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Posted by New Directions In Building Ser on May 17, 2007, 6:45 am
>
> "New Directions In Building Services (Australia)"
>>
>>>
>>>>
>>>>> Gotta love it when the lowest bidder gets the job
>>>>>
>>>>
>>>> So, by that, do you mean it _should_ be done, and just isn't to save
>>>> time/sweat?
>>>
>>> yup... if the lineset is in the slab, a PVC chase is required.
>>>
>>>>>> I have seen a lot of water in the couple of grade-level or
>>>>>> below-grade sets I've pulled out of conduit, and suppose that might
>>>>>> be one objection to using it. (Ken _likes_ it that it's my hands and
>>>>>> not his in that stagnant goop...)
>>>>>
>>>>> There is a reason that your supposed to seal both ends of the chase
>>>>
>>>> The two I pulled _were_ "sealed" somewhat -- one only with foam
>>>> (spray-on) and one with foam and capped with mortar at the outside end;
>>>> and of course, the mortar was cracked. On both, the inside end was
>>>> sealed with foam. I presume the water was from condensation and not
>>>> from leakage. Seems like only a good hermetic seal would prevent the
>>>> pipe from breathing under temperature changes.
>>>
>>> I use the expanding foam on both ends.... it seems to work well enough.
>>> The only things I run through the lineset chase are the lineset and the
>>> control wires. No I don't tie the lineset and wires together or tape
>>> them.....I have had to replace too many wires that were taped or tied. I
>>> don't staple them inside of the walls either.
>>
>> Noon-Air
>> That might be ok where you are but if your talking about apartments or
>> commercial where some form of fire separation/segregation is required.
>> Expanding polyurethene sealants are forbidden in these instances so you
>> might like to/should reconsider and used an appropriate intumescent (fire
>> rated) mastic sealant.
>
> I only use the expanding foam where the lineset is inside of a PVC chase
> inside of the slab. 99% of what I do is single family residential.
> Apartment owners and commerical building owners around here only want the
> lowest bidder.
>
>> As to the practice of pouring concrete over the linesets - sounds like a
>> whole lot of liability exposure to me...
>
> The linesets are encased in a PVC pipe chase inside of the slab so there
> is no direct contact between copper and concrete. The PVC pipe chase also
> makes it a lot easier to change the lineset when needed.
>
Good stuff - yes it's (polyurethene sealant) quite legitimate to use on
single detached dwelling units.
Some more considerations for all you craftsmen ......
Also glad that you use extended radius wherever practical - For R22 I
believe that the rule of thumb for linesets is each 90deg bend is equal to
5m (that's about 15 feet) of horizontal pipe run and the maximum lift for
R22 needs to be kept below 6m (20 ft). An oil trap needs to be used if the
evaporator is below the compressor (or the oil will migrate out of the
compressor then "poof" another unnecessary callout and repair) and if
otherwise the lineset should fall at not less than 1degree back to the
compressor (same reason).
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