Pump location on diverter tee system

bill_105

probably is inconclusive. Boilers just ten years old have manual showing on the return and tank on the other side. But it's now changing. Strange evolution here. In 1930 it was known that the tank placed on the return was beneficial. In the 60's it was actually noticed. In the 90's we finally got it.

StorminMike

Pump Location on diverter tee system

I have a hot water, diverter tee system. The radiation is a mixture of baseboard fin pipe (on the second floor) and in wall gravity convectors (on the first floor). The system heats the house well, but I'm looking to correct some issues this summer:

Whoever replaced the boiler set the system up in a strange order - the water feed is behind the pump, which pumps directly into the boiler. The expansion tank is on the output side of the boiler.

One problem with this setup seems to be that the pressure drop behind the pump causes more water to feed into the system. I set the feeder to 12 psi, and bleed the radiation. After running the pump (but not firing the boiler at all), the pressure in the system is up to 20 psi. (I attached a pressure gauge on the main next to the fill line to get these readings since the gauge on the boiler is obviously ahead of the pump and doesn't have the same reading.) On a couple occasions this has caused the pressure relief valve to drip, and the service guy who came "fixed" it by taking some water out of the system. The second issue, which I understood after reading Dan's books may be related to where the pump and tank are positioned, is that it's very difficult to get all of the air out of the second floor radiators.

I'm interested in knowing how the experts on this forum would suggest moving things around to fix this - moving the pump to the output side of the boiler would be a bigger job than moving the expansion tank to be on the intake side, behind the pump. What are the pros and cons of each method, if any?

Mike

Jim_64

that's too 'complicated' to imagine

post some pics

StorminMike

Pics of system

There isn't anything else in the pipe between the expansion tank and the boiler.

John@Reliable_17

Do it right the first time

#1 Air scoop needs 18" of pipe before it, to work right.#2 Fixing that and moving pump to "pump away" and adding point of no pressure change would only take about three hours of labor ,give or take. This would be $ well spent for you comfort and better for system.

Erich_3

Simple Corrections

Here is what I would suggest. Get rid of the air scoop. Use a Taco Vortech Air Separator on a horizontal line on the supply side before the circulator. Mount the expansion tank under the air separator. The Taco Vortech does not need a minimum pipe length and it is available in five different sizes. Move the circulator to the supply side after the air separator. Here is a link to the Vortech:
http://www.taco-hvac.com/en/products/Vortech®+Air+Separator/products.html?current_category=124

Mark Eatherton

I agree with John...

Why dance around the issues trying to save a few bucks? It will come back to bite you squarely in the hind side. Start with sawzall surgery. WHen you start putting it back together, also take in to consideration the need to quickly and efficiently purge the heating circuits, and the time you would have wasted chasing bubbles will be countered by the time you spent doing the piping correctly.

I've never seen your system, but I bet I can predict one of the "conditions" that happens with the system. I bet that the operating pressure somehow "creeps up" to the point that the relief valve leaks. I say this because the make up PRV is connected at a point that every time the circulator turns on, it creates a low enough pressure that the PRV sends just a little shot of water in to the system. Over time, the pressure rises to the threshold of the relief valve and the vicious cycle starts eating the boiler away because no one is standing there to see the relief valve do its thing.

Set it up right, and be done with it. You will gain a happy customer for life, and won't have to be back there every year bleeding air. You will be back there every year doing a combustion analysis to make sure their family is as safe as they can be.

Remember, you can do it right, or you can do it again, at your expense...

ME

StorminMike

That seems to be exactly what happens.

When I bought the house I noticed the relief valve dripping, and have since paid several different firms to fix it - but none of them were ever able to explain why it kept happening, so I eventually bought a copy of Dan's book, read up on it, and figured out that it wasn't really put together in the right order.

StorminMike

Should the fresh water fill line be moved while I'm at it?

I'll need to re pipe the return in that case since I won't have the circulator there anymore, so I can easily move that elsewhere if it would help.

Bob Bona_4

and don't

forget to move the water feeder to the x-tank tap location, so there isn't unplanned pressure changes, and air in the feed water can get out ASAP.

Erich_3

Make and Model

It would be good if you posted the exact make and model of the boiler. That way we can look at the manufacturers instruction manual and see what they have for piping instructions.

StorminMike

Make/Model

It is a crown AWI162. The installation guide is on the web here:

http://www.crownboiler.com/manuals/content/Residential_Boilers/Gas/AWI & TWI Series Installation Instructions.pdf

The main difference in their diagram seems to be that the fresh water feeder line is right at the expansion tank, not behind the pump the way whomever installed this hooked it up.

Erich_3

I would Move It

You can rarely go wrong by following the installation manual. Unfortunately too many people do not bother to read them.