What no hot water means on a PulsaCoil
A Gledhill PulsaCoil can deliver cold water because the store has not been heated, because heat is not reaching the incoming tap water, or because an individual outlet has a separate problem. A working boost narrows the question but does not prove that the normal charging arrangement works. Identify the generation before following instructions: PulsaCoil 2000, A-Class and Stainless do not share one universal reset procedure or fault-code chart.
Start with the service you have lost. Does water still flow from the hot taps, but cold? Is there no flow at all? Does the kitchen tap work while the shower fails? These are different complaints. “No hot water” is useful as an initial description, but the distinction determines whether the investigation starts with heating, water delivery or an outlet.
Keep electrical covers closed. Stop using an outlet that unexpectedly becomes dangerously hot. If there is water around electrical equipment, burning, smoke or repeated electrical tripping, stop ordinary troubleshooting and obtain urgent professional assistance; do not touch wet switches or repeatedly restore power. This guide explains what the symptoms can and cannot establish. It does not instruct you to reset concealed protection, test terminals or bypass controls.
First identify 2000, A-Class or Stainless
Read the accessible product label and photograph the complete name, capacity and model reference. Use the installation or service paperwork if the label cannot be reached safely. The model matters more than the cupboard shape or the name a previous resident used. An old estate-agent description of an “electric boiler” is not a reliable equipment specification.
Gledhill’s PulsaCoil 2000 manual, issue 11 from June 2008, describes a pump-speed control board and separately arranged immersion supplies. The A-Class issue 9 manual, also June 2008, describes an appliance control board, sensors and an external operation/warning light with a boost control. The currently linked Stainless manual, issue 09 from April 2024, documents a different controller and pump arrangement. These distinctions are reasons to match the document, not invitations to identify internal boards yourself.
A January 2016 DIYnot account demonstrates the practical problem. The resident initially called the appliance a 2000, then corrected it to A-Class after replies had already suggested model-specific actions. That unverified account does not diagnose another system. It shows why copying a reset location from a forum can send you towards the wrong component. If a guide shows controls you do not have, stop and confirm the product rather than searching behind a cover.
| Product label | Use the matching documentation | Avoid assuming |
|---|---|---|
| PulsaCoil 2000 | 2000 user guide and installation revision | A-Class boost/reset and status instructions apply |
| PulsaCoil A-Class | A-Class guide and fitted control arrangement | A wall lamp proves the immersion is heating |
| PulsaCoil Stainless / ECO | Exact generation and manual revision | Legacy controller flashes translate to its pump indicators |
Sources: Gledhill: legacy 2000 manual, issue 11 · Gledhill: A-Class manual, issue 9
Why a thermal store can be warm while the taps are cold
A thermal store keeps heat in its primary water. On the documented PulsaCoil arrangements, incoming mains water for the taps gains heat through a plate heat exchanger; it is not simply drawn out of the stored primary water. A pump and controls manage that transfer. This explains why heating the store and delivering satisfactory tap water are separate functions.
A warm cupboard is therefore incomplete evidence. It does not tell you the temperature throughout the store, whether charging completed, or whether heat is being transferred during a draw-off. Equally, hearing a familiar hum does not establish which component is operating or whether it is doing its job. Avoid touching exposed pipes or immersion bosses to turn warmth into a diagnosis; they may be hot enough to burn.
One useful description is “the usual overnight period has passed, water flows normally at two hot taps, but it remains cold”. Another is “water becomes hot briefly, then changes sharply while flow continues”. Neither description names a failed part, but both are more informative than concluding that the immersion must be broken. An engineer can then distinguish the temperature of the heat source from the temperature and behaviour of the domestic water. This is also why a general unvented-cylinder pressure-valve article is not a substitute for a PulsaCoil investigation.
Boost works but normal overnight hot water does not
If an ordinary, documented boost operation restores hot water, record that result. It suggests that at least part of the system can provide heat and deliver it under those conditions. It does not establish that the other heating path is healthy, or that the full intended hot-water reserve has been restored. Gledhill’s Stainless instructions describe the upper immersion as backup with limited input, while the lower immersion normally provides the main heat source.
Think about the sequence rather than immediately naming the lower element. Was the overnight supply available? Had the timer or tariff changed? Was the unit left in its normal operating state? Did boost provide one short wash or normal service for the household? A professional assessment may need to distinguish the electricity supply, control arrangement and heater itself. A light beside a switch cannot answer all three questions.
Do not use repeated boost success as a reason to leave an unexplained failure indefinitely. It may conceal a charging problem and change when electricity is consumed. However, do not assume an exact financial penalty either: that depends on your actual tariff and use. Preserve the settings and result so the investigation can compare normal charging with boost. Do not bridge supplies, move wires or repeatedly reset an immersion cut-out to make the two modes behave alike.
Check the tariff and timer without altering the wiring
The words “normal”, “off-peak” and “boost” on wall switches describe an intended arrangement. They do not prove the current electricity tariff, the hours when a circuit becomes live, or the way a previous installer connected the equipment. Confirm the tariff and charging periods with your supplier, and compare them with the user instructions and any accessible timer display. Do not assume every London flat shares the same Economy 7 hours.
In the 2016 DIYnot account, the resident later found a single-rate meter and became unsure whether the labels reflected the actual setup. The thread does not establish why the installation had that arrangement or its eventual repair. Its useful lesson is to separate three questions: what the electricity contract charges, when the equipment receives a heating opportunity, and whether it heats during that opportunity.
After a move, meter change or timer replacement, ask for the operating explanation that belongs to this installation. Keep any supplier confirmation of switching times. If other equipment expected to use the same off-peak arrangement also stopped working, report that observation without opening a meter enclosure. If only the PulsaCoil is affected, say so. These comparisons help allocate investigation between supplier-controlled equipment, property electrics and the hot-water appliance; they do not authorise a homeowner to test live circuits.
Sources: DIYnot: resident corrects model identification, January 2016
Hot for seconds, then cold, needs a different explanation
A January 2009 DIYnot resident described a PulsaCoil 2000 producing very hot water before turning cold after a few seconds, later becoming increasingly unreliable. The resident reported warmth around the unit and a recurring buzz. No verified final repair was established in the opened thread. It would be misleading to turn that account into proof that one particular sensor, pump or board is normally responsible.
The question is whether the appliance maintains heat transfer during demand, not merely whether some warm water appears initially. Note whether the change is abrupt, whether it repeats at separate outlets, and whether it began after work on the system. Do not repeatedly run a shower while standing under it to reproduce a scalding or cold-water surprise. Use safe observations from ordinary operation and stop if temperatures are unsafe.
Compare the present complaint with the previous routine. “It used to supply an ordinary shower at this time after overnight charging; now it goes cold almost immediately” describes a change. “A larger bath now empties the available reserve after several showers” describes a different demand pattern. Both deserve assessment, but they should not be merged into a single diagnosis. An engineer needs to establish the heat available and the delivery behaviour before deciding which component, adjustment or design issue explains the shortage.
Sources: DIYnot: intermittent hot then cold report, January 2009
One outlet, all outlets and loss of flow
If the basin and kitchen receive normal hot water but the shower does not, the cylinder has demonstrated some ability to supply hot water. That makes the shower and its local mixing or supply arrangement relevant to the investigation. It does not prove the whole system is fault-free, but it argues against ordering a cylinder part solely from a cold-shower complaint.
If every hot outlet flows but stays cold, explain that clearly. If flow has stopped or become unusually weak, report the cold taps as well. A failure to heat water and a restriction preventing water reaching the outlet are different physical problems. Record whether the change affects one tap, all hot taps, or both hot and cold services. Avoid dismantling strainers, mixer cartridges or appliance connections merely to complete this comparison.
Where an electric shower has its own heating arrangement, its continued operation may say little about the PulsaCoil. Check the appliance description rather than assuming every shower uses stored hot water. In a flat, ask the managing agent whether there is a known water-supply interruption if multiple services have failed. Do not operate unidentified communal valves. Separating these observations can prevent a useful cylinder enquiry from becoming a misleading request for an immersion replacement when the actual complaint concerns water delivery elsewhere.
The small header tank is not a pressure gauge
The primary store is open vented on the documented systems. Mains pressure at the taps comes from the domestic-water side; it does not mean the stored primary water should be pressurised like a sealed boiler circuit. Do not search for a boiler filling loop and raise a pressure reading as a generic cure for cold taps.
The feed and expansion or top-up tank is part of a different arrangement. Current Stainless instructions describe different header-tank configurations and filling provisions, including model-specific labels. An automatically filled older installation and a manually filled unit should not be treated as interchangeable. If the level is safely visible without climbing, moving equipment or opening electrical covers, record what you can see and compare only with the matching user instructions. If it cannot be checked safely, leave that task to the engineer.
A repeated need to add water, evidence of leakage or an unexplained low level deserves investigation. Topping up is not evidence that the underlying cause has been repaired. Do not improvise a permanent hose connection or fill to the brim. For a tenant, report the symptom and request the correct operating instructions from the managing agent. The important distinction is between a model-approved routine task and using water addition as an experiment on an unidentified hot appliance.
Read the correct indicator, not an internet-wide code chart
A-Class and 2000 information should not be merged into one table of flash meanings. A wall-switch lamp, an external warning indicator and an internal pump or controller light answer different questions. A visible lamp may show an operating state without proving that water reached the expected temperature. Record the location, colour and pattern of the indicator you can see safely.
The A-Class manual distinguishes its normal external indication, boost state and fault-attention state. The 2024 Stainless manual has separate professional controller and pump diagnostics. Those are not a reason for residents to remove panels to search for a code. If an engineer asks for a photograph, photograph the accessible display; explain if the information requested would require opening the appliance.
A number read from a controller may be a status or sensor reading rather than an error. Copy any wording exactly and identify the manual used to interpret it. Avoid claims such as “two flashes always means everything is fine” across product generations. If the water is still cold, a reassuring-looking indicator does not resolve the service complaint. The useful endpoint is restored, stable hot water under the intended operating conditions, with an explanation of the fault when one is found.
What a meaningful repair diagnosis should establish
A January 2008 DIYnot resident reported previous replacement of immersion heaters and later a circuit board, followed by another loss of hot water. That is an unverified history, not evidence that the earlier repairs were unnecessary. It does reveal a reasonable consumer concern: how will the next proposed part address the current fault rather than simply repeat a previous attempt?
Ask which part of the process has failed: obtaining heat, storing enough heat, transferring it to the domestic water, or delivering it at the outlet. Ask what observation or measurement supports the proposed repair. You do not need to perform the test yourself or request a lesson in live electrical work. A plain explanation such as “the supply was available but this heater did not operate” is more useful than a parts list without findings.
Supply previous invoices and dates because they distinguish an unresolved complaint from a later, different failure. If a newly fitted part has not restored service, report that promptly to the contractor and ask what follow-up is included before commissioning another replacement. Agree whether the assessment includes the relevant electrical work or needs coordination with another specialist. A clear boundary between investigation, parts and follow-up helps both parties understand what the quotation is intended to achieve.
Sources: DIYnot: recurring loss after earlier repairs, January 2008
Repair or replace: compare the installation, not just the tank
The appliance’s age alone does not settle the decision. A confirmed component fault, a leaking store, unavailable parts and an installation that no longer meets the household’s demand are different reasons for considering replacement. Request the actual findings and separate necessary work from optional improvement. A functioning replacement also needs a suitable supply and controls; a new tank does not automatically correct an unexplained external supply problem.
If someone proposes an unvented cylinder instead of a PulsaCoil, ask how the new design addresses discharge, controls, electrical supply, access and maintenance. It is a change of system, not simply a differently shaped container. Likewise, replacing a thermal store with instantaneous electric heating needs an assessment of the available electrical capacity and intended demand. No universal cupboard-sized substitute is recommended here.
Compare quotations against the same household requirement: which outlets, how they are used, the normal heating opportunities and the expected interruption during work. Include removal, installation alterations, commissioning and making good in the written scope where relevant. Ask for the exact model and its documents. Do not compare nominal litres or a headline supply-only price as though they establish equivalent performance or a complete fitted cost. A repair remains a reasonable option to assess when evidence identifies a repairable fault; replacement should have its own technical justification.
Confirm normal service after the work
Define success using the original complaint. A short period of warm tap water after a daytime boost does not demonstrate that an overnight charging fault has been corrected. Where that was the issue, ask how the normal charging period will be verified and what to do if the next morning’s result remains poor. If the complaint was sudden temperature changes, verify stable delivery in the conditions that previously produced them.
Keep the findings and operating instructions with the appliance records. Confirm which user controls should normally remain enabled, how any boost is intended to be used, and the correct route for future fault advice. For the Stainless model, the manufacturer says annual servicing is not necessary; that does not mean a known fault should be ignored or that every generation has identical maintenance instructions. Follow the documentation for the installed product and ask about any specific recommendation arising from its condition.
For help in London, identify the unit as a PulsaCoil thermal store when enquiring. AK’s engineer attendance is £60; ordinary plumbing work is £160 per agreed hour, with no VAT added. Specialist thermal-store or electrical investigation requires an appropriate scope and separate quotation. Attendance alone does not include diagnosis or repair. Send the label and explain whether normal charging, boost, all taps or one outlet is affected so the service route can be confirmed.