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Natural gas burner vs propane burner performance

lakeside park

Premium Member
Joined
May 2, 2020
Messages
4
Location
Concord MA
Model Number
PRD366GHU
Brand
Thermador
Age
1-5 years
Hi all

I have a Thermador 36" range (2 year old) that is currently on propane. My previous home we had a DCS range top that ran on Natural Gas. This Thermador range is extremely slow to heat a big pot of water for pasta for example and when it does boil and I put in the pasta it takes several minutes for the pot to return to boil. The DCS range we had previously with NG was much faster to boil and much faster to recover to a boil. Both ranges are in the 18,000 BTU per burner range.

I am thinking of replacing propane with NG here at the new house because I thought that the problem with the Thermador stove being slow was using propane vs NG. After reading that propane actually has more BTU/cu Ft than NG, I am beginning to think that changing to NG with this stove will not help the problem. Can you tell me your opinion on this?

The installer came out and looked at the Therm range and said they had it at the burner highest setting to get the most heat out of the burner. I think they may have told me then (2 years ago) it was a propane problem and that propane with the range is actually 25% less heat output than natural gas.

I can't seem to find any data on this topic on the internet.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
39,805
Location
Murray, Utah 84107, United States
Here's the deal, as long as the range is set up correctly for the type fuel you're using, 18,000 BTUs is 18000, BTUs

PROPANE GAS REQUIREMENTS
Inlet Connection: 3/4″ N.P.T. (Minimum 3/4″ diameter flex line) Supply Pressure: 11″ to 14″ water column. (27.4 mb to 37 mb) Manifold Pressure: 10″ water column (24.9 mb)

NATURAL GAS REQUIREMENTS
Inlet Connection: 3/4″ N.P.T. (Minimum 3/4″ diameter flex line) Supply Pressure: 6″ to 14″ water column. (14.9 to 37 mb) Manifold Pressure: 5″ water column (12.5 mb)

For Massachusetts Installations:
1. Shutoff valve must be a “T” handle gas cock.
2. Flexible gas connector must not be longer than 36″.
 

lakeside park

Premium Member
Joined
May 2, 2020
Messages
4
Location
Concord MA
Thermador replied to my inquiry saying there should not be a problem using propane with their range. Now I am wondering if it is the propane gas supply.

After looking at the specs you provided above I went and looked at the propane piping in the basement. They used WardFlex II tubing in the house. https://www.wardmfg.com/ward-flex-2/

They used parallel runs: 3/4" tubing for hot air furnace and DHW, 1/2" tubing for the range. There is about 70" of 1/2" tubing for the range. I am wondering if there is enough gas pressure at the range. The specs you provided above say 3/4" N.P.T.. This may be a dumb question - but what is the point of using 1/2" tubing for the supply line if the range wants a 3/4" connection? I know it is the pressure at the range that matters and that the longer the gas supply line the higher the pressure drop is. Just wondering if the 1/2" tubing is the problem. I put a call into the town gas inspector to ask about that.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
39,805
Location
Murray, Utah 84107, United States
Most of the gas ranges I work on are NAT gas. I can't see a difference between using 1/2" or 3/4" for LP and NAT since both end up at the regulator on the range but I'm not sure.
 

lakeside park

Premium Member
Joined
May 2, 2020
Messages
4
Location
Concord MA
One more message to you - the local appliance store responded to me with this info:

"Hello and thank you for reaching out to us again. I’ve attached the User Manual for the range you have, please refer to page 15. The BTU’s drop from 18,000 to 15,000 when a liquid propane conversion is done. Thermador is correctly stating that propane does burn hotter than natural gas in an environment where the gas flow is equivalent. However, what they fail to mention is that there are nozzles installed to restrict the flow of gas for propane, which subsequently drops the BTU’s by 3,000."

I attached the user manual and it is clearly shown in there about the LP vs NG reduction in BTU. Learn something new every day. Thanks again for your help
 

Attachments

  • PRD366GHU User Manual.pdf
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