Vented t/dryers – optimum hose length?

[leavemetogetonwithit]

Have a customer with a pair of Whirlpool commercial type vented tumble dryers. Due to building not being ideal she has routed both through one vent hose with a sort of Y piece to join them and then a long outlet of several yards.
I was working on one while the one beside it was operating and I could feel a stream of warm damp air on my face as I worked on it because it was coming back up the common vent and into the one I was working on.
Obviously not an ideal situation and I imagine drying will take longer as a result. But will it make much difference to electricity consumption? Should I advise her to make the necessary building alterations?
Mike.

[spanner51]

Re: Vented t/dryers – optimum hose length?

If you connect 2 x 4″ vents together with a y piece, the vent diameter should be doubled, i,e 6″. So the cheapest option for your customer would be to change the venting to 6″ after the Y piece. Of course the best solution is to have 2 completely seperate vents.
Hope this helps.

[johnmac11]

Re: Vented t/dryers – optimum hose length?

Were you changing a cut out stat perhaps?

Seem to get a lot of these with a normal 4″ plastic vent hose which cannot cope with the airflow and blow the thermal stat. These dryers need a 5″ metal vent hose to operate correctly.

John

[leavemetogetonwithit]

Re: Vented t/dryers – optimum hose length?

Thanks for the info, spanner and johnmac. She’s joined up the very short foil hoses presumably supplied with machines to very long plastic hoses. I think they were 6″ but they’re going so far and all behind various furniture that they’re probably holding up the flow.
She complained of very low heat so I took along a “cut out kit including high limit stat” and a stat – the one with the accelerator resistor.
When I arrived a different operator was using it and informed me that it had been working fine for her. I just went ahead and fitted the stats anyway and gave it a bit of a clean out and brought the old stats away to examine when I have time.
I think I’ll give her a ring when she gets back from hols and inform her of the situation.
Mike.

[kwatt]

Re: Vented t/dryers – optimum hose length?

Hi Mike,

The bottom line is, this will cause issues.

You will get a vortex of air where the hoses are joined which will effectively create a barrier that the machine is not designed to push through, you can guess the ensuing problems. As John says more or less, over heat stats will blow.

You get the same thing with some hood installs as well, it just causes the whole thing to grind to a halt.

I’d advise the customer, very strongly, to install separate vents for each appliance and have runs of no more than 3 metres from the appliance with no bends if at all possible. Otherwise, they’re asking for trouble IMO.

K.

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