How do I wire a new Switching Relay into an old system?

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Old 09-14-14, 06:51 PM
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Question How do I wire a new Switching Relay into an old system?

I need some help with with how to wire the 26 Vac power to my gas valve from the relay. I have an old system. It's a 1958 model American Standard Empire 2-GA-6E Gas Boiler. The gas valve is the original Detroit Controls V-575-FW Bi-Flex valve. The boiler was plumbed to run two zones by installing two separate pumps and two control circuits onto one boiler. The existing switching relays are Detroit CA-295s. The contacts are shot and falling apart. I purchased a Honeywell R8845U to see if I could use these models as replacements.
The problem I have is wiring it. I have attached some pictures to help. They include the inside cover diagrams for both old and new relays and or the current "control panel" set up.
My confusion is primarily with the power for the gas valve. The old relays use an external transformer to supply 26 Vac to the gas valve. The transformer was replaced in 1978. I attached a picture of the original wiring. It is similar but uses no "W" terminal. All the white wires are twisted together in a wire nut (see "Control Panel"pic). The instructions of the new relay say to use terminals X1 & X2 for low voltage power. It appears this will supply 24 Vdc out, but I'm not sure. Is there some way to wire this relay in the same configuration as the old relay? I understand basic house wiring, but I'm no electrician and know little about low voltage circuits. I would appreciate any advice you have.
Thanks,
Dan
 
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Old 09-14-14, 07:18 PM
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Let's start with the thermostat. I think you already know where that gets wired, yes?

The 120VAC HOT (black) that was on terminal 1 in the Detroit goes on the L1 in the 8845.

You will also need a jumper (black) from the L1 terminal to the COM terminal in the 8845 as shown in the diagram. It's not a good practice to put two wires under one screw, so bring the black 120 VAC HOT into the 8845 and connect two 'pigtails'. One goes to L1 and the other goes to COM.

The 120VAC NEUTRAL (white) goes on L2 in the 8845. You'll also need to put the WHITE wire from the circ here. As above, 1 wire under each screw, so connect the incoming 120VAC white to the white from the circ, and a short 'pigtail' of white together with a wire nut. Connect the 'pigtail' to the L2 terminal.

The HOT wire to the circulator goes on the NO terminal in the 8845.

To put it another way,

1 = L1

2 = L2

3 = NO

You will still need the transformer. No power is delivered on the X1 and X2 terminals. The wires that were on the " S " terminals in the Detroit go to the X1 and X2 in the 8845.

In other words,

S = X1

S = X2

Polarity does not matter with the S / X terminals.

Please be absolutely certain that you understand the above as I'm sure you know you can toast equipment in the blink of an electron.
 
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Old 09-14-14, 07:22 PM
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Welcome to the forums.

Two of those 8845U's would work fine for you. Since I'm not sure of the load of the gas burner.... I'd recommend still using that transformer on the wall. I could draw you up a diagram but I have one question...

You have two thermostats, each one is controlling a single zone so when the relay is activated that zone's pump will come on and also the gas valve will be activated. What regulates the temperature of the boiler. There needs to be a controller between these relays and the gas valve...... or does that automatic valve have temperature controls built in ?
 
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Old 09-14-14, 07:24 PM
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does that automatic valve have temperature controls built in ?
As I recall, there is some sort of mechanical limit control on those old timers. I personally would look into retrofitting a different high limit control, but without being there to see the boiler, I can't really advise on exactly how to do that.
 
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Old 09-15-14, 05:30 PM
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Thank you NJ Trooper & PJmax!! I do understand N J Trooper's instructions. And thanks you for being specific and simplifying it for me. I plan on wiring it up this weekend. I'll let you know how I make out. FYI, the gas valve does have an adjustable mechanical limit control. I'll attach a couple pics for your amusement. I am interested in the possibility of upgrading it but my knowledge on that is zero. After the switching relays are in and working I may look into it, and I'm sure I'll have questions. Thanks again!

Dan
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Old 09-15-14, 06:02 PM
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I'd be interested in reading those papers but the forum resizes and makes too small.

If you would be so kind, open a free account on Photo and image hosting, free photo galleries, photo editing and upload a high res there, and post a link to the PUBLIC album here.

That old boiler is in really nice shape, given it's age! Unlike me... sadly...
 
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Old 09-16-14, 03:27 PM
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I posted the Gas Valve info on Photobucket as you requested. The link is below. Thanks so much for your help. I'll let you know how I make out. Planning to do it this weekend.

Detroit Gas Valve Photos by danszpics | Photobucket
 
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Old 09-16-14, 04:22 PM
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Thanks! Interesting to see how they did it in the olden times.

It's absolutely amazing that the mechanism has survived and still working for what... almost 60 years? Again, much unlike my mechanisms...

Does it seem as if the temp gauge on the boiler is still reasonably accurate? If so, and if you've kept an eye on it, at what temperature would you say that the burners cut off?

I presume that the item to the left of the gas valve is a pilot safety device given that there appears to be a thermocouple tube going down toward the burner area. Looks as if it shuts the gas down if the pilot goes out. Good thing!

Where does the temp sensor probe from the gas valve enter the boiler? Does it appear to be a threaded port?

I'm asking because if in the future you did decide to go with some modern controls, you would need a place to install an immersion well to mount the new aquastat on.

New controls could be done... you would also need to change over the gas valve though.
 
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Old 09-18-14, 05:32 PM
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I'm surprised it still works so well myself. I do have to keep the dust and cob webs blown off it and for some reason it only works correctly with the cover left off. Must be a thermal thing.

The temp gauge is original and it too works reasonably well (I think). The burners shut off around 195.

You are correct (again) about the automatic gas shut off.

The gas valve temp probe enters through a threaded bushing next to the threaded port for the gauge. I scanned and posted the entire Owners Manual on photobucket. The link is below. Mine is an Empire boiler, but it's the same as the Standard except all the plumbing and controls are enclosed within the outer shell.

If the relay goes smoothly,and I think it will, before I start messing with the controls I want to convert the old expansion tank to a diaphragm style. My pressure gauge follows the temp gauge, but the tank isn't waterlogged. It has an old Airtrol fitting on the bottom of the expansion tank and every few days I have to bleed some air off the top of the tank (from the bottom!). When I do that I'll be looking for some sizing and placement assistance.

I can't tell you how glad I am there's people like you will to offer their knowledge and experience to us guys that would be blowing things up before we learned where we went wrong. Thank you.

1955 American Standard Empire Boiler Photos by danszpics | Photobucket
 
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Old 09-18-14, 06:48 PM
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Thanks for posting that. It's cool seeing how that old stuff worked... and in your case.. still works.
 
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Old 01-23-16, 09:25 PM
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All,

How did that wiring of the Honeywell unit go? I have the same boiler, and existing dual zone relays, with the same issue. Old contacts that need replacement. I can only find the R8845U-1003 with an INTERNAL transformer for sale online. Danz_Old_House seemed to have one without the internal transformer. My old system looks similar to his. If I get this unit, the wiring that was explained previously makes sense to me, but I have serious questions about the internal transformer.

Thanks in advance.
 
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Old 01-24-16, 06:34 AM
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Smile Results of New Switching Relay

The New relay worked perfectly all last winter and is still functioning without issue. I followed NJT's instructions posted on 09-14-14 (thanks again NJT). The unit I installed was a Honeywell R8845U-1003. It did have an internal transformer. That fact was where my initial uncertainty of using it came from. If you follow NJT's direction's the R8845U-1003 will work for sure. It was simple.

:HF2:

Good luck.
 
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