Fastest UFH actuators?

[Jeremy Harris]

Currently I have have a standard (22mmm thread?) 230 VAC thermal actuator that turns on or off the return from the UFH manifold, as a part of the heating /cooling comtrol system.  This actuator is a NC one, that opens when 230 VAC is applied.  We have a minor problem in that when there is a call for heating or cooling there is a delay before this valve opens.  This doesn't matter in heating mode, as the ASHP can unload into the buffer tank, but in cooling mode the only load is the UFH, and because the UFH valve takes 8 minutes to open, it means that the pressure bypass valve opens, and the ASHP shuts down for a few minutes.

 

What I'm looking for is a faster Thermal actuator, that will be a direct replacement for the 230 VAC NC unit, but that will open a lot faster.  The temptation is to drain the system and install a fast acting 12V motorised ball valve, as is fitted to the buffer tank, but that means draining and refilling the system.

Edited October 29, 2017 by JSHarris

[Nickfromwales]

@JSHarris

Wunda just supplied me with a new manifold for a customer to replace the mess that some goon fitted. They recommended the Salus auto balancing actuators which open with stepper motors, a lot quicker than the wax heated ones. Literally open to closed in a few seconds. 

Manufacturers patter

 

Wundas patter and cost

 

These have a pair of capillary wires, one for flow and one for return, to sense temp differentials and balance accordingly. Under max flow I'd say the longest I waited for fully open / closed was around 30 seconds as they struggled a bit against full pump force on one circuit open. Much quicker when the pump potential was divided. 

 

[Nickfromwales]

Oh, and beware any positive close valves as the water hammer 'closed shunt' is rather unpleasant and very much audible. . It causes the flow regulators to jump badly. 

[Jeremy Harris]

Brilliant Nick, exactly what I was after,  With luck the bypass relief valve should remove any hammer issues.

 

The odd thing is that I knew that there were stepper motor actuators, as the diverter  valve failed in our Vaillant and that had a linear stepper motor drive,  I just couldn't find an actuator for a standard valve head.

[Nickfromwales]

I fitted an automatic bypass across the flow and return at the manifold, just before the TMV, and still got a nasty thud with a couple of echoes if I manually shut the valve dead closed. The reason actuators don't come supplied as positive open / closed I believe. 

[Jeremy Harris]

I've ordered one, and will see how it behaves.  It will only operate against a closed circuit in cooling mode, as in heating mode the buffer tank motorised ball valve is always open. so if there is a hammer problem it will only be in cooling mode, and and I think we can live with that for the few time a year that it operates.   After we've planted the trees over the next few months the cooling mode may well not come on as much, either.

[Jeremy Harris]

Just fitted this Salus auto balancing valve, but fitted in a slightly unusual way, as all our loops are run as a single circuit.  I fitted it in place of the normally closed thermal actuator valve that was on the return end of the manifold, not as one of the loop control valves as Salus intend it to be used.  It was a direct replacement for the existing normally closed thermal head, so was easy to fit.  It comes with two clip on temperature sensors (not marked - either can be flow or return) and if these are fitted it will try and maintain a 7 deg C temperature differential across them, whether heating or cooling, it seems.

 

At first I just left these dangling, fitted the valve, wired it up and tried it out.  It's much faster than the thermal actuators, and uses about 1/4 of the power.  The actuator takes less than 30 seconds to motor from fully closed to fully open, and seems to close using a wound spring, as with the power off the gears can be heard winding the pin down to close the valve.  There's no hammer or any adverse effects at all, the UFH just comes on a great deal faster (the old thermal actuator was taking around 8 minutes to open fully).

 

As this device tries to maintain a 7 deg differential between the two remote clip on temperature sensors, I tried it out, with the sensors clipped to the nearest to flow and return pipes.  Our floor was at around 19.9 deg C, and the flow on the mixer was initially set to 25 deg C (it's usually between 25 and 26 deg C, about as low as it will go).  All worked OK, so I then opened up the mixer valve so that it was letting in a flow temperature of around 38 to 40 deg C, straight from the ASHP.  This is where things got interesting, as the Salus valve on the return motored a few times, then set the manifold flow temperature at a very steady 26 deg C!  Normally, with the mixer valve wide open I'd easily see the manifold get up very close to the ASHp flow temperature.

 

So, the bottom line is that this new valve not only turns the UFH on and off a great deal faster, but it also does the job of the mixer valve as well, IF it's fitted where ours is, as the return valve on the end of the manifold.  This seems like a very neat solution to me, as it does away with the need for a thermostatic mixer valve - right now I'm leaving mine set on maximum, but I may remove the remote sensing head and just fit a blanking cap to hold that valve wide open.

 

I didn't anticipate being able to get such good control with this valve, although I'm not at all sure that Salus envisioned anyone would use one like this!

 

Thanks @Nickfromwales for the head-up on these valves.

[Guest Alphonsox]

Thanks for the report Jeremy - Any idea what mechanism the Salus is using for temperature sensing ? Any chance of modifying to run at a lower temperature ?

[Jeremy Harris]

9 minutes ago, Alphonsox said:

Thanks for the report Jeremy - Any idea what mechanism the Salus is using for temperature sensing ? Any chance of modifying to run at a lower temperature ?

 

Unfortunately Salus are keeping things really close to their chest, with very little technical detail about how these work, or even what sort of hysteresis the temperature setting had.  From a very brief play around it seems that the drive mechanism is a geared motor that drives both a threaded rod that drives the actuator pin, and winds up a spring to allow the power off close.  The two clip on sensors seem to be thermistors, I think, and it doesn't matter which is the hot one and which is the cold one, the system just maintains a nominal 7 deg C between the two, if it can.  In my case it seemed to be maintaining about 6 deg C very well, so there could be a bit of a tolerance.

 

The case does look like it will unclip, so I'm tempted to order a spare and take it apart, to see if it can be reverse engineered.  The information from Salus is so poor that it doesn't even tell you that there is an LED that shines through the case and which stays on when the valve is actively motoring, or flashes when it is adjusting the temperature.  The latter process is does in stages.  It seems that the valve moves the pin a bit, waits for a minute of two to see what has happened, then moves the pin a bit more, until after a few minutes it has set the pin at the right place to maintain the set temperature differential.

 

The ability to set this differential on the outside of the unit, using a small adjustment pot, would make this unit very versatile indeed.  As it stands, used as I'm using it, as an entire manifold temperature control regulator, it is pretty close to perfect for our house.  I could use maybe 1 deg C lower in the temperature differential, to get rid of a bit of the residual overshoot, but there may be ways I can do that by repositioning the sensors.  Right now I have them just clipped to the nearest flow and return pipes, but they are long enough that I could strap one to the ASHP flow pipe, where it would see a slightly higher temperature.  It would need a new clip, as the supplied clips are designed for 16mm pipe, but the sensor just slides out of the clip and could, I'm sure, be made to fit a standard pipe clip.

 

It would be nice if Salus released more information on these units, as they seem to be potentially far more useful than the limited information about them might suggest.

[dpmiller]

break into one of the sensor wires and add a pot?

[Jeremy Harris]

11 hours ago, dpmiller said:

break into one of the sensor wires and add a pot?

 

 

Seems possible.  I think I'll buy another one to take apart and see if I can reverse engineer it.  If it does use thermistors, then spoofing the resistance would seem to be the easy way to bodge it.  What would be neater would be to find that the JTAG port is still on the board, that the reprogramming fuse has not been blown and that the code can be reversed engineered to change the 7 deg setting,

[Nickfromwales]

To be honest, I never knew about these until the other week when I priced to sort out my customers Ufh, which had never worked since they moved in around 2007 . Previous plumber had the boiler flow going across the return manifold, entering in the end which should have been capped off with the thermo aviator head / TRV there, then being sucked up through the pump and forced through the flow manifold, through it, and out the other end, going back to the boiler return ( so basically a conriuous recirculating loop which completely

 

Here you can see flow entering the bottom rail, and return leaving the top rail

bypassed all the Ufh loops,if there was no differential pressure greater than the resistance of any one loop ). 

 

Here you can see boiler flow entering the bottom rail via the TRV and boiler return leaving via the top rail   

 

It then gets pulled through the pump

 

What a shambles. 

 

 

This is a development of 12 like properties in a gated complex, and one neigbour has already asked to be booked in for the same overhaul. I wonder if the same tool fitted them all ? If he did, I may be busy until Xmas.

 

[Nickfromwales]

Oh, and the flow temp was unregulated when I got there with the TRV sensor double sided taped to the backer board you see the manifold mounted on. Wtf. The temp dial was showing a bit under 70oC. 

[Jeremy Harris]

That's crazy!  Our arrangement is the older style Wunda manifold, where the flow comes in via a normal radiator-type TRV at the lower left, on the end of the return manifold, but before the pump station.  The remote sensor bulb for the TRV is in a long pocket inside the upper flow manifold and connected via a capillary tube.  The pump sucks from a tee immediately after the mixed flow injection point and feeds the top flow manifold.  The return comes for the right lower end of the return manifold, with an identical valve to the TRV, but with an actuator head fitted so that the UFH can be turned on or off, by just closing off the return.  The ASHP flow and return are bridged by a bypass valve, as well as by the flow and return to the buffer tank coil, although the latter has a motorised ball valve to be able to turn off the buffer tank when the system is in cooling mode.  This is what the system looks like now, with the new actuator in red: