I feel like I have tried everything, need millivolt help!

dynastyss

Hello,

I have been struggling with my direct vent 8160 Luno hearthstone fireplace for the past few weeks now. The issue is the home is over 200 miles away and I have renters coming, so I really need to get the only heating source up and running. This is my third trip in 2 weeks to try and solve this so I want to be thorough and make this my last one.

Current Issue
The Nest still has power and says it is heating, but the fireplace isn't lighting. For a while it was lighting perfectly, then it slowly started turning on and off randomly. Now it just won't turn on. I had a service guy come when it was running decently and he says the thermocouple and thermopile are fine, but they are a few years old at this point. Pilot light never goes out.

Setup
The old set up was a 750ma/24vac transformer to Packard pr380 fan relay that ran to the Nest. That worked for a about a year, then didn't. I replaced the relay and it stopped working quickly after. I then installed the Honeywell R8845u1003 box and that worked for a few days and now it isn't.

https://cdn-images-1.medium.com/max/2000/1*sedTCJaZTDGDW9VSduaxHg.jpeg

Plan
I am going to drive up perform the following:

1. Replace Nest with another Nest (warrantied)
   
2. Clean out inside of fireplace (check the vents and holes for blockages)
   
3. Replace thermopile
   
4. Check the honeywell box and ensure it is wired correctly and the fuses and transformers are ok?
   

Outstanding questions

1. I think there is a chance I crossed the th/tp connections on the honeywell box. Would that make a difference? It obviously worked for a while so I feel like no.
   
2. Should I check for wire shortages? The nest recognizes the RH, W1 and C wire so I feel like that isn't it.
   
3. What else could I possibly be missing?
   

Thanks!

dynastyss

Hmm looking at that photo and others online I realized I never used the ground on the L1/L2 power part. Is that causing my issues? I can make sure to hook that up.

The nest is still powered so that makes me feel like I haven't fried the box? But maybe it blew the fuse and that is why the relays aren't working anymore? I am curious.

dynastyss

Bump!

ratio

Well, if the pilot never goes out then the generator is working adequately.

When the Nest is calling for heat, does the relay in the Honeywell box close? (BTW, I couldn't find that part number.) While the Nest is calling for heat and the fireplace is NOT firing, put a jumper across the thermostat R and W terminals inside the Honeywell. Does the fireplace light? If it does, that implicates the Nest. If it doesn't, that implicates the Honeywell.

Note that a lot of us here aren't too keen on the Nest, for technical as well as philosophical reasons, and if you're depending on it for unattended freeze protection you have a lot more faith in it than I do.

dynastyss

ratio said:

Well, if the pilot never goes out then the generator is working adequately.

When the Nest is calling for heat, does the relay in the Honeywell box close? (BTW, I couldn't find that part number.) While the Nest is calling for heat and the fireplace is NOT firing, put a jumper across the thermostat R and W terminals inside the Honeywell. Does the fireplace light? If it does, that implicates the Nest. If it doesn't, that implicates the Honeywell.

Note that a lot of us here aren't too keen on the Nest, for technical as well as philosophical reasons, and if you're depending on it for unattended freeze protection you have a lot more faith in it than I do.

Thanks! I had a typo in my original post, the part number is R8845u1003

Is there anything you recommend jumping with? paperclip ok?

ratio

Well, the L1 or L2 terminal is at line voltage potential. A short piece of stat wire would be better, easier to hold.

dynastyss

ratio said:

Well, the L1 or L2 terminal is at line voltage potential. A short piece of stat wire would be better, easier to hold.

Ah, so it sounds like a paper clip might be dangerous? I will try to pick up some insulated wire then.

HVACNUT

Pick up a pair of alligator clip jumpers.

Is the gas valve wired correctly?
Thermopile to TH/TP and TP.
X1,X2 contacts to TH/TP and TH.
If it's wired correctly, you can also jump the X1,X2 contacts in the Honeywell. That bypasses the relay and the Nest. If it fires, my money is a bad or incorrect programming on the Nest.
Like @ratio said, the Nest is not exactly a respected product in our industry.

Zman

To be clear. You do NOT want to L1-L2!
Before you change anything, you want to figure out why it would not fire remotely, this should save having to wait for it to fail again and another long drive.

I would first jump R-W to verify that the nest is successfully calling for heat.
I would then Jump X1-X2 to be sure the Honeywell relay is making good contact.

I share the sentiment that Nest is much better at marketing the they are at comfort controls. They are unnecessarily complicated for your application.

If I was forced to use Nest for a vacation home, I would wire a traditional T-Stat in series with the nest and set it to a lower setting. If the other t-stat was out of site of the renters, it would provide freeze protection when the nest doesn't work.

dynastyss

> @Zman said:
> To be clear. You do NOT want to L1-L2!
> Before you change anything, you want to figure out why it would not fire remotely, this should save having to wait for it to fail again and another long drive.
>
> I would first jump R-W to verify that the nest is successfully calling for heat.
> I would then Jump X1-X2 to be sure the Honeywell relay is making good contact.
>
> I share the sentiment that Nest is much better at marketing the they are at comfort controls. They are unnecessarily complicated for your application.
>
> If I was forced to use Nest for a vacation home, I would wire a traditional T-Stat in series with the nest and set it to a lower setting. If the other t-stat was out of site of the renters, it would provide freeze protection when the nest doesn't work.

Thanks!

So I'm up here and a bit baffled. Jumps from x1/X2 at the Honeywell box as well as the r/w posts. Jumps on the stove itself. I get 260 millivolts with burner on and 507 with pilot just on.

Thing was turning on no problem for me. I swapped the nest out just in case and will see if it stays on.

HVACNUT

Look into a Honeywell T6 or Pro 9000 WiFi thermostat. You get what you pay for.

dynastyss

Last update for now is so far after switching the Nest out so good. Can't find any other fault in the system or wiring so hopefully that keeps up for a while. Thanks again everyone!

ratio

As @Zman noted above, you can make the whole thing magnitudes more freeze-proof by adding a backup mechanical thermostat in parallel with the Nest. In fact, I'd place one of these across the W(T) and R(T) terminals inside the relay box. That's purely thermomechanical, no power needed. Along with your millivolt system, that means the heat isn't dependent on line power at all—as long as you have gas you'll have heat! With it hidden inside the relay enclosure, you shouldn't have trouble with tampering either.

dynastyss

> @ratio said:
> As @Zman noted above, you can make the whole thing magnitudes more freeze-proof by adding a backup mechanical thermostat in parallel with the Nest. In fact, I'd place one of these across the W(T) and R(T) terminals inside the relay box. That's purely thermomechanical, no power needed. Along with your millivolt system, that means the heat isn't dependent on line power at all—as long as you have gas you'll have heat! With it hidden inside the relay enclosure, you shouldn't have trouble with tampering either.

That's a really good idea. The only issue is the box is in the crawl space which I have a hunch gets colder than the house. It looks like 60 is the lowest temp one they offer, eh?

ratio

Yes, but someone else might have a lower trip point, IDK. The xfrmr etc., will keep the control box slightly above ambient. If you loose power that heat source will go away. If the crawl space is cooler than the habitable area, maybe it'll keep the house comfortable? It could also be extended to a different location with 18/2 stat wire. Anything mechanical would do in a pinch, the less adjustable the better I think, for your application.

Jamie Hall

Honeywell offers -- or did offer at one time -- a low temperature T87 which goes down to 45. Ideal for your application. Here's the modern equivalent: http://www.truevalue.com/product/Low-Temperature-Thermostat/3659.uts

Zman

The sensor or t-stat can live anywhere in the house. I have put them in owners lockoff closets. Just fish it through the crawl space. A good point was made about power outages, tying a millivolt t-stat to X1-X2 would take care of that.