Why should I pay for Heat Pump or Boiler service !

I wanted to start this blog to share my information freely with people who have outdoor Heat Pumps used for heating and hot water or even indoor central heating gas boilers. Winter is fast approaching and one starts to think about all the things that generally succumb to the cold weather like dreaded car batteries, the central heating boiler and occasionally to a lesser extent the pipe work and filtering concerning the car, home and garden.

With COVID creating financial hardship for a lot of people after losing their jobs, the onset of winter could create unexpected sky high service repair bills. Let me clarify at the outset that I’m not in favour of preventative boiler service which ranges from £120 to £250 according to HOUSEHOLD QUOTES credited here, it's clear that routine maintenance is not only smart but also cost-effective, improve safety where gas is used in the long run and is justified. Within a period of one year however where gas problems are not an issue then it’s is prudent to ask engineers why systems fail frequently and why some parts fail for that matter. I remember on one occasion some years back when the engineer came out Three or four time in a year to replace overflow valves in a combi system fora total valve part costing a few pounds!!

Anyway onto the topic firstly a quick summary of what is a Heat Pump.

Heat Pumps

A Heat pump is a standalone, two-component appliance that uses refrigeration technology and electricity to provide heating and cooling for homes, businesses and other.

The two components – a condenser unit that most often sits outside of a home that produces the heating or cooling, and an indoor unit that typically sits on a wall and passes hot or cool air into the home. The condenser and air handler are separated or “split” by refrigerant line, heat pumps may sometimes be referred to as “mini-splits”. Heat pumps offer extraordinarily high efficiency rates, as well as the opportunity to provide heating and cooling without needing duct work in the home and often referred to as “ductless”.

Heat Pump operation.

To provide heat, a heat pump works by extracting heat from the air outside of your home and transferring it to refrigeration coolant – the coolant is then compressed, which increases the temperature significantly; the coolant is then moved to the indoor unit of the heat pump, which then passes air over the hot coolant, increasing its temperature to accommodate the thermostatic call for heat inside the home.

A heat pump consists of two major parts – a “wall cassette” that is mounted inside your home, and a condenser unit that stays on the outside of your home.  The heat pump’s wall cassette and condenser units are connected by refrigerant line.

The indoor wall cassette is thermostatically controlled to provide you with both heating and cooling. When there is a call for heat, the heat pump will turn on the fan in the outdoor unit to begin the process of extracting heat from the air outside of your home.  The refrigerant line carries this heat to the indoor unit, which then transfers the heat to the air inside of your home via a fan inside the wall cassette.  In cooling mode the process is reversed, transferring heat out of your home and returning cool air to the inside.

Common problems associated with Heat pumps

1. insufficient heat production

A heat pump transfers heat from one place to another. If your pipes are blocked by air or debris inadequate heat is produced.

Insufficient heat production may also be caused from dust in the air filters, low thermostat settings, poor refrigerant flow or faulty valves.

2. Heat pump fails to turn on

If your heat pump fails to turn on, it is more than likely that there is a problem with your thermostat or your unit receiving power.

Check the failure fault codes for modern heat pumps against those described in the manufacturers manual. If you don’t have the manual I would internet search for PDF download on supplier website. If possible you should find a contact number and talk to someone who knows the make and model.

Check the main electrical panel and any other subpanels that would supply power to the unit. The circuit breaker could have tripped and will need to be reset.

3. Blocked water filters

It’s also possible you need to find out if you can do some common clean out of water filters, usually there are three or four of these in the system. The cleaning of the filters can be done once the water supply is isolated.

4. Air locks

With closed loop systems, when water leakes, or there are power outages or during other servicing work, air can be inadvertently be introduced into these systems and the boiler will suffer from trapped air and consequently system will require sequential bleeding. Bleeding pipe work in underfloor pipes, manifold distribution systems is important and has to be done correct sequence or else you end up introducing air again into the system.

The outdoor units can get clogged at the fans or even any open spaces available by insects such as Bees for instance or even birds nests in some cases.

Is advisable to check for any frayed wires around your unit. When it comes to electrical concerns, it may be time to contact a skilled electrical technician.

Central Heating Gas Boilers

Common components of a central heating system using water-circulation include:

  • A supply of fuel, electric power or gas
  • A Gas Boiler or heater.
  • Electric water pump
  • Radiators or a network of water pipes imbedded in floor concrete known as floor heating.

The circulating water systems use a closed loop; the same water is heated and then reheated. A sealed system provides a form of central heating in which the water used for heating circulates independently of the building's normal water supply.

A  conventional central heating system often referred as gravity fed system has many components starting from the roof of the house to ground floor comprise of two cold water tanks, one is an expansion tank for the closed central heating loop and Second larger tank used as a reservoir for domestic hot water, fed to a Hot Water cylinder, which incorporates a three way valve to route hot water for central heating and hot water for washing.the hot water cylinders also can incorporate an electrical Emersion heater to heat hot water only.

A combi (or combination) boiler is an ingenious space-saving idea where all of the above components are essentially incorporated into one box with the difference that the pressure of operation is higher and system response is almost immediate.

Heating boiler troubleshooting

To begin my story I want to say that my Gloworm central heating boiler installed in 2000 is still going strong has never let me down but that sometime in the not too distant future could die on me suddenly. I’m not too sure that I should rip off an old dependable boiler for a new one just because British Gas says so especially as it has an impeccable record.

One report cited here the reasons for boiler breakdown. Looking at this it’s obvious that gas part of any boiler is important to service regularly, but to replace a boiler because it’s old !! I think I need to be convinced.  And what’s with the efficiency rating of a boiler how does that come into play? It’s very difficult to see what component(s) have failed internally to stop or lockout your boiler. Most modern boilers don’t tell you anything except a useless fault code on LCD control panel.

Manufacturers in my opinion don’t go far enough when it comes to writing proper operating manuals for troubleshooting purposes especially for a price tag in the region of £3000. Personally buying a brand new laptop for great deal less has better documentation.

Boiler installation can cost from £1500 to 2500 or even £3000 depending on size of output BTU pumps on the other hand have their own unique problems with installation and maintenance. There are three types of heat pumps: air-to-air, water source, and geothermal. They collect heat from the air, water, or ground outside your home and concentrate it for use inside. air-source heat pumps are also available in a ductless version called a mini-split heat pump. In addition, a special type of air-source heat pump called a "reverse cycle chiller" generates hot and cold water rather than air, allowing it to be used with radiant floor heating systems in heating mode. These systems are very energy efficient and so lend themselves to better integration for instance with underfloor heating. As the heat pumps use electricity  coupling them with solar panel photo voltaic systems is even better. There is a nice article here explaining maintaining and operating these systems.

When a system requires Bleeding

When a heating system has air bubbles, it will not heat your home.

If there are bubbling noises from the system, it means there is air trapped inside. It may not cause a major problem, but it reduces the amount of heat your underfloor heating system generates. In this case, bleeding helps to get rid of the air, promotes heat generation, and keeps your property warm/hot. This piece offers a quick guide on how you can bleed your system efficiently. Older systems with air locks can be very noisy particularly if Taps (faucets in American) are leaking or if mains pressure fed older gravity fed boiler plumbing is getting old. Newer more modern systems incorporating accumulator tanks do not suffer from such annoying problems.

What you can do to bleed the underfloor heating

 The bleeding also applies to wall radiators that require bleeding. But in general the procedure is as follows:

  • Once your underfloor heating is filled with water, it is time to bleed every port. Wait for ten minutes after the system is filled before you vent the ports. It helps to prevent getting air back into the system.
  • Sequentially open pipes with water one circuit at a time.
  • Start venting your underfloor heating. Start with the lower side of your property. Progress to pipes on the upper side. This means that when you are done bleeding your system, you will also be getting rid of water from the upper part.
  • Vent methodically, one circuit after the other.
  • During bleeding, water can flow out of the system’s valves, have a cloth by your side.
  • Drain off any waste.
  • Check Pressure after bleeding.

Once you are done with bleeding, you need to check the water pressure in the system. If it is correct, the pressure will read anywhere between 1.5 to 2.5 bar depending on location in the green band area. If your valve shows in the red marked area, you need to refill the system until you reach the right pressure level.

Summary of actions necessary before you call out HVAC engineer.

1. Always check what information is given on the front panel of boiler or heat pump displays.

2. try find out what fault codes are displayed before you get on the phone to talk to an HVAC engineer.

3. where possible check the maintenance manual to find if there are to-do items maintenance or service schedules such as cleaning the filters and topping up the pressure.

4. If there is no noise or action coming from outdoor fan unit the system may have gone into protection mode and control panel usually will say something like “low flow fault” or “pump low flow”

5. Check the pressure gauges at the top of the boiler tanks to see if system needs topping up through the filler loop should be in the green arc or band and pressure should be above 0.5psi and about 2.5 psi on most heat pumps.


Finishing off the discussion I would like to emphasis that most boilers are well built, although expensive to buy and first install they should run without service for many years. The compactness of the Combi-boiler is its biggest disadvantage when compared to traditional systems with minimum parts that generally lasted longer. To this end it is prudent to take out boiler insurance and ideally with parts included in the service so that it does not stress the household running budgets and be one less thing to worry about in the coming winter months.

The same can be said generally for Heat pump operation and servicing although they are highly automated devices with limited intervention from owners.  When things go wrong the devices require the services of HVAC engineers whose service Bills May end up surprising you.

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