First Time Pool Owner - Backpressure Question

Apr 19, 2014
4
North Texas
Hello, my friend from NC recommended I visit this site since it helped him tremendously. I've read all the chemistry topics and general guidance so I feel at least a little comfortable with the basics. Where things get all wonky is with a strange situation I've run into with my spa/pool heater. Our Jandy system is set up with pool mode and spa mode which basically controls the input to the filter and the output back to the pool or spa. When we fire up the (brand new) RayPak 406A (400btuh) in the spa loop (spa drain in > spa out) the heater fires right up and it works great! But when I put the system in pool mode (main drain in > pool out) the heater says it doesn't have enough pressure to fire. The odd thing is that there is plenty of flow and I have a good prime on my 2hp pump. I've tried everything, completely cleaned out the filter (I get 25psi by the way when it's in the pool loop), I've tried swapping inputs, I've even tried running it with the pool cleaner booster pump running and no avail. I have also tried running it in the spa loop, and swapped the output valve from spa to pool and the second it gets half way there the heater shuts down throwing the pressure code.

Does anyone have any idea why I can't get sufficient pressure when I'm in the pool loop but I can when I'm in spa?

Diagram attached for reference...

Pool Diagram.jpg
 
I would call it okay to weak. I can easily place my hand in the pool and completely stop one of the jets without any difficulty. I should have mentioned earlier that I have taken apart each valve, inspected for damage or blockage and found none at all. I kind of felt like the return line may have blockage but how in the world would I go about figuring out how to address it (and as well, how could it have gotten blocked up since it was in a closed loop system past the filter?) Thanks for the quick reply!!
 
Question: what's the pressure when it's all working good in spa mode? Is there any chance the warning is for too high pressure?

The only other thing I can think of is the situation I have. My controls are all manual. When I move the valves to spa-in-spa-out, and set the temperature using the spa thermostat on the heater, it doesn't work right. Setting the temp on the heater thermostat labelled "pool" allows it to work perfectly. The heater is a dumb beast - it hasn't got a clue where the water is coming from or going to. There are some extra threaded ports on the heater boss that are not drilled through nor connected, and I suspect there might be a second channel in the heater to heat the spa or something. Of course, with no water running through it, it won't work. Maybe you have something similar going on. If you unplug the remote cable from the heater and use the manual controls, how is it then?
 
The warning code I get is (per RayPak manual) insufficient pressure, not too high. I don't have a pressure indicator anywhere except inside the filter vessel but I'm reading 25psi in pool mode and about 30 psi in spa mode. I just can't reconcile the pressure in the filter to the perceived lack of pressure the heater says its experiencing. The manufacturer says they only require 2-3 psi to trip the switch. This one's really got my brain twisted around the axle. Also on the question regarding winterizing, I'm in texas and the pool wasn't winterized.
 
I know this is an old topic but I thought I'd respond to bring some closure!

Sometimes it's hard to miss the forest through the trees... when we had the heater installed, the intake and return lines were reversed. Based on our plumbing everything looked proper but there were distinctive IN and OUT arrows etched into the iron pipe connections on the heater... a quick PVC hack and glue and no more problems...

Not going to hire that guy again! Thanks for your help everyone!
 
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