Ufh manifold, blending valve with ASHP.

[Russell griffiths]

So all my bits turned up for my ufh, but I’m confused with the manifold layout, I was told if I’m fitting an ASHP I don’t need a blending valve, is this right. 

Who has a blending valve and who doesn’t. 

 

Confused as usual. 

[Russell griffiths]

@PeterW  @Nickfromwales Any thoughts chaps. 

[PeterW]

Fiiiiiiggghhttt..!!!

 

Blending valve every time, otherwise even when it’s off you are circulating fluid through the ASHP. 

[Nickfromwales]

11 minutes ago, Russell griffiths said:

@PeterW  @Nickfromwales Any thoughts chaps. 

Blending valve ALWAYS. 

You will need a low temp tolerable one such as the Ivar as normal TMV’s very much dislike low flow temps ( 30oC and below ) but these cope very well. 

[Nickfromwales]

Primarily as max floor temp failsafe is what @PeterW meant to say

Putting a zone valve in and doing as JSHarris did would be an option too, to shift the heat from the sun-baked bits of floor to the colder side of the house. 

[Russell griffiths]

Thank you boys. 

Armed ready for another annoying phone call. 

[Nickfromwales]

Just now, Russell griffiths said:

Thank you boys. 

Armed ready for another annoying phone call. 

Maybe not. You’ve asked the question and you have your answer ?. I couldn’t find those low temp blending valves anywhere else, at a decent price and with an A-rated pump, so if you have everything else then you only need to order that and you’re done? 

[Nickfromwales]

How are you getting on with piping ?

[Pocster]

I’m confused now !

I thought no blending valve for ufh but valve for dhw and ASHP . But I’m confused .... 

[PeterW]

2 minutes ago, pocster said:

I’m confused now !

I thought no blending valve for ufh but valve for dhw and ASHP . But I’m confused .... 

 

Shall we try by talking slowly ........??

 

DHW doesn’t need a TMV on the input to the coil but does need it from the output from the storage whether its UVC or SunAmp or TS. UFH should always have a TMV as you want to blend the floor temp to a maximum temperature to prevent overheating - trusting the ASHP to do that, and also only having the ASHP pump to circulate water in the system is a really bad idea. 

[Nickfromwales]

Every UFH manifold needs a pump and a TMV. TMV’s  cannot be pumped through, they have to be ‘sucked’ on, ergo a pump needs to be downstream of a TMV in a heating setup. 
TMV caps the max temp the floor will ever see, I’m sure there’s a reg there but moot unless you intend to not fit one. You should not ( cannot ) rely on an external Ctrlr to guarantee that the slab / screws won’t see the max temp of the heat source, so if said Ctrlr failed, on an ASHP, you could get up to 55-60oC floor temp which will cook anything that’s not high-temp tolerant, plus it would be a health hazard ( if a toddler or elderly were to end up on it ) or if anyone walked onto it barefooted etc hence the reg. 

UFH manifolds need the local pump to circulate water through the loops, and the ASHP circulation pump send the water to / from the manifold. Think of it like a figure 8, with the two circuits being connected but hydraulically separate eg both pumps can circulate at different flow rates without conflicting with one another. 
The IVAR blending set also has an inbuilt bypass ( so the ASHP pump never sees a closed circuit ). 

[Nickfromwales]

Crossed with peter. 

[Pocster]

2 minutes ago, Nickfromwales said:

Every UFH manifold needs a pump and a TMV. TMV’s  cannot be pumped through, they have to be ‘sucked’ on, ergo a pump needs to be downstream of a TMV in a heating setup. 
TMV caps the max temp the floor will ever see, I’m sure there’s a reg there but moot unless you intend to not fit one. You should not ( cannot ) rely on an external Ctrlr to guarantee that the slab / screws won’t see the max temp of the heat source, so if said Ctrlr failed, on an ASHP, you could get up to 55-60oC floor temp which will cook anything that’s not high-temp tolerant, plus it would be a health hazard ( if a toddler or elderly were to end up on it ) or if anyone walked onto it barefooted etc hence the reg. 

UFH manifolds need the local pump to circulate water through the loops, and the ASHP circulation pump send the water to / from the manifold. Think of it like a figure 8, with the two circuits being connected but hydraulically separate eg both pumps can circulate at different flow rates without conflicting with one another. 
The IVAR blending set also has an inbuilt bypass ( so the ASHP pump never sees a closed circuit ). 

Ok

Here’s my ‘logic ‘ . To automate each zone I have an electrically operated actuator per zone . If no zones are being heated then pump is off . Do I need to automate the mixing ? - or do I not care about that I.e water into the ufh is always blended. ??

[Nickfromwales]

Always blended. 
yes, pump will switch off if you have a manifold wiring centre and have fitted actuators to each loop. ?. 

[Pocster]

2 minutes ago, Nickfromwales said:

Always blended. 
yes, pump will switch off if you have a manifold wiring centre and have fitted actuators to each loop. ?. 

Ok . That simplifies it - blending isn’t something I fiddle with .

Makes life easier ! . Though an actuator per zone and a z wave relay per actuator . It seems strange actuators are closed by default and open when powered . Basically using electric just to stay open - would of assumed they are powered open / closed and then just stay in that position not using power ( like a trv type screw thread to open and close ) . 

[Pocster]

Think I fancy pixie Lott - just saying - bet she knows everything about ufh .

Edited July 11, 2020 by pocster

[Nickfromwales]

48 minutes ago, pocster said:

Ok . That simplifies it - blending isn’t something I fiddle with .

Makes life easier ! . Though an actuator per zone and a z wave relay per actuator . It seems strange actuators are closed by default and open when powered . Basically using electric just to stay open - would of assumed they are powered open / closed and then just stay in that position not using power ( like a trv type screw thread to open and close ) . 

The Salus ones do as they’re geared and use stepper motors to change state. 
Others are a heating element that warms a bag of wax, and take up to 2-3 minutes to fully open / close. 
You cannot use solenoids as the momentum of the water flowing in the loop has enough potential to cause water hammer, hence the slow open / close normally preferred and promoted with the standard wax heads.

Closed by default so you don’t get unwanted flow down one loop when another is calling.

The Salus ones are great, and automatically balance the system by detecting heat on the return pipe and that makes the actuator arrest flow, thus leaving the remainder of the pumps potential to service the longer loops which have not yet returned warm / hot water. 

Edited July 11, 2020 by Nickfromwales

[Pocster]

4 minutes ago, Nickfromwales said:

The Salus ones do as they’re geared and use stepper motors to change state. 
Others are a heating element that warms a bag of wax, and take up to 2-3 minutes to fully open / close. 
You cannot use solenoids as the momentum of the water flowing in the loop has enough potential to cause water hammer, hence the slow open / close normally preferred and promoted with the standard wax heads.

Closed by default so you don’t get unwanted flow down one loop when another is calling.

The Salus ones are great, and automatically balance the system by detecting heat on the return pipe and that makes then arrest flow, thus leaving the remainder of the pumps potential to service the longer loops which have not yet returned warm / hot water. 

Excellent! I’ll check out the Salus ones ! ?

[Nickfromwales]

31 minutes ago, pocster said:

Excellent! I’ll check out the Salus ones ! ?

Wunda are about the best price, but look around.

[Russell griffiths]

 

@Nickfromwales this is the one on the website from the people I got my manifold, is it the same as the one you listed. 

It was originally on my quote but they took it off when they knew I was using ASHP. 

If this is cool I will get it ordered. 

[PeterW]

1 hour ago, Russell griffiths said:

 

@Nickfromwales this is the one on the website from the people I got my manifold, is it the same as the one you listed. 

It was originally on my quote but they took it off when they knew I was using ASHP. 

If this is cool I will get it ordered. 

 

Ask them the minimum temperature the valve will go to - I think it’s 42c from memory which isn’t low enough for ASHP and a decent insulation level. 

[Nickfromwales]

3 hours ago, PeterW said:

 

Ask them the minimum temperature the valve will go to - I think it’s 42c from memory which isn’t low enough for ASHP and a decent insulation level. 

There are 2 options available;

20-60oC

or

30-50oC

 

@Russell griffiths You need the 20-60oC

 

@PeterW These drop down very low and are super-reliable too. A standard thermo-mechanical(?) TMV struggles at 30oC and starts whining and strangling the flow the second it runs out of cold return water to use for blending. I've been fitting these Ivar's on just about every project so can vouch for them doing what they say on the tin, and reliably, particularly on low-energy & 'passive' builds.  

 

 

 

Pump UK Mixing Kit

£243.36 inc VAT

Ivar Uni-Mix Underfloor Heating Pump Mixing Kit

This is a well engineered Manifold Pump Mixing Unit manufactured in Italy, offering excellent flow rates, with an adjustable water temperature range from 20° C to 60° C making this perfect answer when commission the underfloor heating system for the first time and need to build up the heat very slowly and avoid cracking on a screed floors.

Edited July 12, 2020 by Nickfromwales

[Andrew]

With these blending valves, if the temperature of the hot is lower than the temp set (e.g. blending valve set at 30 degrees, hot feed at 25 degrees) will they just let the hot through unrestricted and not mix in any cold?

[Nickfromwales]

2 minutes ago, Andrew said:

With these blending valves, if the temperature of the hot is lower than the temp set (e.g. blending valve set at 30 degrees, hot feed at 25 degrees) will they just let the hot through unrestricted and not mix in any cold?

Yup.

The valve is actuated by the TRV style head and that gets its reference via a capillary wire that is connected to a thermo-probe ( which is inserted into a pocket to detect the flow temp after the pump, eg after return water has been blended back in already ) and the TRV head will only open if the flow temp is less than the setting on the TRV head. The valve is normally fully open, so it promotes great full flow rates when the UFH starts up and asks for heat, and only starts to close as the temp set at the probe meets the temp set on the head.

There is no 'cold' to speak of, just the available return water and whatever temp that is.

[dpmiller]

I went with a similar but cheaper option that controls right down to (IIRC) 25c and has an integrated bypass and inlet restrictor ( there's a more basic one without, bit using the same thermohead  I think)

 

https://www.amazon.co.uk/Universal-Underfloor-Heating-Thermostatic-without/dp/B076KK1KQF/ref=sr_1_119?dchild=1&keywords=underfloor+pump&qid=1594565525&sr=8-119