Mystery relays

Brewster

Please, can someone help me understand a strange thing bolted onto our boiler? It was here when we moved in and we never understood why. We have hydronic heating, no air conditioning. We should understand what we have, so we don't mess anything up as we make changes.



We have an Ultimate Plus boiler with a Beckett oil burner, indirect HW zone, and 7 baseboard radiator zones. Each baseboard zone is switched by a Lennox thermostat, which has two mercury switches inside. The zones receive hot water through Taco valves. The boiler has two Honeywell controllers: the higher one seems to power the pump and the burner, and the other (with a red push button and TT and FF terminals) is attached to the burner.



When the top mercury switch in a thermostat calls for heat it powers the top two terminals on the Taco valve for its zone. When the valve has meandered down to open, it connects the 24V power to the third terminal, which feeds to the TT terminals on the top Honeywell (8716) controller. As well as switch mains power to the burner and pump in a controlled way, it seems to monitor and control the water temperature.



The two mystery relays are bolted onto the side of the boiler, next to the burner. They each close the circuit across the TT terminals on the Honeywell (R8184G) burner unit. Relay 1 is actuated by the signal from the HW tank thermostat to the top terminal on its Taco valve. Relay 2 is actuated by the second mercury switch in any of the zone thermostats. That comes in on a yellow wire from each of them, merged and going straight to the relay. These second mercury switch on each thermostat seems to switch on and off about a degree higher than the top one that's connected to its Taco valve.



I can sort of see a small reason for relay 1. It may serve to speed up the heating of circulation water if the HW tank calls for heat, giving it a head start while the Taco valve opens. That seems like it would only be a slight benefit, however – I think the Taco valves take under 2 minutes to open. But how could relay 2 help?



Only recently, I noticed someone (heating engineer?) had added a bare wire that jumps the TT terminals on the burner controller! So the relays now make no difference at all - the bottom controller always has a TT signal! It wasn't done because either relay failed – I tested them and they both actuate and switch perfectly. I asked the engineer who cleans the boiler about the relays, but he says he didn't fit them and doesn't know why they are there ... maybe something about prioritizing hot water, he suggested. I haven't asked him about the jump wire – I only just spotted that!



So, please, is it ok running 'jumped' all the time, or would we do better disconnecting the jump and putting the relay switching back to control the burner TT circuit again?

Many thanks!

JStar

Deep breath

A lot of information in there to process. Do you have any pictures of the relays, with and without the covers on? Maybe some of the other parts, too.

Paul48

?

8716.....Isn't right. Is it L8151A? I may be wrong, but it sounds like someone was saving on purchasing a zone valve control.

Brewster

Answers, sort of ...

Thanks, both of you!



JStar, sorry for the barrage, and sorry, I don't have pictures. Although they have many unused contacts, the relays are doing a very simple switch. Relay 1 connects the two T terminals on the Honeywell R1884G burner box whenever the hot water tank calls for heat, and relay 2 does the same when any of the second mercury switches in the Lennox wall thermostats make contact. A picture would just show a tangle of wires anyway. I could draw a circuit diagram, and try to look for a model number on the relays, if that would help?



Paul48, thanks. I don't really know the official designation of the top Honeywell box. It is gray with no number on the outside. The circuit board inside just has the number 8716 (or 8718) stamped on it near its bottom left.

icesailor

Control:

Are you sure that your R1884 G isn't an R8184G control? It seems to me that what you are describing is an R8184G oil burner control with a Honeywell R854 relay or equivalent

Brewster

R8184G & pictures for JStar

Yep, icesailor, that's right.  The '18' was a typo late last night.  Sorry.  (I did get it right in the first post). 



There seems to be a relay inside that box which switches mains power to the Beckett burner unit.  Then the two separate relays bolted on nearby are Cutler Hammer D5PR3T 24V coil, 10 amp 120VAC units in D5PA1 sockets.  They are 3 pole double throw, although only a small part of that capacity is used to make the TT connection on the Honeywell box when they actuate. 



In response to the demand last night, I borrowed a camera.  Here is a picture of the overall boiler and a close-up of the relay arrangement near the burner.  I removed one of the two relays, to show the mounting more clearly.

Paul48

Yep

Somebody was saving money. They should have used a 2- Taco ZVCs or similar.

Brewster

Thanks Paul48

Thanks, Paul48,

Each thermostat just has its own zone valve (see picture - this is ceiling level). Am I best to keep this relay system and lose the TT jump wire, or is there something that should be added (like ZVCs) that will make this all work better?

Paul48

Hmmm

I'm hesitant to say without knowing exactly how everything has been wired. There's 2 schools of thought..........."If it ain't broke, don't fix it", or "make it right". If you decide on the latter, dope it out, and plan on rewiring the whole thing. If you try to "fix" bits and pieces, you'll make it harder in the long run. Don't remove anything until you "know" exactly what you have, not what you "think" you have.

icesailor

OMG!!!

OMG!!

7-Taco 572 Taco zone valves. That takes 3 40 VA transformers and a lot of wires.

#2 and #3 on the zone valves are the switch that starts the burner and circulator. I have never seen anything like what you have. A Honeywell RA845 would have done it or a Taco 501. Because all the valve power heads are gold, they could have used a Taco ZC 506 zone valve controller and an expansion control.

Its basic electricity but with a rats nest like that, one could get a headache just trying to figure it out.

All I can say about the person who wired that is, He's smart and we're not.

Paul48

Info

https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-0618.pdf  If you look at figures 4 & 5, you are using a line voltage controller, the honeywell hi-limit controller (model still TBD), so the T-T terminal on the protecto-relay should be jumped.

icesailor

Wiring:

Yeah, but paul.

That's an 8184G controller. You don't need all that foolishness to make that work. The TT terminals are jumped out for the zone valve use burner safety control. and #2 and #3 terminals on the 572's connect to the TT on the 8184. If you have a second zone for the indirect, you use the ZC/ZR. Most electricians are so bad at control wiring that when I find a clueless one, I just tell them to wire it up, don't turn it on, and if there are any problems, I will fix it.

The easiest and most effective way is a no-brainer. Any other hard way takes brains. I mean trains.

Paul48

ice

In an earlier post, he made mention of removing the jumper. I was just trying to make my point clearer, that he shouldn't make small changes to what is already there.I'm concerned that there may be more than 1 feed.Identify what he has,dope it out, and re-wire the whole thing correctly.Make sense?

Brewster

So should we abandon the relays?

Many thanks, both of you.   I suppose it is flattering to know that what we have is rare, although an “omg!” from an expert is also quite scary!  Yes, icesailor, there are three transformers lined up behind the 8 Taco valves  on the ceiling, connected in parallel, to supply the 24V – see attached picture.  



I have also attached a photo of the main Honeywell controller – the one higher up on the boiler that receives the  TT signal  from each of the zone valves (terminals 2&3), after they have been opened by their thermostats.  That also seems a little quirky to me, as you can see it has a “HI” control set at 140°F, although the boiler exit temperature is always 186°F!



What I was trying to get at originally was that, although the TT terminals on the lower ProtectoRelay are jumped, we also still have this little arrangement connected to them with two relays actuating their time away.  Presumably it was used at one time without the jumper that now makes it irrelevant, or why would anyone have installed it?  If the jumper was NOT there, the burner would get its TT signal only if (1) the HW tank called for heat (before that zone valve is open) or (2) one or more of the SECONDARY mercury switches in the Lennox Thermostats was actuated, seemingly a little bit after a room has called the Taco valve for heat, from the primary mercury switch on its thermostat.



Could there be any benefit to doing it this way?  Do we need to keep the third lead from the thermostats hooked up to relay 2 for any reason, and keep any benefit from the earlier call to the burner when HW tank needs heat that comes via relay 1?  Or should we just lose all that and rely totally on the jumped TT connection?  Thanks again!

Paul48

Aquastat

That's a triple aquastat, designed to maintain the boiler at a constant temperature. They are using the relays to hold the burner out until there is a call for heat or hot water. If the boiler operates at over 180 degrees, either the gauge is wrong, or the aquastat is not working. Look on the bottom of that box, there may be a sticker with the model number of that aquastat.

billtwocase

indirect?

is there an indirect hook to this? That is an Ultimate boiler from Natick Mass. That is either a PFO-3T, or a PFO-4. If there is a coil plate behind that left jacket, that is where the control well belongs. Those long capillary tube controls are always off 20-40 degrees. It should be an L8151 control. If you want to cold start this unit, unplug the blue wire and cap it off. It will no longer maintain temp, but the low limit will continue to control the circulator. These were a great boiler until Dunkirk bought them out. I put in dozens

Paul48

What

is that wire coming out of the left side,by the hi, lo, diff?

icesailor

Easy:

Its so easy for some to wire something and make it so very hard.

Paul48

Cobbling

The work of a shoemaker.

Brewster

Latest data

Wow! You guys are quick. Thanks.



Sorry, Paul, I just had a look under the aquastat - I even unscrewed it and looked behind - but I can't find a label or model number anywhere. The only number is the one mentioned before, stamped on the circuit board, 8716. The wire coming out of the left of the box is a signal wire from the sensor (temp and pressure?) that pokes into the pipe where the hot water leaves the boiler, upper right .



I think I see your point. If the aquastat is designed to always maintain the boiler temp within a high range, the relays would prevent that when there was no call for heat anywhere - especially helpful in summer. Yet it sounds as if Bill suggests that unplugging the blue wire in the aquastat would achieve the same thing much more easily.



Bill, I don't think there is a coil plate behind the left jacket - all I see is a 'boilerplate' in the top right, and a huge cast iron box. I don't see any precise model designation unfortunately, just its energy ratings and serial number (109G87).

icesailor

In that case:

In that case, and it has no "tankless" coil inside, ands there is just a blank plate bolted to the block with the capillary tube going in to it, all you had to do was to turn the operating control (lo limit circulator) down to 110 degrees or such. The burner would only run when the zones called for heat and the burner would start.. You could set the "Hi Limit" to whatever you want. Say 150 degrees. If it gets too cold outside and the house won't heat up to the thermostat setting, you turn it up ten degrees.

Like I said before, if the electrician or installer knew what they were doing, it would have been a no brain, easy job. The B-1, B-2 controls the burner, C-1 and C=2 runs the circulator and the safety control on the burner is jumped on the TT. The TT is in the control. ZC/ZR control any other zone circulator with a relay like a R-845 or SR 501. Obviously, the full functions of the control isn't being addressed.

IMO.

Paul48

Right

It is the capillary tube. It is temperature only. https://customer.honeywell.com/resources/techlit/TechLitDocuments/60-0000s/60-2553.pdf

Paul48

Poor Choice

That's a poor choice of aquastats for that boiler, but as said, you can work around it. The only thing left is properly controlling the zones. Taco makes different versions of their expandable zone valve controls. You can come up with any combination that gives you what you need at the best price.I believe 6 is the max for a single control, so you have to get 2. http://www.taco-hvac.com/uploads/FileLibrary/100-5.1.pdf

Brewster

Thank you!

Thanks, icesailor and Paul 



Actually, for a few years the aquastat has been set as shown, with the lower limit as low as it will go (~110F) and the upper limit at 140F.  He did that when the water started to boil, saying we may need a new aquastat, but they were too expensive, so this would fix it.



At these settings, the boiler still keeps the water hot all the time (cycling up to 186F) even if there are no apparent calls for heat.  I have just taken away the jump on the TT terminals on the burner safety control, and now the relays come into effect, and it seems to only heat when there is a call for hot water from the tank or a zone. 



Many thanks guys, I think I now have enough information to sort out the best control option.  The next step is to convert to gas and pick a new boiler.  Every heating engineer we have talked to has recommended a different one, so I'll read all I can here about the different types and makes, and come back here to the font of all heating knowledge if there are still specific questions.

billtwocase

probe loaction

First, the 8716 inside the control is a date code. Second, can you post a pic of the "boiler plate"? If it is a blank plate, and not a cast over, the control well should be there instead. This is why you are overheating

icesailor

That Aquastat:

Many years ago, I put in a few real canine boilers that all had that control with the capillary tube. Everyone of them started to overheat and boil water. I had them doen to 140 degrees or less before changing them. Weil McLain had a series of them with the controls mounted on a ABC Burner with the primary control as part of it. It was also a dog.

icesailor

That Aquastat:

Many years ago, I put in a few real canine boilers that all had that control with the capillary tube. Everyone of them started to overheat and boil water. I had them doen to 140 degrees or less before changing them. Weil McLain had a series of them with the controls mounted on a ABC Burner with the primary control as part of it. It was also a dog.

Brewster

More pictures!

Hi icesailor - at least it is encouraging to know we're not the only ones, and it probably wasn't something we did ... and also that we are thinking of replacing the boiler for a more efficient gas one!



Hi Bill - that makes sense (8716), as the boiler was installed late in 1987.  Is 16 the week number?  As requested, here is a picture of the left side, then a close-up of the boiler plate.  I don't think there is anywhere there to insert a capillary, although there may just be a possible entrance on the left at the top near the rear.  I have also attached a new picture of the front, showing the connection from the aquastat to the capillary on the right a bit more clearly.



many thanks!

icesailor

Sharp Knives:

Another cheap boiler that drove the sharp knife into the heart of hydronic heat in America. That well location is about as bad a location as you could find. Unless the well has an 8" insertion, and the capillary tube is pushed to the end, it will never properly measure the heat in the boiler, causing severe overheating. The next problem comes if the return is directly below the supply. Then, when the pump is running, it may take a short cut and not circulate water into the back of the boiler sections. Where the boiler will put lots of heat into uncirculated water.

The ones I put in were gas boilers what were set on a steel base and a chamber installed. They burned out through the back in ten years, A 4 section was usable. I put a 5 section in and the only section that had tapping's was the front one.

If it became important to you, you can replace the control with a Honeywell that is a one size fits all, digital electronic one. It has an electronic wire connection that is the sensor and you mount the control wherever you want. My only complaint with that control is that it is slow acting through its self checking feature.