Good choice of tank inlet valve?

[Tim S]

Hi,

Just got my 27 litre feed+expansion tank, which is long and slim to fit in the available space.

27 litres is on the small side of just about big enough - calculated expansion is about 10 litres (upto 80C working temp on 350 litre system) and might go as far as 15 litres if the system boiled (though at that point I care little if it starts going out the overflow).

On my tank this equates to about 10cm height gain in the water level in the tank going from cold to hot. Nominal cold water level will be set at aroun

8-10cm giving a working height of about 18-20cm which seems about right for mounting the valve and overflow.

So I don't want to use a normal arm ballcock - too much rotation stress as the ball will end up submerged at some point. I'm sure the tank will cope, but it seems bad to engineer excessive stresses in when it's avoidable.

So the obvious answer is a vertical float valve. But which one.

Choice seems to mostly be

Torbeck side inlet : part number 18198 on

Fluidmaster, part 15887 on same page.

Any pros or cons with either make?

Are there any other makes?

Cheers

Tim

[Onetap]

Yes. They're not rated for boiling water, which is why they're not used on F&E tanks.

[Tim S]

Onetap coughed up some electrons that declared:

Oh.

Any other suggestions, or am I back to brass ballcocks?

I could put a metal reinforcing plate behind the valve inlet. The tank is GRP so it's pretty strong, but like I said, no point in over stressing it...

Ta

Tim

[Tim S]

Tim S coughed up some electrons that declared:

Although another thought comes to mind... I was going to stick a little electric level sensor in too - as a boiler cutoff should the tank run dry (eg system has a minor leak and the mains water is off, like when we're on holiday). Plenty of those in RS for surprisingly reasonable money.

I could just as well use that signal to drive an electric water valve to fill it...

In fact that's a very good idea... Depending on the level sensor I might even get down to only two holes in the tank - outlet and overflow. Fill could be direct through lid and level sensor could be top mounted depending on type.

Being a GRP tank (and not cheap), I relish not the prospect of drilling any more holes than necessary...

I like this idea...

Cheers

Tim

[YAPH]

Yes, it's proper practice to put in a metal reinforcing plate. And brass ball'ocks is the way to go IMHO :-)

[Tim S]

YAPH coughed up some electrons that declared:

Thank you John. I was looking through RS thinking, hmm solonoid valves are cheap, so are optical level sensors (20 quid). But I was also thinking about the poor sod who might have to maintain this in the future and the fact that I have to wire a load of stuff with a relay and a PSU up before I can even get water in...

Do you reckon a fully submerged ball (at final temperature) is likely to cause me any problems in terms of strain?

Cheers

Tim

[YAPH]

Any float ball in a well set up system is liable to be operating fully submerged at maximum expansion. Shouldn't be a problem. If you're expecting the header to run hot much of the time you might fit a copper rather than plastic ball (I think BES do them). Probably ought to be fitted on all systems but more observed in the breach.

[Tim S]

YAPH coughed up some electrons that declared:

Thanks John, that's put my mind at rest. The one known factor with a ballcock is I *can* bend the arm to get any desired level (in this case, cold level needs to be as low as possible).

Excellent - can order the parts now - cheers.

Tim

[John]

I had never thought about the stresses on a tank wall due to the ball valve being submerged. I have experienced the washer getting really crushed due to this excessive pressure on the lever arm. Surely a better design is called for which will withstand such forces better. I personally don't like the split pin used on the old style brass ball valves - surely a weak link.

[Andrew Gabriel]

Sealed system?

[John]

Agreed

[Onetap]

The plastic floats on ball valves to the relevant BS will withstand boiling water. Copper ones are a PITA. The electronic level systems I've seen had at least 2 electrodes; low, water on and high, water off. ISTR they also had additional high-high and low-low sensors to shut off the plant and/or operate an alarm.

Solenoid valves aren't reliable for water shutting off (except washing machine ones, for some reason). They're usually solenoid-operated pilot valves that operate a diaphragm valve. The only one I ever used for water shutting-off duties (a 28mm job) failed and was replaced with an electric powered ball valve. I think the small washing machine type are just solenoid types, but don't know the details.

The ony other variation I've seen on this was a tiny ball float valve which operated a 6" diaphragm valve outside the tank. It was a delayed action thing, the water was off or 100% on, no trickling through a partially open float valve. The little float valve exerted or released pressure on the upstream side of the diaphragm, the same principle as combi diaphragm valves. The pipes from the float valve to diaphragm valve were 1/4". It was an American-made thing by that lot that make water softener valves for every softener manufacturer, Aqua summat. It worked really well but baffled every plumber who saw it.

[Tim S]

Onetap coughed up some electrons that declared:

Ta - I'll look into this too...

I guess that will be for hysteresis - to prevent random wibblings.

I was looking at optical sensors - the internal reflection type.

Do you have a lead for the electric ball valve? Or was it just a regular zone valve? I'm looking for something to control rads with (15mm would be OK). Cheapest 24v (I really want 12v, but 24 is OK, mains is not) solution seems to be a thermal wax valve, but as the valves will go in the roof voids, I'm free to use anything.

That's interesting - thanks

Cheers

Tim

[YAPH]

If you're into a bit of DIY (:-)) Sunvic's mains MOMO valves actually have

24V (IIRC) relays driving the motor. They're driven off the mains by small bridge rectifier + capacitor circuits which you could remove and rewire so that all the control side was 24V, with only mains powering the actual motors. Being MOMO they don't keep consuming power when open, only when moving from open to closed or v/v.

[Onetap]

It was a Belimo 1/4 turn ball valve with an actuator on it on the mains water supply. It wouldn't be suitable for LTHW. A 2-port zone valve would be cheapest for your application. If you're shutting off rads you should have a variable speed pump or a pressure control valve.

[Tim S]

Onetap coughed up some electrons that declared:

OK - I found some references.

Unfortunately, 12 or 24V seem rare as hen's teeth and expensive (12v=marine use = stupid markup, Honeywell make a 24V version but buggered if I can find a supplier). Because the room stats are incapable of switching mains, I don't really want to have a relay box and another cable loop everywhere (and the extra design hassle of keeping mains and SELV provably separated at each point). The stats (Heatmiser) are 12V supply, but their tech said I'd be fine switching 24V, which sounds like a -12/0/+12V supply to me :)

Indeed. I'll either use a Grundfos Alpha+ or a Wilo Smart (latter is cheaper).

Cheers

Tim

[YAPH]

Don't forget the old resistor-glued-to-a-TRV trick. Labour intensive to make and you have to be able to get into the TRV to get at the temp sensing element, and of course it operates arse-about-tit: apply power to shut it off (but about 1 Watt will do IIRC). But cheap as chips, materials-wise.

[Tim S]

YAPH coughed up some electrons that declared:

That's a good idea. Basically a TWA in reverse. TWA (Thermal Wax) seem to be the mostly likely component for the job:

It's certainly a fallback - advantages, the thermal head is still available as a fallback if the fancy bits break (big override switch on pump) and it's doable directly from 12V, so I'd need about an amp or so spare on the PSU to handle 8 rooms.

Reckons the Honeywell TRV head looks a possibility - plastic and even slots to bring cable out of. Definately the cheapest, with that head being 10-15 quid + valve.

I have come across a couple of hard to get 24V TWAs (Emmeti Topway was one IIRC). Not too expensive, more like 30 quid. Have to go hunting again for them..

Cheers

Tim

[YAPH]

Those were the ones I used, for precisely that reason. Prolly even got some kicking around (I never got the Tuits installed to make the system work as envisaged :-(). My posting on how I did it is still kicking around on th'interwub somewhere ...

[Tim S]

YAPH coughed up some electrons that declared:

Did you go for a metal clad resistor or just something normal in the couple of watt range?

It would probably take less time to make these up than to source a sensibly priced TWA. And I could dispense with the -12V supply and the extra wire in the loop.

Need a relay to invert the signal (Heatmisers are SPST call for heat) but that would be a weedy little thing and all SELV - can go in the junction box.

I did ring Heatmiser. They couldn't recommend a 12 or 24v valve - they said use a mains relay or their fancy wiring centre (which is quite nice and gives you the 12V supply). I said as much, but pointed out I'd have a star topology which meant a lot of cable going to one corner of the house - my scheme is a bus topology with local drops of 12V/GND and RS485 and a tiny junction box to connect the local programmer valve - much less bulk of cables.