Piping arrangement repair question

JP2347

I have a house with what looked to be an attempt at a primary series loop. A well respected,  trusted guy at the supply house told one of our installers to pipe this system this way.  We're not pumping away for starters and here's what's happening and some more details: 1st pump- domestic storage tank, 2nd pump cast iron radiators,  3rd pump in floor, and then yes the air separator and expansion tank before the pump and not after on the return there.   The relief valve won't pop in front of me but after a day or two it does.  We have a 150,000 btu dunkirk boiler set to 19 psi on the fill with a 30# pressure relief valve, and im wondering as well, if it's possible, either the system isn't seeing the expansion tank or if that expansion tank is to small when I correct the piping arrangement. I did the amtrol calculation chart and I have an amtrol EX-90 tank on there and there are 7 radiators with the dimensions as follows (3)36x17, 40x17, 43x17
(2)20x38, 20x28, and a 25x25 these were very close approximates measured.  Any help would be appreciated,  I plan on moving the tank, feed and pump on to the supply side for starters in hoping that fixes my issue.  I'll attach pictures and see what you guys suggest.   Thanks 

EBEBRATT-Ed

You should always pump away. But I am not 100% sure that's your issue. The primary loop is pretty short I don't see a ton of resistance there.

What I would do before moving everything which will cost $$$ is find out what the problem is.

1 Start off with a cold (or at least cool) system with the water at 12 psi. Crank all the zones up to make them call and watch the pressure and see waht it does. If you get much over 20 you need more expansion tank. Check the air pressure in the tank before you start 12psi with 0 water pressure on the bladder.

2. I would get a couple of decent pressure gauges on there. Put one on the drain valve to the right of the primary pump with a hose adapter. And take the relief valve off the boiler and stick a tee under it with a gauge on it.


That will tell you what direction to go with.

Is the radiant return valved off?

JP2347

No, the picture I had it the radiant valve off sorry about that.  So I've ran this system three times on separate visits and it will get up to 25 psi from 15 cold on each visit I've been there. It takes a while to get there but it does and so I wasn't sure if I needed a bigger tank or not; or if repiping the tank, pump, air separator&feed over might fix this.  The old tank these installers took out was an ex-60 so that's what's throwing me off, is maybe the system isn't seeing the tank with how it's piped; I could be wrong though. 

mattmia2

What did you set the precharge in the tank to? Why aren't you running it at 12psig cold fill?

EBEBRATT-Ed

@JP2347

Ok so the pressure when hot is getting to 25 and with the ex tank connected closer to the pump suction than it is to the pump discharge you are pumping away. The problem is the boiler 30# relief valve is on the pump discharge which may cause the relief to open.

In reality the primary loop won't have 5 psi of resistance but I can see where you could have an issue.


It would be cheaper to add or change the expansion tank that should get the hot pressure below 20 psi and you should be ok

Where you get in trouble pumping toward an expansion tank it's because of high resistance in the piping.

IMHO for this job with a short primary loop I don't think it matters much if you pump towards or away as the primary loop resistance is low.

It's the boilers location in the loop that is the issue.

You could move the pump to the boiler discharge and leave the expansion tank as is (like Weil McLain does)

JP2347

Technically with that expansion tank being after all the closely spaced tees wouldn't that exp tank/air separator be on the return and also the other pumps from the secondary loops be pumping to a degree into the expansion tank? I get what your saying though with that being your primary loop

EBEBRATT-Ed

@JP2347

I think you need to check the expansion tank and put on a few gauges. If your getting to 25 on the suction side of the pump and discharging into the boiler that could get close to the relief valve setting.

If the tank is ok you could go for an additional tank or just put a larger one in.

or you could move the pump to the boiler discharge.


Weil Mclain used to (maybe still do) ship their boilers with the circs mounted on the return. They didn't want to change to pumping away. So they showed in their instructions putting the expansion tank on the return on the suction side of the pump so they could continue shipping boilers wit the pump mounted on the return.

If you move the pump to the boiler discharge and leave the air sep and ex tank as is you will be pumping away as the pressure drop through the boiler is low. It will put the boiler under a lower pressure being on the pump suction and keep the relief valve from opening.

Your choice but I would confirm what is happening with gauges and check the tank air pressure.

Have you ever checked temperatures across the boiler supply and return with the heat cranking to check the TD? You could be overpumping the primary

JP2347

My tank is pumped up to 15 psi I repiped some things ill update tomorrow once I hear from the customer. I was at 125 on the boiler didn't get enough time to stay and watch get to temp.   I had another client to get to. Here's the new updated pictures and yes I need different supports for that expansion tank it is supported for now but it looks ugly. No td I ran of time for today 

EBEBRATT-Ed

Good job looks nice that should fix it as long as the ex tank is large enough

JP2347

Amtrols website called for an ex-60 but I put an ex-90 🤷‍♂️. Net output of 125000