Most of us moved to Hawk's Bay from houses with a gas or oil boiler: switch it on, and twenty minutes later the radiators are too hot to touch. So the first winter here can be a bit unsettling. You put your hand on a radiator, it's barely warm, and the natural reaction is to turn the thermostat up to 25, or switch the heating off and on again, or start poking at the controller on the hot water cylinder.
Don't. Lukewarm radiators are exactly how a heat pump is supposed to work, and most of the "fixes" people try actually make the house colder and the bill bigger. This guide explains what's going on, how to set things up, and answers the questions that come up on the noticeboard every autumn.
What we've got
Every house on the estate has the same basic setup:
- A Samsung Generation 6 air-to-water heat pump, supplied and commissioned by Joule. The big box outside with the fan is the heat pump itself.
- A hot water cylinder (a Joule Cyclone) in the hot press, with a small Samsung controller fitted to the front of it.
- Room thermostats, usually one per floor, so two in most houses. These are what you actually use to control the heating.
- Radiators, filled with water mixed with glycol (a kind of antifreeze).
The full manual is in the Knowledge section: Durkan Heat Pump Samsung G6 Handover Manual. It's worth a read, but it's written for engineers more than residents. This guide pulls out the parts you actually need.
How a heat pump works, in two minutes
A boiler makes heat by burning gas or oil. A heat pump moves heat: it pulls warmth out of the outside air (yes, even on a cold Irish day there's useful heat in it) and pumps it into the water in your radiators. It works like a fridge running backwards. A fridge takes heat out of the inside and dumps it out the back, and the heat pump takes heat from outside and dumps it into your house.
Because it's moving heat rather than making it, a heat pump can give you around three units of heat for every unit of electricity it uses, sometimes more on a mild day. That's where the savings come from.
There's a catch, though. The heat pump is most efficient when the water it sends round is only warm, not hot. Push it to make very hot water, like a boiler does, and the efficiency drops sharply. So instead of blasting very hot water through the radiators for an hour, it sends lukewarm water round steadily, all day, and keeps the house at an even temperature.
Boiler vs heat pump at a glance
| Old gas/oil boiler | Our heat pump | |
|---|---|---|
| Water in the radiators | Around 70°C, too hot to hold your hand | Roughly 35–50°C, warm to lukewarm |
| How it's run | Blasts on, then off, on a timer | Runs gently and steadily, day and night |
| Warming up from cold | 20–30 minutes | Several hours |
| What tells you it works | The radiators are hot | The room is at the temperature you set |
"Weather compensation": the clever bit
The heat pump automatically adjusts how warm it makes the radiator water based on the temperature outside. On a mild October day the radiators will barely feel warm at all. On a frosty January morning they'll be noticeably warmer. This is automatic and it's deliberate. It's one of the main ways the system keeps running costs down, so there's nothing for you to adjust.
"My radiators are lukewarm. Is that normal?"
Yes. This is the most common question by far, so here's the short version:
- Judge the room, not the radiator. If the room is sitting at the temperature on the thermostat, the system is working perfectly, however cool the radiator feels.
- The radiators are bigger for a reason. Heat pump radiators are sized to give out plenty of heat at a low temperature, because they have more surface area.
- Our houses hold heat well. A well-insulated house only needs a gentle, steady top-up, not a blast.
It's worth a closer look if a radiator is cold at the top and warm at the bottom (that's trapped air, see the questions below), if one radiator is stone cold while the others are warm, or if rooms aren't reaching the temperature you've set, even after a full day.
Setting your thermostats
This is the part that makes the biggest difference, and it's simple: pick a comfortable temperature and leave it alone.
- Set each floor to a temperature you're comfortable with, typically somewhere around 19–21°C, and leave it there day and night. The heat pump only runs as hard as it needs to keep that temperature, so "always on" doesn't mean "always working flat out."
- Don't turn the thermostats off, and don't turn them right down. Joule's manual is clear that the heat pump works best when the thermostats stay as close to a constant temperature as possible.
- Going out, or want it cooler overnight? Drop it by no more than 2 degrees below your usual setting. That's the manual's limit. Any lower and the heat pump has to work much harder to catch up, which usually costs more than you saved.
- Turning it up higher doesn't heat the house faster. Setting the thermostat to 25°C when you want 21°C won't get you to 21°C any sooner. You'll just overshoot later and pay for the extra.
- Upstairs and downstairs can be different. Many people keep the bedroom floor a degree or two cooler than the living floor, which is where the two separate thermostats come in handy.
- In summer, when you don't want heat at all, the manual says to set the thermostats to 16°C rather than switching anything off.
Leave the controller on the cylinder alone
The Samsung controller on the front of the hot water cylinder is for engineers, for setting up and diagnosing the system. The manual says plainly: "Please do not use the Samsung Controller to control your heating."
In normal use its screen shows Zone – Set – 0.0 – Heat on the left and DHW – Set – 48deg – Standard on the right ("DHW" just means domestic hot water). If yours looks like that, leave it be. The only times you'd normally touch it are the hot water options below, or to read an error code.
The numbered knobs on the radiators
Each radiator has a round knob on the side numbered 0 to 5. It's a thermostatic radiator valve, and it controls only that one radiator. As the room warms up, the valve gradually closes and lets less warm water through. The higher the number, the warmer the room gets before it closes. 0 shuts the radiator off, and 5 is fully open.
How to use them alongside the wall thermostats:
- In the room with the floor's thermostat, leave the knobs on 5. The wall thermostat decides when that floor gets heat. If the radiator knobs in the same room are turned down, they close before the room reaches the thermostat's setting. The thermostat then keeps asking for heat that never arrives, and the heat pump runs on for nothing.
- Use the knobs to turn individual rooms down, such as a spare bedroom you don't use or a bedroom you like cooler. Somewhere around 2 or 3 suits a room you want a bit cooler.
- Don't use them as on/off switches. Turning a radiator to 0 and back to 5 every day has the same problem as switching the heating off and on: the heat pump works much harder to catch up. Set each room once and leave it.
- If a room never warms up, check its knob hasn't been knocked down to 0 or 1. It happens more often than you'd think, especially when furniture gets moved.
Hot water
The cylinder is kept at 43–48°C all the time. When it drops 5 degrees below that, the heat pump switches over to reheat it. Two things follow from that:
- Hot water takes priority over the heating. After a few showers in a row, the heat pump stops heating the radiators for a while to reheat the cylinder. If the radiators go a bit cooler for half an hour after the morning rush, that's why. It's normal.
- 48°C is plenty for showers and washing up, though it's not as scalding as an old boiler system could be.
A few controller features worth knowing about:
- Forced mode, when you've run the cylinder low (after a bath, say) and need hot water quickly. On the controller, press the right arrow so DHW is highlighted in blue, press OK, scroll to Forced and press OK. This runs the heat pump and the electric immersion together. Remember to switch it back to Standard afterwards, because the immersion is expensive to run.
- The weekly hot water clean, Tuesdays at 3am. The system heats the cylinder to 60°C once a week to kill off any legionella bacteria (the bug behind Legionnaires' disease). If you hear it running in the small hours of a Tuesday, or the electricity use spikes then, that's the reason.
- Going on holiday? You can switch hot water to Economic mode, or turn the hot water function off. Put it back to Standard when you get home.
Common questions
Should I turn the heating off at night or when I'm out?
No. Set it back by up to 2 degrees if you like, but don't turn it off. A heat pump is slow to bring a cold house back up to temperature, so switching it off means it then runs flat out for hours to catch up, often with the expensive backup heater helping. Steady is cheaper.
Can I switch the heat pump off at the wall in summer, or when I go away?
No. Both the builder's guide and Joule's manual are firm about this: don't turn the heat pump off at the power supply. In cold weather it protects itself from freezing by running its pump now and then, which it can't do if it has no power. Turning it off can put your warranty at risk. The builder's guide says it should only be turned off by a qualified person during the annual service. To stop heating in summer, set the thermostats to 16°C. To save on hot water while you're away, use Economic mode.
There's steam coming out of the unit outside, and the fan has stopped. Is it broken?
Almost certainly not. On cold, damp days, frost builds up on the outdoor unit. Every so often the heat pump runs a defrost cycle: it stops the fan, warms the unit up to melt the ice, and the meltwater gives off a cloud of vapour that looks like steam or smoke. It usually lasts a few minutes, and then the fan starts again. The radiators might cool slightly while it happens.
Call an engineer if the unit stays encased in thick ice, the fan never restarts, or the "steam" looks dark or smells of burning.
Why does it take so long to warm up?
Because it's designed to keep the house warm rather than heat it from cold. The manual says you should feel the radiators start to warm within about 10 minutes of a thermostat calling for heat, but getting a whole cold house up to temperature can take many hours. That's another reason to leave it running at a steady setting.
A radiator is cold at the top but warm at the bottom.
That's trapped air, which is common in newer systems. Bleed it: put a radiator key on the small valve at the top corner, open it gently until you hear air hissing out, hold a cloth underneath, and close it as soon as water appears. Radiator keys cost a couple of euro in any hardware shop.
Upstairs feels warmer than downstairs (or the other way round).
Heat rises, so the upper floor often runs warmer. Just set the two thermostats separately until each floor feels right, then leave them.
There's a code starting with "E" on the controller.
If the controller shows an error code starting with E (for example E911) and the power button light is flashing, write the code down. Then contact your service engineer, or Joule's support line on 01 623 7080. They'll want the code, plus the model and serial number from the unit. If your house is still within the builder's 12-month warranty, report it to customer@hawksbay.ie instead.
Is it expensive to run?
All your heating and hot water are on your electricity bill now, so winter bills will be higher than you're used to for electricity alone, but you have no gas or oil bill on top. Running it steadily, at a sensible temperature, without lots of Forced hot water, is the cheapest way to use it. If you're curious whether solar panels could take a bite out of the bill, see Solar Panels and Home Batteries: A Beginner's Guide.
Does it need servicing?
Yes, once a year, by Joule or a Joule-recognised engineer. That's a condition of the warranty. The glycol in the system should be changed every three years, which can be done at the same visit. See Yearly Home Maintenance for the full list, and the Directory for a heat pump service company that offers a group discount when four or more households book together.
A few practical tips
- Give it a week. If you've been fiddling with the thermostats, set them to a comfortable temperature, don't touch them for a few days, and see how the house feels. Most "my heating isn't working" worries disappear once the system is left to settle.
- Trust a thermometer, not your hand. A cheap room thermometer tells you far more than touching a radiator does.
- Don't dry clothes on the radiators. The builder's guide asks us not to, it blocks the heat from getting into the room, and the extra moisture in the air is the last thing a sealed modern house needs.
- Keep the outdoor unit clear. Leave space around it for air to flow, and don't let leaves, bins, garden furniture or snow pile up against it.
- Remember to switch Forced mode off. It's the easiest way to accidentally run up the bill.
- If your house is new, the builder's guide asks you to keep the heating as low as possible for the first six months while the house dries out, to stop the paintwork cracking.
- Ask a neighbour. Everyone on the estate has the same system, and someone on the noticeboard has almost certainly had the same question.
Compiled from the Samsung G6 handover manual supplied by Joule, the Durkan Hawks Bay Home Owner Guide, and general SEAI heat pump guidance. Always check your own manuals for the last word, as settings can vary from house to house. If you spot anything outdated here, let a committee member know so we can update this page.