G and J

As someone wrestling with wall thickness vs room size I sympathise. I’ve been experimenting with Jeremy’s heat loss spreadsheet and actually insulation cost vs heating cost payback is much worse than I expected, specifically meaning that after a certain level extra insulation just doesn’t pay back sensibly….. But! I’ve a horrible feeling that if I design by spreadsheet I might get the optimum financial balance but will I get the most comfortable? I guess that might simply translate for the OP into a bit of central heating rebalancing.

OK, I’m officially confused. That doesn’t look like a clever zero volt switch. If you’ve only got a two core cable back to the ASHP then presumably that’s just on/off, so how does the pump know whether to cool or heat? I’ll take deep breaths and try and stay calm whilst hoping for a comforting circuit diagram to ease my perturbations.

And ever it is thus. It seems the minute we buy anything they bring out a better one which is kinda annoying but that’s progress. Except sometimes ‘better’ is just different and it does the same job. C’est La vie.

I’ve that ‘I’m being dumb’ feeling but please could I see a circuit diagram of the above.

Meaning I can’t just use a normal physical switch, or at least, I then have to use it through another zero volt switching device. I'm guessing this is to protect vulnerable components in the heat pump?

So it presents different connections for above and below set point, and you use that to switch between heat and cooling mode. If so, in winter if you light your woodburner (you might have to instal said woodburner first), the system could then go into cool mode.

What stat are you using?

Methinks the hard part will be the control system, especially the user interface. I hope to use the DAF model based on a single switch (instead of the gear knob). Heat-Off-Cool. I might make it look clever by having a bank of flashing lights and some 50’s Ipcress File computer type noises alongside said three position switch, maybe even an “Achtung! No Gerfingerpoken! Verboten!” sign in red letters too. This will be above a non-latching, push to make switch behind a really big red button labelled “in case of nuclear fall out, steam or excessive farting, press once” which will be the user interface for the MVHR.

Has that got 3 connections (common, no, & nc I mean)?

That’s how we will start, and hopefully stay. If faster cooling is needed the valves and a volumiser will be added laterer.

Sorry about the delay, wanted to have a quick word with them before I posted. It’s a company called Heat, Space and Light.

Yep, two storey our bedroom upstairs and not huge solar gain as not huge windows and few south facing. I’m now erring towards a single zone UFH and fancoil run just above dew point as per @JohnMo. So at least I’ve got someone to blame lol I could mount an A2A cooling unit in our cold loft, I guess I’d worry about noise and servicing it, as it’ll be a crawl through fink trusses by the time I’ve laid all the insulation up there with some crawl boarding on top.

Am I correct in thinking the pump is running all the time? i.e. the water is constantly flowing round the system thus allowing the ASHP to monitor?

Actually in the ceiling void or hung from the ceiling itself? If the latter I do understand….. except some of the units can be mounted next to a wall into which the drain could pass.

Adding up all the various things said it feels to me like the answer is put in a drain in case but don’t expect it to actually drain much; keep things constant and the house will run well; simple weather compensation will mean the only thing I’ll have to do manually is close the bedroom door on really hot days. Leaving me more time to operate my coffee maker. Spot on!

So, if one has both the slab and fancoils all run together in a single zone, then one cannot run supercool for too long before the floor gets condensy (today's invented word!). But if the fancoil at 12c cools a bedroom v quick is it ok to boost the lot for say 10 to 15 mins without risk of wet floors?

It could drain to any convenient waste pipe using a dry trap methinks, and if a continuous fall is the difficulty then some Fancoil instructions say you can run the pipe to make a deliberate gentle u bend so as long as it has a fall from the unit to start with it’ll work perhaps.

If you have the capability of setting the flow temp automatically just above the dew point then no drain required. Ok, you won’t be able to run super cold so it’ll take longer to cool each room, but it’ll still be better than not having any cooling in each bedroom. If you do go for supercool you’d have to isolate the slab anyway or risk condensation on flooring - not an attractive look - so the above dew point working sounds brill. What kit do you need to implement Rough Lawrence?

So, I’ll assume you are using the fancoils for cooling. Sadly I can’t answer your pipe question, I guess the insulation is only there to stop the pipes dripping condensation if you run your heat pump cold enough to cause condensation. If I’ve understood what’s been said it may be enough to run the pump just above the dew point - but that might mean bigger fancoils as the delta between room ambient and water temp will be lower. But if you do run it above dew point you won’t need insulation on the pipes at all. I'm guessing if you do run it real cold then you’ll need insulated pipes and the drain will become very needed. But hey, sorry if we made you feel left out of the fan(coil) club lol

I want everyone happy, me. Everywhere. All at once. Oh, and I only want it to rain at night.

Oh ok, I’ll install aircon then. My aircon will be a split system with separate heat pump to internal distribution system. AKA ASHP and a fancoil. There, everyone is happy lol

So I need to find one that fits above our bedroom door…

In the 90’s I used travel lodges a fair bit and these ideas have reminded me of them. I can never remember hearing the airflow or being much too hot in summer either. Winter was different, they used have the heating on crazy. So I’ve unconsciously been inspired by a cheap roadside hotel chain. Outstanding! 😕

I did wonder if that would be enough to cool the bedroom sufficiently. I kinda thought well, a drain won’t cost much to allow for condensate if used that way, and allowing for a zone valve to be able to be added later if needed to isolate just the fancoil would be easy too. As for the volumiser, if five days a year for a few hours a day the heat pump ran short cycles would that matter?

Given the recent warm weather it's not terribly surprising that bedroom cooling has been exercising our grey cells. (I wonder if there's a correlation between time of year for design and later overheating issues?) We are committed to ASHP (with some cooling capability) running wet UFH downstairs and electric UFH in all bathrooms, with electric points in case but otherwise no heating provision upstairs. But we also want cooling in the bedroom. The most sensible option for us appears to be a single fancoil unit in our bedroom itself, probably built into the ceiling, but I thought it prudent to ask you guys for a sanity check - not on me, I failed that long ago - but on the plan/placement. The thinking is: The fancoil location is good for pipes inc. the condensate drain, and is away from the bed and behind a wall to help with the noise. Under normal conditions the fancoil will be dormant and not needed for heating though it could of course be turned on to heat. Under mildly warm conditions front and rear windows will be opened to deal with the excess heat. When running the fancoil will push through a lot more air than the MVHR. When in overheat conditions the doors to the bedroom and ensuite will be closed, as will the windows, and the MVHR will keep the air fresh without carrying away all the cool air. So folks, is the above a good plan?