@cathyem1 - that's good news. Now we need to check it is the right weather compensation. It is all a bit esoteric, but not hard to grasp. These units have nine weather compensation curves (a curve is a set of settings) eight of which are presets but number 9 is the custom one where you get to set the settings. For a primer on weather compensation curves, please see here, this being a section an article posted over the weekend that is intended to be a primer for people new to heat pumps.

The actual curve 9 settings are behind the tradesman's entrance, but you don't have to go through the back door to see what curve you are using. Unlock the wired controlled, then use the top left Menu button and arrow keys to get to PRESET TEMPERATURE > OK > right > WEATHER TEMP SET and press OK. You should see a line that says ZONE1 H-MODE HIGH TEMP (zone 1 because you only have one zone which is zone 1 and H-Mode means heating as opposed to cooling mode) and this should be ON.

Now the quirky bit: you have to turn it OFF and back ON to get to confirm it is on Curve 9 (I have't found a simple way to see what the curve setting is). Make sure ON is selected (if it is OFF you can omit this step) and then press the on/off button (top right) to turn it OFF. Next press the on/off button again to turn it ON and it should give you a choice of numbers 1-9 with 9 selected. If it isn't selected, then select 9, then OK and then back out using the back button.

Once you have done that ie confirmed it is on curve 9, then we can do the final bit of checking the custom settings for curve 9. But first we need to know you are on curve 9. Or should that be cloud nine? 

I see @transparent has posted about the missing tundish and safety drain pipe, well spotted. I can confirm when those pressure release valves go bang, they do it in style, and go BANG! My installer's plumber plumber managed to blow one of mine while doing the power flush by connecting the mains pressure directly to the radiator circuit and the whole house shook. It also released a LOT of water.  

@cathoderay Thank you for the advice about the curve and confirmation of the omission from our system. I have copied the post to the chap that came this morning for his comments.

Message from the MD of the company that supplied our system in response to your comment.

“Your system isn’t pressurised as we retained the tanks in the loft to allow you to retain the shower pumps as discussed. Therefore it does not need the emergency discharge as it is not under high pressure and the pipe is capped off as a result.” Now I'm going to sit in a darkened room for a bit to let my blood pressure get back to normal 😉

Whoops! Better safe than sorry though, with this sort of thing. If it is an open system with a header tank in the loft it won't go bang.

When you have a chance, can you check the weather compensation curve you are on (see my post at 3:02pm today for details on how to do this). 

Posted by: @cathyem1

↑

Your system isn’t pressurised as we retained the tanks in the loft to allow you to retain the shower pumps as discussed.

How clear was the issue made to you when you mentioned having a shower pump?

Is it just the DHW system which is unpressurized?

What about the water which supplies the radiators from the external heat pump?
Where is its pressure-relief valve and tundish?

Water expands when it is heated.

A tank in the loft has an expansion pipe which allows the water to spill back into it.
When it does so, some small amount of the heat is lost as vapour.

In a system with a header tank, the water pressure of the ground-floor radiators will be higher than those on the upper floors.
They have a greater mass of water above them.

The result is that more heat is delivered to the ground-floor radiators.
To reach the bedroom radiators, the pump has to push the water uphill.

In the more common pressurised central heating system, the pipework is closed.
There is no header tank open to atmospheric pressure.

Instead the system is filled to around 1½ Bar using pressure from the mains water supply.
This uses a 'filling loop' with a manual valve at each end.

All radiators and the heat pump are now at the same pressure, and the flow is evenly distribute, irrespective of their location.

@cathoderay Sorry for the delay. I’ve just followed your instructions and we are on Curve 9.

When the chap was here the other day I requested he reduce the heat of the flow from 45 to 40 just to see if it would still reach the comfort level we wanted. Cut to the chase - it didn’t. I returned it to 45° again. 

Posted by: @cathyem1

↑

Sorry for the delay. I’ve just followed your instructions and we are on Curve 9.

No problem. Curve 9 as you know is the custom curve, the one you want to be on.

Posted by: @cathyem1

↑

When the chap was here the other day I requested he reduce the heat of the flow from 45 to 40 just to see if it would still reach the comfort level we wanted. Cut to the chase - it didn’t. I returned it to 45° again. 

This doesn't quite make sense. You are either:

(1) on a fixed flow temperature in which case I'm pretty sure this is how you set the fixed flow temp

or

(2) on weather compensation, in which case it is the weather compensation curve that sets the flow temp, based on the curve settings

The number in the centre of the left panel (heating panel) is confusing. As I seem to recall, when it has a tear drop icon by it, the number it shows is both fixed and meaningless and you can't change it, if you try, you get the 'weather temp set function is on' message (because you are on weather compensation). If you can change it, you are not on weather compensation - but we think you are!

The only way to be sure you are looking at the actual flow temp is to go into OPERATIONAL PARAMETER menu page 4/9 and look at the TW_O PLATE W-OUTLET TEMP, that is the current flow (leaving water) temperature.

Before going further, can I remind you of the primer on weather compensation available here. 

Now we need to check your weather compensation curve (WCC) settings. These are only via the FOR SERVICEMAN menu. 2 3 4 and through the door. Then down to number 3 HEAT MODE SETTING, OK (Enter), and then take a note of the values shown for:

3.8 T1setH1

3.9 T1setH2

3.10 T4H1

3.11 T4H2   

These are the 'coordinates' for the left and right hand ends of the WCC, the numbers you see there are your current WCC settings.

Don't for now change anything, just note the values and 'OK' out of the serviceman menu back to the home page. Note you have to 'OK' the settings even though you haven't changed them

Note that  going into and exiting the serviceman menu as you have just done is inclined to turn the unit off (OFF in the middle panel). Give it a few moments and it should turn itself back ON.

Once you have the numbers for 3.8 to 3.11 post them here, along with a comment about whether you are currently too hot, too cold or just about right.

@cathoderay ok, I've gone into the control panel and here are the readings.

I'm a bit warm currently, but my husband likes the heat. 

@cathyem1 - those settings are a good enough staring point for a radiator system (no underfloor heating), which is I think what you have. What they mean is:

When it is -2 degrees outside, set the flow temp to 45 degrees

When it is 15 degrees outside, set the flow temp to 35 degrees

This is often abbreviated to 45 @ -2 and 35 @ 15.

In between -2 and 15 degrees outside, the 'curve' sets the flow temp based on the line joining the two end points. Thus if the outside air temp is half way between -2 and 15 degrees (~6-7 degrees), then the flow temp will be halfway between 35 and 45 degrees (~40 degrees), and so on. Note that although I have used the termflow temp here, what we are really talking about is the leaving water temp (LWT), the temperature of the water as it leaves the heat pump.

Posted by: @cathyem1

↑

I'm a bit warm currently, but my husband likes the heat. 

You will have to work this one out between yourselves! For setting up the heat pump, you can now move into the trial and error stage. Let it run for a few days, or at least until we get some variation in outside air temp, and see what the indoor temp/comfort levels do. If all is OK, carry on as you are. If, overall, between the two of you you want the house to be a bit cooler, try lowering the weather curve by one degree, and then give it few days to see how you like it. You lower the weather curve by lowering the LWT at each end, in you case the first, left hand, end point would come down from 45 degrees to 44 degrees, and the second, right hand, end point would come down from 35 degrees to 34 degrees. You change the numbers on the controller by going in to the first screen shown above and using the the up/down arrows to change the number, and then OK out back to the home page as before. The other numbers (-2 and 15) stay the same. 

From then on, trial and error continues, until you hit on a curve that works for you. It won't always be perfect, eg on sunny days in spring you may get significant solar gain (warmth from the sun) that pushes your room temps a bit higher than they would be, in gold wet windy weather you may get the opposite, a bit of 'building wind chill', depending on how exposed you are. I tend to get quite a lot of both (relatively exposed to the west so plenty of afternoon sun when it is out, but also exposed to the prevailing weather, so also exposed to the bad weather when it arrives). Some people (me included) tend to tweak their weather curve according to the season eg I expect I will lower it a bit as spring starts to arrive. But you don't have to do this, just be aware that the settings aren't carved in stone, they can be changed at any time if and when it makes sense to do so. 

Never forget that the ultimate and most important gauge of whether your heating system is working is you. If you are cosy and comfortable, then it is working, whatever the numbers on the dials say.   

@cathoderay thank you for all this information. The LWT was lowered to 40° at my request to the chap who came to visit the other day. It was far too cold for us so I adjusted it back to 45°. I will have a go at tweaking by 1 or 2° and see how we go over the seasons.

I'm keen to save some money 😉

Posted by: @cathyem1

↑

The LWT was lowered to 40° at my request to the chap who came to visit the other day. It was far too cold for us so I adjusted it back to 45°. I will have a go at tweaking by 1 or 2° and see how we go over the seasons.

As I said before, this doesn't really stack up. You either:

(1) run with weather compensation (curve 9) in which case you can't set the LWT directly, only the curve end points as described above, and thee curve sets the LWT

or:

(2) run with a fixed LWT which you can set (and the weather comp settings are irrelevant as not in use).

Not sure which you did when you did 40 to 45 degrees! There are two ways to answer the question:

(1) where did you make the change, from 40 to 45 degrees?

(2) what does the current LWT show (via OPERATIONAL PARAMETER) over a period of a few minutes?

Question (1) is the easier one to answer, and should provide a definitive answer.

Posted by: @cathyem1

↑

I'm keen to save some money

Aren't we all! I have just seen what the last month's heating has cost me, and it wasn't pleasant! But getting onto weather compensation with the lowest possible LWT consistent with comfort is the first thing to do (at the heat pump level) to reduce costs.