HughF

Yeah, been working well today, after some hard work this morning recovering from being off from 23:30 till 05:30. Seems to be ticking along quite happily at the lowest modulation, until it warmed up this afternoon.

My cheap as chips r290 mini split really struggles when it’s below 5 outside. Put it on last night and it was defrosting within 20 mins…

Still going, using 930w from the mains - finally….

I’ve bumped it to 5 degrees, it was at 1…. And it’s been running for the last 20 mins without stopping 👍 It’s ramping up and down, but it hasn’t stopped. I also bumped the weather comp up 1 degree as it was a little low at the current OAT. kP is 5c kI is 100 secs (iirc) kD is 0

my suspicion is that I’ll need to spend a day or so playing with the PID settings. But for now, another fan coil to get on the wall.

Can I get this to modulate, can I heck….. It starts off all fine and dandy running at about 1800w, then after a minute or so it decides it isn’t hitting the setpoint fast enough so ramps to full power, overshoots, then won’t start to modulate before it’s too late. I’ve upped the stop-temp to 5 degrees to give it some more modulation overhead, that’s doesn’t seem to make much difference. Still looking at these PID controller values and wondering what a good set of numbers would be.

An update on the high-mass slab…. I pump 27 degree flow around it for 18hrs a day at 3ltrs/min, the house stays at 21 ish, all good. The ufh pump is on a plug top at the moment, the heatpump scheduler turns the ashp on at 05:00 and off at 23:30. I’m running without a thermostat. Will add a timeclock to the ufh pump so I have some sort of automatic control.

Bingo, PID tuning basics: Tuning Methods of a PID Controller - CTRL ALT FTC

Taken from the attached: "On the other hand it is possible to save energy by controlling the minimum inverter frequency in order to avoid the compressor working with very low COP. For this reason the minimum inverter frequency has been calculated by the control algorithm on a case-by-case basis. It generally depends on the outside temperature and has been set between 30 and 35 Hz. We experienced that working with an on/off modulating frequency stopped at the minimum value is sometimes more efficient than working at constant low frequency values." Interesting... +402200110.pdf

Yep, job for tomorrow.

It's better, but not perfect. Watched it shoot strait past the setpoint and end up 2 degrees above, then the compressor stopped. Dropped it to 15 secs, will keep an eye on it. Any idea what the other settings in here do? I know it's a PID controller, but tuning these isn't my strongest subject... At least the house is warm, but It would be nice if it would modulate down better.

Found it, it was at 200secs… dropped it to 30, let’s see what happens. its not helped by the ambient air temperature sensor being attached to the evaporator. Unit fires up, fan starts, temperature sensor drops due to air movement, setpoint increases, unit ramps up, unit turns off.

I really like this idea, won’t lie.

Interesting, I’ll investigate.

Does a very good job of the defrost too, very quick. I just watched it do a other one and it was sub 2 mins.

I’m still none the wiser about the time clock and temperature settings for that. I emailed Chris about it but not heard back yet. Still also struggling with it short cycling, it seems to want to run hard up to the setpoint, overshoot, then wait for the compressor restart delay timer to expire. Which at -2 and pushing 45 degrees, into a bunch of wide open rads, the ufh slab and two fan coils, surprises me…

HPC is progressing, not as fast as it should, but it’s progressing. They’ll get it done. Hopefully the Chinese reactor design at Sizewell C will be easier/cheaper to build. EPR is probably one of the most complex

Update: haven’t touched the lockshields forks month, but I managed to get the ufh plumbed and wired up. Still one fan coil down so we’re just ticking along with emitter rejection slightly under the minimum modulation value of the heat pump, so we’re still cycling. Hoping to get the electrician back on site this coming week to get the kitchen second fixed and the last fan coil installed. That should give us 1100-1400w more emitter capacity and bump us above the 3.3kW minimum. Hoping to see the heat pump settle down to its 800w minimum then and just tick along in the background.

I think the RHI was really meant to help cover the capex of these ‘new fangled heating things’ 🤣 and it, weirdly, ended up rewarding the largest consumers the most. Taxing the dirty stuff seems to work for cars, so it should work for home heating too, we just need more cheap, clean electric available. Bring on Sizewell C is all I can say.

‘Works in UK homes’ means ‘costs less than a gas boiler’ to most folk. We installed one because we couldn’t realistically find a way to get a flue out of the house without it getting in the way.

And just done its first defrost cycle. Which I was a bit paranoid about given that I don’t have a buffer or a volumiser in circuit. Defrosted in under 5 mins, thermal switch in the fan coils shut them down when the flow dropped below 35 and fired them back up again after the defrost was complete. Result….

Is it possible to vacuum extract chopped fibreglass from a 50mm cavity and then have it replaced with blown beads? Recent renovation work has uncovered areas of the cavity that are poorly filled, and as this is our forever home, I’m keen to have the insulation replaced with something that’s going to last long term. Not concerned about moisture as it’s rendered blockwork.

Homely is also complete turd when it comes to packaging and end user interface. The damn thing is micro usb powered and only has an app as the front end. What’s actually needed is an opentherm to modbus converter that will read the load compensation calculated flow temp from a proper smart thermostat, and convert that to a weather comp curve adjustment value. The vaillant sensocomfort will modify the curve up and down as required to reach the target room temp, automatically (as far as I can tell).

It’s for copper press fittings for water and gas. MLCP jaws are also available, and that’s also suitable for water and compressed air.

That’s all you really need, M in 15/22/28.