6-port Ball Valve

[le-cerveau]

A follow on from my previous question:

Has anybody had experience of these 6-port Ball valves?

   

It is designed to switch a radiant panel between a heating source to a cooling source and I was considering using it in reverse to switch the ASHP between the 2 destinations in my design.  I am considering it because it is a ball valve which completely isolates and can have equal flow between outputs:

I would have to put in a bypass into the ASHP supply as it takes 80-90 seconds to change and has a dead (no flow point).

This one is the Siemens VWG41.20-4.25-4.25 (20mm connection 4.25m³/h through each way)

 

Edited June 25, 2016 by le-cerveau

[Jeremy Harris]

I've no experience of them but they look like a neat solution.  I bet they aren't cheap, though!

[PeterW]

Most Siemens Building Systems stuff has very good interface control - I expect the motor head has control switches that indicate its position so a bypass wouldn't be needed as you could shut off any pumps if the switches weren't open. 

I'd expect no change from £2-300 ...  

[le-cerveau]

I have tried to google the price but was totally unable to find any info, without a Siemens account.

[Trw144]

There must be a simpler and cheaper way to switch where you are sending the heat. Do you have a rough schematic?

[le-cerveau]

Trw1444, the schematic (current) is on the previous post (link at top)

[le-cerveau]

Update,

I am getting nowhere with the 6-port valve suppliers (unsurprisingly) so will have to revert the design, however I have found a supplier of 3-port ball valves that are ANSI/FCI 70-2-2006 Class VI leak proof (the top rating) so should do.

Downside cost, I will need a 28/32mm valve and a 20/25mm valve, these are £199 and £108 respectively (they are full bore) and I need the large one as I have one on the ASHP supply side so full flow required.  Actuators will be another £200-£300 each, however a normal 32mm 3-port motorized (crappy, shoe/paddle) valve would be about £150 so in the grand scheme of things not a miles away, but probably worth paying for the ability to isolate the TS when cooling.

[Jeremy Harris]

Have you looked at the low voltage Chinese ones?  I know that a lot of Chinese stuff is not great, but I'm impressed with the quality of the DN20 ones I bought. 

What sort of flow rates do you have that necessitate a 28mm or 32mm valve?  That's massive, as a 15mm valve will flow enough for around 10 kW or so at typical ASHP temperatures.  I'm using 22mm (DN20) valves, but they are over-kill when I looked at the flow rate and worked out the pressure drop (after I'd bought a box of DN20 valves................).  I could easily run our ASHP at full power through a 15mm (DN15) valve, with less flow restriction than there is in the 22mm corrugated coil inside the buffer tank.  In fact the lack of flow restriction caused a small hiccup, as it seems the ASHP (like a boiler) needs to see some restriction in the circuit in order to confirm that the pump is running (what's often referred to as "pump kick" detection in boilers).  It's the reason I have a thermally actuated valve on the UFH manifold, as that has enough flow resistance for the ASHP to reliably detect the pressure increase when the pump's running.

My philosophy was that most valves fail (that's based on my experience of  central heating valves having failed in every house with wet central heating we've owned) so there was merit in buying relatively cheap, but well-made, valves and keeping a stock of spares.

For example, these £15 DN20 motorised 2 port valves will mate to 22mm pipe (via a compression to iron adapter), are cheap enough that you can use two to make a three way valve with common wiring (look at the wiring and switch options on the diagrams and you can see how to connect two together to work in opposition, from two wires or three), and you could buy a lot of them for the sort of money you're looking at: http://www.ebay.co.uk/itm/Motorized-Ball-Valve-Electrical-Valve-DN20-G3-4-12V-2-wire-3-wires-/201564641525?var=&hash=item2eee3058f5:m:mpjP6_x5zwaHxqXmPnZZWig

If you needed 4 valves to make a double three way, then buying say, 12 valves would cost you £180 and you'd have two complete sets of spares.  Mine have been working faultlessly for a year, and looking at them I strongly suspect that the only part that might fail is the motor, and that can be changed without touching the wet side.

[le-cerveau]

Jeremy,

The 28 and 32mm was from the water out from the ASHP’s.  The 2 manufacturers I am currently looking at have a 28mm (1-3/32”) or 32mm (1-1/4”) connection for water supply and return so I just went with that.  That was agnostic of power or flow rate, 7-12 kW and 21.1 – 46.0 l/min max flow rate (interestingly the highest is for an 11kW version that also supports a 16kW unit).  This gives me a flow rate (basic no account of pressure loses) of 0.44-0.95 m/s. (Calculations below)

If I extend this to work out flows in various pipes I get:

So it depends on the ASHP I use.

My house need 4kW of heat (worst case) add in DHW pre-heat and a spare so it doesn’t run at full power (defrost issues) 8-9kW is probably more than enough so 25mm keeps me below 1 m/s and 20mm in the 1-2 m/s range, that reduces the price of my original Class VI valves to £108 and £83 but still expensive.

I was trying to reduce the number of motorised valves but as you say 2-port valves are cheaper and more readily available.

I also did some generic flow calculations to show volume range through various pipes at various velocities, may be useful to some people:

[Jeremy Harris]

Our ASHP has 1" BSPM fittings, but they are massively over-sized for a 7 kW maximum rated pump.  The total flow through our UFH when it's running is only around 7.5 l/min, that's through all three loops, hence the reason for me saying that 15mm is enough and 22mm is really overkill, unless there are long pipe runs from the ASHP to the system. 

The thing to look at is the basic physics, what the temperature increase will be for a given power and a given flow rate. A 12 kW heat pump with a flow of 20 litres/minute will produce a temperature increase between the flow and return connections of 8.6 deg C at full power.  In our case the maximum flow rate is around 7.5 l/min and the maximum temperature differential we see across the flow and return on an extremely cold (-7 or so deg C) day is about 4 deg C, so the heat pump is, in reality, only ever delivering around 2.1 kW, and that's only very rarely, most of the time the temperature differential between flow and return is 1 deg C or less, so the power is right  down around 500W or so.

If you needed to deliver 4 kW with a temperature differential of, say, 4 deg C to your heating on a very cold day, then the flow rate needed would be 14.2 l/min, well within the capability of 15mm pipe and DN15 valves, but fitting DN20 sized valves and 22mm pipe might be useful on long pipe runs..

You can easily work out the flow rate from the heat capacity of water (about 4200 joules per litre per deg), the power needed and the flow/return temperature differential (which will be lower than normal for a low output UFH system).

[le-cerveau]

Jeremy (my simple maths),

Worst case heat load (PHPP) = 4057W
Worst case ∆T (only 350m² UFH pipe) = 1.27K

4.057kW = 4057 joules = 243420 joules/min
Divide by 4200 = 57.957
Divide by ∆T of 1.27 = 45.63 l/min (based on floor ∆T).

If I assume each pipe (200mm spacing) pushes out more heat that the floor itself and have a flow/return ∆T of 4K then it is 12.49 l/min.

So you say a 4K ∆T on the coldest day is realistic that gives a flow rate of 12.5 l/min which is <1m/s using 20mm valves (both manifolds fed from one valve) for the TS/LLH (Low Loss Header) to the UFH.

9kW ASHP running at full power to TS/LLH through 20mm valve still in the 1-2 m/s range.

I suspect I can stick with 20mm valves and will probably take your advice in using multiple 2-port ball valves.

[Jeremy Harris]

Looks right to me. 

It's surprising how low the flow rates are, isn't it?  It really made me question quite why there were such massive ports on the back of our small heat pump.

I think a lot of heating people are still thinking in terms of high heat output boilers and houses with high heating demands, where the flow rates may well be higher and need larger pipes and fittings.  I found I have to have our UFH pump on its lowest speed, any more and it just makes more noise with no change in the flow rate.  The same goes for the ASHP pump on its lowest speed, too, if I run that on a higher setting it just blows open the pressure bypass valve.

[le-cerveau]

So here is my latest update of the system:

A higher quality .pdf version: Heating-DHW-Design(2-port).pdf

There is a lot but you can break it down into constituent parts by:
1. ignore the UFH manifolds and see the supply-flow to them.
2. Ignore the Cold water side.
3. MVHR pre-heater is just thinking aloud (probably won't happen).

Some explanations:
TMV 3 prevents the UFH drawing heat from the top of the TS unless the bottom is cool (ASHP failure....)
TMV 4 allows the ASHP to provide the duct-cooler with 8C water but limits the UFH to about 18C.  When warm (20C) water is circulating it will try and draw through the cold side (LLH), the alternative is all the way through the LLH, ASHP and TS (highly unlikely)

I think it all makes sense and I am using just 4 motorized valves, the remainder and mechanical (on way) or thermo-mechanical (hopefully).

[Jeremy Harris]

That's similar to the logic I have, except that I allow the hot water pre-heat to have priority over cooling.  Our buffer tank is only used to store warm (35 to 40 deg C) water, and I allow the thermostat on that to over-ride the house call for cooling, so if that thermostat calls it turns the ASHP off, switches the ASHP to heating mode, closes the UFH valve, opens the buffer tank valve and then turns the ASHP on again, to bring the buffer tank back up to temperature.

My thinking was that hot water was more important than house cooling and was likely to only be for a relatively short duration, so the effect on the house temperature would be small (it takes a while for the UFH to warm up and it will carry on recirculating cool water for some time).

[le-cerveau]

My thoughts for hot water were that the boiler could cope if there is DHW whilst there is a cooling call as during the cooling season the DHW demand is lower (incoming cold is warmer) but nothing is set in stone so I could easily change the control strategy to prioritise hot water.

[le-cerveau]

Thinking I could put a small buffer in instead of a LLH, to account for DHW calls when cooling and also reduce stop/start for the ASHP in cooling mode.

I mean small buffer tank like the Vaillant 40L one they use with their ASHP.

[PeterW]

Last time I checked the Vaillant buffer was some ridiculous price (north of £350...) and it made sense to go to Newark Cylinders and get myself a custom cylinder made for about half the price. 

I may still do this but it's dependent on whether I need it or can get the HP if we go that way to cope with the volume of water in the UFH as being enough. 

[Jeremy Harris]

My experience, with a small-ish UFH heated/cooled area (around 65m²) is that there isn't enough volume (strictly speaking heat capacity, I think) in the UFH when the ASHP is in heating mode, but it is fine when it's in cooling mode.  So, I don't use a buffer in cooling mode at all, and there is no indication of short cycling, the heat pump can pretty much always modulate down enough to stay running continuously when it's being asked to cool the floor. 

I believe this is because of two factors.  I have a feeling that the cooling capacity of the ASHP is lower than the heating capacity (I can't find the cooling capacity in the spec, but I'm basing this on the Genvex heat pump having a lower cooling capacity than heating capacity).  The second factor is that in cooling mode it is taking away a lot more heat than it ever supplies in heating mode, because the solar gain is probably 5 or 6 times greater, in terms of power, than the heating requirement in cold weather, and the floor gets a fair bit of that solar gain (less now the reflective film has been fitted, I'm sure).

On the other hand, when I tried to run the UFH in heating mode without the buffer the ASHP did short cycle.  Short cycle is probably the wrong term, because it has a time limit between starts and so that kicked in, but the unit was definitely turning on and off several times, rather than just modulating up and down.  Switching the 70 litre Newark buffer (around £130, IIRC) into the circuit made a significant reduction in the number of starts in heating mode, such that I'm pretty sure it only does one start, even in cold weather, before turning off for several hours, perhaps days, before coming on again.

[TonyL]

I arrived here looking for information on the same application that OP was interest in. 

 

I came across a new Johnson Controls six-port valve that would appear suitable. I know the OP will have solved their problem by  now, but wanted to leave some details here in case others found it useful. 

 

The valves are VG1611BL (3/4")  and VG1611AF (1/2"), and the actuator is VA9905-KGA-1. www.hvac-sanitary.co.uk have them in stock, and the price for the 3/4" valve and actuator is about £450 (inc VAT). 

 

This valve is somewhat novel in that it rotates 270 degrees to switch between the sources/destinations. Johnson Control have a video on YouTube that explains how this allows them to get more flow through the valve than competitor products. Not cheap, but a good solution if you need to switch both the flow and return lines of your heat pump between two destinations. 

[TonyL]

Further to my post, anyone seeking to use a six port valve to switch a heat pump between differnent destinations also needs to consider the pressure in the pipework as the valve effectively creates two seperate systems (with some common pipework that includes the heat pump). Normally a single expansion vessel would be used to accomodate the expansion and contraction of the circuit operating through the heat pump. While there is a single circuit, a single expansion vessel (if appropriately sized) will be fine, but using a six port valve would seem to need at least one appropriately-sized expansion vessel per seperate system.  

 

The Johnson Controls valve lacks a seal at the OFF position that can be used for isolation, and this provides a degree of protection against over-pressure. In theory, this would allow any overpressure at the heat pump to be disippated to a expansion vessel in either of the two systems, but this only works when the valve is used to isolate the heat pump from both systems. For safety, I am inclined to add a third expansion vessel on the common piping to the heat pump. 

Edited December 23, 2021 by TonyL