Caleffi 3 way mixing valve and boiler shutoff

chippy2

hi. I installed a.Caleffi 3 way mixing valve with preset 140 degree cartridge. So it opens supposedly at 140. The problem seems to be that the burner and primary come on and the burner hits the high temperature limit before the three-way valve opens. Is there a way to mitigate this problem?

I have a Pensotti DK2 with a Hydrostat 3250

My primary loop is literally 16’ total length and the 3 way is piped correctly. The bybass loop - before the valve opens- however is about 5’ total. How to fix the problem?

hot_rod

how quickly does it hit limit? What circ is on it?

chippy2

circulator was the existing cast iron Taco007 that I moved from the return side To the outlet side. On cold start the burner ran 5 mins and hit 180 the shut off. Took longer for the 3 way to open. Once system is running and calls for heat it seems to be already opened

chippy2

also not sure it’ll the pump is too strong but my Caleffi mixing station is connected with closely spaced Tees and does pull much hot water into the manifold! !?!

hot_rod

On the manifold is a hydraulic separator, this H fitting. You need to remove that when you have close spaced tees feeding the manifold.

You have two hydraulic seps piped, the manifold and closely spaced tees. It will not flow properly.

The H fitting at the manifold is on union nuts to remove and move the piping up.

The 3 way should start to open within seconds of the boiler firing. Open full at 140F

Could be it is seeing a "blended" water temperature not boiler supply??

chippy2

assuming it is piped correctly

mattmia2

is the system branch of the thermostatic valve cold? if the manifold isn't circulating from the main loop in to the heating loops the boiler will shut off on high limit very quickly because none of the output of the boiler is being moved in to the system.

EdTheHeaterMan

lots of close up photos. Can't see the big picture. Can you step back a little for the next photo. Reminds me of the guy who said he had a tire inflation problem here:

Your photos remind me of the person that posted this query on a Auto Repair DIY site. They insisted there was a problem with the tire valve because the tire would not inflate.

Am I not understanding how this tire valve works? I have been adding air to this tire valve for over 30 minutes and the tire will not inflate. Can someone tell me what I'm doing wrong here?

Then someone asked for a picture from farther back. Now we get the real story. A completely different possibility for the outcome.

I don't think it was the tire valve. LOL

@hot_rod was able to pick out a problem right away. I would look at that first because it is an easy fix. Just move the manifolds a little.

Next photo is hard to see what goes where, So the answer to your query:

IS THIS RIGHT?

Is: maybe?!?

But I’m not sure all the arrows are pointing the right way. I was told that the arrows need to be on the inside of the pipes so the water can see which way it is supposed to go.

Actually, I think some sarcastic SOB probably put those arrows in the wrong direction. Everyone knows that the exhaust is supposed to come out of the barometric draft regulator, so that red arrow is definitely wrong.

hot_rod

Yeah, if for some wiring reados the boiler pump would come on without any load pump, the boiler may rocket up to limit before the valve responds.

But the manifold piping needs to be corrected.

https://www.youtube.com/watch?v=ET9Lv0_HHm8

Kaos

Need full pictures of the primary loop. I think your primary circulator is the wrong location, it should be either right at the boiler return or the boiler supply not the other side of the mixing valve. I think that is why the boiler is overshooting.

chippy2

hope this is better ..right side pipe is return and has the mixing valve and left side is leaving the boiler.

Primary circulator was moved after expansion tank. But, most Caleffi mixing valve illustrations show it between the valve and the boiler on the return side 🙁

I’m not sure there is enough return pressure to open the cold side of the valve? Boiler shuts off, primary loop circ stays on a while but the primary loop is cold to the touch half way around the loop and up to the 3-way valve!

“Flying by the seat of my pants “

chippy2

https://forum.heatinghelp.com/discussion/comment/1903878#Comment_1903878

thanks Bob! I removed the 2nd separator that came with the mixing station as you indicated and now just have the closely spaced tees with a check valve. Circulator runs but still does seem to pull hot water effectively from the primary loop. Wondering if the 3-way valve is staying closed which is causing the “real” problem here 🤔

Kaos

Your primary pump is in the wrong location. As you have it, if the valve is cold and in bypass mode all the water is through through the bypass pipe and you won't circulate water through the boiler that is why you are hitting the limit.

Need to move the pump to either of these two location:

chippy2

thanks. Trying to understand how this helps though. Currently the two areas circled get up to the max boiler temp of 180 (or too hot to hold) but the return above the valve is stone cold still. What would the circulator do to improve that? Could the valve be faulty? It’s brand new…. Not sure how I can check that?

Kaos

In the current location, when cold, water flows through your primary loop, through the mix valve bypass port back to the pump. Next to zero flow through the boiler. No boiler flow, you hit the high limit.

In the other location, when cold, water flows through the boiler then through the bypass port back to the boiler. Now the mix valve is exposed directly to boiler water so when it goes above 140F, it opens and allows flow through the primary loop to your emitters. That is exactly what you want.

chippy2

ok so the primary circulation the way I have it currently doesn’t allow any circulation through the boiler OR primary loop with a cold 3-way valve I guess.
Although with enough ghost heat in the area I would have thought that the valve would open anyway 🙁

hot_rod

Here is how the instructions show it when used for boiler protection. The pump pulls from one or two ports

I have never tried one with the pump in that location. There are most commonly used when a large cold load is present, like a buffer or large radiators.

I think if the boiler fires you would have a heat load calling? Why would the boiler just fire if there is no heat call?

chippy2

yes boiler only fires when called for heat. Primary loop circ comes on too but flow in primary loop is blocked until that valve opens. I mistakenly thought that there’d be “some” flow in the loop but…

I will repipe the circulator and hopefully it will solve my problems 👍

jesmed1

https://forum.heatinghelp.com/discussion/comment/1903906#Comment_1903906

@Kaos is right about the circ being in the wrong place. Think about what happens when the valve is half open. Return water will want to "short circuit" backwards through the valve into the supply side, which is the shorter path back to the circulator, instead of taking the longer path through the boiler. So even with the valve partially open, there will be little or no flow through the boiler loop. So you need to move the circ to either location he circled. Yes, then it will be on the "wrong" side of the expansion tank, but at least you will have heat.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1903912#Comment_1903912

The valve never really closes, it is open either to the boiler or to the system. It modulates those ports. IOf the boiler is below 140,it is open 100% back to the boiler. As it warms some of the flow starts going to the system.

So with any heat call some flow starts going to the system. But the boiler pump needs to be moving water through the valve pushing into the boiler.

Move the boiler pump and also remove the second hydraulic separator at the manifold.

chippy2

OK I moved the primary loop circulator.
still has the issue that the return is still below 100degrees even 25 min after the boiler shut off for high temp limit. Primary circulator and 1 secondary remain on as the T-stat is still calling for heat.

see pic. The temperatures are correct on the mixed return but there is still way too much bypass crossing over from the boiler outlet side. At this rate the first 1/2 hour of calling for heat will take too long and if 3 secondary loops were calling for heat at startup there would be a ton of cold water WANTING TO RETURN but forcing the 3-way valve to remain mostly closed on the primary return. That seems a$$backwards from a circulation perspective right?

Update: it finally fully opened after

30+ minutes

hot_rod

if you want the valve to open quicker, install the lower temperature sensor.

Switch to a 115 degree sensor, the 18 differential gets you 132 boiler protection.

Did you correct the duel separators? Remove the H fitting at the manifold?

jesmed1

Are you sure those gauges are reading correctly? The last pic shows a hot supply of 130 coming into the bypass, a return of 120, and a mixed return into the boiler of 140…which is impossible. The valve output temp can't be higher than both input temps.

Even if the bypass really was fully open as you say, the temp would have to be the same on both the return in and the mixed return out. But one reads 120 and the other 140?

So it looks like at least one of those gauges is off. Maybe not a big deal, but if you want better accuracy you can wrap each pipe with some black electrical tape and shoot each one with a cheap IR thermometer to find out which gauges are off, and by how much.