ASME LP Tank - Do you have 2 Regulators?

[CoachStreamr]

Originally Posted by Old-Biscuit

Air MUST be purged out of tank using propane VAPOR....VAPOR source must exchange the volume 4-5 times to purge AIR from tank THEN tank can be filled with LIQUID propane (normal fill)


Purge procedure...........see pg 10/11
http://www.bergquistinc.com/sites/de...s/Handbook.pdf

That's a great handbook/link, thank you

I do see where it says repeat those steps 4 times (total time 15 mins or less) on page 11. The chart below it shows that at after the 4th purging there is still 6.25% of air in the tank.

It's odd they show the % for the 5th and 6th purge but only state you have to repeat those steps 4 times. Looks like there is always some air in there, ~1.56%.


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[Old-Biscuit]

Originally Posted by CoachStreamr

That's a great handbook/link, thank you

I do see where it says repeat those steps 4 times (total time 15 mins or less) on page 11. The chart below it shows that at after the 4th purging there is still 6.25% of air in the tank.

It's odd they show the % for the 5th and 6th purge but only state you have to repeat those steps 4 times. Looks like there is always some air in there, ~1.56%.


.

Would have to pull a vacuum on tank to get ALL air out.

[CoachStreamr]

Originally Posted by Old-Biscuit

You have ONE service/vapor valve that feeds TWO 2 stage Regulators because ONE feeds coach propane system and ONE feeds generator.

Two separate systems -two separate regulators.
Because each of those 290 Series (605H Regulators) have a MAX flow rating of 160,000 btu

The Marshall Excelsior MEGR-298 comes in 3 versions
'298 ........rated at 175,000 btu
'298H-----rated at 225,000 btu
'298L------rated at 120,000 btu
All 3 have 1/4” FNPT Inlet x 3/8” FNPT Outlet - 90° Vent


I would use TWO 298s (175k/each) as replacements

Fridge is roughly 2200 btu (large rv fridge)
Water heater
*Atwood-----6/gal (8000 btu), 10 gal (10,000 btu)
*Suburban....12,000 btu (6/10/12 gal)
Furnace----25K to 40K depending on model
Stove top
*1 High burner-----9000 btu
*2 Low burners----5000/ea btu
Oven...roughly 2200 btu

Using HIGH capacity numbers.....80,000 btu
Gen btu rating?? Roughly 120,000 btu

**Regulator btu rating should be twice the demand so regulator is not maxed out
160,000 btu rating is 'normal' for RV LP demands
It is also adequate for Gen Demands
Hence the need for TWO regulators


I would replace EVERYTHING from nipple on Service valve outlet to the fittings on both hoses.
Using the 298 regulators...one for each system

I seem to not be able to find the BTU requirements of the Generac NP-66G generator (with LP fuel kit obviously).

I do have the Suburban water heater, the Furnace is a 42K BTU I think (maybe only 40K), 3 burner stove top (no oven), 2014 Dometic 2-way Fridge.

Yesterday, I had also asked Marshall Excelsior about mounting recommendations for 2 of their MEGR-298 regulators and the reply this morning from one of their Technical Sales Engineers:

It doesn’t happen very often that someone uses two regulators like that. I really don’t have any documentation or recommendation of how to do it. The method in the pictures you sent looks like it would work fine.

Most people use a single regulator that has enough capacity for the whole system. It could be that when your system was set up, there wasn’t a higher capacity regulator available, without going to a residential regulator. If you add up all the max flow requirements (in BTU/hr) for all your appliances and the generator combined, it may be less than the 225,000 BTU/hr capacity of the MEGR-298H I mentioned earlier, and you might be able to use one regulator for everything.

@Old-Biscuit - Your post makes sense, I don't think there would be enough 'headroom' if I only used a single MEGR-298H regulator as suggested by them (unless the generator is less than 60K-80K BTU (again, I can't find the requirements of this model). Marshall Excelsior seems to suggest you don't need headroom (~double the capacity), just a large enough regulator to handle the total capacity of appliances and generator

If I went the single 298H route, I'd have to connect both legs of the output (Appliances and Generator) somehow to the 298H's output. But again, using your numbers, the headroom would only be around ~30K BTU assuming the Generac uses up to 120K BTU. Perhaps I should try longer to find the requirements for this Generac LP generator.

I'm not sure about modern Coaches but we looked at a lot of DP's from 1995 to 2002 and most seemed to have the standard LP generator vs Diesel. Is it safe to say all of them have 2 regulators?

Are LP generators still used in modern DP Coaches and if so, what are their regulator setups?

I'm trying to figure out how to mount two MEGR-298.



.

[Old-Biscuit]

Originally Posted by CoachStreamr

I seem to not be able to find the BTU requirements of the Generac NP-66G generator (with LP fuel kit obviously).

I do have the Suburban water heater, the Furnace is a 42K BTU I think (maybe only 40K), 3 burner stove top (no oven), 2014 Dometic 2-way Fridge.

Yesterday, I had also asked Marshall Excelsior about mounting recommendations for 2 of their MEGR-298 regulators and the reply this morning from one of their Technical Sales Engineers:

@Old-Biscuit - Your post makes sense, I don't think there would be enough 'headroom' if I only used a single MEGR-298H regulator as suggested by them (unless the generator is less than 60K-80K BTU (again, I can't find the requirements of this model). Marshall Excelsior seems to suggest you don't need headroom (~double the capacity), just a large enough regulator to handle the total capacity of appliances and generator

If I went the single 298H route, I'd have to connect both legs of the output (Appliances and Generator) somehow to the 298H's output. But again, using your numbers, the headroom would only be around ~30K BTU assuming the Generac uses up to 120K BTU. Perhaps I should try longer to find the requirements for this Generac LP generator.

I'm not sure about modern Coaches but we looked at a lot of DP's from 1995 to 2002 and most seemed to have the standard LP generator vs Diesel. Is it safe to say all of them have 2 regulators?

Are LP generators still used in modern DP Coaches and if so, what are their regulator setups?

I'm trying to figure out how to mount two MEGR-298.



.

The Gen btu is roughly 120,000 at FULL load

Lots of LP Generators are liquid with their OWN pickup tube set at a higher level ---same with diesel
Mounting if the two 298s would be same as current 290s...horizontal with clamps at outlet to the bracket.
New regs are going to be very similar in size to the old regs.

I looked for higher rated 2 stage RV regs.....the 298H @225K was highest.
It would work majority of time cause you would never have ALL propane appliances in service at full demand AND generator running at FULL Load.

SO the 298H would work ----just split the outlet from reg into 2 separate feeds -------'T' and elbow set up---just like inlet side is now except on outlet side

[CoachStreamr]

Originally Posted by Old-Biscuit

the 298H @225K was highest.
It would work majority of time cause you would never have ALL propane appliances in service at full demand AND generator running at FULL Load.

I see your point and both the refrig and the hot water heater in this Coach can go electric (the hot water heater switch is on the kitchen sink cabinet).

Originally Posted by Old-Biscuit

SO the 298H would work ----just split the outlet from reg into 2 separate feeds -------'T' and elbow set up---just like inlet side is now except on outlet side

I was going to go the Qty. 2 MEGR-298 way from your initial post.

Now it seems perhaps I should go with just Qty 1 MEGR-298H and split the output and this is your recommendation as well?


Fridge is roughly 2200 btu
Suburban....12,000 btu (6/10/12 gal)
Furnace----42,000 btu
Stove top
*1 High burner-----9000 btu
*2 Low burners----5000/ea btu

Using HIGH capacity numbers.....75,200 btu
Gen btu rating?? Roughly 120,000 btu

Total 195,200 btu (all on LP full load)
Total without Fridge and Suburban Hot Water (switch to electric): 181,000 btu

Between 30,000 and 44,000 btu headroom - Is that enough not to cause problems with the appliances' pilot lights?

I supposed if there are issues, I could add a MEGR-298 with the MEGR-298H in the future and use the H for the generator leg.


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[Old-Biscuit]

Originally Posted by CoachStreamr

I see your point and both the refrig and the hot water heater in this Coach can go electric (the hot water heater switch is on the kitchen sink cabinet).




I was going to go the Qty. 2 MEGR-298 way from your initial post.

Now it seems perhaps I should go with just Qty 1 MEGR-298H and split the output and this is your recommendation as well?


Fridge is roughly 2200 btu
Suburban....12,000 btu (6/10/12 gal)
Furnace----42,000 btu
Stove top
*1 High burner-----9000 btu
*2 Low burners----5000/ea btu

Using HIGH capacity numbers.....75,200 btu
Gen btu rating?? Roughly 120,000 btu

Total 195,200 btu (all on LP full load)
Total without Fridge and Suburban Hot Water (switch to electric): 181,000 btu

Between 30,000 and 44,000 btu headroom - Is that enough not to cause problems with the appliances' pilot lights?

I supposed if there are issues, I could add a MEGR-298 with the MEGR-298H in the future and use the H for the generator leg.


.

Plenty of control range with just the 298H high flow reg.

IF 'I' was redoing MY propane tank reg system I would go with just ONE Reg.....that's ME.
(and like you I could had another later IF ---IF---propane flow issues came up)


Pilot flames???

You have pilot flames.......
RV Oven would......old style gas WH would, really old style fridge would, really really old furnace would, stove top burners might.

Any RV appliance with spark electrode does NOT....flame is the MAIN Flame

[Isaac-1]

My concern would be response time lag on the regulator if there is a sudden load surge on the generator and an associated sudden drop in pressure to the other propane appliances. Such as the potential for a flame out on the small flame used on the refrigerator. A second regulator eliminates this issue. In a constant load or slowly varying load situation I suspect a single regulator would do fine, I just don't see generator operation as such a load.

[CoachStreamr]

I'm going to go with a single MEGR-298H and if there are issues in the future, I can add a standard MEGR-298 to the system.

The owner of Northwest Coach (doing the tank replacement) also is recommending going with only 1 higher capacity regulator. I'm just waiting to hear back about availability of that the MEGR-298H.


Also got more information back from a Technical Sales Engineer @ Marshall Excelsior:

As an optimum target, most regulators are happiest right in the middle of their capacity range. As you approach the high end of the listed capacity, the outlet pressure starts to draw down, or “droop”. Most regulator capacity ratings are at 20% droop, which is the point where there is enough flow going through it that the output pressure droops by 20%. This droop is usually insignificant until you get into the top 20% or so of the range. At very low flow conditions, you can start to have some instability of output pressure, since the orifice seat is very close to closing off. It looks like you would only be in that upper 20% range if everything was running at the same time. Only you can estimate how likely that would be.

The other factor that you can’t really calculate is the sudden flow surge when a generator starts up, or opens up for a sudden demand, especially if other appliances are already running. That’s something you can only determine from experience, and maybe that’s why your RV was set up with a separate regulator for the generator. There have been many cases where we have recommended going to a higher capacity regulator (MEGR-298H vs MEGR-298, or MEGR-253H vs MEGR-253) just for that purpose of handling the startup flow surge from a generator or on demand water heater.

In your case, my suggestion would be to start with one MEGR-298H and see how it goes. Test it out by starting the generator with all the appliances on, and try out different scenarios. 6600 watts is not that big, as generators go, and I think the MEGR-298H will be able to handle what you need. If you find that it doesn’t, it’s not that hard to add a second regulator and arrange it just like your current setup.

.

[CoachStreamr]

Pics of new Single High Capacity Regulator and new tank