WM VHE-5 problem

Grumpy_2

I ran across a VHE-5 today that is on a converted 2-pipe system. The supply water temps will not increase above 120°F. Return water is at 106°, supply hangs in there at 116° +/- a degree or two. Boiler is in constant fire mode, but water temps never change. Any ideas?

Paul Mitchell_2

just a guess

I would have to guess that it is way undersized. Or possibly there is a supply problem with the gas. Maybe you are not really getting the proper BTU's out of it. Was this a problem forever or new this year?

Grumpy_2

This is the 5th year of operation, system has always been good until now. No problems with it through several cold spells of 0° or so in past years, but it is stuggling to heat the structure now in 25° weather. Gas pressure is right on the money. I have closed off 60% of the emitters just to see if the boiler temp will rise, no change in supply temp at all, the delta T reduces to 5-6°. High limit is set at 190° but it never gets close. It never shuts off because it can't satify the load. Why this happened all of a sudden has me stumped.

STEVE N

a few questions

Grumpy,
My company sells Weil Mclain so I do have some knowledge on your problem boiler. I have a few questions. What circ is on it and has it been changed? Is there a bypass from supply to return? I will check at work tomorrow and see what I can find for you.

Steve

Grumpy_2

It has a B&G 100 on it,and I don't know if it is original to the boiler. Also there is a by-pass between the return and supply. I did close the bypass in an attempt to raise the supply, but that didn't work either. Since my temps are so low, I now have the bypass at about 30% to allow for boiler protection, but since I can't get the supply temp up, it isn't doing much good right now.

STEVE N

a few more questions

Grumpy,
I have a few more questions, Did you happen to take off the collector and check the sections for soot? I know its unusual but I have ran across it once where the family owned pets and the burner tubes got hair in them which really messed up the burn and actually sooted the sections so bad it actually caused a insulation effect... and poor boiler performance.

I am assuming that this is natural gas? Test the outlet side of the gas valve while its running and see what your residual inches on the water column are.

I will check in tomorrow then check with my Rep

Steve

Constantin

I have a dumb question...

... have you turned off the water feeder to the system? Imagine if you had a leaking return somewhere where you can't see it and the boiler keeps getting "replenished" with 40°F hot water. That could be your problem.

Grumpy_2

Ok Steve, I'll have a look at those situations today. Thanks for your help.

Grumpy_2

I checked for that possibility, no leaks found, and water pressure remains constant at 18psi, running and static.

Dale

Stack temp?

What's the stack temp?, too high and a dirty heat xchanger and the heat goes other than the water, also does this have a thermostatic bypass? sometimes they don't open enough. Have you clocked the gas meter? does that match input specs? what's the delta tee from the rads? Is the pump amps normal for flow, I wonder if you are missing some impeller.please let us know what you find.

[Deleted User]

I would check

the secondary heat exchanger. If dirty, a problem. If the fins are rotted off, a bigger problem.