Mobile home oil tank (C) Daniel FriedmanHow to Inspect the Cooling Systems of Mobile Homes, Double wides, Trailers

  • MOBILE HOME COOLING SYSTEMS - CONTENTS: Mobile home air conditioning system inspection guide - Common mobile home cooling system defects / manufactured home cooling system and ductwork defects. Mobile home insulation defects and remedies to reduce and cooling costs
  • POST a QUESTION or READ FAQs about how to troubleshoot & fix problems in manufactured home or mobile home cooling or air conditioning systems

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Mobile home heating & air conditioning systems:

How to Inspect the heating and cooling systems in mobile homes, trailers, double-wides, multi-wides:

How to spot common and dangerous defects in heating equipment incuding furnaces and boilers, inadequate heat distribution, freeze-ups, and safety hazards.

How to save heating or cooling costs for mobile homes and trailers or multi-wides. Page top sketch was provided courtesy of Carson Dunlop Associates, a Toronto engineering, education, and home inspection company.

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Mobile & Manufactured Home Cooling System Defects

Mobile home oil tank (C) Daniel Friedman

General Characteristics:

[Click to enlarge any image]

Question: I was startled out of my skin to see a cat jump into the living room from a floor vent

(Aug 29, 2012) Maxine Payne said:

The red tag was apparently covered up when vinyl siding was installed. Now I want to sell the property, but I can't because I do not have the red tag number. How do I get the red tag number?

(Aug 29, 2012) Greg Filian said:

The flashing of the lights mentioned are they in the whole house or just one outlet? If it's just one outlet it may be just the outlet, if it's the whole house the problem may be at the main connection.

(Sept 8, 2012) Gail said:

I am looking at buying a double wide through an estate sale. The "trustee" of the estate is the deceased owners daughter, who know very little to anything about mobile homes (as I).

I am hiring an inspector, how ever he wont be available for 3 weeks and I have an immediate concern...
While standing in the living room I was startled out of my skin to see a cat jump into the living room from a floor vent ( vent cover was pulled off) I looked into the vent and it appears to be completley open - no duct work - just a view of the ground beneath. The daughter said that that was common and is there for ventilation. LOL Tell me this isnt so!


Thank you SO much for the wonderful cat - HVAC system question.

Yes I can tell you "it isn't so" - that is, it is not good practice to simply leave floor vents in a home open to the outdoors such that anything, including a cat (or worse, a raccoon) can hop in for a visit.

I can imagine a few reasons why you might have found the missing duct work and open floor vent, all adding up to some more trouble and work for you. For example most likely there was a heating or heating and cooling system that used air but that has disintegrated, been damaged, fallen off, or was simply removed and abandoned.

Sometimes too, when warm or cool air delivery into a home is poor in flow rate or quantity, people try to improve system operation by adding more return air to the system by just cutting an opening that lets outdoor air into the system somewhere. The problem is this is the most expensive possible way to heat or cool a home since it's a "one way" design - we take un-conditioned air from outside, heat it or cool it, then try moving it into the living area.

Really the most significant implication of the cat in the hat, I mean cat in the vent discovery in your possible future home's heating sysem is that it's a red flag to watch out for other work done or "problems solved" by the same person on that home - as you may find other amateur workmanship that lengthens the list of repairs and improvements needed to make the home safe and habitable to normal standards.

Keep me posted, and send along photos if you can (use the CONTACT US link at page bottom or top) - especially if ... the cat comes back.

Daniel Friedman

I suppose a less ridiculous explanation that the owner could have invented might have been to explain

"Oh I forgot to tell you, that's just Marion, my mom's cat. Marion comes with the house. The hole in the floor is her pet door."

Air Conditioning Checklist of Common Defects in Mobile Home & Manufactured Home Air Conditioning or Cooling Systems

Below our photographs illustrate several unsafe conditions at a house trailer's heating system inspected by D Friedman & S Vermilye during a mobile home site safety investigation. Notice that when the door to this central air handler is closed return air from the occupied space cannot reach the equipment.

Mobile home furnace (C) Daniel Friedman Mobile home furnace (C) Daniel Friedman

In addition to the absence of return air to the heating furnace we notice that

Reader Question: Why does my doublewide always feel uncomfortably warm

Why does my doublewide always feel uncomfortably warm especially at night when trying to sleep and even with the temperature at 70 to 71 degrees? - Daniel Phipps 4/16/2012


Daniel that question has me stumped. There are so many possible reasons:

- a medical problem
- windows shut
- no ventilation
- bedroom close to a heating appliance that is "on" such as a water heater
- air conditioning system that is not working properly, has a blocked filter, blocked cool air return, dirty blower fan, etc. - see MOBILE HOME COOLING SYSTEMS discussed here

Check your own sensations against actual room temperature - I'm not sure if that's what your comment about "even with the temp .." meant.

General Characteristics of Mobile Home Cooling Ducts

Common Mobile Home / Doublewide HVAC Duct Defects

Question: my homeowners insurance covers "accessible ductwork" from the air conditioning - what does that include?

I have home owners insurance, and it says it covers "accessible ductwork from the air condtioning unit to the point of attachment at register" what does that mean? Is my ductwork under the house covered? - Anonymous 7/17/2012


Discussion of "accessible" building components vs inaccessible

Anon: re "accessible ductwork" - indeed that word has been the subject of lots of debate - the final answer lies with your insurance company and perhaps the onsite tech. Generally for building inspectors the term "readily accessible" is used to mean that the component can be approached, seen, touched, without having to cut anything apart or disassemble anything not intended to be opened by a homeowner.

For a service technician, "accessible" means it's reasonably possible to get to it - in my OPINION - without having to cut holes in ceilings, walls, floors. So if "under the house" is an area that can be physically accessed, say by entering a crawl space that is not itself so tight or unsafe as to be not enter-able, then in my OPINION the ducts are accessible.

When we debated this question at a home inspection association it was after an inspector had fallen to his death while crawling up a building-mounted but loose roof access ladder. He felt that he HAD to access the building roof but there was no other means for him to do so. He was killed.

A result of that terrible experience was a decision that ultimately we do not ever want to demand that anyone, inspector, nor service technician, attempt to "access" a building component or area if s/he has a reason for not doing so, such as a personal judgement about safety.

However that doesn't mean that a problem needing attention goes forever ignored. Rather it means that ultmately arranging safe functional access may take more time, trouble, and special arrangements. And cost accordingly.

Readers should also see MOBILE HOME PLUMBING where we further discuss oil tanks, oil piping, and water heaters for mobile homes. Page top sketch courtesy of Carson Dunlop.

Question: fixing or replacing mobile home or doublewide ductwork invaded by rats

23 January 2015 Chuck said:
I have a doublewide mobile home with the air ducts in the cieling. A rat has gotten into the air duct and chewed insulation and now insulation is blowing through the vent. I am going to have a company put a camera up there to find the break so it can be fixed. My question is would it be easier for me once I knew exactly where the break was to just go in from the roof. It seems alot faster and less expensive than tearing out the cieling and replacing sheetrock, tape and bed and repainting, not to mention the mess in the house. What are your thoughts?



If your doublewide has a conventional continuous metal roof over an inaccessible space then you won't do well trying to cut into the roof and you risk creating a point of future roof leaks. I'd be inclined to work from the interior. But then I haven't seen your home.

If there is an attic access (which some doublewides have) then of course it'd make sense to get into that space and remove and replace the ductwork and any contaminated insulation.

Further, if there were rats in the ductwork, you want to replace ALL of the ductwork and insulation where rats were nesting lest their pee and poop and other debris become a health concern later on.

Mobile Home & Trailer Home Insulation & Ventilation Defects, Diagnosis, Repair, Improvement

This topic has moved to a separate article at MOBILE HOME INSULATION

Manufactured & Mobile Home Cooling Standards & Codes

Full text of the manufactured and mobile home heating standards can be found in

PART 3280—MANUFACTURED HOME CONSTRUCTION AND SAFETY STANDARDS [PDF] newer copy retrieved 2017/07/13 - faster-loading

See Subpart H, Heating, Cooling and Fuel Burning Systems in that document.


Updated through January 2018 - Steve Vermilye, New Paltz NY and Daniel Friedman, Poughkeepsie NY, Hudson Valley ASHI Chapter Seminar, Newburgh NY, January 4, 2000, NY Metro ASHI Fall 99 Seminar, Holiday Inn Crowne Plaza, White Plains NY, October 2, 1999.


Continue reading at MOBILE HOME INSULATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see WALL CONVECTORS Heating / Cooling


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