Non working Superior fireplace

Reply

  #1  
Old 11-29-20, 03:40 PM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Non working Superior fireplace

Hi folks,

Please pardon my newbie post. I'm posting to get confirmation on my diagnosis only because there is gas involved and I don't want to kill myself or my dog. That said, here we go.

The fireplace is 21 years old and installed new when my home was built. Years ago, I started having trouble with the burner shutting off intermittently. It gave up the ghost a number of years ago and I elected to live with no fireplace until today.


It is a Superior DVT5-CMNS


The Gas Valve is a Robert Shaw 7000MVRLC which I understand is a 710-502

I have yet to test the thermocouple as I am waiting for alligator clips to arrive next week. I figure I should test that, just to make sure it is in good working order before I tear the thing apart to replace the gas valve.

With the pilot on, the thermopile reads about 480 mV. When I flip the switch to "turn on" the fireplace, the voltage drops about 30mV. So, I know it is at least in working order.

Using a crib sheet I found online, I went straight to the gas valve. I first measured TH/TP and TP. I got Infinity.

Just for giggles, I measured TP and TH and got about 6-ish ohms. Based on these two readings, my cheat sheet says the gas valve is kaput.

Changing the valve looks pretty straight forward. I looks like I remove the gas line and a bunch of sheet metal screws. Once that's done, I pull the unit up and out, to make the swap. Here are my questions:

Should I replace the flexible gas line? I'm guessing, yes.

Can I use yellow Teflon tape or should I use some sort of pipe dope?


There appears to be some sort of insulation, sealant or something around the edges of the panel that the valve hangs from. I've also noticed some sort of hard stuff around the thermocouple/thermopile wiring and the pilot. I I elect to replace the pilot assembly, what should I use as a sealant.

Did I forget anything?

Thank you in advance for the help.

Brian
 

Last edited by PJmax; 12-05-20 at 06:04 PM. Reason: imported/resized pics
  #2  
Old 11-29-20, 04:11 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
Gas valves rarely go bad. It's more likely starving for voltage. With a millivolt system.... there is no room for any loss of voltage or bad connection.

If you opt to change the pilot assembly.... it's a good idea.... you can use high heat silicon to seal any opening that are currently sealed.

From Th/Tp to Tp you said you get 480mv and that drops to 450mv when the burner is operating. That's pretty normal. Now when burner is operating.... measure from Th to Tp. You should see the same voltage you measured previously. You probably won't see the same but much lower. That is loss in the thermostat, safety and manual switch circuit. You cannot have any loss in that loop.

You need to check for loose connections.

DVT5 manual (pdf)
 
  #3  
Old 11-30-20, 05:52 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Hi Pete,

Thank you for the reply. The burner does not come on. However, there is a voltage drop when I flip the wall switch that would normally turn on the burner.

I'll snug up the wire terminals and have another go at it.

Thank you for the installation manual. I actually have the one that came with the fireplace.

Brian
 
  #4  
Old 11-30-20, 06:05 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,474
Received 755 Votes on 694 Posts
The voltage you are getting is low. My gas logs were intermittent this season with 470 mv. I installed a new thermopile which is putting out about 760 mv the stove is back to operating reliably. I would definetely get a new pilot assembly on order and give it a try.
 
  #5  
Old 11-30-20, 08:12 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Thanks for the information, @Pilot Dane. I had thought the voltage to be on the low side, even though the recommended min is 325mV. I'm going to wait for the alligator clips to arrive on Wednesday so I can test the Thermocouple.

I've removed the Thermopile and switch wires to the valve for testing. When the alligator clips show up, I'll re-attach the wires and make sure the connections are snug. I can also test the voltage on from the Thermopile directly from the wire terminals, using the alligator clips.

At this point, I'm thinking if I am going to replace the pilot assembly, I might as well put in a new valve. They aren't all that expensive. Since I have to almost take the whole thing apart just to get to the pilot assembly, what's a few more fasteners and fittings to swap out the valve?

I'll be in touch. Thanks again, folks.
 
  #6  
Old 11-30-20, 10:38 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
The valves are not always easy to change and will need to be adjusted.
The thermocouple just holds the pilot valve open.
It's the thermopile that opens the main gas valve.
 
  #7  
Old 12-01-20, 08:48 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Hi Pete,

Are you talking about the inlet and outlet pressures on the valve? The existing valve has inlet and outlet pressure taps. I cannot find any information on how to adjust those pressures, only how to measure them.

I cannot find an exact match to the control valve that is in my fireplace. The replacement that I have found is the 710-502. The pictures I have found of those valves do not show the two taps. But, they do have the pressure regulator on them.




Or, are you talking about adjusting the pilot light? As I understand, we want a nice strong blue flame. I see the adjustment screw is just beneath the on/off valve.

It looks like I'll need to install a drip leg, too. :-)
 
  #8  
Old 12-01-20, 08:58 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,474
Received 755 Votes on 694 Posts
Don't replace the gas valve at this point. The pilot assembly & thermopile are the problem 98% of the time.
 
  #9  
Old 12-05-20, 02:39 PM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts



I jumped the door switch and set the wall switch to the ON position. Using a paper clip, I jumped the TH and TH/TP terminals. I got FIRE! It remained on for the short time I tested it. The wall switch worked to turn the burner off. I have tried jumping the wall switch, but that does not work.

With the thermopile disconnected from the terminals on the gas valve, I lit the pilot and measured the voltage coming from the thermopile. I got around 500 mV to about 510 mV. With the thermopile wires connected to the terminals and the pilot lit, I get slightly less voltage, about 475 mv. With the burner on, I get about 318 mV at the gas valve terminals. I did not think to disconnect the thermopile wires from the gas valve and measure the voltage with the burner on. I was too excited that the burner actually came on.

I disconnect the wires from the gas valve terminals and measured the resistance across TH/TP and TP. It's OPEN (O.L). I next measured the resistance across TP and TH and got about 6.2 ohms.

The crib sheet I have says if TH/TP and TP is open, the valve is bad. For the resistance across TP and TH it says 1.5-1.7 ohms is good.

Is there anything else I should try before I rip it apart? Thank you for the help.

New thought....Pete suggested replacing the pilot assembly. Is the thought that a new thermopile will generate enough voltage to power the two stupid switches in the circuit?
 

Last edited by ossodiseppia; 12-05-20 at 04:24 PM.
  #10  
Old 12-05-20, 06:50 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
Looking at the working valve diagram.
TH/TP is nothing more than a splice point. It connects to nothing inside the valve.
TP connects internally to one lead of the valve solenoid coil.
TH connects internally to the other lead of the valve solenoid coil.

When the pilot is lit.... you'll get +/- 400mv on TH/TP and TP. Note that voltage.
When you short TH/TP and TH.... the TH/TP and TP voltage will drop to +/- 350mv.
That means under load..... the thermopile is producing 350mv.

Now measure from TP to TH. You should measure 350mv. If it's lower...... it means you are losing
voltage thru the safety switch, door switch or thermostat. There can be no loss in the thermostat loop.

I used 400mv as a reference voltage. That is typically the minimum. This voltage is VERY dependent on pilot flame size. If the pilot isn't full size the voltage will be low.

It is extremely common to find the pilot air mixture area with spider webs and to have a partially clogged pilot orifice.
 
  #11  
Old 12-07-20, 05:21 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Hi Pete,

Thank you for that explanation. I don't have a thermostat, but I do have door and wall switches. I'll remove the wall switch and twist the wires together. I'll remove the door switch and use the wires to turn on the burner. Ill measure the voltage and report back here.

I'm no expert, but the pilot flame looks pretty good to me. My third picture shows the pilot with a nice blue flame. The picture below is one I took this morning. It all appears to be pretty clear on the top side of the pilot.



Thank you for the reply.
 
  #12  
Old 12-07-20, 06:16 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,474
Received 755 Votes on 694 Posts
I often test the thermostat/switch circuit with a paper clip or piece of wire. If the pilot is lit and you are calling for heat but the burner doesn't light I use a paper clip or wire to jumper TP/TH to TH. If that kicks the fire on then there is too much resistance in the thermostat/safety switch loop.
 
  #13  
Old 12-07-20, 12:56 PM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Thanks, Dane. That's what happened the other day.
 
  #14  
Old 12-08-20, 05:38 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts


This appears to be the culprit. After all that hoopla, it ends up being am inexpensive part. It seems to work when it wats to. A new one is on the way. I'll replace the wall switch as well, they are cheap.



I also noticed this when I put the door back on to test the switch. I really don't know how that happened, this is the first time the door has been off.



Hopefully the new switch will cure the problem. Thank you for all of the help.
 
  #15  
Old 12-09-20, 10:35 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
It only takes a switch to be slightly corroded to have a major effect.
The biggest reason is that you're only dealing with under 1 volt of power. Not much room for loss.
 
  #16  
Old 12-10-20, 09:59 PM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Thanks, Pete. Both switches were suspect. But, both passed initial continuity tests. I felt I should look at every aspect of the fireplace to be thorough. After all, it's over 20 years old and parts won't be around forever.
 
  #17  
Old 12-11-20, 06:59 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,474
Received 755 Votes on 694 Posts
One of the stoves I fixed a couple weeks ago that I thought I fixed started acting up again. First I thought it might be the thermopile but it was quitting at a pretty high voltage where it should work. This one has a thermostat/off/on switch and is wired to a normal home's type digital thermostat. The stove is always used in thermostat mode. I checked the resistance through the switch and it was sorta high so I replaced it. The stove worked 8 out of 10 times I tested it. Then I finally set the thermostat to call for heat and checked the resistance at the wires at the stove so I could see the wiring's and the thermostat's resistance. Sure enough... it was the thermostat all along. One of the more frustrating things I've had to debug in a while.
 
  #18  
Old 12-15-20, 07:39 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
I'm going to put closure on this. I got the replacement switch yesterday and installed it and a new wall switch. I've cleaned the glass up making the fireplace look new again. So far, it's been working flawlessly and I am really stoked to have it working again.

I got some grief on another forum for wanting to fix my own fireplace. I was called cheap. There are many reasons for wanting to fix something myself and none of it has to do with money. Thank you so much for the help and patience.


 
  #19  
Old 12-15-20, 09:20 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 24,474
Received 755 Votes on 694 Posts
Never mind the cost. Having a service person come to your home often means someone has to take a day off work and then there is the whole COVID isolation. I quite often find it quicker and more convenient to fix things myself with no concern for the cost.
 
  #20  
Old 12-20-20, 07:13 AM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
I fixed it but it broke! My victory was short lived. The thing is on the fritz, again. I going to replace the pilot assembly because I get a voltage drop when I turn on the wall switch. The drop is about 140mV from 530mV to 390mV..

I tried the jump wire between TP/TH to TH, but the burner will not come on.
 
  #21  
Old 12-20-20, 09:53 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
The drop is about 140mV from 530mV to 390mV..
Measured where ?

Keep in mind there are two places to measure.... the thermopile itself.... TP - TP/TH and what is actually appearing on the valve..... TP - TH.

What ever is measured at the thermopile needs to match what you see on the valve.
 
  #22  
Old 12-21-20, 06:13 PM
O
Member
Thread Starter
Join Date: Jan 2019
Location: United States
Posts: 14
Received 0 Votes on 0 Posts
Pete,

I measured the voltage at the terminals on the gas valve. First, with the wall switch off then with it on. When I turned it on, that's when there was a voltage drop.

Next, I disconnected the thermopile wires from the gas valve terminals. I measured the voltage directly from the wires. It was the same as the voltage when the wires were connected to the gas valve terminals and the wall switch off.

I've ordered the pilot assembly and it's going on come hell or high water. My hope is that a new thermopile will produce a full 750 mV and my fireplace will be back in business.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: