Pleaee help with Ecodan control

[Tom]

Hi all, believe it or not we might actually be moving in tomorrow,  so today I fired up the ecodan but struggling to get much heat out of it. 

For a start, the Wunda thermostats seem to randomly stop calling for heat and reset themselves to 10c, but I'm also struggling with the ecodan controller. It all seems.to switch on fine and the ASHP runs but the flow water temp to the manifolds hovers at around 15°. I've taken some pictures of the controller, any ideas?

[Tom]

[JohnMo]

Disconnect all the third party thermostats, you just don't need them.

 

Tell.us more about the system, buffer no buffer, as much info as possible.

 

Has the system been commissioned?

[Tom]

29 minutes ago, JohnMo said:

Disconnect all the third party thermostats, you just don't need them.

Yep, I know, but as its currently set up I need at least one to call for heat.

 

30 minutes ago, JohnMo said:

Tell.us more about the system, buffer no buffer, as much info as possible.

No buffer. Two 12 port manifolds, one thermostatic mixer on each fully open.  8.5kW ASHP 300l uvc, low loss header. Though tbh, irrespective of what the plumbing is downstream of the ashp, it's just not producing very how water - the pipe coming from it is barely warm.

 

33 minutes ago, JohnMo said:

Has the system been commissioned?

Yep. 

 

 

[nod]

I’m guessing you’ve tried the installer 

They really should come out on the day you move in 

 

Id a similar issue a few weeks ago 

Went round in Circles with the manual 

Called the installer who was home with Covid 

He just said let me face time you 

and reset everything 

Ten minutes and it was all sorted 

Your ok if your like John Mo and know what you are looking at 

Ours was something to do with outside temp compensation Yep meant nothing to me either 

So annoying when it’s probably something really simple 

[ReedRichards]

12 hours ago, JohnMo said:

Disconnect all the third party thermostats, you just don't need them.

 

Well if the system was set-up to operate with third party thermostats you most probably DO need them.  You might ultimately be able to disconnect them when you have found your way around the controls but it's too ambitious to do this in the first instance.

 

My advice would be to disable use of weather compensation and set a fixed water temperature near the high end of what your heat pump is capable of.  This is not the most economical way of operating your heat pump but it removes a level of complexity and potential for error and therefore should give you a better chance of telling if there is a fundamental problem or not.    

[trialuser]

I found this video helpful when setting up my ftc5. It looks as if you have got your offset turned down 2 degrees from what the curve is set to which also wont help. You could also try changing it from comp curve to say fixed flow of say 35 degrees just to test if that works. Sorry I don't know anything about external controls.

 

[Tom]

Thanks all, sorry for the delay in replying with thanks, been absolutely taters deep in moving stuff.

The ecodan has been on just about non-stop for the last 36hrs and the place seems to be coming up to temp. The flow to the ufh still only reads as 25° on the manifolds even with the compensation disabled and set at 45°. I presume the temp is reduced as the recirculating pumps are mixing the cool return with the flow?

Anyway, we're in, and the place is warmer than a caravan, so it's a definite improvement. After 4 years it's taking a bit of getting used to though! First night I was a bit like Crocodile Dundee in his hotel room

[JohnMo]

So this is the first proper start/run.

 

The way the heat works and it makes zero difference what the target temperature is initially.

 

The heat pump starts, it monitors flow and return temperature. It tries to establish a steady return temp, and then sets flow temp to approximately the target dT (difference between flow and return temperature) above the return temp. It will not add more flow temperature until dT reduces.

 

So if have many tonnes of house to get up temperature that has spent its whole life unheated it takes a while. This doesn't mean your settings are correct or even close, but the realities are houses when just built are very damp the water contents require loads of heat to start drying.

[joth]

2 hours ago, Tom said:

The flow to the ufh still only reads as 25° on the manifolds even with the compensation disabled and set at 45°. I presume the temp is reduced as the recirculating pumps are mixing the cool return with the flow?

Yeah, if the ASHP is driving ufh only then you don't really need mixing valve. Is it adjustable? Else you're just stuck with whatever it is set to

[Conor]

You've probably figured this out by now, as posts above have explained, but a heatpump normally works to a set delta of flow temperature. Let's say 5c. So if your slab is 10c, the initially the water coming out will be close to 10c. So your heatpump will only deliver 15c. It will slowly ramp up to the set flow temp, e.g 30c. You can change the settings to deliver the required flow temp regardless of the return flow temperature. This just costs more. You'll get a COP of 1.5, rather than 5.

[ReedRichards]

10 hours ago, Conor said:

You've probably figured this out by now, as posts above have explained, but a heatpump normally works to a set delta of flow temperature. Let's say 5c. So if your slab is 10c, the initially the water coming out will be close to 10c. So your heatpump will only deliver 15c. It will slowly ramp up to the set flow temp, e.g 30c. You can change the settings to deliver the required flow temp regardless of the return flow temperature. This just costs more. You'll get a COP of 1.5, rather than 5.

 

That's not at all the way my LG heat pump works; it will ramp up to the set flow temperature without caring about the return temperature.  When it gets to the set temperature it will continue at a fixed pump speed or an "optimum" pump speed or it will target a specified delta T between flow and return temperatures.  And it does all this at a much much better COP than the 1.5 suggested above (unless it was very very cold outside).  

[JohnMo]

9 minutes ago, ReedRichards said:

will ramp up to the set flow temperature

You must have one powerful heat pump, that can take a new house water flow temp straight up to target temp with a big deltaT and not risk damage to compressor.

 

My instructions clearly state

 

EVAPORATOR WATER FLOW The nominal water flow rate refers to a 5°C temperature difference between the evaporator inlet and outlet. The maximum permitted flow rate features a 3°C temperature difference while the minimum one has an 8°C temperature difference at the nominal conditions as shown in the technical sheet. Insufficient water flow rates can cause excessively low evaporation temperatures causing the safety devices to trigger and stopping the unit and, in some extreme cases, forming ice in the evaporator and resulting in serious failures to the cooling circuit.

[ReedRichards]

4 hours ago, JohnMo said:

You must have one powerful heat pump, that can take a new house water flow temp straight up to target temp with a big deltaT and not risk damage to compressor.

But I don't have a big delta T, why should I?  When the heat pump starts up my radiators don't give out much heat so the return water temperature is only slightly different to the flow temperature.  The gap widens as the flow temperature increases but it never gets more than the about 5 C or so that the radiators are balanced at.  @JohnMo, you'll have to explain the mechanism by which you could get such a large heat loss as to give you a big delta T.

[JohnMo]

7 minutes ago, ReedRichards said:

But I don't have a big delta T, why should I? 

Not really comparing apples with apples. OP is starting system for first time on a new build.

 

If I'm running WC, flow temp goes to target with a couple of mins. But not so when batch heating or doing a cold start of system. Takes a few hours to get there.

 

8 minutes ago, ReedRichards said:

you'll have to explain the mechanism by which you could get such a large heat loss as to give you a big delta T.

Cold house first time heating comes on (op case above), or first heating of the season with UFH. Even without cooling prior to heating season, floor is only around 19 to 20. In my case I have 100L plus of water, plus 56T of concrete to heat, so return temp stays low for a long time. Delta T is capped at the max allowed by flow rate and heating kW output. As return creeps up the dT stay constant and flow temp increases with return. Example from a batch charge from the other day, to show what I mean. Run started at 00:30 and was stopped to do DHW at 06:30. Window in image is 4 hrs.

 

 

 

[ReedRichards]

Okay, @JohnMo, you're specifically considering trying to heat up a cold floor with a huge thermal mass.  But, I presume, enough thermal conductivity that all the floor remains at much the same temperature.  Does concrete/screed have a high thermal conductivity?  I've always assumed that it doesn't, like stone.  But if it manages to extract a lot of heat from the pipes then I suppose it must.

 

Sorry, I can't work out your picture as it has no labels.    

[JohnMo]

2 hours ago, ReedRichards said:

Does concrete/screed have a high thermal conductivity?

Yes - Normal concrete: Has a thermal conductivity of around 2.25 W m−1 K−1.

The thermal conductivity of air is around 0.025 to 0.03

water is around 0.6 W/mK at 20°C

 

2 hours ago, ReedRichards said:

Sorry, I can't work out your picture as it has no labels. 

Good point 

Red is flow temp, green is return temp, yellow is power 

Edited Wednesday at 21:33 by JohnMo