Many ways to set up an ASHP

[Stones]

Heated to a max of 50C, cylinder normally sits at 48 / 49 C when fully charged.

[Jeremy Harris]

1 hour ago, joe90 said:

Just spoke to my  neighbour who has an ASHP (he’s a plumber) and he runs his DHW at 48’ and it very rarely defrosts so that looks good for our location!?. Yes @JSHarris, I will run it and see how it settles down, measure consumption and decide in the future if changes are needed. How do people measure their water temp, I tried a mouth thermometer from when the kids were young but when it gets above 40 it has a fit!!!

 

I bought some really cheap little thermometers on eBay.  Not super accurate, but good enough, and they come with a remote probe that's waterproof, so you can stick it under a running tap (and wait, as they only sample the probe every 30 seconds or so) or you can tape the probe to a pipe, under a bit of pipe insulation.  The batteries seem to last a couple of years.  These are the ones I have scattered around the place, I only really used them when setting things up; they are cheap enough to be considered disposable, really, at £0.99 each from China: https://www.ebay.co.uk/itm/Digital-LCD-Fish-Tank-Aquarium-Thermometer-With-Waterproof-Probe-Black-631F/123254839016?epid=2292557761&hash=item1cb28f96e8:g:-3cAAOSwg0hbXPzc:rk:2:pf:1&frcectupt=true

 

If you search for aquarium thermometer or fish tank thermometer you will find others that are similar, and some from UK sellers that are a bit more expensive.

[joe90]

@JSHarris, just bumping this, your thoughts?

 

@JSHarris as your ASHP is very similar to mine, I have been going through all the settings again now I am beginning to understand how it works. Parameter 106 is (1) external heat source or (2) defrost, and the default setting is external heat source (1). Surely with no external heat source installed this should be set as 2?. 

 

[Jeremy Harris]

I'll check ours and get back to you, as I don't have a record of having ever changed parameter 106 on my crib sheet.

[joe90]

......stop press...... finally got the ASHP running, left it overnight but the thermometer on the output only shows 25’ despite the command unit specifying 40’??? Not put it into DHW mode yet as I wanted it to settle down to make sure it ran ok. Will do checks today to see what if anything is wrong.

[Gav_P]

@joe90 I don’t think I’ve seen mine get an output temp above 30’. 

 

Normally only about 25’

[Ed Davies]

What's the return temperature and flow rate?

 

The heat pump won't raise the temperature of the water that much in each cycle round. Picking one arbitrary (but reasonable sounding number) out of thin air, one circulation pump says it does 0.33 m³/h. That's 330 litres/hour = 5.5 litres (or 5.5 kg)/minute = 0.092 kg/s. The specific heat capacity of water is just under 4200 J/kg·K so it's capable of carrying away 386.4 J/s (= watts) for each kelvin (°C) of temperature rise. If your heat pump is putting in 5 kW then the temperature rise will be 5000/386.4 = 13 °C.

 

If your flow rate is higher (might well be as that 0.33 m³/h is against the maximum allowed head, I think) then the temperature rise will be smaller.

[Gav_P]

4 minutes ago, Ed Davies said:

What's the return temperature and flow rate?

 

The heat pump won't raise the temperature of the water that much in each cycle round. Picking one arbitrary (but reasonable sounding number) out of thin air, one circulation pump says it does 0.33 m³/h. That's 330 litres/hour = 5.5 litres (or 5.5 kg)/minute = 0.092 kg/s. The specific heat capacity of water is just under 4200 J/kg·K so it's capable of carrying away 386.4 J/s (= watts) for each kelvin (°C) of temperature rise. If your heat pump is putting in 5 kW then the temperature rise will be 5000/386.4 = 13 °C.

 

If your flow rate is higher (might well be as that 0.33 m³/h is against the maximum allowed head, I think) then the temperature rise will be smaller.

Yeah what he said! ?

[Gav_P]

Temp differences for me can be up to 10’ between flow and return, however it’s normally much less only a couple of degrees. 

 

 

[joe90]

10 minutes ago, Ed Davies said:

What's the return temperature and flow rate?

 

The heat pump won't raise the temperature of the water that much in each cycle round. Picking one arbitrary (but reasonable sounding number) out of thin air, one circulation pump says it does 0.33 m³/h. That's 330 litres/hour = 5.5 litres (or 5.5 kg)/minute = 0.092 kg/s. The specific heat capacity of water is just under 4200 J/kg·K so it's capable of carrying away 386.4 J/s (= watts) for each kelvin (°C) of temperature rise. If your heat pump is putting in 5 kW then the temperature rise will be 5000/386.4 = 13 °C.

 

If your flow rate is higher (might well be as that 0.33 m³/h is against the maximum allowed head, I think) then the temperature rise will be smaller.

 

I left it running over night into a 90 litre buffer tank, I thought if you specified a set water temp it would get up to that eventually? I don’t know the flow rate but the wilo pump is set at 3 out of max 6 (mid range) if it’s too slow the ASHP switches of and error code 9 which is lack of flow rate.

35 minutes ago, Gav_P said:

@joe90 I don’t think I’ve seen mine get an output temp above 30’. 

 

Normally only about 25’

 

What set water temp have you specified?  I don’t have a return temp thermostat, I will put one in and see.

Edited November 20, 2018 by joe90

[Jeremy Harris]

@joe90, what heating curve parameters have you set?  These must be set to the correct values (all of them) to get the right flow temperature in heating mode.  I posted this in the other thread for 40 deg C output in heating mode and 12 deg C in cooling mode (it's exactly the settings I have set up in our unit):

 

On 12/10/2018 at 13:40, JSHarris said:

 

 

There are two separate settings, one for DHW that's a fixed flow temperature, set by parameter 113, the other a variable flow temperature for heating, set by the heat curve that parameter 112 refers to.  There are a range of pre-defined, numbered, heat curves that can be selected by parameter 112.  All offer weather compensation to different degrees, except for the case when parameter 112 is set to 0.  In this case the user defines a custom heat curve using the custom set points in parameters 119, 120 and 121 for heating.

 

For cooling using a custom curve then set parameter 117 to 0, then use parameters 122, 123, 124 and 125 to set the shape of the cooling curve.

 

The settings I use (just for heating and cooling, I don't use the DHW mode) are these, which fix the flow temperature at 40 deg C in heating mode and 12 deg C in cooling mode:

 

112 = 0

117 = 0

119 = 19

120 = 40

121 = 40

122 = 40

123 = 14

124 = 12

125 = 12

[Gav_P]

1 minute ago, joe90 said:

.

What set water temp have you specified?

I don’t have a buffer tank, so the demand is from the UFH, which is 22’ (room temp).

 

i also don’t have the command unit, so the ASHP is running the standard heat curves. 

 

Interestingly it doesn’t ever seem to be working very hard... I assume the room stat is calling for only a degree or 2 of heat so doesn’t take much to bring the UFH back up to temp.

 

I haven’t seen any signs of icing, even in single figure temps with fog etc. 

 

 

 

 

[joe90]

5 minutes ago, JSHarris said:

@joe90, what heating curve parameters have you set?  These must be set to the correct values (all of them) to get the right flow temperature in heating mode.  I posted this in the other thread for 40 deg C output in heating mode and 12 deg C in cooling mode (it's exactly the settings I have set up in our unit):

 

 

 

 

Yes, I did see this but mine appears different, I set 100 to 1 (dry contacts), I don’t have a 112 or 117 and 116 thro 126 don’t appear. I also changed 302 from 1 (heat and cool) to 2 (heat only). Perhaps it might be worth trying to set a heating curve, perhaps 3 (max 45’).?

[Gav_P]

All the programming aside, shouldn’t it be as simple as @joe90 asked? I.e. the thermal store is asking for heat (upto 40’) and will keep asking until it reaches temp. The ASHP should keep incrementally increasing the circulation temp until it reaches its max parameters (40’ or 45’ depending on what joe has set it to) or until the demand is met ? 

 

Am I simplifying too much?

 

 

[joe90]

Just now, Gav_P said:

Am I simplifying too much?

 

I hope not ?

[Ed Davies]

Indeed, if it's just heating a 90 litre buffer tank (and that's not losing heat anywhere) then the return temperature ought to be ramping up quite quickly, in less than an hour. My return temperature question was on the assumption that it was heating the slab.

[Gav_P]

2 minutes ago, Ed Davies said:

Indeed, if it's just heating a 90 litre buffer tank (and that's not losing heat anywhere) then the return temperature ought to be ramping up quite quickly, in less than an hour. My return temperature question was on the assumption that it was heating the slab.

Understood. And that applies in my situation 100%. 

 

But joes seems like it’s limiting itself to 25’.... probably something to do with the pissing about with the command unit ?

[joe90]

The manifold pump was on but the slab is up to temp, I have switched the manifold pump off so the buffer should store heat, presumably the 40’ (or near) that I set the command unit too?.

[joe90]

I have once again checked all the parameters (to make sure I did not make a silly mistake) and heating set point is now 40’. I have installed temp readers on flow and return from the buffer tank and both read 25’.  The ASHP is running (but not hard) and I will give it an hour or two to see if it changes.

[Jeremy Harris]

We're in the midst of clearing out of the old house, so I don't have time to go over to the new house and have a look, but there may be a parameter that I think disables the custom heating curve, which may be why you can't set the right heating (not DHW) temperature.  The unit treats heating and DHW as two separate functions, with different operating regimes and settings, and the manual is not clear as to which settings only apply to DHW (which I think they refer to as sanitary water) and which only apply to heating.

 

As this is a new board, I'm near-100% certain that all the parameters have to be set initially from the command unit, and there are some that tell the board the type of machine it's running, IIRC.  With a bit of luck I may get some time after the removal truck has done it's thing tomorrow to take a look at all the settings and jot them down for you.  By just copying exactly our set up you should at least be able to get heating at 40 deg C, and once you have that then fine tuning it for what you need should be fairly straightforward, as it will just be a matter of changing one parameter at a time and seeing what effect it has.

[joe90]

Thanks @JSHarris, gosh I wish you well with your removal, there is no rush as I am also multitasking. I am not dealing with DHW at the mo so I can concentrate on just one thing at a time. After an hour of heating with the ASHP  with no manifold pump running (hoping to charge the buffer to the required 40’) flow and return are still running at 25’. ?

Edited November 20, 2018 by joe90

[joe90]

Ha, it’s just turned itself off, no error codes so I suppose it’s fulfilled it’s heating requirement, but it’s not 40’ !!!!!, still 25 -26.

[Gav_P]

Is the TS still calling for heat? Or has the demand stopped?

 

if it’s still calling for heat, then it’s almost definitely a HP related issue.

[Gav_P]

Does the command unit report the temps it is getting from all the sensors in the unit?

[joe90]

7 minutes ago, Gav_P said:

Is the TS still calling for heat? Or has the demand stopped?

 

if it’s still calling for heat, then it’s almost definitely a HP related issue.

 

Ha, just checked and the room stat temp was reached (we are having a cold snap, the wife has a cold so topped the house up with a heater). Have upped the room stat temp to 30’ and the ASHP fired up. But it’s still only achieving 25’ !!!!. In fairness 25’ is ok to feed the UFH bit it does not provide a chunk of hotter water to provide a “buffer” which is what a buffer tank is for. Plus I want to know why it’s not doing what it’s told.

13 minutes ago, Gav_P said:

Does the command unit report the temps it is getting from all the sensors in the unit?

 

No, not that I can find.