Simplify This! Control of DHW/UFH/Fancoil

[Duncan62]

I'm at the crunch point for getting a Heat pump and associated controller - and am wondering how everyone else has done this?

System: 

DHW = UVC directly fed from Heatpump / Immersion fed from Inverter from PV.

UFH = 1 Zone fed from Heatpump with 1 extra UFH pump

FanCoil = (cooling only) 1 zone fed from heatpump, flow goes to fancoil first then into UFH and back to Heatpump (to add volume to avoid buffer)

 

4 x 2 way valves (could simplify by ditching valve3 and associated return)

1 x UFH pump

 

Currently I plan to control the valves and pumps via home automation (velbus in this case) - so the controller does not need to do that.

 

Will I need a heat pump that has a contact closure for Heat Demand or Heat Satisfied (Maybe a second for Cooling Demand / Cooling Satisfied)?

 

The samsumg Gen 7 i'm looking at: It seems the wired controller is what calls for heat from the control box, with no option for an external signal to call for heat? 

 

 

 

controlkitmim-e03cn.mim-e03eninstallationmanual.pdf

[JohnMo]

What are 4x valves doing and why?

 

Do you really need the UFH pump?

 

Simple way is interlock heating and DHW 2 way valves one open the other closed or wise versa, or make it even simpler a 3 port diverter. Then run everything on or off. If you don't want fan coil fans on for heat just set a target temp in the controller of fan coils so fan doesn't come on.

 

Then set a WC comp curve to suit for heating and most likely a fixed flow temp for cooling.

 

What does your system look like? An sketches?

 

 

 

 

[Duncan62]

2 minutes ago, JohnMo said:

1. What are 4x valves doing and why?

 

2. Do you really need the UFH pump?

 

Simple way is interlock heating and DHW 2 way valves one open the other closed or wise versa,

 

3. or make it even simpler a 3 port diverter. Then run everything on or off.

4. If you don't want fan coil fans on for heat just set a target temp in the controller of fan coils so fan doesn't come on.

 

Then set a WC comp curve to suit for heating and most likely a fixed flow temp for cooling.

 

5. What does your system look like? An sketches?

 

Thanks so much,

 

Ans 1: I've over complicated it, cleaner is below, with 3 valves, to control direction of water flow for the three scenarios. (DHW, Heat,Cool)

 

Ans 2: can I get away with only having the HeatPump pump for 300m UFH loops?

 

Ans 3: I cant use a 3 port valve as the home automation cant handle that, so would need 2x 2 port to do the same job.

 

Ans 4: Regards fan coil - is it ok to send hot water though it? usually they have separate circuits for hot water (maybe due corrosion?) - so sensible to avoid sending hot water into FCU if not needed? (hence additional valve)

 

Ans 5: The system sketch I have so far is above - UPDATE BELOW - thank you for suggesting some simplification.

 

 

 

 

So I can interlock 2x 2 port valves so that when one opens the other closes - thus only needing to send out 1 signal.

 

 

3 valves - 1 open for each type of operation respectively, DHW, Heating, Cooling - Other two respective valves closed.

 

 

 

[JamesPa]

13 minutes ago, Duncan62 said:

Ans 4: Regards fan coil - is it ok to send hot water though it? usually they have separate circuits for hot water (maybe due corrosion?) - so sensible to avoid sending hot water into FCU if not needed? (hence additional valve)

Yes, my fancoil (Mitsubishi i-life2 slim) does both heating and cooling through the same pipes. 

 

The reason for 4 pipes (I understand) is to do with the fact some buildings are plumbed this way and perhaps also so that cold can go in at the top and hot at the bottom thus optimising performance.

[Duncan62]

12 minutes ago, JamesPa said:

Yes, my fancoil (Mitsubishi i-life2 slim) does both heating and cooling through the same pipes. 

 

The reason for 4 pipes (I understand) is to do with the fact some buildings are plumbed this way and perhaps also so that cold can go in at the top and hot at the bottom thus optimising performance.

 

Ok, i'll check with the manufacture. Great news if so - Would eliminate another switch/valve. UPDATE BELOW.

 

Heating: Hot water is sent though FCU in winter, no fan, returns through UFH to do its job heating the slab.

Cooling: Cold water is sent though FCU, fan on, and returns through UFH loop to cool the slab too.

 

Therefore: I can interlock 2x 2 port valves so that when one opens the other closes - thus only needing to send out 1 signal to control both.

 

 

 

Anyone know how which HeatPumps have a simple contact closure connection for Heat Demand and Heat Satisfied on their internal control boxes - so that I can control that from the automation too?

 

 

 

Edited September 26 by Duncan62

[JohnMo]

20 minutes ago, Duncan62 said:

2: can I get away with only having the HeatPump pump for 300m UFH loops?

Are you sure you are calculating the pressure drops correctly. Your head loss on UFH isn't large as all loops run parallel to each other 

 

20 minutes ago, Duncan62 said:

Ans 3: I cant use a 3 port valve as the home automation cant handle that, so would need 2x 2 port to do the same job.

Easy don't use home automation. But control single for a 3 port valve is power off to heating, power on for DHW. So not complex.

 

20 minutes ago, Duncan62 said:

Ans 4: Regards fan coil - is it ok to send hot water though it? usually they have separate circuits for hot water (maybe due corrosion?) - so sensible to avoid sending hot water into FCU if not needed? (hence additional valve)

You wouldn't send DHW heating water through it, but UFH water no issue, better than stagnant water 6 to 8 months of the year.

 

As laid out you are powering 1x valves at 7W each nearly all year and another some of the year. Let's say 10W x 24 hrs a day and 365 days a year, so about £25 a year. A 3 port diverter would take power only when doing DHW a MoMo type diverter only uses power while moving, so almost nothing per year.

 

3 minutes ago, Duncan62 said:

Anyone know how which HeatPumps have a simple contact closure connection for Heat Demand and Heat Satisfied on their internal control boxes - so that I can control that from the automation too?

Most do. But do you really need it. Mine has those contacts and they joined. So always have a demand for heat, this doesn't mean the heat pump runs, just that it can, the basics are it's programmed to run WC. A normal WC curve will start at say 20 degs outside and lowest flow temperature from ASHP. But this can start at 10 degs outside if you want, I'll to stop possible over heating at warmer temperatures. The heat pump then senses return temp and fires up if needed. My heat pump hasn't fired up in the last 2 days, because it's sensing the return temp hasn't dropped far enough to require additional heat heat.

 

If on a low time of use tariff you can play games with above.

 

1. Batch charge floor like a storage heater.

2. Program a second set point so you have WC in background but force charge floor at higher flow rate in off peak periods, so heat pump backs off when return to normal flow temperature.

3. A hybrid approach to batch charge in milder weather but transition to full WC as temps drop. Good for heat pumps that are a little to big for house.

 

None of this need much smart stuff to do.

 

[Duncan62]

Thank you @JohnMo that is a great insight.

 

I think I'm in over my head a bit with this, but I am doing my best to learn (have been reading here for years now)

 

My reason for adding automation in the mix is because I'm not sure I could get the FCU controller to play with the DHW/UFH controller and HP.

Thus I need to call for Heat/Cooling separately, adjust the valve/switch position separately, and run the fan on/off + UFH pump separately.

 

The fan control, UFH pump control and switch control are straight forward.

 

Calling for heating/cooling is what I'm unsure about as the HP manufacturers do not make it easy to see if this can be controlled by something other than their proprietary controllers.

 

 

Are the 3 port switches spring loaded to return to a default, without power?

I'm in first fix now, so I'm trying to finalize what I need, as the electrician is getting a bit prickly. 

What is the minimum viable solution?

 

 

 

[Duncan62]

[JohnMo]

39 minutes ago, Duncan62 said:

Are the 3 port switches spring loaded to return to a default, without power?

In general yes, but you need a 3 port diverter, not a mid point valve - MoMo are not spring return generally.

 

40 minutes ago, Duncan62 said:

What is the minimum viable solution?

A 3 port diverter, this driven by the ASHP controller. Directs water to DHW or heating system.

 

Fan coils - are really just a radiator in a box. But put out almost zero heat without the fan on. So no harm water flowing. They do not need any valves except for isolation valves.

 

What fan coils are you installing?

[-rick-]

1 hour ago, Duncan62 said:

Ans 4: Regards fan coil - is it ok to send hot water though it? usually they have separate circuits for hot water (maybe due corrosion?) - so sensible to avoid sending hot water into FCU if not needed? (hence additional valve)

 

Related: Does your fancoil have big enough diameter pipes to flow everything through it? Pipe from heatpump to UFH will be 22mm or 28mm depending

 

Also, when cooling what water temp do you plan to use? If it's above dew point then should be fine, but if you need it below dewpoint for the fancoil to put out enough cool then you may have a problem then feeding on to the UFH. The DT between the in and out of the fancoil will vary depending on load so likely can't be relied on to warm up the water above dewpoint before going into the floor.

[Duncan62]

3 minutes ago, JohnMo said:

In general yes, but you need a 3 port diverter, not a mid point valve - MoMo are not spring return generally.

 

1. A 3 port diverter, this driven by the ASHP controller. Directs water to DHW or heating system.

 

2. Fan coils - are really just a radiator in a box. But put out almost zero heat without the fan on. So no harm water flowing. They do not need any valves except for isolation valves.

 

3. What fan coils are you installing?

 

1. In this case how do I call for cooling? And what will turn on and modulate the fan coil fans? (I agree if heating either DHW or UFH, this is all sorted in the HP control box an wired controller, its adding cooling and controlling that that is difficult)

 

2. Excellent, as depicted below (removal of powered valve/switch)

 

3. Trox PWX 120-2. 5 outlets = 4 bedrooms + living room https://www.troxuk.co.uk/fancoil-units/pwx-ea11f88aee974359

 

 

[Duncan62]

3 minutes ago, -rick- said:

 

Related: Does your fancoil have big enough diameter pipes to flow everything through it? Pipe from heatpump to UFH will be 22mm or 28mm depending

 

Also, when cooling what water temp do you plan to use? If it's above dew point then should be fine, but if you need it below dewpoint for the fancoil to put out enough cool then you may have a problem then feeding on to the UFH. The DT between the in and out of the fancoil will vary depending on load so likely can't be relied on to warm up the water above dewpoint before going into the floor.

 

This is a very good point, I was going to run 15mm to the fan coil, but should probably use 22mm?

 

FCU is large, so will run above due point to avoid issues, should still provide adequate cooling.

 

 

[-rick-]

Just now, Duncan62 said:

This is a very good point, I was going to run 15mm to the fan coil, but should probably use 22mm?

 

Looking at the spec for the fancoil looks like its either 15mm or 22mm. Getting the 22mm would be the minimum you'd want if installing in-line with the UFH and that assumes you are running a pretty small heatpump <= 7kw?? (guess). Even then it's pretty small and might be a problem (others have better knowledge here I'm at my limit).

 

Just now, Duncan62 said:

FCU is large, so will run above due point to avoid issues, should still provide adequate cooling.

 

Good

[Duncan62]

Just now, -rick- said:

 

Looking at the spec for the fancoil looks like its either 15mm or 22mm. Getting the 22mm would be the minimum you'd want if installing in-line with the UFH and that assumes you are running a pretty small heatpump <= 7kw?? (guess). Even then it's pretty small and might be a problem (others have better knowledge here I'm at my limit).

 

 

Good

 

Yes, 5kW heat pump.

 

22mm make sense if running in series with UFH. Will need insulating. will be quire large to feed through walls.

[Duncan62]

Simplest Solution - Spring return 3 Port Diverter. Heating water travels via FCU in 22mm pipe before UFH manifold.

 

 

 

 

Bypass FCU option - Same as above but FCU is bypassed in UFH use

 

 

[Duncan62]

THOUGHT: 

 

Can the normal heat pump controller and associated house thermostat be used to call for cooling too?

 

Then it can run the cooling water automatically?

 

Id then simply need to turn on the fan coil fan, which is easy.

[Duncan62]

 

Simple is best. Samsung Gen 7 heat pump comes without a circulation pump. Thus 1 pump in plant room. Direct system one zone.

[JohnMo]

And if you have PV export, just export and leave the heat pump to do DHW at a CoP of 3+. And leave the cost of the diverter in the bank