermostat, and how
they connect up electrically and adjusted.

Obviously the actuators are wired into the thermostat somehow, is the
power to the pump also fed via the wireles thermostat control valve? Or
does is the pump powered continuously?

There is also the mixer valve, with the extended temp probe, does this
need any special considerations? It does not seem to have any
electrical connections. What do I set this to? It seems I have 2
thermostats here, one measuring the heat going out, and then the room
thermostat closing the return when the room gets too hot.

Any help/advice gratefully received!!


Not sure about your exact system, but this is how MINE is wired.


From the switched live to the whole system, I go through the timer and
the master thermostat to run the motorised valve that controls the
entire UFH.

This MV contacts run the subsidiary pump *and a relay*, whose contacts
are between switched live and the boiler/pump. You need a relay so that
e.g. calls for DHW do not start the UFH pump going. I.e. you cannot
directly parallel the UFH pump and the boiler pump.

The auxiliary pump circulates water around the UFH as long as the stat
calls for it. The mixer valve on mine is a 4 port wax capsule type
thing, that senses the flow temp in the UFH and either lets in more hot
water, or simply recirculates what is there already if its hot enough.

I have a second thermostat which sits between timer switched live output
and a couple of units that clamp on the manifold to cut the kitchen
circuits, as there is an Aga in there and extra heat is almost NEVER needed.

Somewhere I have a diagram of all this.

On Mon, 25 Feb 2008 22:51:16 -0000, Onetap wrote:

It's manually adjusted so you need to be able to reach it to tweak it
up or down as the weather changes.


That there lies the problem, the whole lot is going under the living room
floor, with a small service hatch under the carpet to get to it incase of
servicing.

I explained this to the supplier. My understanding was that I set the 3
port mixer once, and then the wireless room thermostat and actuators
(which fit on all 3 of the cold returns from the UFH) switch off the flow.

I will contact the system suppplier today, as see what they say.

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On Mon, 25 Feb 2008 23:14:21 -0000, Onetap wrote:

On 25 Feb, 22:15, "Mark Gillespie" wrote:

Oh, and BTW there should be negligible pressure difference between the
flow and return connections (your red and blue lines).

You'd usually do this by connecting it to a local low loss header (aka
cross-over header).
This is a bit of straight pipe with an isolating valve at one end and
a lock-shield regulating valve at the other, like a radiator. The tees
for the F&R to the mixing valve ar along the middle bit of the pipe.
I'd do it in 22mm. You need to restrict the flow with the regulating
valve because the LLH has negligible resistance & will be a roaring
short circuit if not regulated.

The water flows along the low-loss header at the same rate when the
primary pump is on, whether the UFH/secondary pump is on or off. The
UFH pump draws water from the LLH as the mixing valve requires it and
returns an equal volume of water to the LLH. Primary flow must
secondary flow or you get mixing by reverse flow in the LLH.

Connecting it like a radiator (flow to red, return to blue) is wrong,
'cos the primary pump would then exert a differential pressure across
the mixing valve ports and interfere with its operation by the
actuator.

You need the primary pump running all the time the UFH is in use. This
is a bit of a bummer if you don't want the rest of your radiator CH on
all the time but need your UFH on continuously; you then need zone
valves.

You can only avoid the need for the primary pump if the mixing valve
set is connected from/to a thermal store.




Didn't understand a single bit of that :-)

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"Mark Gillespie" wrote in message
news
On Mon, 25 Feb 2008 23:14:21 -0000, Onetap wrote:

On 25 Feb, 22:15, "Mark Gillespie" wrote:

Oh, and BTW there should be negligible pressure difference between the
flow and return connections (your red and blue lines).

You'd usually do this by connecting it to a local low loss header (aka
cross-over header).
This is a bit of straight pipe with an isolating valve at one end and
a lock-shield regulating valve at the other, like a radiator. The tees
for the F&R to the mixing valve ar along the middle bit of the pipe.
I'd do it in 22mm. You need to restrict the flow with the regulating
valve because the LLH has negligible resistance & will be a roaring
short circuit if not regulated.

The water flows along the low-loss header at the same rate when the
primary pump is on, whether the UFH/secondary pump is on or off. The
UFH pump draws water from the LLH as the mixing valve requires it and
returns an equal volume of water to the LLH. Primary flow must
secondary flow or you get mixing by reverse flow in the LLH.

Connecting it like a radiator (flow to red, return to blue) is wrong,
'cos the primary pump would then exert a differential pressure across
the mixing valve ports and interfere with its operation by the
actuator.

You need the primary pump running all the time the UFH is in use. This
is a bit of a bummer if you don't want the rest of your radiator CH on
all the time but need your UFH on continuously; you then need zone
valves.

You can only avoid the need for the primary pump if the mixing valve
set is connected from/to a thermal store.




Didn't understand a single bit of that :-)

Well I only read it because you said that! Seemed quite understandable in an
english sense, however, I couldn't help thinking that a low loss header with
the regulating valve stopped down to avoid the short circuit would
necesssarily limit the flow to the UFH in an undesirable way. Is this not
the case?


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

On 27 Feb, 08:25, "Bob Mannix" wrote:

Well I only read it because you said that! Seemed quite understandable in an
english sense, however, I couldn't help thinking that a low loss header with
the regulating valve stopped down to avoid the short circuit would
necesssarily limit the flow to the UFH in an undesirable way. Is this not
the case?

It shouldn't be, you want to limit the primary flow to the maximum
that would be required by the UFH/secondary. Anything more than that
would just pass straight through the low loss header and back to the
boiler. Most of the time the UFH would operate at part-load and so the
mixing valve would only be drawing a small portion of the water
passing through the LLH.

You'd be better off setting the mixing valve up as an injection mixer,
so that it only handles the smaller primary flow; you then get a
smaller mixing valve. As described above, a mixing valve is handling
all the UFH/secondary flow rate which is larger.

It all makes sense, honest guv.