Water Heaters - Boiler Relief Valve Problem

The relief valve on my KV85 Burnham hot water boiler keeps going off. I replaced the valve but the problem persist. The Boiler has a tankless coil hot water system. On reading some post I checked the compression tank pressing the air valve at the bottom to see if its water logged. Nothing came out. When the relief valve goes off for an extended period I hear knocking in the radiator throughout the house. I understand from previous post that a leak in the coil may be a possible issue. If so, can the coil be repaired? or must it be replaced? I am pretty handy, what step do I take to replace or repair the coil IF that's the problem. I have suffered with the problem of the the relief valve going off several time per day and has to be reset / flipped manually. Thanks for you help

I don't like it when you tell me the radiators/baseboard are knocking. That tells me (without enough info) that the boiler is heating much to high.

We need you to get us some information.

Find the temperature/pressure gauge. I need to know what the both the readings are when the boiler is dormant, and when it is running, and up to temp(high point when boiler shuts off). I also want to know, does the relief valve (PRV) constantly leak, or just while the boiler is running, or up to temp.?

You could have any of the following problems...

Bad expansion tank - PRV would only leak when boiler is hot or up to temp. pressure reading of 30psi
Bad fill valve - PRV leaking constantly, pressure reading of 30psi
Leak in hot water coil - PRV leaking constantly, Pressure reading of 30psi
Boiler control not working properly - PRV only leaking when boiler is running, Banging of pipes, may have normal pressure readings but abnormally high temperature readings causing steam.
Bad relief valve ( which you replaced )

Get back to us as soon as possible.

Just checked the boiler. It apparently just shut off. Exhaust is still hot. Temp 220 / psi 30. The area below the PRV is wet. Water clearly was running but stopped. There is no dripping.

Strangely, the knocking I mentioned only occur when the PRV is open for a while. Eg the occasional knocking let me know that the valve is releasing. Even stranger, the knocking occur even when the thermostat is not calling for heat -- radiators are cold. Hope the above info help you to narrow your diagnosis of possible causes. You stated that you are concerned that the boiler may be to run too hot. What would cause that? The expansion tank is relative new.

A hot water boiler system is a closed system, (similar to the cooling system in your car), so you can go higher than 212* before the water will boil, But when air is introduced, as when the relief valves leaks by, you will get pipe banging because your boiler is producing 220* which is turning to steam.

First off I would turn down the Hi-limit control to 180* and the low to 160*. In the winter you can turn them up no more than 20*.
Next, why is the pressure up to 30psi?

I need to know what the pressure is when the boiler just comes on or is off for a while.

I was able to observe the system perform its low / high cycle this morning. It came on at a low temp of 195* / psi 10. It shut down at about 215* but temp continue to climb after is shuts off and stoped at 220*(as a result of it being a closed system as you stated). Psi stopped at 30 at shut down cycle. As the psi moved close towards 30 * the PRV begins to drip and I could hear the steam being released. How do I make the adjustments you proposed? How do I adjust the low / high cycle in temp and psi. I use a 1.35 nozzle. I doubt if that have anything to do with it.

Good Morning:gmorning:

First off, the problem is definitely the expansion tank. I have very rarely been able to just pump air into them, You will need to replace the tank.

To change the temp settings, you need to find the operating control. It should be a gray electrical control box. Loosen the screw and remove the cover. There should be two tiny sometimes red knobs with little pointers. Check their settings and make adjustments as I previously stated.

Sounds like a fix. Appreciate you sharing your valuable expertise. I will purchase and install an expansion tank tomorrow, make temperature adjustments as you suggested and then report back. Till then. . .

Earl:thumbup:

I just changed the expansion tank, thankfully the psi stabilized. The system shuts down at about 22 psi as opposed to near 30. Unfortunately the temperature gauge still exceeded 220 (The high low setting on the box is 165/185, so I did have to adjust it) Here is how I proceeded. I shut down the system, installed the new expansion tank. I drained off some of the water from the boiler which lowered the psi as well as the temp. I waited until the temp dropped to about 170* before switching it back on. After switching the system back on, the psi stabilized as I stated but the temp we back to it's old ways. I hope by morning it will some how adjust itself. If not would the issue then be a leaking heating coil? It that':confused: s the case would the coil have to be replaced or can it be repaired?

If your pressure comes down when the boiler is cooler, the fast fill or the tankless coil are not the problem. With either of those items, the pressure would stay at approx. 30 psi at all times.

Sometimes the temp setting and the temp gauge will read differently because of locations.

You could also have a faulty temp gauge or control sensor.


How is it running today? Maybe you should lower the fill pressure to 12 psi. If all is well it would run from 12 - 17 psi during operation. To lower the fill pressure let the fill valve fill to stopping. If higher than 12 psi, you will need to make an adjustment to the fast fill pressure reducing valve.

BTW - Did you purge the system after replacing the expansion tank?

It running relatively normal. No spill or dripping from the PRV.

Yes, I did purge the system AFTER replacing the ET. Come to thing of it, I may have had the valve to the ET closed at the time.

I tried to play with the temp adjustment a little this morning -- placing both settings a little lower.

I don't know if this means anything -- I have noticed over they year that when the system is powered down for a while (no oil or power outage) the area around the tank less coil housing drips. I assumed that it simply had to do with expansion / contraction realities. Just thought I would mention it.

I shut the power down an hour ago. I want to observe how it progress with the temp much lower than I have had it so for.

I am wondering now if the system may have been running at high temp for years, but only manifested now because of the ET failure, which triggered PRV release. I that senerio reasonable?

I will examine the sensor, gauge, etc at replace as necessary.

Any thought on the drip around the coil area when the system get cold from being down for an extended period?

Hi

As far as the coil drip is concerned, I would agree that the reason for the drip is caused by expansion/contraction of the boiler combined with the gasket getting older and does not flex like it used to. In fact it is probably hard, so don't touch it. If it starts leaking when the boiler is running, replace immediately. If you need to drain down the boiler for any other servicing, I would consider replacing the gasket at this time. They are not too expensive and if you wait too long you may not get the bolts out. If the bolts look bad, spray them before making a final decision about replacing the gasket.

All is well. No more spills or drips from the PRV. I cannot thank you enough for walking me through the necessary fixes.

I will take your advise and change the gasket before it fail. Bolts are a little rusty. Over the next several days I will be spraying them occasionally with WD40.

Thanks again for generously sharing you knowledge. It's abundantly clear that you do know your stuff.

"May your tribe increase"

We make a good team, You be the hands and eyes, and I will be the knowledge. Good job:thumbup::thumbup::thumbup: