Hayward H250FDN Indoor Venting Install

[Carbon8]

Hi, I am replacing a Hayward millivolt H250 pool heater installed in a shed and vented vertically. The new heater is a Hayward H250FDN negative pressure venting. The old install had a huge draft hood and I cannot find anywhere if the new heater requires a draft hood or wether I run B vent directly from the heater?

I would like to keep the current B vent installation which is 7". The new heater negative vent adapter has a 6" C vent adapter. Can I run C pipe from the heater to a 6" to 7" increaser with the B adapter to tie into the existing vent?

[Admin]

The indoor draft hood used with the H250 is not used with the H250FDN.

If the heater is in an unconditioned space you must install B-vent from the water heater to the existing B-vent.

[Carbon8]

I understand the draft hood from the H250 is not used with the H250FDN. I assumed that there is a specific draft hood for the H250FDN. The vent kit for the FDN is just a plate with a C flange adapter. I cannot find any info on the FDN requiring a draft hood.

The H250 vent is 7" and the H250FDN is 6". The FDN is also a couple of inches lower in height. Removing the draft hood from the existing install leaves about 40" to replace and transition from 6" to 7".

I am adding an 18" section of 7" B vent below the existing elbow that leads to the tee then up and out through the roof. Directly on top of the heater will have a section of 6" C vent to make up the transition between the heater and the B vent. A 6" to 7" increaser will transition the 6" C to 7" B vent connector.

I could have had a longer 7" B section, but I used what I had. The vent sizing in the manual allows for an increase in vent diameter and the new C vent section basically replaces the old draft hood and is in conditioned space.