Problem with LP Gas appliances, new house, help?

Our new manufactured home is nearly ready for move-in. We have electricity and water. We just needed the propane gas guy to come out and hook up the hot water heater, furnace and stove.
Well, the stove is fine, but the other two aren't . He starts them up but after a minute the flame turns from blue to yellow. He says they just aren't venting for some reason. He went up on the roof and the stacks look okay. He called his supervisor and described it on the phone, thinking maybe he missed something, but they're stumped.
I could see if one was buggy, but both? They aren't in the same location in the house, though they aren't far apart either. The hot water heater is in a cupboard on the end of the house, accessed by an outside door. The furnace is in the laundry room. There's a bedroom between them.
Of course, it's Friday so we can't reach anyone at the manufactured home dealership. Left a message for them.
We're supposed to move in Monday. We gave our notice at this horrible apartment, and we scheduled the movers to get this stuff Monday and bring our stuff out of storage Tuesday. I just checked and they're booked up for the whole week so we have to keep our dates.
So, I guess we'll stay in a hotel until it's fixed.
Does anyone have any idea why they aren't venting? Why the flames are burning yellow instead of blue? Please help.
Thanks so much,
Maxi
Email addy upon request.
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maxinemovies wrote:

<SNIP>
I wouldn't automatically assume it's a venting issue, just because these guys said so.
Could be a problem with maintaining supply pressure or incorrect ng/lp conversion parts.
Time to get a competent installer in there who can track it down.
Jim
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That would be my guess also. Could be a defective pressure regulator or restricted flow. The range takes about 8,000 Btu per burner. The heater may be 60,000 or 100,000 and is just not getting the fuel it needs.
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