ASHP & triple glazing

[Moxi]

So is the point of the curves to find one that fits your requirements for (say) 75% of the time and then the HP uses the temperature sensors and ramps up or down around that curve to meet the temperature for the 25% of the time ?

Or do you find the curve that delivers the heat at the coldest point of the year and then the HP deals with everything above that ?

Moxi

[Joeboy]

Do you think you'll settle on a heat curve number that works for you?

The whole point of heat curves is that they're supposed to control how the HP reacts to outdoor temperature. If you're cranking it up when the weather is cold and down when is milder then it isn't doing its job...

Fair question. Aye on what the heat curve is there for. We are still improving on the thermal envelope and the changes are apparent. None of it will be settled until the 3g and doors go in. Then I'll know where to start from and what to expect.

To run the system efficiently I have to find the lowest tolerable setting and then go up a notch. I expect that to be 0.25 once the 3g goes in but hoping for 0.2.

What I'm doing now is to leave a record of what a well Installed HP can do in a reasonably insulated home this far North. Long after I'm settled, done and enjoying my HP lifestyle this record will be here for people with good intentions who are making the decision with heads garbled with misinformation or influenced by press sensationalist advertising of shite installations.

It's worth taking my time to do this even though I'll not know the impact it has. Just good to know it's there for someone.

[Joeboy]

So is the point of the curves to find one that fits your requirements for (say) 75% of the time and then the HP uses the temperature sensors and ramps up or down around that curve to meet the temperature for the 25% of the time ?

Or do you find the curve that delivers the heat at the coldest point of the year and then the HP deals with everything above that ?

Moxi

The heat curve is a band of temperature that the HP will operate within. I'm not fully au fait with the detail of how it responds. That'll take me some time. There are other links and protons for breakfast blog has some good detail

[Moxi]

ahh ok so its more the first case that I wondered about - getting a curve that straddles your normal operating temperature and select that to let the HP do its thing and maybe at a seasonal point change to another curve - so when its all settled and you "know" your heating you might have two or three curves that you select at different times of the year to get the optimum from your HP, or if you live in a place where the temperature range isn't massive one curve might do everything you want at a CoP that you are happy with.

Thanks

Moxi

[Joeboy]

ahh ok so its more the first case that I wondered about - getting a curve that straddles your normal operating temperature and select that to let the HP do its thing and maybe at a seasonal point change to another curve - so when its all settled and you "know" your heating you might have two or three curves that you select at different times of the year to get the optimum from your HP, or if you live in a place where the temperature range isn't massive one curve might do everything you want at a CoP that you are happy with.

Thanks

Moxi

Aye, that's about it Moxi, well put. Not quite a magic bullet, more a magicish with occasional human intervention. By getting a handle on HP performance at 0.25 and 6 degs outdoors, wbs on at my known very low & slow setting I'll be able to feel the benefit once 3g is in and we'll have a record going forward. 0.25 is holding well and increasing the home temp alongside the wbs.



Been into loft space again and improved the insulation around the drain cock, impeller housing and additional AAV. Did another few bits including the magnaflow filter housing.



Before


After


Used the insulation bag trick from yesterday







I know the installers are operating at a high level but time is money and the insulation can be improved by the owner. I have no idea how much heat that wee work saves and onward into the house. Taken on the 24/7 running though its worthwhile doing?

Surely not? Mist be a data typo.

[Stinsy]

So is the point of the curves to find one that fits your requirements for (say) 75% of the time and then the HP uses the temperature sensors and ramps up or down around that curve to meet the temperature for the 25% of the time ?

Or do you find the curve that delivers the heat at the coldest point of the year and then the HP deals with everything above that ?

Moxi

The curve controls how the HP reacts to outside temperature. You don't want it ramping up flow temp too quickly because that'll hit CoP too hard and will result in the inside target temp being hit too quickly and therefore cycle the HP excessively. And on the other hand if the curve isn't aggressive enough, you won't get enough heat on the coldest days.

[Joeboy]

Well, this is working well. Let's try 0.2.





It looks like this

[Joeboy]

0.2 was too big an ask without 3g. Felt it in about 40 minutes. Bumped back up to 0.25 and will leave there for next couple of weeks.

Check out the trailing 24hr consumption.

There is/can be a lot of adjustment in these systems and it's worth doing.

[Joeboy]

I've knocked 40 minutes off the dhw for tomorrow and dropped the heating temp to 18 degs, leaving heat curve at 0.25. This is the last count for tonight. After this it's HP only with no wbs. Sub 17kWh on the trailing 24hrs to run the HP.

I wonder how low it will.go?

[Andy]

The curve gives a starting point for the calculated flow temp based on the outside air temperature. A perfectly sealed house in a black box where the outside temp is modified would mean the heat loss is perfect and the curve would work perfectly. However, things like air replacement in the house caused by wind outside and solar gain through the windows mean it is never going to be perfect. It will be heating too much or too little based on the extra environmental factors. That's then where the active adjustment comes in and the internal temperature is monitored and extra corrections added based on that. Make sure the sun doesn't land on your internal or external temperature monitoring or that will throw off the calculations.