I've had a Triangle Tube Prestige Excellence 110 combi (small internal DHW tank) running since March, 2009. The small DHW tank works fine for our empty-nest.

I've been trying to eliminate a banging (water hammer?) in one of my three space heating zones pumped by the 110's internal pump. I'm not convinced it's water hammer - it may be due to poor installation of this zone's piping .... a lot of it is buried between a very old basement ceiling and a "newer" ceiling installed in the '70s.

The noise only happens when this one zone is "on" and the 110 control switches to DHW heating priority - 20-to-30 seconds after either a shower or the wash machine starts. I hear the banging noise almost simultaneously with the internal valve stopping the space heating flow and opening the flow to the DHW tank. If two or more zones are "on", then it doesn't do it.

I've talked with my installer (a very competent guy) and he had me verify that the expansion tank was plumbed in the right location (it was) and he had me check the expansion tank's air pressure (it was OK). So lately I've been tightening up the few locations where the piping in the noisy zone is exposed, but the noise is still there.

In a Nov 12, 2010 posting (partial below) a forum member said there was a "special pressure relief tube that needs to be plumbed in". I'm wondering if this might be something that was missed in my installation. Can the member (or other readers) give me some detail on what that might be?

Thanks in advance for any help you can give me.

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Member jgalak wrote ..."No experience with the Excellence (just the Solo 110), but based on what the factory training taught about the Excellence, there are 2 issues you need to be aware of:

1) The DHW tank in the Excellence is very small. .....

2) If you are zoning with circulators, there are no special issues. However, because of the way an internal valve works, if you zone with valves, there is a special pressure relief tube that needs to be plumbed in. If this is your situation, let me know, I'll post more details. Not sure if this issue is in the Excellence manual, but it's something they emphasized at the training (for good cause)."

 

Not to say that the tank pressure is or isn't the problem, but exactly how did you check it?

I don't know if jgalak is still visiting us or not, but you might try a private message to him and ask about the details. (I don't know them...)

 

Thanks.

I did send the request to jgalak privately several weeks ago, but heard nothing back. I'll try again tonight.

I checked the expansion tank pressure with a tire gauge .... not very accurate but it indicated 10 psi.

 

And you looked in the manual to no avail?

Before you checked the tank, did you drop the boiler pressure to ZERO? If not, you won't get the correct reading. You would get a reading on whichever pressure was HIGHER... if the tank were at say 5 PSI, and you had 10 PSI on the boiler side, your gauge would read 10 PSI, NOT the 5 PSI of air that was actually in the tank.

So, if you close the water feed valve to the boiler, drain a little water off the boiler until the gauge reads zero... THEN check the tank, you will get an accurate air charge pressure reading.

You should do this at LEAST every two years... those tanks lose about 1-2 PSI per year.

Either way, if the gauge IS accurate, 10 PSI is on the low side.

 

Hey, sorry, haven't been on. First off, I agree with NJ Trooper - my first concern would be to check the expansion tank air pressure when there is no pressure on the water side of the boiler - NJ Trooper posted the directions above.

As to the pressure relief tube for the Excellence install - I doubt it's your culprit, as it generally causes problems when all the zones close, not when one is open, but I suppose it's possible. Here's the issue - if you zone with valves, when a valve is closed, there is no waterflow through it at all. The Excellence has an internal shuttle valve that switches the boiler output side from space heating to DHW heating. This is a positive shut-off valve - when the valve is in the DHW position, there is no waterflow from the zone side at all.

The problem occurs when zone valves are installed on the return side of the zones, (or, if they are on the supply side, when there is a long piping run between the boiler output and the zone valves). It sounds like you have the system piped through the boiler, so look at Fig 11 in the Excellence boiler manual. If you are plumbed exactly as shown, and the distance between the boiler and the zone valves is short, no problem. But if the zone valves are on the return side, here's what happens (imagine the zone valves, 5, aren't placed as drawn, but are rather to the right of the zone load):

When a zone calls for heat, the internal shuttle valve (the thing just downstream of the CH circulator in Fig 11) switches to send water to the zones, a zone valve opens, and water flows fine. As the water heats up and expands, the "excess" water goes to the expansion tank. All is good. But once the heating call ends, the zone valve closes, and the shuttle valve goes back into the DHW position, cutting off the supply manifold from the expansion tank . The zone is already cut off from the return manifold by the zone valve. The result is that as the water in the zone cools, there's no way for the "excess" water that was previously pushed into the expansion tank to get back to the zones. As a result, the contracting water can cause a partial vacuum, which leads to banging, "sucking in" air through joints and valve seats, and even water hammer as the zone valve re-opens on the next heat call. (note that the same thing happens if the zone valves are on the supply side, but the piping run from the boiler to the zone valves is long - the problem occurs in that long run)

The pressure differential valve won't help with this - it's designed to relieve high pressure on the supply side, not low pressure.

The solution is to put a small capillary tube between the supply and return manifolds. This will allow just enough flow to relieve the pressure and allow the water from the expansion tank to migrate back into the zone plumbing. Another solution is to just use P/S piping.

 

I do need to ask this: Are you certain that the valves are installed in the proper 'direction'?

 

Thanks guys. Good questions and comments ... I'll relay to my installer and have him come check the expansion tank in the proper manner. Will update the forum with any findings.

RogerDUB

 

Checking the expansion tank is an easy DIY project, if you feel up to it. Simply do this:

1) Close the makeup water valve. This is the valve that lets more fresh water into the system, it should be somewhere between your house's cold water lines and the PRV (pressure reducing valve).

2) Close all the zones - either set all thermostats to not call for heat, or just turn off power to the zone valves, so that they close.

3) Open the boiler drain, or any other drain valve that is not cut off from the expansion tank by a zone valve (or the boiler's aforementioned shuttle valve). Ideally, there should be a drain right next to the expansion tank somewhere.

All you need to do is crack it and let out enough water that the pressure gauge on the boiler (small dial) goes to zero. As soon as it hits zero, close the drain valve.

Be careful, the water may be hot! Either put a bucket under it, or run a high-temp garden hose from the drain valve to a sink or other drain.

4) Using an auto tire pressure gauge, check the charge in the expansion tank. There's usually a small plastic cap on the end opposite the pipe that needs to be unscrewed, and under that will be a stem that looks just like a tire fill stem. Measure the pressure there.

If the pressure is in the 12-15 psi range (for a 2 story house), you are fine. If it's much less, the tank needs more air - probably something you shouldn't add yourself. If there's any water coming out as you measure, the tank is blown and needs to be replaced.

 

How come why not? I usually think that if someone can fill a bicycle tire, they can charge an expansion tank, no?

 

Because I have no idea how tall his house is, and what the pressure was set to on the PRV (should match the tank charge, no?). So while sure, it's easy enough to charge to 12 psi, what if he needs more (or less)?

There's no harm in checking though - if it's much more or much less than 12-15psi, then it needs further investigation - maybe it's ok, maybe it's not.

 

I guess good point... I'm sure we could instruct on what to set to though...

I do doubt however that it's related to the water hammer though.