UFT-199 Rumbling on high fire

MGI

I (heating contractor) have a HTP UFT-199 boiler that is experiencing a bad rumbling in the combustion when in high fire. I have checked manifold pressure, performed combustion analysis, etc. Burner plate was removed and inspected for the typical PVC crumbs, all clear. The unit only has problem in high fire, and when it does, it’s scary. The whole unit shakes! I’m hearing of an issue with some of these having a problem with the burner / body assembly being undersized. Any help would be appreciated as I wait to hear from the manufacturer. Have locked boiler into low fire so they at least have hot water for now. Thanks.

Alan (California Radiant) Forbes

The heat exchanger is not happy. Check the pump to make sure you're getting full flow at high fire. If it's a 3-speed pump, turn it up a notch.

It could also be some kind of build up inside the heat exchanger. It may need to be flushed with a scale remover.

STEVEusaPA

What do you mean you 'checked manifold pressure'? What was it in low fire, then high fire?
What were the combustion numbers in low fire, then high fire (if you got them)?
Pressure drop on light off?
Gas piping? Type? Diameter?
Any error codes/history’s?
Did you scroll thru and check all the parameters?

mattmia2

Isn't there a flap in the intake or exhaust that had an issue in early versions?

GroundUp

Low flow perhaps, how's it piped?

Zman

GroundUp said:

Low flow perhaps, how's it piped?

That's my bet.

MGI

It’s a combustion issue, not heat exchanger. Unit was in service for 3 years. The flame pulses intensely when in high fire. I have 7.5 “ wc inlet on gas valve. Not a pumping issue.

Zman

What is the supply/return delta on the boiler control at high fire?
What were the combustion numbers high and low?
How much and what type of piping is between the meter and regulator and the boiler?

coby

High efficiency boilers have traps, clean. probably plugged up (really condenses during high fire ).

pecmsg

MGI said:

It’s a combustion issue, not heat exchanger. Unit was in service for 3 years. The flame pulses intensely when in high fire. I have 7.5 “ wc inlet on gas valve. Not a pumping issue.

OK

And how do you know this? You've posted no information except for incoming gas pressure.

pecmsg

MGI said:

It’s a combustion issue, Not a pumping issue.

Where are your Combustion Analyses #'s?
Where are your Delta T & P #'s

MGI

At this point I think I will close the post. Thanks for the input, but the boiler is being condemned. The exhaust tube is cracked and it has rained inside the boiler. Thanks anyway. I don’t want to seem ungrateful for the feedback, but the responses seem to have gone off topic. For example, a flow rate of water may cause boiler noise, but will not make a flame shutter. Again, thank you.

pecmsg

MGI said:

The exhaust tube is cracked and it has rained inside the boiler.

We didn't go off topic you didn't answer questions needed to properly diagnose the problem.

Why is the exhaust tube cracked on a 3 year young unit? I can think of a few reasons, You might want to get the installing contractor back and find out.

BillyO

I had 3 boilers already with same problem. HTP knows about this. they replaced all 3 without any issues. interior of boiler condensing and all parts started corroding. hopefully this was within parameters of post. Good luck

Alan (California Radiant) Forbes

MGI said:

I don’t want to seem ungrateful for the feedback, but the responses seem to have gone off topic. For example, a flow rate of water may cause boiler noise, but will not make a flame shutter. Again, thank you.

Do you see how this works? We ask a lot of questions and give you a range of likely causes based on a vast, cumulative body of knowledge, eventually zeroing in on possible solutions.

MGI

Thank you BillO. I have seen this on others branded boilers with same exact design. Was the confirmation I needed. I really didn’t mean to offend anyone here as I know there are a lot of clueless people posting things and have no right owning a screwdriver, but I assure you I’m not one. The cracked exhaust is really a Kiturami mfg defect and I know the material has been changed on that. Thanks again all.

ch4man

clueless,,,,, wow

MGI

By clueless I meant homeowners posting.

Jamie Hall

MGI said:

By clueless I meant homeowners posting.

Son, a number of us are homeowners... or at least we are not professionals in the sense of making a living installing and servicing heating and ventilating equipment. As in most things, a blanket indictment is, perhaps, unwise.

Zman

When I get stumped troubleshooting, I want people to challenge my assumptions and throw out questions that I didn't think of. That's how the really tough ones get figured out.
The discarded questions about flow may be the solution in the end. Inadequate flow may have cause the HX damage, if this is the case, history will repeat itself.

fenkel

What about overheating the hx... was the post purge set on unit? What was the design temperature for heating system?
Was postpurged function bypasted by using an aftermarket zone or relay controller?
We've installed several ufts and add time to the post purge timeout function...
We noticed that the boiler would shut down and retain its heat..