Glycol questions

bergger

I agree with @ScottG.  Replacing old Rhomar with new you will not see a color change to know if the old has been replaced with the new.  Color is a good indicator if you are replacing the old Century with the Rhomar as one is yellow and the other is greenish.  As Scott mentioned I would just push in a bit more than your system requires and call it good.  Since the color change is not going to be noticeable I would also recommend using a shop vac to suck out the old fluid at the end of the line as you pump in the new.  It's the method I used on our 2021 400 and I think it just helps in removing the old and limiting the mixture of old and new glycol.  

manyman297

I agree on color change. Did a Rhomar exchange (just replacing original Rhomar with new) and noticed almost zero color change.

ScottG

Here's an image from Alde that shows the intended flow of glycol through the expansion tank. It sounds like nuCamp is now hooking these up in reverse. I'm curious to know if there is a reason for the change, or if it makes any practical difference in the operation of the system. Presumably it was designed this way for a reason, but it's not immediately obvious to me what that might be.

AnOldUR

@ScottG. My guess is that the system draws from the higher port to reduce sediment from being pumped through the plumbing.

ScottG

Greenhil said:

...

As far as possibly needing to “pull” the old glycol from the other drain, I’m thinking I can use a wet vac if necessary. .

...

And, yes, if you were inclined to completely empty the system first, I think this would work much the same way as drawing the old glycol out through the expansion tank.

However--just in case this is what you were thinking--I wouldn't vac and pump at the same time. This might be how the Alde's proprietary bottom fill pump works, but if so that pump probably has a carefully balanced push-pull, and a recirculating feature. Try to duplicate this with a shop vac and I suspect your new glycol will get sucked out as fast as you pump it in!  :-0

Greenhil

ScottG said:

Greenhil said:

...

As far as possibly needing to “pull” the old glycol from the other drain, I’m thinking I can use a wet vac if necessary. .

...

And, yes, if you were inclined to completely empty the system first, I think this would work much the same way as drawing the old glycol out through the expansion tank.

However--just in case this is what you were thinking--I wouldn't vac and pump at the same time. This might be how the Alde's proprietary bottom fill pump works, but if so that pump probably has a carefully balanced push-pull, and a recirculating feature. Try to duplicate this with a shop vac and I suspect your new glycol will get sucked out as fast as you pump it in!  :-0

Thanks - this makes sense. I can’t see why it would be necessary to use a vacuum. With nothing, apparently, between the tank and the drain, I hope pumping will be enough. 

qhumberd

ScottG said:

Here's an image from Alde that shows the intended flow of glycol through the expansion tank. It sounds like nuCamp is now hooking these up in reverse. I'm curious to know if there is a reason for the change, or if it makes any practical difference in the operation of the system. Presumably it was designed this way for a reason, but it's not immediately obvious to me what that might be.

Just for my clarification, I marked my 2019 400 expansion tank before doing my last flush. I have stayed with Century and not had any issues. When I did my flush and fill 2 years ago I used tap water (many gallons) followed by distilled water before refilling with fresh Century fluid. I believe my flow is like the diagram above so in my case the hookup has not changed. The small and large drains seem reversed in the diagram but NOT the direction of flow.

The hose from the port on R returns to the Alde and the hose attached to the larger port on L  receives fluid from the last convector in the loop.

So when starting the flush  with the 12 V pump in my 2019 the flush water is entering on the R hose  and pushing fluid thru the Alde and around the loop and out the L hose. In this picture the old glycol is just starting to come out from the L hose below, that hose being attached to the larger port on the reservoir. In the shop vac method the pull would be on the L hose below to drain the system, and the new fluid would be pumped in the R hose.

And as @AnOldUR said, the larger port coming from the convector loop would be a place for any debris in the system to settle and not return to the Alde boiler

ScottG

@qhumberd, I agree regarding the diagram. My expansion tank looks yours, with the offset port located to the right of the center port when looking at the front of the unit.

I also like @AnOldUR's hypothesis that the large recessed inlet provides a sediment trap to reduce the likelihood of debris being drawn out the tank and into the pump/boiler.