Calibration of Water Temp Instruments; Hot Water Heating System

[Vince]

On Wednesday I had service done on my oil burner hot water heat sytem. The boiler is a Peerless WBV3, has an embedded hot water coil, L8124 triple Aquastat control.

Just as the service tech was writing out the bill, leaning on the boiler cabinet, the temperature/pressure relief valve blew off excessive T/P. Scared me; made him chuckle, I think.

The water pressure was at 10 psi. The Aquastat was set for

180Hi/160Lo when the relief valve blew open. The water temp gage on the boiler indicated about 190 F.

Tech reset aquastat for 160Hi/140Lo.

I presume that the gage on the boler is more accurate than the aquastat sensor or it should be the sensor to calibrate by. Opions on this ???

Is there a need to clean out the domestic hotwater coil? The boiler was installed in Jan 1992.

I have watched the boiler water temp gage in the past. I have seen that the water temp continues to rise after the fire was shut down. But this was the first time that the relief valve blew open.

de ~ Vince ~

[Bob]

That's a pressure relief valve, NOT a pressure/temperature relief valve.

[Vince]

Well that is an interesting comment.

The tech referred to it as a T/P valve. It is located at the rear wall of the Peerless WB3V boiler. As I mentioned, the tech reset the acquastat settings (lowered) and no blow off since WEDnesday evening.

There is a pressure relief valve at the front side and is connected near the domestic hot water heat exchanger (embedded coil).

In fact, the installer in 1992 failed to include that pressure relief valve, and the town plumbing inspector spoke up to me. I then told him the name of the guy that did the installation. This led to a litigation between the heating guy and the town gov.

[m Ransley]

You mean the tech was there and couldnt figure it out, Start by looking at the Pressure Relief that blew and read its Lb rating. I dought its

10lb, so start over in your thoughts, its pressure related and the boiler is showing 10lb.

[Bob]

That size Peerless comes with a 30psi relief valve already installed, so it' s doubtful that the installer removed it during the installation. It's most likely that your town requires a combination pressure/temperature relief on the domestic hot water systems. They are normally 210deg.F, and anywhere from 75 to 150psi. They do make domestic hot water pressure only relief valves, but if your boiler had that much pressure in it, the boiler would have been severely leaking. If the relief went off on temperature, then the boiler would have probably been jumping all over the floor.

What may have happened, is the boiler temp and corresponding pressure went down to room temp during the service. Then, either the automatic water feeder or the technician added water. After the boiler heated up, the pressure went above 30psi, and the relief went off. The 10psi pressure you saw was probably after the relief went off. Those relief valves don't change their setting, they usually just start leaking.

[Vince]

Hi Bob:

TNX for your info and comments.

Th>That size Peerless comes with a 30psi relief valve already installed, so it'

To be clear, I am not referring to the relief valve that came with the Peerless WBV3 when I mention the valve that blew off.

Upon inspection by the town, there was no relief valve of any kind at the domestic hotwater output side of the coil.

I have tried to take a closer look at the markings that are on the relief valve located at the domestic hot water output. I was able to see WATT, a 125 arc line, 150 arc line, and a 175 arc line. This was approved upon reinspection by the town plumber. I presume that this valve is set to release at 125. Now would that be degrees F or psi units ? ? ? My guess is that it is degrees F units for that valve.

Yes, the service tech read the gage's indicator as 10 psi. He shut down the oil burner and then operated the Fast Fill lever on the INPUT water pressure regulator at that point.

I kinda hope that your theory of what might have happened is the case, because with the 160Hi/140Lo settings at the acquastat, my wife has already shown concern that there is NO Hot Water, again,,,,, after service..... She complained today while the system room thermostat was in the setback position. (BTW, I am on Long Island in NYand we have 45F today outdoors.

So, perhaps I can raise the settings back to 180Hi/160Lo ?? and keep a large bucket under the boiler's relief valve. The basement is unfinished, so a small flood can be tolerated.

[Vince]

I mean the gage indicated 10 psi after blow off. There is not enough clearance for me to view any markings at the boiler relief valve. It will require a strong light source and a mirror.

The service tech's conclusion was that the triple acquastat and the boiler's temperature gage were not in agreement. Thus, he reset the acquastat to a lower setting: 160Hi/140Lo.

I monitored the boiler's water pressure and water temperature gage a few minutes ago, began with the system not calling for heat ( a fire ).

The boiler water pressure indication was 28 psi and the boiler water temperature was sitting at 155F. I ran the hot water into the washing machine while monitoring further.

The oil burner came on at about 145 F and it shut down at about 155F. The psi was at 29psi and the water temperature rose to about 175 degrees F.

[Bob]

I can't remember ever seeing a P/T relief that wasn't 210 deg. F, so those markings may be pressure.

Normal residential boiler pressure is 10-12 psi. The tech should not have added water unless he had reason to believe the gauge was wrong. If the boiler relief keeps going off at 30psi, then you either have a leaky automatic water feeder, or a problem with your expansion tank. What was the original service call for?

There's no danger in turning the 8124 back up to 160/180 (always make sure you keep 20 deg. between the hi and lo.) You also might want to turn your dif to 5 deg. The burner will cycle on and off more, but your water temp will be more constant. If your wife isn't happy, you can't be happy.

[Vince]

Original reason for service was no hot water/no heat. He first replaced the nozzle and in-lin filter (my parts). He then checked the transformer, which gave no spark. Also vacuumed cleaned boiler and flue pipe to base of chimney. Refused to vacuum clean the combustion chamber.

(The system was tuned and vacuumed on NOV 18th, '05. There was a (slight) puff back last week, and now the xfrmer went bad !) He changed from a 0.85 GPH to a 0.75 GPH nozzle because the fire was too large when burning cleanly and excessive back pressure with a Carlin CRD101 burner pak.

I'm thinking about changing to natural gas. Can my Peerless WB3 be re-setup with a nat gas burner ? I wouldn't need to worry abt blowing a hole into the back wall or about soot flying in the laundry area.

[Bob]

Ignition transformers go bad all the time, but it's a good bet that it was weak on Nov. 18th. As for the puff-back, NEVER push the reset more than once. That combustion chamber doesn't need vacuuming. Any soot in it will burn off.

In the future, if you want someone to guarantee their work, let them use their own parts. If you don't, they can always blame it on your parts.

That boiler is rated at either .60 / .85 / 1.10. I never saw one with a Carlin 101, but with a Beckett, anything over .60 is too large, because it's only a 3 section boiler, and the rear wall of the firing chamber is too close to the burner end cone. This is true about all brands of 3 section boilers, but Carlins tend to overcome some back pressure problems.

The only way to change to natural gas, would be to put in a power gas burner, but I suspect that you'd have similar firing problems, and with natural gas, instead of a puff-back, you just might not wake up the next morning.

[m Ransley]

Boiler is 28lb at 155f ? did you say its a 35lb relief? What is cold lb on boiler . I have 3 storys boiler in basement-4th level and keep lb at

12-15 cold. On my recently new boiler it would rise stearily as temp rose till at 160f it blew the 35lb relief, Solution, after arguing for a year and hack trying different gimmicks and blaming me I had the boiler guy do other work then refuse payment till he fixed it, he did and Weil mcLain was right, expansion tank was to small, it got fixed. Either he overfilled it, auto feed is bad, or expansion tank probablt to small. Lower water level to 12-15 cold- 90f or less and see if it rises with temp. Turn off auto fill, they dont last anyway. If it raises with temp its the expansion tank.