I bought a Heat Pump

akwexavante

Reed_richards is a very knowledgeable chap especially with the more advanced settings etc. Whatever you decide to do I'd try one thing at a time otherwise you won't know what's working and what's not and you'll end up in a mess. 

I personally would start by leaving the more adventurous changes until later and start with the more simple stuff like just turning down the room stat and explore the adjustment of the tvr's room to room. 

grahamm

akwexavante said:

For me the installer is wrong. A room stat is for you to set a temperature that's comfortable for you

Their explanation (as far as I understand it) is that that the aim is to get the whole house stable at 21 degrees, based on a weather compensation curve that will change the output of the pump to compensate for the heat loss of the home depending on the outside temperature.

If TRVs start closing off radiators, that will result in the water circulating in the system to not cool as much, so the pump sensors will think that the house is too hot (because the water coming back to the system is warmer) and reduce the output, cooling the whole home. Actually most of the radiators don't have TRVs any more, the only ones that do were ones that didn't need to be replaced (some needed to be upsized or were swapped between rooms), but they're set to max.

If rooms are at different temperatures, it creates a heat flow from the hotter rooms to the colder rooms which is (apparently) less efficient than getting it globally stable.

akwexavante

Unless a home is "open plan" and without doors I'd agree. Close doors between rooms. All your rads should have tvr's except just one, "your bypass radiator". 

You've said your tooooo warm with a room stat set at 24, common sense would suggest that you turn it down. 

I have a 2 bed end terrace with a room stat set at 18 and all tvr's set on 3 except the bathroom at max and main bedroom set at 2 and in the coldest month of the year arguably February I only use 210kw of electric and I'm snug as a bug in a rug. I keep all doors closed. 

grahamm

akwexavante said:

Unless a home is "open plan" and without doors I'd agree. Close doors between rooms. All your rads should have tvr's except just one, "your bypass radiator". 

You've said your tooooo warm with a room stat set at 24, common sense would suggest that you turn it down. 

The point is AIUI that an ASHP system doesn't work like a conventional boiler system. The installer joked that, if he could, he'd get rid of the thermostats entirely and replace them with an on/off switch if people were going to be away to stop people tinkering with the settings and, instead, letting the weather compensation system do its job.

QrizB

akwexavante said:

For me the installer is wrong.

I think the installer is correct, for a properly balanced system running fully under weather compensation (WC).

The problem sems to be that the WC curve is too high.

akwexavante said:

A room stat is for you to set a temperature that's comfortable for you and 24 is very high and clearly it's uncomfortable for you too! So ignore the installer and set it to a lower temp and wait a couple of days for things to settle.

For a system running under WC, the room thermostat servers as a backstop. The heat pump should control the temperature of the circulating water to match the heat loss from the house. Only if things aren't quite right will the room temperature rise above expected levels and bring the thermostat into play.

akwexavante said:

Again the TRV's are for you to adjust to suit yourself. I prefer a warm bathroom so my trv in that room is set at max, whereas I like a cool bedroom so that trv is set at 2 and so on throughout the house.

Again, WT should reduce or eliminate the need for these controls.

QrizB

akwexavante said:

I have a 2 bed end terrace with a room stat set at 18 and all tvr's set on 3 except the bathroom at max and main bedroom set at 2 and in the coldest month of the year arguably February I only use 210kw of electric and I'm snug as a bug in a rug. I keep all doors closed. 

Is that with a heat pump? Running under weather compensation?

Edit: Sorry, I see you've posted details of your setup a page or two back in this thread. You've got a well-insulated two-bed mid-terrace with five radiators - I guess bed/bed/bath/kitchen/lounge? That's a compact and easy-to-heat home, congratulations, a good choice

grahamm

QrizB said:

The problem sems to be that the WC curve is too high.

Yes, but I've now reduced the setting by 4 degrees, however the temperature is currently sitting at 23.7 degrees instead of 21.

I don't know if that's because the weather it getting colder now. I can keep tweaking it down and maybe that will make a difference at some point.

Reed_Richards

I went out for the day and a lot of responses!

What your installer was trying to achieve is entirely feasible but it only works if you have the weather compensation curve set exactly to match the heat loss from your house.  To me it seems like you've been thrown in the deep end in the hope that you manage to swim.

Pure weather compensation also only works if you have all the radiators perfectly balanced so all the rooms in the house heat up at the same rate.  TRVs are an easy (lazy?) way of not having to do that.  And it also only works perfectly if your house is so well draught-proofed that you can enter and leave your house without letting in any cold air that would cool it.  And it also only works if you don't have a lot of south-facing windows so you don't get thermal gain on sunny days.  And you must never light a fire or use any other form of extra heating.  So you do need a room thermostat as a backstop and if you have the perfect set-up you can have that a set only a degree or two higher than your desired temperature.  In my case my advice would be that for the present you set your thermostat to give you whatever temperature feels comfortable.

Unless your installer spent a day balancing all your radiators and working out at the very least exactly what Leaving Water Temperature was appropriate to keep your house at 21 C then your installer has no reason to believe what they have done was adequate.  They cannot have done that because you wouldn't be so far off the correct AI settings.  I don't know how experienced they are because they are acting like someone who watched all the online videos but didn't try it in practice. 

Clearly you don't have your weather compensation set up correctly, it's giving you Leaving Water Temperatures that are too high so your house gets too hot (and you'll be spending too much money to achieve that).

Let's find out what your weather compensation parameters are.  Were you told how to access the installer settings on your controller?  Did you find the manual I posted elsewhere online?  Somewhere you will find this illustration:



           You need to enter the Installer settings and find what the LWT and Outdoor temp, min and max, are for Auto Mode.  If we can find out what they are at the moment then we can try to change them to stop your house getting too hot.  Post back if you cannot work out how to find these settings and I will tell you step-by-step.  

Reed_Richards

The other thing you might have is an MCS Compliance Certificate (not the same thing as an MCS Certificate but if you have one then hopefully you have the other).  This is an excerpt from mine.  There is actually a mistake, the Design External Temperature should be -3.7 .  But it tells me that (if my system behaves as designed) then the LWT should be 50 when the External Temperature is -3.7 or less.  That gets me half way to knowing what my Weather Compensation Parameters should be.   

grahamm

Reed_Richards said:

           You need to enter the Installer settings and find what the LWT and Outdoor temp, min and max, are for Auto Mode.  If we can find out what they are at the moment then we can try to change them to stop your house getting too hot.  Post back if you cannot work out how to find these settings and I will tell you step-by-step.  

I found the images below by going to 

Auto Mode

Seasonal Auto Temp

Target Temp/ Outdoor Temp

I think they're the same as what you are referring to.

The Target Temperature started at 49 degrees and I'd reduced the AI number until it was at -5 without any effect, but I note that your picture above mentions that, in AI Mode, I can "shift" the Target Temperature by 5 degrees (I didn't actually know what changing that number did, prior to now)

A few days ago, I reset the AI to 0 and reduced the Target Temperature to 47, with no result, so I've now got it at 45, but it still doesn't seem to be doing much. 

I suppose if I set it to 44, that's the equivalent of the -5 change to the AI setting I had previously, so that may be why I'm not getting any change now.

I could try something drastic like reducing the Target Temperature to 40 and seeing if that does anything...