How to control an Ecodan with UFH manifolds?

[ADringer]

Hi all,

 

I've had a Ecodan for a year now and originally it was set up with just rads on a single loop. This was easy to control as I had the Mitsubishi wireless controller (PAR-WT50R-E) which turned on the HP when triggered by temperature.

 

I'm just at the end of a house renovation and have now got UFH upstairs and down. Both floors have their own manifolds with pump, and each loop has it's own thermostat. 

 

My issue is that the wireless controller and room thermostat works independently from each other - a room could call for heating but the wireless controller doesn't so no heat, or the controller turns on but if no rooms ask for heat then it's a waste of energy, and potentially lots of short cycling if the heat has no where to go.

 

I'm wondering how people have wired theirs up? My plumber and electrician haven't worked with ASHPs before so haven't really been able to give any guidance on this.

 

I can think of two possible ways (I'm not a plumber/electrician, so what I'm suggesting is probably completely wrong!):

 

1. Essentially ignore the room thermostats (have each loop permently open) and have the wireless controller as the main thing to turn on the HP. But how does the pump on the manifold turn on when required? I don't want the manifold pump to run continously if there is no heat.
2. Have the room thermostats used as a 'max' value so that it's pretty much always open. This way the HP is running continuously at a low flow temp. When people say they run the ASHP 24/7, do they actually mean the whole time? As I think it would it this case if the room thermostats aren't wired to turn off the HP.

 

The main thing I'm having trouble understanding is how to get the pumps on both the manifolds and Ecodan to run when there is a call for heat - is there an obvious wiring solution that I'm missing?

[JohnMo]

Basically set your system to run on weather compensation mode.

 

Your thermostats become limit stops. So set slightly higher temp than you want.

 

You will need to set the WC curve and flow temp.  Basically keep turning the flow temp down until most the house is always the temp you want.  The thermostats should not be made to control.  Rooms that are to warm, decrease the loop flow, room to hot the opposite.

 

Set a nighttime set back of a couple of degrees.

[ADringer]

17 minutes ago, JohnMo said:

Basically set your system to run on weather compensation mode.

 

Your thermostats become limit stops. So set slightly higher temp than you want.

 

You will need to set the WC curve and flow temp.  Basically keep turning the flow temp down until most the house is always the temp you want.  The thermostats should not be made to control.  Rooms that are to warm, decrease the loop flow, room to hot the opposite.

 

Set a nighttime set back of a couple of degrees.

 

Ok, so by this do you mean drop the flow temp down so it's low enough that it's always running as heat loss equals heat input? Thereby avoiding my whole control issue as everything is always on?

 

is it fine to leave the manifold pump to always be running?

 

is setback on the flow temp? If so, not sure how to do that on the ecodan without manually changing it every time on the local controller.

 

[JohnMo]

Yes.  Setback the local controller will have that built in, as one of the Target temperatures. Not sure if how they do it?

[joth]

@JohnMo solution is the most efficient one but takes a bit of setting up so installers often won't do that. Also some users will find it confusing that turning a roomstat up high won't cause the room to get any hotter.

 

For completeness the alternative is ditch the wireless stat and use the room stats to call for heat from the ASHP same as they normally would from a boiler. The requires an UFH wiring center at the manifold actuators with a "dry contact" relay output to call for heat, and wires this into the zone 1 or zone 2 call for heat inputs on the ecodan FTC

You can still use weather compensation. But the system can easily short cycle and run at low efficiency if rooms call for heat at different times to each other. (in my system I have logic controller manage the call for heat and it will only do so when a certain % of rooms need heating)

[JohnMo]

9 hours ago, ADringer said:

 

is it fine to leave the manifold pump to always be running

Yes.  Pump wear when stop and starting, very little wear in steady state running.  They do consume energy but a modern pump is in the range 10-30w.

[markocosic]

Ditch the separate UFH pumps?

 

Feed the while lot directly fed from a big pump at the heat pump. Run the whole lot on the heat pump controller weather compensated.

 

Room thermostats can still "trim" hot rooms down (locally "call for no heat" as it were" but for the most part do nothing because your output is limited by the weather comp and they stay open.

[HughF]

2 hours ago, markocosic said:

Ditch the separate UFH pumps?

 

Feed the while lot directly fed from a big pump at the heat pump. Run the whole lot on the heat pump controller weather compensated.

 

Room thermostats can still "trim" hot rooms down (locally "call for no heat" as it were" but for the most part do nothing because your output is limited by the weather comp and they stay open.

Sounds good - should be easy enough to double up the pumps at the HP end if required, and piggyback off the PWM to the main pump to give PWM control to the other, external pump. I'm planning to run the PWM and PWM Common signals from my iVT-9 into the house to feed a second pump if required, but under full PWM control from the Carel pCO

[MortarThePoint]

@JohnMo to confirm the strategy:

 - control heat flow by varying flow temperature (called Weather Compensation), colder outside means more heat lose so higher flow temp.

 - use manual manifold flow valves to set relative flows into each room

 - ASHP runs constantly (when outside temperature is below some threshold?)

 - no room thermostats needed 

 - no manifold actuators or controllers needed

Edited October 21, 2022 by MortarThePoint

[dpmiller]

@HughF Have you worked out what the PWM protocol is for the pump? Is it Grundfoss-specific?

 

I've a series pump, but it's set to a fixed value to let the internal one handle the modulation. Even 8.5kW is very flow-hungry...

Edited October 21, 2022 by dpmiller

[JohnMo]

34 minutes ago, MortarThePoint said:

@JohnMo to confirm the strategy:

 - control heat flow by varying flow temperature (called Weather Compensation), colder outside means more heat lose so higher flow temp.

 - use manual manifold flow valves to set relative flows into each room

 - ASHP runs constantly (when outside temperature is below some threshold?)

 - no room thermostats needed 

 - no manifold actuators or controllers needed

That's about right.

 

You will need the controller for the heat pump, or boiler only.

[MortarThePoint]

35 minutes ago, JohnMo said:

That's about right.

 

You will need the controller for the heat pump, or boiler only.

 

Awesome thanks.

 

I guess there is a maximum outside temperature above which the ASHP turns off as it would be being asked for too little power.

[JohnMo]

On my boiler the default was set at 20, I changed mine to 11.

[MortarThePoint]

8 minutes ago, JohnMo said:

On my boiler the default was set at 20, I changed mine to 11.

Neat, so no heating until it's below 11C outside.

 

I like the strategy but note the following drawbacks:

 - can't preferencially heat rooms being used (e.g. study during week day working hours and living room in evenings and weekends, or bathrooms at certain times of day)

 - without energy storage, can't take advantage of Economy 7 cheaper electricity

 - Increased wear on pipes / flow restrictors due to constant flow (?) No idea if that's a reasonable concern

 - home politics as the wife doesn't have a little box on the wall to tell what to do so she has to tell me instead

 

Even so, it seems an excellent approach.

[JohnMo]

One thing that springs to mind is the manifold pump, you can either have a mains outlet with a switch on the wall, think @joe90 does that.  I have a thermostat in the hall (which I manually turn up to start pump) and wiring centre, but that is just hang overs from the system I installed.  I also have Salus auto balancing actuators on three loops to automatically set a base line, which I have adjusted everything else around.

[PhilT]

21 minutes ago, MortarThePoint said:

 

Awesome thanks.

 

I guess there is a maximum outside temperature above which the ASHP turns off as it would be being asked for too little power.

On mine there is no max ambient temp at which the unit turns off. It only turns off when target room temp at the central controller is exceeded by one degree, however that is transmitted from a room/rooms. This applies in all three modes; WC, Auto and target flow temp.

[JohnMo]

The other way with UFH is to batch charge the floor, but you really need a thick floor.  I have a 100mm concrete, charged it a 30 degs for about 6 hours over night.  At the end of that time the house was at 18.5 deg, an hour later at 19 and stayed there until bedtime.  Only disadvantage is you have to fiddle with it, as on really cold days the house started to cool to much over the day as the heat loss didn't match heat input.

[joe90]

32 minutes ago, JohnMo said:

One thing that springs to mind is the manifold pump, you can either have a mains outlet with a switch on the wall, think @joe90 does that.  I have a thermostat in the hall (which I manually turn up to start pump) and wiring centre, but that is just hang overs from the system I installed.  I also have Salus auto balancing actuators on three loops to automatically set a base line, which I have adjusted everything else around.

Yes I have a room stat in the hallway that operates the manifold pump and draws water from a buffer tank heated by the ASHP.

[HughF]

5 hours ago, dpmiller said:

@HughF Have you worked out what the PWM protocol is for the pump? Is it Grundfoss-specific?

 

I've a series pump, but it's set to a fixed value to let the internal one handle the modulation. Even 8.5kW is very flow-hungry...

From what I can tell, it's an industry standard. The below taken from some Grundfos literature:

 

Some medium UPM pumps are controlled via a digital low-voltage pulse-width modulation (PWM) signal, which means that the speed of rotation depends on the input signal. The speed changes as a function of the input profile. These communication signals are standardised in the VDMA Einheitsblatt 24244 "Wet runner circulating pumps - Specification of PWM control signals"

[HughF]

6 hours ago, dpmiller said:

@HughF Have you worked out what the PWM protocol is for the pump? Is it Grundfoss-specific?

 

I've a series pump, but it's set to a fixed value to let the internal one handle the modulation. Even 8.5kW is very flow-hungry...

I know you have a volumiser/buffer of sorts, but how are you finding the pumps-in-series thing working out?

[dpmiller]

15 minutes ago, HughF said:

I know you have a volumiser/buffer of sorts, but how are you finding the pumps-in-series thing working out?

 

Series works well here; if I was doing it again I'd do the whole circuit in 28mm as the 22mm is just a wee bit noisy and restrictive tho

[markocosic]

What deltaT is the system running / can it run?

 

What is the minimum flowrate the heat pump will allow?

[ADringer]

On 21/10/2022 at 08:12, JohnMo said:

That's about right.

 

You will need the controller for the heat pump, or boiler only.

 

Regarding @MortarThePoint  suggestion - that makes sense about having it run constantly, but how do you control the pumps on the manifolds? These should only run when the heat pump is generating heat. 

 

On 20/10/2022 at 08:03, joth said:

@JohnMo solution is the most efficient one but takes a bit of setting up so installers often won't do that. Also some users will find it confusing that turning a roomstat up high won't cause the room to get any hotter.

 

For completeness the alternative is ditch the wireless stat and use the room stats to call for heat from the ASHP same as they normally would from a boiler. The requires an UFH wiring center at the manifold actuators with a "dry contact" relay output to call for heat, and wires this into the zone 1 or zone 2 call for heat inputs on the ecodan FTC

You can still use weather compensation. But the system can easily short cycle and run at low efficiency if rooms call for heat at different times to each other. (in my system I have logic controller manage the call for heat and it will only do so when a certain % of rooms need heating)

 

@joth What are you using for the logic controller to only do it when a percentage of rooms need heating? I think this is what I'm missing

[joth]

1 hour ago, ADringer said:

@joth What are you using for the logic controller to only do it when a percentage of rooms need heating? I think this is what I'm missing

I'm using a Loxone miniserver, but that's for everything in the house, it'd be overkill just for this one purpose.

 

[JohnMo]

2 hours ago, ADringer said:

Regarding @MortarThePoint  suggestion - that makes sense about having it run constantly, but how do you control the pumps on the manifolds? These should only run when the heat pump is generating heat

Mine is controlled from a thermostat if there is a requirement to heat the pump runs.  The thermostat is set slightly higher than required room temperature, I just located it the hall.

 

With a heat pump, there is a slight disadvantage running rooms with heating off and others on, the internal heat loss between rooms, means a higher flow temp is required for the heated room, so you CoP goes down.  It actually becomes as cheap to heat the whole house.