Aquastat problem

[gorsuchmill]

I'm having a problem getting the aquastat (4006B) to kick on my circulator when the boiler (Solo 40) gets up to temp. The aquastat is supposed to activate the circulator when the water temp exiting the boiler reaches 160*; however, mine won't come on even when the boiler reaches its temp limit of 182* or so. I've moved the aquastat to within 3" from the back of the boiler, but to no avail. I was thinking there might be air in the system, but I've bled repeatedly and the issue hasn't improved. Oddly, the expansion tank exit, which is at the same height as the supply exit on the back of the boiler, always feels hotter to the touch than the supply.

This has been a frustrating issue because I can have a hot boiler that cycles on and off; however is not delivering any hot water to the zones that are calling for it. Any ideas?

Thanks in advance.

 

[flyingcow]

make sure its a 4006B not a 4006A. Can't remember which I got, but had a small goof on the suppliers part. Double check the paperwork. and look very close to the tags on the stat

 

[gorsuchmill]

Definitely the 4006B. I can get it to kick on when I turn the dial down, then turn it back up after the water flows for a bit. This is a real hassle because I can ask my wife to load the boiler with wood, but having her monitor the status of the aquastat and circulator function becomes problematic. Regardless, it's supposed to activate the circulator without any tinkering and I simply can't figure out why the hell it isn't working.

 

[WoodNotOil]

The aquastat on the supply pipe in a well in the Tarm piping setup has always baffled me. Why not in a well on the actual boiler instead of in the pipe? As a result it responds slowly. They suggest keeping it at 140*. At that temp you should have no problem as it will actually kick on when the boiler is hotter than that. There is also the 5* differential to consider on the aquastat. Make sure you set it for 5* and not 20*.

 

[gorsuchmill]

Thanks Wood. The literature actually states to set it at 160*, and I was told by a rep that I could turn it down as low as 150*. However, even at that reduced temp it responds very slowly despite the boiler temp reaching 183+*. I agree, it seems that a well on the top of the boiler would have been better. That said, do you use 140* and, if so, how quickly does the aquastat respond? Does it come on within the first cycle or does it take a few cycles before enough hot water gets into the vicinity of the stat to kick it on? One of my concerns is 140* water being circulated into the boiler and causing condensation. Maybe that shouldn't be a concern because though the stat is set at 140*, the water in the boiler is much higher.

Lastly, have you noticed the expansion piping to be hotter to the touch than the supply piping? That seems to be the case with my system, which is odd; however, might suggest locating the stat on the expansion side would be better.

 

[chuck172]

The Solo40 has a well on the top of the boiler, its for the 210* over-heat zone. You could probably switch aquastats and then adjust accordingly.
Where in the literature does it say set the aquastat to 160*?

 

[jebatty]

I have a strap-on aquastat mounted on the boiler return line right after the Termovar, set at 155F. If I have the balancing valve set to be quite low (reduces boiler feedback flow), then when it comes "on" output temperature actually is close to 170F (which is OK). If I increase the feedback flow, that 170F will drop close to the 155F set-point. Tells me that with very low feedback flow, the water is cooling too much by the time it reaches the aquastat sensor. You may want to adjust your feedback flow and see what difference it makes.

 

[gorsuchmill]

Thanks Jebatty, but I have the Termovar Loading Unit, so it is "self-balancing".

Chuck, the literature actually indicates a setting of 165* for the 4006B on the trouble shooting flowchart shown in section 5.2 (p. 50). Are you using a lower temp?

 

[chuck172]

Sorry, I found on page 22, "The honeywell L4006B aquastat close on rise control. It is set at 160#"
Mine is set at 140*. According to my Tekmar differential controller, The aquastat actually turns the circ. on at 155*.

 

[twitch]

I also have an aquastat on my supply (I think it's the 4006B) that I have to set to 145* for it to close at about 163* on the boiler temp guage. I have it in a well in a 'T' of the supply, and added the heat transfer goop later, but it didn't help. I have the differential set to 5* so it will shut down at 140*, which is fine with me because my fan low limit is set to the same.

Someone in another thread talked about wiring the pump switch (not used on Tarms in the U.S.) to a relay to temporarily kick on the pump to get the hot water flowing to the aquastat so it would stay on.

 

[twitch]

Here's a pic of my aquastat in relation to the supply. I should have put it on the first 'T' coming out of the boiler, but didn't know any better. I think it just takes some time for the water at the aquastat to get hot enough to start because the water is not flowing and is going to be cooler than the boiler water.

 

[WoodNotOil]

Twitch - mine is piped the same as yours and does take some time as well. I rechecked the manual and confirm the 160* setting. I still think setting it a little lower than that will help. I like the idea of sticking it in a well on the top though. The only problem being that the aquastat would be located under top cover. I wonder if the Honeywell sensors can be extended at all? Anyway, it works ok the way it is. It is hard to not obessesively tweak these things...

 

[gorsuchmill]

In order to get the stat as close to the back of the boiler as possible I used a 2" nipple immediately out of the boiler, then a T which contains the stat. This brought the center of the stat well to within 3" of the back of the boiler. I also threaded the well in a tad farther so that it extends 1/2" or so into the supply path. Unfortunately, the problem still exists. I haven't tried the heat transfer goop, but I'm willing to try anything to resolve this PITA. What is the name of it?

Also, I still haven't seen any comments regarding the expansion port. If you get a chance, put your hand on the pipe emanating from the expansion port and see if it feels hotter than the pipe leaving the supply port. It seems to be the case on my system, which doesn't make logical sense to me given that both ports are at the same height in the system. If this indeed is the case, it may make sense to locate the well to the expansion port side or the top of the boiler somehow.

Thanks again for the feedback.

 

[flyingcow]

The Solo40 has a well on the top of the boiler, its for the 210* over-heat zone. You could probably switch aquastats and then adjust accordingly.
Where in the literature does it say set the aquastat to 160*?

I've got the innova and thats what we had to do. Can't remember ,but got the wrong stat, so it was wired to the well out of the overheat. Just as chuck pointed out. Works very well. Will set up correctly when we the correct stat.

 

[gorsuchmill]

I just noticed that the expansion port is modestly higher than the supply port by a few inches. That would likely explain why that port always feels hotter to me and may suggest a better location for the 4006B. Any thoughts?

I've also considered Chuck's suggestion of relocating the stat to the overheat port on the top of the boiler, but I'm not sure what to do with the overheat stat. My concern would be that the overheat stat would not be as responsive in the old 4006B location. I suppose I could reduce the setpoint for the overheat stat, but what would be a good setting?

 

[flyingcow]

call tarm, let them help you diagnose whats going on. Good customer service I've found.