October 27, 2026
Posted by: editor
Category: RECD & Emission Control Devices

Often yes, with conditions. Third-party RECD maintenance is workable for routine checks, readings and housekeeping when the contractor is competent and keeps proper records, but specialised work and anything that touches the device’s type-approved configuration usually needs the original supplier’s procedures, parts or written approval.

The safest arrangement for many sites is a split: a local contractor handles the frequent, low-risk tasks and the RECD supplier handles the specialised ones. This article walks through how to decide, what to check before signing, and how to hand the work over without losing history or compliance evidence.

Who is asking this question

The answer depends a lot on who is asking. Three situations come up again and again.

The housing society with a DG AMC contractor

A residents’ welfare association already pays a local firm to service its diesel generators every month. The RECD supplier is based in another city and charges travel for each visit. The DG contractor offers to “look after the filter too” for a small add-on. The managing committee wants to know whether that is safe and whether it saves money. If you are at the purchase stage, our RECD planning guide for housing societies covers the earlier decisions.

The factory with an in-house maintenance team

A plant has its own electricians and mechanics who already maintain the DG sets, compressors and boilers. They are capable, but nobody on the team has worked on an emission control device before. The plant head wants to know which RECD tasks the team can absorb and which should stay with the supplier.

The multi-site owner consolidating vendors

A retail chain, hospital group or telecom operator has RECDs from two or three suppliers across a dozen sites. Procurement wants one national service partner for everything to cut admin effort. The engineering lead is worried about warranty, parts compatibility and who will answer when an inspector arrives.

All three are asking the same core question: can someone other than the original supplier maintain the device without creating a warranty, performance or compliance problem?

What “maintaining an RECD” actually involves

“Maintenance” covers very different jobs. Some are no harder than checking a battery. Others need procedures, special tools and a clear understanding of how the specific design works. Splitting tasks into tiers makes the decision much easier. Our general RECD maintenance guide explains the routine itself; here the focus is on who should do each part.

Tier 1: routine tasks

These are the frequent, low-risk jobs:

Visual inspection of the housing, flanges, clamps, bellows and supports for cracks, leaks, soot tracks or corrosion.
Recording readings that the system displays, such as differential pressure (ΔP) or exhaust temperature, where the design includes these sensors.
Checking alarm lamps or controller status messages and noting them in the log.
Cleaning the external surfaces, sensor housings and cable glands.
Reviewing DG run hours and load against the RECD log.
Confirming insulation and heat shields are intact.

A competent DG contractor can usually do Tier 1 work well, provided they are told what “normal” looks like for this particular installation.

Tier 2: specialised tasks

These need written procedures, specific tools, genuine parts and often the supplier’s authorisation:

Removing and refitting the filter element for cleaning or ash removal, where the design allows it.
Replacing a sensor, transmitter or thermocouple.
Changing controller settings, alarm thresholds or calibration values.
Regeneration-related work where the design uses active or assisted regeneration.
Diagnosing persistent high back pressure or repeated alarms.

Ash, for example, is the non-combustible residue from lubricating oil additives that builds up in wall-flow filters and cannot be burned off; DieselNet’s explanation of ash in particulate filters shows why removal needs care. A contractor who blows out an element with high-pressure air in the wrong direction can damage it permanently.

Tier 3: supplier-only or approval-needed tasks

These affect what the device actually is:

Replacing the filter element or core with a different part.
Modifying the housing, inlet or outlet, or bypass arrangements.
Removing or relocating components.
Changing the device to suit a different DG set.

Anything in Tier 3 can affect the type-approved configuration. These jobs should only happen with the supplier’s involvement or written approval. For element replacement specifically, see our sibling post on replacing an RECD filter core vs the complete assembly.

Task tier table

Task	Tier	Skills or tools needed	Risk if done wrongly
Visual check of housing, joints and supports	1	Basic mechanical skill, torch, checklist	Missed exhaust leak or cracked support
Recording ΔP and temperature readings	1	Knowing where to read, log format	Trend lost; blockage not spotted early
External cleaning, gland checks	1	Basic tools, isolation of DG	Damaged cable or sensor if pressure-washed
Log and run-hour review	1	Attention to detail	Late warning of loading problems
Element cleaning or ash removal	2	Supplier procedure, lifting gear, gaskets, PPE	Cracked element, gasket leak, reduced capture
Sensor replacement	2	Correct part, wiring knowledge, calibration	Wrong readings, false alarms or no alarms
Controller setting changes	2	Supplier access, settings record	Alarms disabled, regeneration mismanaged
Regeneration-related work	2	Design-specific procedure	Overheating, element damage, fire risk
Element or core replacement	3	Supplier-approved part and method	Configuration no longer matches approval
Housing modification or bypass	3	Supplier approval, engineering review	Compliance failure, warranty loss

Four conditions to check before you switch

Before agreeing to switch RECD service provider, or adding RECD work to an existing DG AMC, check these four conditions. If any one of them fails, the hybrid model discussed later is usually the better route.

Condition 1: warranty status and terms

Start with the warranty document, not with what anyone says verbally. Many supplier warranties cover defects in materials and workmanship but exclude damage from improper handling, unauthorised repairs or non-genuine parts. Our guide to RECD warranty terms, parts, labour and exclusions explains what to look for.

The warranty impact of third-party service varies by supplier. Some allow routine inspection by anyone; some require only that records are kept; some insist all intrusive work is done by authorised personnel. Do not guess. Write to the supplier, describe exactly which tasks the new contractor will do, and ask for a written reply confirming whether that affects cover.

If a claim does arise later, the quality of your records will matter. Our sibling post on what to record when raising an RECD warranty claim covers the evidence that helps.

Condition 2: type approval and configuration integrity

CPCB type approval relates to a particular device configuration tested on a particular basis. CPCB’s published system and procedure for compliance testing of RECDs on in-use DG engines up to 800 kW requires at least 70% particulate matter capture efficiency, with testing by recognised agencies such as ARAI and ICAT. You can find CPCB notices and documents on the CPCB website.

If a contractor fits a different element, removes a component, changes the inlet arrangement or swaps a sensor for a “similar” one, the installed device may no longer match what was approved. That can matter during an inspection. Our guide on how to verify that an RECD on your DG set is CPCB-tested shows which documents link the device on site to its approval. Keep those documents with the service file.

Condition 3: access to manuals, parts and settings

A third party can only maintain what they understand. Ask whether you, as owner, have:

The operation and maintenance manual for this model.
The general arrangement drawing as installed.
A parts list with part numbers for consumables and sensors.
A record of controller settings, if the design has a controller.
A route to buy genuine parts, either directly or through the supplier.

If the supplier will not sell parts to anyone other than its own engineers, a third party cannot do Tier 2 work properly. Our post on the RECD spare parts list to request helps you close this gap. Sensors are a common pain point; the sibling article on specifying replacement RECD sensors without losing compatibility explains what details to capture.

Condition 4: evidence of contractor competence

A good DG mechanic is not automatically a good RECD technician. Ask the contractor for:

Names and experience of the technicians who will attend.
Examples of other RECD or exhaust after-treatment equipment they maintain.
Their written procedure for each task they propose to do.
Evidence of safety training for hot work, working at height and lockout/tagout.
Sample service reports from other sites, with client details removed.

Training matters on both sides. Our sibling post on RECD operator training skills to check before handover has a skills list you can adapt to assess the contractor’s technicians.

Original supplier vs third party vs hybrid model

Once the four conditions are clear, compare the three realistic models. None is right for every site.

Factor	Original supplier only	Third party only	Hybrid (supplier for Tier 2/3, local contractor for Tier 1)
Design knowledge	Highest	Varies; often limited	Supplier knowledge applied where it matters
Warranty risk	Lowest	Highest unless confirmed in writing	Low if supplier agrees the split
Visit frequency	Often quarterly or less	Can be monthly or weekly	Frequent local checks plus periodic specialist visits
Response time to faults	Depends on supplier location	Often fast for first response	Fast first response, specialist follow-up
Parts access	Direct	May be difficult	Supplier supplies parts for Tier 2/3
Annual cost	Usually highest	Usually lowest	Middle
Record quality	Supplier format	Depends on contractor	Needs a common log format
Accountability	Single point	Single point, less expertise	Two parties; roles must be written down
Compliance support at inspection	Supplier documents ready	May lack approval paperwork	Supplier documents plus local logs

The hybrid model works well when the supplier is far away but responsive for planned visits, and the local contractor is already on site regularly. It needs one discipline above all: a clear written split of who does what, and one shared log.

Does RECD maintenance by non-OEM affect compliance?

The short answer is that the owner remains responsible, whoever does the work. State Pollution Control Boards issue consents to the DG set owner or occupier, not to the service company. If an inspector finds the RECD damaged, bypassed, poorly maintained or not matching its approval, the consequences, which can include sealing and penalties, fall on the owner.

That changes how you should think about contracts. A service agreement can make a contractor liable to you for poor work, but it does not transfer your regulatory responsibility. If you operate in Delhi NCR, remember that CAQM directions on DG set use, including during GRAP stages, still apply to your site regardless of service arrangements.

Make sure whoever services the RECD can produce what an inspector may ask to see. Our walkthrough of what happens during a pollution control board inspection lists typical requests. Most of them are documents the owner should hold, not the contractor.

Never accept a suggestion to bypass or remove the RECD to keep the DG running during a fault. That is a compliance risk and may also affect engine safety. If a blocked element is causing high back pressure, the DG should be managed according to the supplier’s guidance until the fault is fixed. Our explainer on how exhaust back pressure affects a DG set covers why this matters.

How to do an RECD service handover to a new contractor

Most problems with a change of service provider come from poor handover, not poor technicians. Plan it like a small project.

The information pack

Before the new contractor’s first visit, assemble a pack. Keep the original with the owner and give the contractor a copy.

General arrangement drawing showing the RECD, exhaust route, supports, sensor positions and access points. Our guide on what an RECD GA drawing should include helps you check it is complete.
Operation and maintenance manual for the installed model.
Baseline readings at commissioning, such as clean ΔP at a stated load, exhaust temperatures and back pressure, where measured.
The last 6 to 12 months of RECD logs and DG run-hour records.
A backup or written record of controller settings and alarm thresholds, if applicable.
The parts list with part numbers and the approved source for each.
Warranty documents and the supplier’s written reply on third-party service.
Type approval, test certificate and installation documents.
Contact details for the supplier’s service desk and escalation contact.

The joint site visit

Ask the outgoing service provider, or the supplier, to meet the new contractor on site once. Walk through:

The physical layout, access route, lifting points and isolation points.
Where each reading is taken and what the normal range has been.
Any known issues, past repairs or recurring alarms.
Safe isolation of the DG before any work on the exhaust system. Use a written lockout/tagout procedure; the OSHA page on controlling hazardous energy is a useful reference for building one.
Hot surface risks. Exhaust components stay hot long after shutdown, so agree minimum cool-down times.
What the new contractor must not do without approval.

Record who attended and what was agreed. A signed one-page note is enough.

The first 90 days

Treat the first three months as a probation period for the new arrangement.

Period	Focus	Owner’s check
Days 1–30	Contractor takes Tier 1 readings each visit using the agreed log format	Compare readings with baseline; any unexplained jumps?
Days 31–60	Contractor flags any trend or alarm to the owner and supplier within agreed times	Were escalations made on time and correctly?
Days 61–90	Joint review with supplier of logs and any Tier 2 needs	Is the split working? Any gaps in parts or skills?

At day 90, decide whether to continue, adjust scope or revert. A structured handover log helps; our sibling post on building an RECD shift-handover log gives a format that service visits can feed into directly.

Contract clauses to include in an RECD AMC with another company

The following list is a practical checklist, not legal advice. Have your contract reviewed by someone qualified before signing. For general negotiation points, our guide on how to negotiate an AMC contract for your generator is a good companion.

Scope by tier. List the exact tasks the contractor will perform, mapped to Tier 1, 2 or 3. State clearly that Tier 3 work is excluded unless separately approved in writing.
Genuine or approved parts only. Require parts that are genuine or approved in writing by the RECD supplier, with invoices or delivery notes kept on file.
Record keeping. Specify the log format, the readings to be taken on each visit, and that records belong to the owner.
Reporting of readings. Require a short report after each visit with readings, observations, actions and recommendations, sent within an agreed number of days.
Response time. Define response times by severity, such as a critical alarm vs a routine query. Our post on RECD service response commitments explains how to set realistic targets.
Escalation. State when the contractor must escalate to the supplier rather than attempt a fix.
Liability for damage. Address responsibility for damage caused by the contractor’s work, including to the element, sensors and DG set.
No unauthorised modification. Prohibit any change to the device, its configuration, settings or bypass arrangements without written owner and supplier approval.
Compliance support. Require the contractor to support the owner during inspections, for example by attending if requested and providing records promptly.
Safety. Require written safe work procedures, PPE and lockout/tagout on every intrusive job.
Handback. Require the contractor to return all records, settings backups and documents at the end of the contract.

Risk matrix for third-party RECD maintenance

Use this matrix to discuss risks with the committee or management. Likelihood and impact are typical judgements; adjust them for your site.

Risk	Likelihood	Impact	Mitigation
Warranty dispute after third-party work	Medium	High	Written supplier confirmation of allowed tasks; keep all records
Element damaged during cleaning	Medium	High	Restrict element work to supplier or supplier-approved procedure
Wrong replacement sensor fitted	Medium	Medium	Specify part numbers; approve substitutes in writing
Controller settings changed or lost	Low	High	Settings backup; restrict access; log any changes
Readings taken inconsistently	High	Medium	Standard log format; baseline comparisons
Slow escalation of a developing fault	Medium	High	Defined escalation triggers and response times
Configuration no longer matches approval	Low	High	No modifications without approval; check against GA drawing
Records lost when contractor changes	Medium	Medium	Owner keeps master records; handback clause
Unsafe work on hot exhaust	Medium	High	Cool-down times, lockout/tagout, PPE, competent supervision

The pattern is clear. Most high-impact risks sit in Tier 2 and Tier 3 work, and most high-likelihood risks are about records. That is why the hybrid model is often the sensible middle ground.

Illustrative example: housing society with 2 × 500 kVA DG sets

All figures in this example are illustrative and are used only to show the method. Your quotations will differ.

A society of 400 flats has two 500 kVA DG sets, each fitted with an RECD (see our RECD page for 500 kVA DG sets for background on this size). The DG AMC contractor visits monthly. The RECD supplier is about 300 km away. The committee compares three options.

Option A: supplier AMC for the RECDs

Supplier AMC: ₹42,000 per set per year, with four planned visits.
Annual cost: ₹42,000 × 2 = ₹84,000.
Typical response to an unplanned fault: within 72 hours, because of travel.

Option B: local contractor does everything

Add-on to the existing DG AMC: ₹18,000 per set per year, monthly checks, includes element cleaning.
Annual cost: ₹18,000 × 2 = ₹36,000.
Typical first response: within 4 hours, as the contractor is local.
Supplier has not confirmed in writing that contractor element cleaning is acceptable.

Option C: hybrid

Local contractor, Tier 1 only, monthly: ₹12,000 per set × 2 = ₹24,000.
Supplier, one annual Tier 2 visit covering both sets: ₹20,000 per set × 2 = ₹40,000, plus one travel charge of ₹8,000 = ₹48,000.
Annual cost: ₹24,000 + ₹48,000 = ₹72,000.
First response within 4 hours locally; specialist follow-up as needed.

Comparing the numbers

Item	Option A	Option B	Option C
Annual cost	₹84,000	₹36,000	₹72,000
Cost per flat per year (÷ 400)	₹210	₹90	₹180
Saving vs Option A	—	₹48,000	₹12,000
First response to a fault	Up to 72 hours	About 4 hours	About 4 hours
Warranty confidence	High	Uncertain	High if supplier agrees split

Per-flat figures: ₹84,000 ÷ 400 = ₹210; ₹36,000 ÷ 400 = ₹90; ₹72,000 ÷ 400 = ₹180.

The downtime and risk angle

Option B looks attractive on cost. But suppose an incorrect cleaning method cracks one element and the society must pay for a replacement outside warranty, with an illustrative cost of ₹1,50,000. That one event would cancel more than three years of saving: ₹1,50,000 ÷ ₹48,000 = 3.125 years.

Response time matters too. Assume the society experiences three RECD-related alarms a year. Under Option A, waiting up to 72 hours each time could mean up to 3 × 72 = 216 hours a year with an unresolved alarm, during which the DG may need to be run with care or not at all. Under Option C, a local technician can check readings, connections and obvious causes within about 4 hours, so the worst-case first-response wait is 3 × 4 = 12 hours, with the supplier called in only when Tier 2 work is actually needed.

For this society, Option C costs ₹12,000 a year less than Option A, gives much faster first response and keeps warranty risk low. Option B should only be considered if the supplier confirms in writing that the contractor’s element cleaning method is acceptable.

Signs your current arrangement is not working

Review any third-party RECD maintenance arrangement at least once a year. Warning signs include:

Readings missing from logs, or identical readings every visit.
Alarms acknowledged but not investigated.
Parts fitted without invoices or part numbers.
Supplier and contractor blaming each other for the same fault.

If you see two or more, hold a joint review before switching provider again.

FAQ

Can my DG AMC contractor maintain the RECD as well?

Often yes for routine Tier 1 tasks such as visual checks, readings and log review. For element cleaning, sensor replacement, controller changes and anything affecting the approved configuration, get the RECD supplier’s written approval or keep those tasks with the supplier.

Does third-party RECD maintenance void the warranty?

It depends on the supplier’s warranty terms. Some warranties exclude damage from unauthorised repairs or non-genuine parts. Ask the supplier in writing which tasks a third party may perform without affecting cover, and keep the reply on file.

Who is responsible if the RECD fails an inspection after a contractor serviced it?

The DG set owner or occupier remains responsible to the State Pollution Control Board. A service contract can make the contractor liable to you for poor work, but it does not move regulatory responsibility away from the owner.

What documents should I give a new RECD service company?

At minimum: the GA drawing, O&M manual, commissioning baselines, recent logs, controller settings record, parts list, warranty documents and type approval paperwork. Keep the originals yourself.

Is a hybrid service model better than a single provider?

For many sites, yes. A local contractor handles frequent routine checks and fast first response, while the supplier handles specialised work. It works only if the split of tasks and the log format are written down and agreed by both.

Planning a Change to Your RECD Service Arrangement?

Aceget supplies CPCB type-approved retrofit emission control devices for DG sets from 25 kVA to 2500 kVA. If you are considering a local contractor for routine work, talk to us first about which tasks suit your installation and what records will keep your warranty and compliance file in order. You can review our type approval certificates or contact the Aceget team to discuss a service split that fits your site.

Can a Different Service Company Maintain an Installed RECD?