MasterTemp 250 vs. 400 heater parts

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Bazul

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Aug 5, 2017
7
Becker
So over the winter mice got into the heater through the blower and FILLED the kettle full of insulation and acorns. It took me a while to determine that's what was going on but when I did I completely disconnected the heater and brought it into the garage. The heater was up against the house so working in the garage made life easier and I could work after dark. Since the heater was originally installed in 2010, I figured I might as well do some preventative maintenance (maybe the real mistake) so I ordered Stack Flue Sensor, Thermistor, Pressure Switch, Hi Limit Switch 135°F, Gas Shutoff Switch 140°F, Igniter and a new orifice for the blower (mice chewed themselves a bigger opening in the grate and that's how they got into the blower). I also bought some 1/4" wire mesh and did a DYI mouse proof job on the heater as a whole.
  • Compatible Replacements for Part Numbers: 42002-0024S, 42001-0053S, 42001-0060S (3902), 42002-0025S, 42001-0063S.
  • Igniter Replacement Kit 77707-0054
I'm thinking I'm pretty cool...

As I'm attaching the last part on the heater in the garage (side panel that was facing the house) I notice the sticker that says MasterTemp 250. I could have sworn it was a 400.

Question #1: I surmised that the sensors I ordered and installed should be the same for both. They all fit fine and flow is flow, temp is temp, etc. Am I correct?

Question #2: When I now fire up the heater, the blower blows, gas flows (watching the natural gas gauge on the house). I think I'm hearing a click from the igniter (I'm not sure) but eventually the blower stops with a service heater light. I don't get any sensor indicator warning lights on the back of the control board...but I do get 3 red blinks from the Fenwall reporting "ignition lockout". Do I need to tear the whole thing apart again and put the old igniter back?
 
You can check part #s to see if the parts are the same. For the ignitor, did you replace it? I imagine that part is the same. They are consumable as well and last 3-4 seasons at best. Fragile too.
 
Bazul said:
So over the winter mice got into the heater through the blower and FILLED the kettle full of insulation and acorns. It took me a while to determine that's what was going on but when I did I completely disconnected the heater and brought it into the garage. The heater was up against the house so working in the garage made life easier and I could work after dark. Since the heater was originally installed in 2010, I figured I might as well do some preventative maintenance (maybe the real mistake) so I ordered Stack Flue Sensor, Thermistor, Pressure Switch, Hi Limit Switch 135°F, Gas Shutoff Switch 140°F, Igniter and a new orifice for the blower (mice chewed themselves a bigger opening in the grate and that's how they got into the blower). I also bought some 1/4" wire mesh and did a DYI mouse proof job on the heater as a whole.
  • Compatible Replacements for Part Numbers: 42002-0024S, 42001-0053S, 42001-0060S (3902), 42002-0025S, 42001-0063S.
  • Igniter Replacement Kit 77707-0054
I'm thinking I'm pretty cool...

As I'm attaching the last part on the heater in the garage (side panel that was facing the house) I notice the sticker that says MasterTemp 250. I could have sworn it was a 400.

Question #1: I surmised that the sensors I ordered and installed should be the same for both. They all fit fine and flow is flow, temp is temp, etc. Am I correct?

Question #2: When I now fire up the heater, the blower blows, gas flows (watching the natural gas gauge on the house). I think I'm hearing a click from the igniter (I'm not sure) but eventually the blower stops with a service heater light. I don't get any sensor indicator warning lights on the back of the control board...but I do get 3 red blinks from the Fenwall reporting "ignition lockout". Do I need to tear the whole thing apart again and put the old igniter back?
Click to expand...
Only difference in parts is the heat exchanger/manifold and the air orifice for the fan. You didn't replace those, so no problem there.
 
20240531_144921.jpgOK. Not the ignitor so I took it apart again and fully opened the kettle, before I just vacuumed out through the blower mount hole. Some debris, I'll give it a thorough cleaning hopefully it's that corrosion causing flame sense current to get lost theory.
 
What is the condition of the refactory blankets?
 
ajw22 said:
What is the condition of the refactory blankets?
Click to expand...
Interestingly, the only insulation in those heaters is what you see down the center of the copper tubes, the burner is down there and the bottom of the drum could get very hot otherwise. There is no other insulation. I've only opened 6 or seven of these heaters that far, but have never seen any insulation. When checking the exhaust temps, which should be in the 300+ degree range, you see that the temperature on the outside of the exchanger but against the drum walls is really not that hot compared to inside the tube bundle.
Unlike other types of heaters (ones in a box not a MasterTemp) where the flame is in a chamber below the exchanger and needs the refractory to keep it in the combustion chamber these type use the heat exchanger to collect heat that would get to the steel drum and the fan/blower directs the heat out the exhaust.
This is all that is listed when searching for Sta-Rite/Master Temp insulation kit:
1717200044999.png
 
1poolman1 said:
This is all that is listed when searching for Sta-Rite/Master Temp insulation kit:
View attachment 579725
Click to expand...
Yeah, that is what I was asking about.

1717200044999-png.579725
 
That is correct. Those are the only insulation pieces I found when opened, they sandwich the copper pipes from the manifold and they seem in fine shape.

So what's my next step to solve the ignition lockout indicated by 3 red light blinks from the Fenwal?

I start the heater either manually with a jumper or via automation and it shows 128 then r=8. It makes it past all the initial sensor checks. The blower starts and runs for a few seconds (maybe 15-30) I assume as a safety to make sure there's no sitting leaked natural gas. Then a click and gas starts to flow. I see the gas meter run and hear it squeaking. This only lasts a few seconds (3-5), I can smell a little natural gas coming out of the exhaust then I get the lockout warning light from the fenwall, gas stops flowing, the blower runs for 15-30 seconds and the heater shuts down.

Could I have 2 bad ignitors? Would this be the behavior I'd expect from a bad ignitor?
 
It can be a bad ignitor. You can do some diagnostics on it and see if it is heating, examine it visually, check the resistance of it which should be 50 ohms, and check there is 120V AC going to the igniter when the heater starts.

Have you checked your gas pressures, static and dynamic, with a manometer?

Or it could be Heater Flame Sensing - Further Reading
 

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I have not tested gas pressure. I don't have a manometer and it's been fine for 14 years though I suppose there's always a first time for everything to change.

Next steps I think are to do some work on solidifying ground after reading on flame sensing from the article from the Wiki.

I'll probably get scolded for this but I also tried manually lighting by shooting flame down the exhaust with a torch. Doing this I was able to get the familiar jet engine sound which it does NOT do during normal starting sequence. It doesn't light at all and no jet engine sound which leads me to suspect 2 bad ignitors. However even lighting with torch, it stops almost immediately with ignition lockout though maybe the stack flue sensor comes into play in that scenario. I also suppose a bad flame sensor would also take place lighting manually.
 
Bazul said:
I have not tested gas pressure. I don't have a manometer and it's been fine for 14 years though I suppose there's always a first time for everything to change.
Click to expand...

Your house must be different then mine where everything beaks as it gets old.

My gas meter broke and needed to be replaced by the gas company.

You can have sediment buildup blocking the gas line or in the gas valve.
 
Ignitor: Good. I started it with the ignitor out and exposed with the gas off and it lit up just fine.
Flame sense ground: Sanded and cleaned the ground points in the control box and I ran new grounds as instructed in the Wiki (both location #1 and #2). I'm assuming you can't OVER ground.
Gas block switch: I bypassed the switch in case that was bad, I found a thread about that. No help.
Water leak? I don't think so. It's dry in there even with the pump running water through the copper lines in the heater. I assume corrosion is from past condensation or something?

None of these changed anything. All things (pre-start sensors) are go and it starts the blower for about 30 seconds, then gas flow for about 3-5 seconds, doesn't light and then shuts down and runs the fan for about 30 seconds. No sensor warnings on the back of the board, 3 red blinking lights indicating ignition lockout on the fenwal.

I think gas pressure, new gas control or new Fenwal are the only things left to try? The gas runs for about 5 seconds and I can smell gas from the exhaust when it runs. Do I buy a manometer? I've never done anything like that before but may be cheaper than hiring it out even if I only use it this one time.

What am I missing? I'm not quite on suicide watch but I'm definitely deep into heater frustration. :) After all this I hate the thought of giving up and spending $4K on a new heater and I don't know what's left for a pro to do to this heater.
 
20240602_153226.jpg
OK, I've got a good RMS Multimeter (Fluke 87V). To test flame sensor I'm not sure what setting it should be on, and am I testing during the short period of time (3-5 seconds) that gas is flowing or should I be able to test while it's just sitting there idle?

Re: gas pressure static and dynamic. Mastertemp 250, natural gas...what should it be?

New Fenwal, I'm seeing several options online on sites like Amazon ranging in price but none have my same 35-662NNN-NNN number. Does this number have to match and do I trust the lower priced options. I want to trust it but don't want to just pay more for no reason.

20240602_150513.jpg

Also, here's a picture of my new ground wires. One to the stud (Location #1 and another to the control box Location #2 just to be safe):

20240602_150945M.jpg20240602_150445M.jpg

I think it's odd that it ran for a little while post mouse eradication this year and then stopped (this seems electrical to me) and that the gas never lights even though it starts with a strong gas smell and I know that the ignitor works.
 
Well, as many things like this that I try and figure out myself go...they'd go a lot easier if I wasn't so stupid. :rolleyes:

I'm looking through this whole post again trying to figure out what I missed and I ran across this reply from about 2 weeks (and 20 hours of kneeling on rocks) ago.

Only difference in parts is the heat exchanger/manifold and the air orifice for the fan. You didn't replace those, so no problem there.
Click to expand...

Oh, air orifice for the fan...I DID replace that. It's what the mice chewed through to get INTO the fan and thus the kettle. Luckily I saved the old one. Looking at them you'd hardly notice the difference but sure enough the hole on the new 400 one is bigger. I put the old one back on and...I'm elated but can't believe I burned all that time. Especially when I had it working and didn't put 2 and 2 together and realize that it stopped working again after I put that new orifice on as the last step of mouse proofing the system.

And of course I can't return it since I screwed the screen on it. Anyone need a new orifice for a 400?

Thanks everyone for TRYING to help, these things are FRUSTRATING!!!

20240602_172602.jpg
 
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