Noodles on the Loose
.... My understanding from the Inspector is it's the combination that creates the problem because when the exhaust hood is on it could create negative air flow in the water heater exhaust and pull carbon monoxide into the truck rather than venting out.
My first thought is the Insp. is a bit of an oxy-moron here. See the same can be said of poor placement of the Hood exhaust or the fresh air intake into the truck. So the hood is recirculating the 'hood exhaust' through truck. ... But what I think the Insp. is implying is that air flow for the hood exhaust might draw fresh air 'backwards' though the WH exhaust into the truck.
First, this would be a problem of any gas fired appliance if the fresh air intake for the hood exhaust is not sufficient. So another gas fired and independently vented WH will not solve his concerns.
Second, I don't think the WH will work if this happens. Check with the manufacture about safety features to prevent this.
One of the manufacture's diagrams seems to show an installation where the exhaust is room vented and a near by wall exhaust fan. So an option might be to wall mount the WH to the end of the kitchen hood and pipe the exhaust under the hood or though the end of the hood into the exhaust chamber. Then the exhaust will be thought the hood exhaust.
Most exhaust hoods in these application (truck/trailer concessions) are over powered. You only want enough air flow so that if you hold a tissue just above the front edge of the range/grill you can see it slightly move towards the hood exhaust. If you can feel the air moving in the truck, it is too much. ... But, some owners like this high air flow during the hot weather months to cool the work area. This is up to you.
So for the Insp, I still think he is an oxy-morron. ... if the hood exhaust is pulling the CO (WH's) back into the truck, it is also exhausted along with the fresh air drawn in from the windows & doors. So the CO can not build up, but the WH will not work correctly. ... You need to plan for fresh air intake to match the exhaust of the hood. Generally, the open counter window will be sufficient. But, if you plan on keeping the window & door closed, then another wall intake vent is required.
Only other option ... is electric WH or exterior mounted gas wh.
post edited by edwmax - 2013/02/18 13:17:10