Gas heater needs 2750 RPM to fire

[jmcmd1980]

The pool builder set my Jandy filter pump to run at 2250 in pool heater mode and 3450 in spa mode/spa heater mode. They set the system to run at 2750 RPM from 9 AM to 6 PM and gave no further instruction. I have been experimenting with variable pump speeds to save electricity. I have been running the pool at 1750 RPM and pool skims, generates chlorine, my champagne spa overflows, though understandably less than at 2750 RPM.

The only problem, is my heat screen shows "Check Flow" at under 2750 RPM. If I put the pool in "Pool Heat" mode, the pump speed increases to 2250 at set, "Check Flow" still shows on the screen, the heater comes on line, but when the gas fires, it goes off after a few seconds. If I increase the RPM to 2750, the heater comes on, gas ignites, and pool heats to my set temperature.

Is the need for 2750 RPM to run and fire the heater due to the nature of my construction and plumbing? I can increase the pool VSP setting from 2250 to 2750 RPM if this is the obvious answer. I do have a check valve in the outflow line of the heater and the flap is not open much at the 2250 or 2750, but open half or more at 3450. I have a manual bypass valve also.

Any thoughts, greatly appreciated.

Jim

 

[mas985]

Is the need for 2750 RPM to run and fire the heater due to the nature of my construction and plumbing?

Probably. 2750 RPM is a bit high for the heater which indicates either very high head loss plumbing or perhaps flow may be redirected around the heater (i.e. heater bypass).

Can you describe your plumbing system in detail and show a few pictures of your pad equipment?

Is this a new pool?

What is the filter pressure at full speed?

What size pipe was used and how many suction/return runs are there pool to pump?

How many returns are in the pool and what size eyeballs are used?

 

[jmcmd1980]

Probably. 2750 RPM is a bit high for the heater which indicates either very high head loss plumbing or perhaps flow may be redirected around the heater (i.e. heater bypass).

Can you describe your plumbing system in detail and show a few pictures of your pad equipment?

Is this a new pool?

What is the filter pressure at full speed?

What size pipe was used and how many suction/return runs are there pool to pump?

How many returns are in the pool and what size eyeballs are used?

New pool 6/8/23
Pressure at 3450 is about 22-25
3 returns
Not sure of pipe size, see picture, looks pretty big, I took a picture of an eyelet.

I have a champagne spa and a sun deck. The spa fills from the bottom in pool mode and in spa mode, it fills from the spa jets Jets and the pool is off filtration wise. I have an auto fill, and also the hole in the skimmer to drain excess water.

Thanks

 

[mas985]

Your heater does have a bypass and some of the water is being bypassed around the heater which lowers both the flow rate and pressure in the heater. Close that valve so that NO water bypasses the heater and you will be able to run on lower RPM. However, that also means at higher RPM while in SPA mode, the jets will be weaker due to higher head loss. So you may want to invest in another actuator that turns on/off the bypass depending on the mode.

 

[jmcmd1980]

Your heater does have a bypass and some of the water is being bypassed around the heater which lowers both the flow rate and pressure in the heater. Close that valve so that NO water bypasses the heater and you will be able to run on lower RPM. However, that also means at higher RPM while in SPA mode, the jets will be weaker due to higher head loss. So you may want to invest in another actuator that turns on/off the bypass depending on the mode.

Thanks for the great advice!

 

[JamesW]

For the VSSHP270DV2A pump, you should be able to run at about 1,730 to about 2,400 RPM assuming the head loss is not excessive.

What heater do you have?

As noted, close the bypass completely.

Never run the heater with the bypass open as this will destroy the heater.

Be 100% sure that you know how to operate the bypass correctly.

If I increase the RPM to 2750, the heater comes on, gas ignites, and pool heats to my set temperature.

 

[JamesW]

Check the heater inlet temperature and compare it to the outlet temperature to see what the temperature rise is.

The SWG temperature is the heater outlet temperature.

The Temperature rise is Outlet - Inlet = Temp. Rise, which should be 16.8 degrees or less.

https://cdn.fluidrausa.com/-/media/zodiac/global/downloads/sl/54409_sl.pdf

https://cdn.fluidrausa.com/-/media/zodiac/global/downloads/h/h0707401.pdf

Energy Efficient Pool Pump: ePump 2.2 & 2.7 HP | Jandy

Looking for an Energy Efficient Pool Pump? This Jandy ePump 2.7 HP will bring the Perfect Pool Experience. Buy Now w/ a Pool Pro Near you!

www.jandy.com

 

[JamesW]

Pressure at 3450 is about 22-25

25 psi is about 58 feet of head loss for the returns and you need to add the suction, which we can estimate to be about 12 feet of head loss for a total of about 70 feet.

Close the bypass and see how much speed is required to operate the heater and check the temperature rise.

Check the filter pressure when the heater operates.

Your filter is undersized, which is typical for Florida.

Remove the filter cartridge to see how dirty it is and clean it to see how much difference that makes.

 

[JamesW]

 

[JamesW]

You need to rotate the valve by about 30 degrees counterclockwise to close the bypass completely.

You want the wide part that says "Off" to be towards the bypass.




Why is this spot wet?

 

[JamesW]

Setting heater bypass valve

My pool is about 5 weeks from fill. The pool installer gave very little information and training and I have been using TFP for expert assistance. Could someone advise me on setting my heater bypass valve? Should I open it completely to the heater during seasons I use the heater for the pool...

www.troublefreepool.com

 

[jmcmd1980]

I ha

For the VSSHP270DV2A pump, you should be able to run at about 1,730 to about 2,400 RPM assuming the head loss is not excessive.

What heater do you have?

As noted, close the bypass completely.

Never run the heater with the bypass open as this will destroy the heater.

Be 100% sure that you know how to operate the bypass correctly.




View attachment 521704

I have a JXI400N. So when you say to close the bypass completely , you mean to have completely open the flow to the heater and not bypass it at all ? Does the bypass stay closed, full flow to the heater, when in pool or spa heat mode, and the RPMs ramp up per programming?

 

[jmcmd1980]

You need to rotate the valve by about 30 degrees counterclockwise to close the bypass completely.

You want the wide part that says "Off" to be towards the bypass.


View attachment 521722

Why is this spot wet?


View attachment 521723

I am not sure of the wet spot, I’ll check it out. So does the bypass stay closed when using spa mode with or without heater, pool heater and the RPMs ramp up for programming?

 

[jmcmd1980]

25 psi is about 58 feet of head loss for the returns and you need to add the suction, which we can estimate to be about 12 feet of head loss for a total of about 70 feet.

Close the bypass and see how much speed is required to operate the heater and check the temperature rise.

Check the filter pressure when the heater operates.

Your filter is undersized, which is typical for Florida.

Remove the filter cartridge to see how dirty it is and clean it to see how much difference that makes.


View attachment 521718

Will do, I actually cleaned the filter and basket yesterday evening.

 

[JamesW]

You can use this formula to estimate the flow based on the temperature rise.

Y = temperature rise.

X = flow in gpm.

Y = 672/X

X = 672/Y.

For example a flow of 40 gpm should be a temperature rise of 16.8 degrees.

A temperature rise of 11.2 degrees should be about 60 GPM.

As you can see, flow below 40 gpm results in a big temperature rise.

If the water temperature is 86 degrees and water boils at 212°F, then a temp rise of 126 degrees will result in boiling of the water and the heater will probably explode or be seriously permanently damaged.

A flow of 5.3 GPM or less will likely cause the water to boil and seriously damage the heater.

plot Y = 672/X, y from 6 to 60 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

plot Y = 672/X, y from 6 to 150 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

 

[JamesW]

The manual says that 30 GPM is the minimum flow, which is a temp rise of 22.4 degrees.

I would want at least 40 GPM for a 400,000 btu/hr heater.

Your pump can do more than 100 GPM, which is the maximum flow that the heater can manage.

Any pump speed over 2,400 RPM can theoretically get to 100 GPM.

So, you need to know if the flow is above 100 GPM so that you can partially open the bypass.

However, if the bypass is open and the heater gets insufficient flow, the heater can be instantly and permanently damaged.

Note that the heater does not have a flow switch, it has a pressure switch which will close if the pump is on regardless of the flow through the heater.

All JXi heaters utilize an internal bypass mechanism and thermal regulator valve (TRV) to accommodate flow rates delivered to the heater from a minimum of 30 gallons per minute (gpm) to a maximum flow of 100 gpm.

https://www.jandy.com/-/media/zodiac/global/downloads/h/h0574300.pdf

 

[JamesW]

You can use a spring bypass with a 2 to 7 pound (PSI) spring to automatically open once the flow exceeds 40 gpm.

You can find various spring bypass valves with different ratings.

Pentair makes a spring bypass for their heat pumps with a 12 pound (PSI) spring, but I don't see what good that does since the 12 psi should never be reached for their heaters.

In any case, I would use a real flow switch instead of relying on the pressure switch which is a bad idea for heaters with a bypass.

Bypass Valve - 5 PSI Spring - 1520 Series Parts - INYOPools.com

Bypass Valve - 5 PSI Spring - 1520 Series - INYOpools.com has the largest selection of swimming pool and spa replacement parts with over 70,000 parts in stock. Order today and save!

www.inyopools.com

R172305 - UltraTemp Water Bypass Check Valve - 1.5 Inch Socket - Pentair

This is a Pentair Water Bypass Check Valve, 1.5 inch socket, with a 12 pound spring for UltraTemp Heat Pumps. This check valve is also designed for the Thermaflo Heat Pumps.

www.poolweb.com

Pentair R172305 check valve has a 12 lb (12 psi) opening pressure.

This is a Pentair Water Bypass Check Valve, 1.5 inch socket, with a 12 pound spring for UltraTemp Heat Pumps. This check valve is also designed for the Thermaflo Heat Pumps.

 

[JamesW]

https://www.praherplastics.ca/wp-content/uploads/2023/03/praher_plastics_pool_catalogue_2023_march.pdf

 

[JamesW]

I got lucky...now I need help adding a flow switch

Evening, TFP World! We have an autocover that stays closed except when the pool is in use or needs to be left open to breath. Today, it was a beautiful day, so I left it open most of the day. I did not appreciate how much Crud was coming off the trees, and allowed both skimmer baskets to get...

www.troublefreepool.com

 

[jmcmd1980]

The manual says that 30 GPM is the minimum flow, which is a temp rise of 22.4 degrees.

I would want at least 40 GPM for a 400,000 btu/hr heater.

Your pump can do more than 100 GPM, which is the maximum flow that the heater can manage.

Any pump speed over 2,400 RPM can theoretically get to 100 GPM.

So, you need to know if the flow is above 100 GPM so that you can partially open the bypass.

However, if the bypass is open and the heater gets insufficient flow, the heater can be instantly and permanently damaged.

Note that the heater does not have a flow switch, it has a pressure switch which will close if the pump is on regardless of the flow through the heater.

All JXi heaters utilize an internal bypass mechanism and thermal regulator valve (TRV) to accommodate flow rates delivered to the heater from a minimum of 30 gallons per minute (gpm) to a maximum flow of 100 gpm.

View attachment 521754

View attachment 521755

View attachment 521756

View attachment 521757

https://www.jandy.com/-/media/zodiac/global/downloads/h/h0574300.pdf

So basically, the pool company set things to run at 2750 RPM for 9 hours per day with a partially open heater bypass. That RPM speed is adequate to provide enough flow to the heater at baseline so as to not get the “check flow” message, and the speed increases further for champagne spa mode per their programming.

To run at 1750 RPM, I need to close the heater bypass valve completely to avoid the “check flow” heater message. When I put the system into “spa mode”, I would need to partially open the bypass valve to the heater to reduce some of the flow to the heater, visually half open check valve, either manually or with an automatic flow switch as you describe.

Am I understanding correctly? Thanks!

Jim