Heat Pumps - post here.

poker--addict

Mine also runs at 5-6KW, I dont think its capable of running at 1.5-2Kw, guess that's the newer inverter tech? I might try knocking off weather comp though

newhouse87

https://www.boards.ie/discussion/comment/121482036#Comment_121482036

Do you mean 5-6kw consumed an hour or output? My heat pump modulates flow rate down to approx30% of its capacity when lwt reached to maintain delta t. Usage drops dramatically when lwt set point reached which happens quite quick @29deg flow. at higher flow temp, its running over 2kw an hour.

feelings

https://www.boards.ie/discussion/comment/121481955#Comment_121481955

can i ask what size is the house? trying to compare usage. thanks.

newhouse87

https://www.boards.ie/discussion/comment/121482062#Comment_121482062

2605 sq ft/242sqm.

ColemanY2K

my new 8kW heat pump will be switched on today or tomorrow. the plumber says it'll take a week to get the house up to temperature (underfloor heating). to clarify its a new build bungalow, 2077sqft (193m2).

i had a 2.5kW electrical heater running the other day and after about 2 hours the house was noticeably warmer (the current temperature in the house without heating is circa 10 degrees during the day).

the insulation between the joists has yet to be laid. That's a task that will start this weekend.

will it really take a week?

newhouse87

https://www.boards.ie/discussion/comment/121482202#Comment_121482202

Has to be heated up slowly, don't want screed cracking, may not be a week though.

ColemanY2K

https://www.boards.ie/discussion/comment/121482219#Comment_121482219

ah fair enough. the screed was poured in early september so has had plenty of time to cure which i hope will limit the cracks (the floor is to be polished).

graememk

https://www.boards.ie/discussion/comment/121482036#Comment_121482036

When yours kicks in, how long does it run for?

Or is it running all the time?

Mines inverter driven, so I can see it ramping up when it starts (power wise).

How big is the house too?

5-6kw is a massive draw. If you are getting a decent COP, the heat loss on the house must be big, or if your heat loss is low

newhouse87

https://www.boards.ie/discussion/comment/121482252#Comment_121482252

I wonder are the back up heaters kicking in like i saw? Reckon most heat pumps these days are inverter driven so doubt that's an issue.

poker--addict

I mean it uses about 5kw per hour (consumes), my heating ~55KW per day, kicking in and out. It could be 70 during a cold snap. DHW not included. House is large, ~350sqm.

It is UFH, so I tend to set the temp back a lot during the day, and that sees it working most of the night putting heat into slabs for the day.

zoom_cool

https://www.boards.ie/discussion/comment/121480864#Comment_121480864

I didnt import it there is a distributor in Ireland walls are mass concrete with 120mm EPS floor is 150mm EPS

newhouse87

https://www.boards.ie/discussion/comment/121482449#Comment_121482449

Thats a big house tbf. The kicking in and out method using stats is not most efficient, the heat pump has to raise temp for 1 room, then it shuts off, an hour later another room might call and has to repeat process. Have you tried running from say 9am to 9pm and setting it off overnight?

graememk

It could be an older one that doesn't vary.

But 5kw is a big ol' motor to be starting without an inverter though.

I'm using 20kwh/day with 140m2 so 0.142kWh/m² with a cop of 3.5, just dropped a heatpump in and ran it (I did change one rad as it wasn't good enough)

55kwh/day on 350m2 is 0.15kwh/m²

Newhouse87 was 20ish too at 242 = 0.08kWh /m²

newhouse87

https://www.boards.ie/discussion/comment/121482798#Comment_121482798

Im at14kwh for heatpump and dhw in these condiitons.

graememk

https://www.boards.ie/discussion/comment/121482809#Comment_121482809

0.05 then. 😁 A third of what I'm using!

Not the worst way to compare given different house sizes.

Although bungalows would have more loss Vs 2 storey houses etc.

DC999

https://www.boards.ie/discussion/comment/121482449#Comment_121482449

If you're into watching YouTube for tutorials, have a look at some heatgeek stuff on disabling zones or finding what is causing unexpectedly high usage. How To OPTIMISE Heat Pump Settings! (youtube.com). Skill Builder + Heat Geek one to troubleshoot a bad HP setup: Heat Geek Gives His Verdict on John’s Nightmare Heat Pump (youtube.com). Am sure there are more too.

And this Urban Plumbers fella is really into HP efficiency: How To Install an Ultra Efficient Heating System - Heat Pump + UFH. (youtube.com). He's Heat Geek trained afaik. His videos are class. He's really into it. Some of his videos go over the settings like weather compensation.

It's worth noting all the settings now and stats, make a change and see if that makes it better or not. Your large house with UFH will likely take a few days to show changes. If you've an infrared temp monitor (~€25 from Amazon), you could record the temps of the UFH slab, temp at bottom and top of rads and the feed in and out of them. Record room temps, kWh of electricity, COP....

newhouse87

https://www.boards.ie/discussion/comment/121482845#Comment_121482845

Yeah im in bungalow, as you can tell from my username its newhouse ha. House retains heat v well, kitchen 21 this morning even though heating off since 9pm last night. Def happy i dezoned and changed to lowest possible flow temp instead of weather curve which is supposedly the wrong to do. By running longer it gives slab time to absorb heat rather then stat method which may only run heat for few hours then switch off before having to come back on again few hours later.

poker--addict

Heat geek is great, after 2 years trying to step through the options methodologically, I believe the installation (as per heatgeeks main point) was not optimal, so it is a case of making the most of current setup. I must look on amazon for one of those infared temp viewers though, might help to balance things.

munsterfan2

240sqm house, this is my usage for the week of 4 - 10 December. so 72kwh on heating, 19kwh on hot water. ( 1 EV on the Zappi using close to 160kwh, other EV on external socket using 28kwh ). 4 adults in the house, who all like long showers. All the EV charging is at energia night rate. about .05 /sq m

newhouse87

https://www.boards.ie/discussion/comment/121483727#Comment_121483727

what in particular do you think is not optimal?

johndoe11

Just looking for some settings advice for the heating curve on my IVT/Bosch heat pump. It works very efficiently, but have noticed some installer setting which were incorrect and I've have started experimenting to find other that might set incorrect. The manual states the most important settings for setting the heat curve are below, with the last 2 being the key settings:

• maximum flow temperature (set to 48deg)
• room temperature offset (No room controller so not relevant to me)
• minimum outside temperature (set to -6 for the midlands)
• system (flow) temperature which is defined as (the flow temperature that should be reached at minimum outside temperature)

I'm happy with the first 3 settings, however the last one is set at default 45deg, this seems high to me for -6c outside temp. Below is an excerpt from the manual. Anyone have any advice on this? I'm think the flow temp at -6 should be around 39 or even a bit less (something like line 2 below).

Nelbert

The answer is it depends. If you've really low heat loss your flow temps can be lower.

Someone advised previously that the best way is to keep reducing until the house feels cold and that you've hit your limit then.

You probably won't be popular doing that experimentation though.

For reference A3 rating, ok airtightness, 2 storey plus dormer, ufh downstairs, rads upstairs. Flow temp of 35⁰ has been ok the last week or so.

Although today was mild and floor fully heated on night rate and solar gain (lots of south facing glass) over the day brought my kitchen to peak approx 28⁰ around 2pm. Today is the type of day I find challenging to balance, cold overnight leads to UFH calling for heat, bright mild morning churns in on top. 2 years at it and still not perfected it.

championc

If it was an upgrade, then there should be a design document where the rads and pipework are sized based on heating rooms to xx deg at the lowest possible temp (you say -6 deg), accounting for the calculated heat loss.

The calculation should give the flow temp needed to deliver the necessary heat

magformer

Quick and possibly dumb question as I try to figure out why my heat pump is consuming so much electricity:

The conventional wisdom that a heat pump should run all the time for maximum efficiency - what exactly does "run" mean here? My (split) system has the heating and DHW circuits, the circulation pumps and the outdoor compressor/fan unit. The circuits are always on which I think means that I have water moving around the UFH and rads all the time, except possibly during the DHW cycles.

Should the outdoor unit be running all the time or is it normal for the compressor to cycle? The recent operation log shows heat demand cutting in and out, sometimes as frequently as every 5-10 minutes. But it's not clear to me whether this is problematic short cycling if the outdoor unit isn't coming on each time.

It's a Yutaki S Combi split system.

Thanks!

johndoe11

Thanks for the replies. Not an upgrade, it is installed a few years in a A2 newbuild (now A1 with solar). I'll have a play around with it and see what happens.

graememk

https://www.boards.ie/discussion/comment/121492570#Comment_121492570

On normally means "switched on" and actually turns on when there is a call for heat. When it's really cold out a lot do be running, but on a low power.

The heatpump shouldn't be kicking in and out every 10 minutes. Ideally it would run at a lower power. Is the heat demand stopping and starting or the heatpump starting or stopping.

The compressor usually cycles because the return temperature gets too hot. Possibly due to a multitude of reasons

Possibly too high a flow target temperature, too much zoning, over sized heatpump,

How much power are you actually using? Vs size of your house, a few here in the last few days have been getting 0.05kwh/m²

magformer

https://www.boards.ie/discussion/comment/121492712#Comment_121492712

Thanks for explaining.

The Hitachi controller seems to distinguish between "Thermo-on/off" and "Demand - on/off". This isn't explained anywhere in otherwise reasonably detailed documentation but I think now that "thermo" indicates a call for compressor operation. I am not entirely clear what the condition is of a circuit that is demand-on but thermo-off.

Digging into the logs a bit more, this cycling is all "thermo-on/off" so I suspect it is the heat pump/compressor that is kicking in and out rather than just the heat demand. Have tried tweaking the flow temps up and down over the last few months, including with installer but this condition persists.

I don't have precise power metering for the heat pump itself yet but overall daily consumption including other domestic demand is anywhere between 33 and a whopping 55-60kWh daily. This is an A2-rated refurb. The heat pump unit is a big double-fan thing, 11kW. The majority of this is almost certainly the heat pump. Area is 225 sqm.

The DHW is only set to 48-50 but the electric heater randomly kicks in, almost like it's struggling to heat a tank. But not always - sometimes it's fine. I think this accounts for the very high usage days (50kWh+). But it seems to me that with current temperatures outside, even 33kWh is very high for a properly like this.

graememk

I'll not get started too much on the ber ratings.. but I dare say with solar and now a heatpump I'd nearly be an A3.. and still no change in insulation.... Anyway.

More questions to help you figure some of this out. I don't know the system or machine but even asking the questions might shed some light on things.

Is your house warm enough, or is it cold or too hot?

What controls the call for heat?, is there a thermostat somewhere? Can you force a demand on/off by changing thermostats?

What is it set to (or is there multiple?)

Is there much zoning going on? Is it all underfloor heating?

What are your flow temperatures set at?

magformer

https://www.boards.ie/discussion/comment/121493098#Comment_121493098

Answers all a bit complicated because the installer was back to change a few things recently when I insisted the system didn't seem to be working correctly.

--Is your house warm enough, or is it cold or too hot?

Now it's mostly too hot (22-23) but sometimes ideal (21-22) - the variance is partly the changing flow temps with weather comp I think, but also solar gain and maybe occupancy/activity around the house.

There is UFH downstairs, rads upstairs. Initially the system was installed with a single circuit. Low flow temps seemed to work well with the UFH but the rads just weren't heating the upstairs rooms in any meaningful way. They never got colder than 17 but the point was that there was a very significant and uncomfortable delta between upstairs and down. We need at least the option to have slighter hotter bedrooms (e.g. small babies). Increasing overall flow temps would achieve this but make the UFH rooms too hot. So installer came back and put in a mixer valve and split the system into two circuits. Now upstairs gets just a few degrees higher flows, but seems to make all the difference. That was only a few days ago - can't see any real difference in the electricity use but quite big difference in upstairs comfort. All very apparent because the rads react quickly. I thought having separate flow temps for rads vs UFH was quite common so not sure why we didn't start with that.

--What controls the call for heat?, is there a thermostat somewhere? Can you force a demand on/off by changing thermostats?

Two sets of controls: The Hitachi panel that came with the unit which includes a stat and Heatmiser stats, one for each UFH room and single one for rads zones. The Heatmisers open and close the circuits but they can't call for heat afaik. TRVs on rads too. For this troubleshooting phase I just leave everything turned up/wide open. Except one or two days for a large UFH zone where overheating has been an issue. Originally the Hitachi panel had a single room stat and was an influence on weather comp to some extent. I complained that it and all Heatmisers are absolutely hopeless in terms of accuracy - I think they are all reading their own heat accumulating in the wall box, so readings are 2-3 degs above actual. Seems to be a known issue with the Heatmisers at least.

So the Hitachi panel caused the system to think internal temps were higher than reality, bumping flow temps down just a bit. It is also in the wrong place - a warm utility room shared with the indoor heat pump unit. Rather than fix anything with the stats, the installer just switched to weather comp only. So now I think there are no internal temp factors considered by the system.

In short, right now I can't force demand on/off as it's set up with these controls.

--What is it set to (or is there multiple?)

Heatmisers all v high (25-30+) just to make sure zones stay open. Hitachi was previously 20-23 - I tried high and low but seemed to make no real difference to power consumption. Comfort would noticeably increased at 23 without obvious higher power consumption. That control is offline now anyway.

--Is there much zoning going on? Is it all underfloor heating?

Just as above. There is a permanently open zone (no stat) covering the hall and a few downstairs rooms. I think that is good practice so that there is still a good bit of water moving even if the zoned areas are closed? As I understand it, the system was designed really for room stats to prevent overheating only if necessary but as mentioned they can't communicate with the heat pump or call for heat.

--What are your flow temperatures set at?

Installer has just bumped them up slightly with the new rads circuit. At 5 degrees outside, it's currently 33 on the rads circuit and 28 on the UFH. This is probably a bit too hot for both right now, but not far off ideal comfort for bedrooms. I will try reducing but as I understand it these are not crazy temperatures. Power use seems to be comparable when flow was previously mid twenties so I don't really understand what's going on. If too low, the house can start to feel a bit cold still with high power use.

DHW was 48, installer has just bumped up to 50. There have been occasional days where the tank has failed to heat for no clear reason and, as I mentioned, I'm still getting random electric heater usage. Again, I think this is a relatively sensible DHW temp?

One other observation but not a very scientific one is that the floors with UFH seem warmer to walk on than you would think for a <30 deg flow temp.

So with these flow temps, I'm on 42kWh total for today. This is my consumption pattern last night (midnight to 7am) when base load is really stable - apart from what is probably a drier at the beginning, those 2+kW spikes I'm pretty sure are the compressor just kicking on and off which I suppose is all adding up over 24hrs.

I'm being more or less fobbed off by everyone responsible for the install but none of this seems right - not far off a 400 euro electricity bill just for Nov is wildly beyond expectations. Insulation, triple glazing, MVHR, added everything possible to limit energy use. I don't think there are major heat loss issues.

ColemanY2K

https://www.boards.ie/discussion/comment/121492507#Comment_121492507

Have you considered brise soleil to reduce solar gains? They can be a simple fixed system or a more complicated automated system where solar gain is needed at certain times. It may seem counterintuitive to some people but there's days in winter in Ireland where it can be particularly bad what with the sun lower in the sky.