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Ideal Boiler NO HW Fault Code


The Ideal fault code NO HW no hot water operation Q & A or require an engineer for an emergency boiler repair.


The Ideal Boiler Fault Code NO HW Error Common Q & A


Just below, we have a list of common questions relating to the NO HW fault code on the Ideal boiler.

Ideal Boiler NO HW Fault Code
  • What does the Ideal boiler NO HW fault code mean?
  • Is the NO HW fault code a dangerous fault?
  • Should I reset my boiler to fix the NO HW fault?
  • What are the main reasons the NO HW fault occurs on Ideal boilers?
  • How would the heating controls cause the NO HW fault code to be displayed on my boiler?
  • Will my boiler engineer be able to test the heating controls to determine if the problem is faulty wiring, or broken controls?
  • My boiler engineer has found a wiring issue to/from the PCB, what could have caused it?
  • What causes excessive internal boiler vibrations?
  • What causes the fan and pump to vibrate excessively?
  • How would the diverter valve on my Ideal boiler contribute to the NO HW fault being displayed?
  • Can a sticking diverter valve be fixed?
  • My boiler engineer thinks the problem lies with the PCB, does this sound right?
  • How can my boiler engineer test to see if the PCB is malfunctioning?
  • My heating engineer thinks the PCB on my boiler needs replacing, how much will it cost?

What does the Ideal boiler NO HW fault code mean


If your boiler is displaying either NO HW or NO DHW on the display panel, it means the hot water function on your boiler isn’t working; showers and taps will be running cold.

However, when this fault code is being displayed, your heating should be functional. If your heating isn’t working, you’ll see the NO CH fault code displayed on your Ideal boiler.

Is the NO HW fault code a dangerous fault


Most faults that are dangerous are related to gas supply, or those whereby the fan isn’t working on your boiler. The fan takes harmful flue gases from your boiler and pushes them out of the flue. So, if this wasn’t working, your boiler would lock out as it presents immediate danger to people in your property.

The NO HW/DHW fault code is rarely dangerous. However, depending on the exact model of boiler you have, it may lock out before displaying the fault code.

Should I reset my boiler to fix the NO HW fault


You shouldn’t reset your boiler until the problem has been fixed. Gas Safe heating engineers are qualified to work on gas boilers, and they’ll be able to fix the problem. Once they’ve managed to locate the problem and fix it, they’ll reset your boiler which will clear the fault code.

What are the main reasons the NO HW fault occurs on Ideal boilers


  • Heating control problems (cylinder stat and timer)
  • Wiring to and from the printed circuit board (PCB)
  • Diverter valve fault
  • Faulty PCB

How would the heating controls cause the NO HW fault code to be displayed on my boiler


The first step is to make sure the heating controls are all on and receiving power from the boiler.

Your boiler engineer will need to check that the boiler is communicating with the cylinder stat (where applicable) and the boiler’s timer. If they’re not, the problem is going to stem from:

  • Wiring to/from these controls
  • Faulty heating controls

Will my boiler engineer be able to test the heating controls to determine if the problem is faulty wiring, or broken controls


After ensuring the heating controls are turned on, power can be tested to each unit using a multi-meter. If there’s not power to the unit, your heating engineer needs to determine if the fault is down to poor wiring and connections, or whether it’s faulty heating controls that are causing the issue.

If wires or connections are loose, that’s going to cause intermittent signals to/from the PCB. In turn, it’s likely that the NO HW fault appears randomly; sometimes your hot water works, and sometimes it doesn’t.

Whereby it is loose connections or wires causing the problem, your heating engineer will be able to re-secure them. However, if the problem lies with the controls, they’ll need to be replaced.

My boiler engineer has found a wiring issue to/from the PCB, what could have caused it


On most occasions, wiring issues come from either a boiler vibrating excessively, or water damage. And damage caused to wires/connections will cause signals to be lacking in strength. That’s going to cause the heating controls to work intermittently. The controls may not be receiving a signal for hot water.

What causes excessive internal boiler vibrations


Boilers will vibrate, to an extent. But, if you’ve heard your boiler making more noise than usual, there’s another fault at hand. And, there’s several things that could be causing the noise, including:

  • Air locks in the pump
  • Limescale build-up on the heat exchanger
  • Loose parts, such as the pump
  • Parts that are excessively worn, such as the fan

When excessive boiler vibrations occur, they can loosen connections and wires. If these connections are usually what carry signals to the PCB for hot water, this is what’s causing the issue.

This is a simple fix; your boiler engineer can re-secure all wiring and connections.

But, they’ll need to locate the root cause of these vibrations.

What causes the fan and pump to vibrate excessively


These are the two parts that vibrate the most when they wear. Typically, we find it’s the pump’s/fan’s bearings that have disintegrated. When this happens, they can grind on the shaft (wearing it out), and even cause the pump/fan to partially stick.

If the component’s general condition is good, they can be reconditioned. However, if they’re beyond repair, they’ll need to be replaced. You should expect to pay around £250 for a new pump, and a similar amount to replace the fan.

How would the diverter valve on my Ideal boiler contribute to the NO HW fault being displayed


Your diverter valve is the part in your boiler that channels water to either heating, or hot water for taps and showers. So, when this part is faulty, you’ll get an inconsistent supply of hot water, or no hot water at all.

Like other moving parts in the boiler, the diverter valve can wear out. When this happens, it’s prone to sticking. In the case of the NO HW fault code here, it’s likely it’s stuck on the heating side. That means when you turn on your boiler, it can only heat radiators; the valve isn’t able to flick to hot water.

Can a sticking diverter valve be fixed


It’s unlikely that your diverter valve can be fixed. Although the sticking can usually be rectified, it’s likely to happen again soon. And, as you’re already paying your boiler engineer to take apart your boiler to find and fix the fault, it makes sense to have the diverter valve replaced.

The replacement diverter valve is likely to take around 1 day to fit (but, your engineer will need to order parts from their local plumbing merchant). And, you should expect the cost of the new diverter valve (including parts) to be in the region of £450.

My boiler engineer thinks the problem lies with the PCB, does this sound right


All electrical components in your boiler are controlled by the PCB. That means parts such as the gas valve, air pressure switch and even the diverter valve. It’s the PCB that tells these parts when to work, and when to shut down. It gives and receives signals from these parts, and when it notices a fault, it displays that fault (in the form of a fault code) on your boiler’s control panel.

So, it stands to reason that if a PCB is faulty it could:

  • Be displaying incorrect fault codes
  • Giving and receiving incorrect signals, that lead to intermittent boiler operation

If your boiler has been working intermittently, you should have your PCB tested. Intermittency comes in many shapes and forms including:

  • Boiler cycles on and off for no reason
  • Hot water/heating works sometimes, but not others

How can my boiler engineer test to see if the PCB is malfunctioning


They’ll want to start by checking the terminal strip that links to the PCB. They’ll be looking for obvious signs of loose connections or wires. If they find any, these will need to be re-secured.

If a visual inspection doesn’t highlight the potential problem, they’ll need electrical testing equipment to check the PCB, wiring and connections are getting power. They’ll use a multi-meter to test this.

My heating engineer thinks the PCB on my boiler needs replacing, how much will it cost


A cheap PCB replacement would be around £350, with typical costs in the region of £450-500. The cost will vary depending on the boiler you have.

And, when spending this kind of money on boiler repairs, you need to ensure your boiler has longevity in it. Your engineer can check other parts that are likely to fail and are expensive to fix. This includes the gas valve, air pressure switch and even the diverter valve.

If your boiler is exceptionally old and these parts are likely to fail soon, a replacement boiler would be a better option than an expensive repair.

Other Ideal boiler issues


For more boiler issues regarding the Idea Boiler then please visit the Ideal Boiler Problems And Cures page.