How many thungs can you do wrong designing an underfloor heatingmixer?
 

Bearing in mind this is the cheapest assembly I could get - and the
hydraulic components are all standard (and look of sufficient quality).

Other units with similar components cost twice the price (like £300, I
kid you not!). This one was at least not much more than the sum of the
important parts including a Grundfos pump.


https://drive.google.com/open?id=1cW...89f43PlPAyKj0i


I am however amazed by the ability of some fab shop to cock up the
overall assembly:

1) The pump fouls the surface this is attached too (rear projection of
pump centrifuge inlet). All it needed was the mounting plate to be bent
with longer ears to bolt the clamps to.

That can be solved by packing it out from the wall on washers or wood. I
might try for thick penny washers interleaves with heavy rubber washers
to give a bit of vibration isolation in addition to the bands that go
under the pipe clamps.



2) Stupid: Grey box. 2 cables. 2 glands. So let's heatshrink the cables
together and take them in one gland and make the strain relief
questionable. And use a small box so everything is wedged in tight.


3) Worrying: 2 single insulated (as far as I can see) tails for the
thermostat, running into the end of an exposed conductive part and no
means of earthing.

The device carries no markers to indicate Class I or Class II, although
an earth terminal is provided (for looping through to the pump)/

I do not believe it meets the criteria for a Class II appliance. If I
were to use it as is, I would want to earth it. Not as easy as it seems
- either a banjo and a pair of brass nuts on the thermostat thread, or
an earth bonding pipe clamp on the main feed pipe in. No point in
bonding to the backplate - insulated by rubber from the hydraulics.

================

I might be of a mind to chase this up with the manufacturer if I can
find them, or trading standards (I think the reseller won't understand
the issues).


I however will sideskirt the problem, by ignoring the stat (which was
the subject of another thread).


Think I'm going to U turn on my last theory to use a radio controlled
rad valve and use a normal zone valve, with the contacts controlling the
pump, assuming the contacts are beefy enough[1]

1 - Pump is max 1A. Motor startup currents should be assumed to be
Ix10, so we need 10A contacts to be safe from burning out. Off to look
now...


Then all I have to do is control the zone valve, which is simple and
clean and roughly what people expect...


--
Email does not work

How many thungs can you do wrong designing an underfloor heating mixer?
 

In message , Tim Watts
writes
================

I might be of a mind to chase this up with the manufacturer if I can
find them, or trading standards (I think the reseller won't understand
the issues).


I however will sideskirt the problem, by ignoring the stat (which was
the subject of another thread).

Not been following closely but.... thermostats can be fitted to the
manifold to protect the heating circuit from mixer valve failures where
this is not limited by the boiler o/p temp.


Think I'm going to U turn on my last theory to use a radio controlled
rad valve and use a normal zone valve, with the contacts controlling
the pump, assuming the contacts are beefy enough[1]

1 - Pump is max 1A. Motor startup currents should be assumed to be
Ix10, so we need 10A contacts to be safe from burning out. Off to look
now...


Then all I have to do is control the zone valve, which is simple and
clean and roughly what people expect...



--
Tim Lamb

How many thungs can you do wrong designing an underfloor heatingmixer?
 

On 03/11/18 19:55, Tim Lamb wrote:
In message , Tim Watts
writes
================

I might be of a mind to chase this up with the manufacturer if I can
find them, or trading standards (I think the reseller won't understand
the issues).


I however will sideskirt the problem, by ignoring the stat (which was
the subject of another thread).

Not been following closely but.... thermostats can be fitted to the
manifold to protect the heating circuit from mixer valve failures where
this is not limited by the boiler o/p temp.

The instructions mention 43C - which suggests this one is N/O and closes
when hot water appears. I will test that with a meter in a moment. Also,
it's in the wrong place for O/H protection.

But you're quite right - over heat protection would be a very good idea
- shoving 60C+ (upto 90C if the boiler gets run to max) would be very
very bad for the screed!

I'm just going to put 13A plugs on the pump tails for now via a 13A
ZWave switch that's controlled by my heating system. I'll figure out how
it likes to run then wire it in properly to suit. I'm certainly thinking
of including an O/H pipe stat as a fail safe, but I think you can buy
those as a separate unit and clip them on.

--
Email does not work

How many thungs can you do wrong designing an underfloor heatingmixer?
 

On 03/11/2018 11:22, Tim Watts wrote:
That can be solved by packing it out from the wall on washers or wood. I
might try for thick penny washers interleaves with heavy rubber washers
to give a bit of vibration isolation in addition to the bands that go
under the pipe clamps.


I save all my non-ferrous 2p pieces for this situation.

Drill a hole and voila, a non-rustable washer.