strange pressure problem

Pinball

I installed this system over a year ago. It has been working flawlessly until now. The first problem was a leaking relief valve (blowing off at 20lbs). I went to the house and found the pressure climbing to 30lbs only when more than 2 zones would call for heat. I replaced the relief valve and the expansion tank (ruptured blatter).
worked fine for 2 days.customer called and said pressure had climbed to 20lbs when boiler fired. and would drop to 12lbs when off. I set the pressure to 12-15lbs and shut the feeder off to check to see if it had gone bad.
Pressure was fine for a couple of days and I went there to replace the feeder.When I got there, I noticed that when the boiler fires, the pressure climbs to about 20lbs and stayes there, UNTIL the primary circ. shuts down. Then it instantly hits 30, for a couple of seconds. The only thing left I can think of is the indirect water heater. I really hope thats not it, The supply house said I would have to pay for a new one up front until the MFG can verify a leak.(I feel I'm at their mercy!) Also the customer refuses to spend a dime.(they paid over 600k for the house less than six months ago, and does not really care about warrantee issues) I guess it's the cost of doin business :( anyway is there anything in the piping that anyone can see that maybe a problem?
your help is greatly appreciated
PS. This was done for a friend of mine (builder) long before I discovered "the Wall" I have learned a lot just hanging out and reading since but this one has me baffeled
Al

S Davis

Pump

One thing I have seen is the main pump causing low enough pressure behind it to cause the fill to feed water into the system, what size pump is that on the main loop it looks like a UP26-64 it might be over sized depending on the head loss through the boiler.

S Davis


Apex Radiant Heating

Mark Eatherton1

Got drawings???

Al, I can't tell anything really from the photogs. Can you generate a drawing showing the locations and relationship of the pumps, boiler and expansion tank?

Are you pumping away from the expansion tank AND towards the boiler with your primary, or what?

ME

Ray Landry

Here's a couple of thoughts...

1) The expansion tank doesn't have the proper pressure in it to handle all of the system water content

2) The primary pump has a check valve, and when it closes, the water which used to be able to expand into the radiant system, is now trapped in a much smaller boiler loop, and if the expansion tank is a problem, the pressure is climbing because of this

Pinball

Thanks Mark,
Im not sure how to "draw on this puter thing but I can tell you, The boiler has 3/4 tapping comming out, after the relief valve, I increased it to 1-1/4 then the air scoop (#30 extrol hanging under it) aprox 10" to the indirect piping (3/4" secondary with it's own circ and flow valve) then another 10" to a up26 circ. Another secondary about 10" from that and then into the boiler.

All circs are pumping away (Primary UP-26 and two secondarys UP-15(?)

Al

Pinball

Hmmm?
The circ don't have checks but that is an interesting concept...

Pinball

It is a NTI Trinity and The circs are the exact ones they recomend. It does have a high head, and is a condensing boiler

Thanks

Al

Big Ed

Directions

I would lke to see the directions from the manufacture. I don't like the look or the feel of the 1 1/4" -3/4 " through the boiler primary loop. I would like to see a bypass across the boiler. I see alot of pent up pressure bouncing off the compression tank........ maybe I am blind.

Pinball

Hi Ed,

The boiler itself is prepiped from internal with 3/4"

The Book and the MFG rep. says to increase it as soon as possible. According to them, it's the restriction through the HX that gives it the efficency. Also I have two secondary loops, one with 12 zones (3000ft.1/2" pex-al-pex) and one for the indirect. I don't think I could feed all that on a 3/4 main.

However you did give me an idea, someone else (a while back) said I could pipe the boiler as a secondary with it's own circ.
What do ya think?
Al

Uni R

Ultras

Should work; W-M's instructions for Ultras show it just like that. However, your layout is practically straight out of the installation guide and I doubt that it is the cause. The only other thing they suggest might be a scoop on the secondary. Do you use both the primary circ and the indirect circ for hot water calls?

Why not just isolate the indirect and see if you still get the spike? If it spikes then you can cross it off the list of suspects.

Big Ed

Heat Exchange & Pressures

I always thought with heat exchanges that it's best to decrease pressure for collecting of energy while increase pressure for dispersing of energy.

Maybe the Risistance is for a larger delta T ???

Tony_8

My opinion

I've not installed or serviced a Trinity, in particular, but this seems to be a piping issue.

The length of 1/2" pipe between the scoop and tank can have an effect on that momentary boost in pressure, also that ball valve may not be full port, compounding the problem. Sounds like you have quite a bit of volume in the system, as a whole. That would explain the 2 or more zone thing, more water = more expansion, hence, more tank.

I believe (MHO) that you would be better served by piping the boiler in as a secondary loop with it's own circ. No flow problems for any part of the system that way.

jesse the great

im pretty sure you should put a #60 expantion tank in give that a try

jim_49

I think your problem is very easy to fix. Install a ceiling hung EXPANSION TANK and leave the EXTROL TANK still on the system. Sounds stupid to have 2 expansion devices on one system, but trust me you will not have any more problems, been there done that.... From my past experience in doing this, I found it best to put the extrol tank on the return side and the ceiling tank on the tap on top of boiler or air purger..