No Hot Water 1st Warm Day after installing Outdoor Reset (Vision 1)

SENorthEast1895er

I did a DIY install of a Vision 1 ODR this week, and everything was going fine until I got a cold shower today. After talking to our upstairs tenants, they said the hot water has been finicky lately.

Today was the first warm-ish day (looks like reset curve was calling for <120 degree water) and it made me wonder if somethings going on with my plumbing.

The hot water here has always been somewhat finicky; previous owners installed a too-small tank (given that it's a 2 unit), so it's set up to run with the tank t-stat at its highest ("Scalding Temps") and run a tempering valve off of it.

That being said, I don't remember getting a shower that cold in all my years living here (we were the tenants upstairs for years until we bought the place 18 months ago).

I thought the Munchkin would ignore the reset curve when the Hot Water tank called for water and go to 185, but looking at the manual closer, it looks like that programmable setting isn't for use with Mechanical Controls (only works with the Vision 1).

So I'm wondering if
- that doesn't work in my configuration and I'm just dumping reset-curve temp water into the hot water tank.
- the zone valve is busted in the open position and the tank is constantly getting reset-curve temp water going through it.
- something else.

I've disconnected my ODR to see if the issue persists.

Pic of plumbing in comment below (I was having trouble getting it in here without it cutting of my post).

SENorthEast1895er

Was having trouble putting this in original message.

Rich_49

This boiler in the picture is piped improperly , not P/S . It should have at least 2 circs , one boiler circ and one system circ . It would be best with a zone valve controller , higher Cv zone valves or no zone valves and 3 circs , boiler , system , DHW .

Besides that I believe the hot water has always been finicky is most likely because the coil in the indirect is piped reverse of what it should be and possibly a control issue . This indirect was meant to have a counter flow , mosyt indirects shoul . Supply water should enter the IDH through the top port and return out the bottom . This may very well be your biggest issue to address .

HomerJSmith

It should have at least 2 circs , one boiler circ and one system circ .

YES.
ODR is going to close down the sys pump, since you have only a sys pump you aren't going to get any hot water. Using a zone valve for the DHW, you are going to have to dump the ODR.
The Munchkin has program settings for the heating sys and settings for the DHW. You may get around this with a zone control like a Taco ZVC but are still hampered with one pump and an ODR.
I always pump into the highest resistance (personal preference), the Munchkin's heat exchanger is the highest pressure loss (resistance). You are pumping away from the highest resistance.
You have a bypass between the intake and output of the boiler. That's not needed unless the pump isn't pushing enough flow of water thru the boiler heat exchanger creating short cycling. The bypass isn't needed to maintaining 130 degree return water temp into the boiler because the Munchkin is a condensing boiler with a stainless steel HX. Having hot water returning thru the bypass to the input to the boiler guarantees you will never get into condensing mode. It looks like a 140M boiler which need 14 GPM flow thru the HX. which is why a P/S configuration is important. A P/S configuration with Zone Valves requires a differential pressure valve with a fixed speed pump to maintain that flow thru the boiler.
I don't see an expansion tank in your pic.

SENorthEast1895er

@HomerJSmith @Rich_49

Yeah, I figured out my problem pretty quick by just disconnecting the ODR.

The Munchkin 925 install manual has a Retrofit piping guide which employs a single circ on supply side. I'm not enough of an ace to know how closely my system follows that, but there are allowances for non-P/S systems in the 925.

No such luck in the Vision 1.

Why higher CV zone valves?

Also, what is counterflow?

Expansion tank is overhead.

I literally just tried getting around the issue with a Taco 403 ZVC. Level 1 HTP support said it would work to trigger the boiler by using the the TT line off of the Zone Valves (rather than the indirect end switch to the boiler aquastat, which resulted in the same problem; only 1 TT line when I need two)

However, the ZVC shuts down the circulator as soon as the the thermostat kicks off.

This resulted in the boiler continuing to run after the circulator was shut off, as the Zone Valve takes some time to close. Water temps crept up from 185 at shut-off to 211, when I turned the circ back on to cool things down.

Level Two HTP tech support said it wasn't possible after explaining the issue.

I can't really see any other way to wire it that would prevent the boiler from firing if the circulator is off.

I'm very concerned about getting that bypass valve adjusted appropriately, due to the issues you mention. I don't see anything in the Vision 1/925 Status menu options that would give me flow rate through the boiler; is there any further diagnostics that I can run or ways I can ensure I'm meeting spec w/o missing condensing mode.

HomerJSmith

CV Is the measure of flow thru a valve. The lower the CV number the less flow, the higher CV number the greater the flow. It is the resistance of flow thru a valve at a given pressure. Higher the CV the better.
@Rich_49 is referring to the direction of the flow in the heat exchange in an indirect tank. The normal thinking is that the boiler hot water supply should go into the coldest water in the tank first, that is the lowest part of the tank, the lowest connection to the heat exchanger. However, for several reasons it is better if the boiler supply water goes in at the top of the heat exchanger which is counter to normal thinking, counter flow.
It is the connection of the expansion tank in relation to the pump that I was interested in.

SENorthEast1895er

@HomerJSmith

 another major issue with the water heater is (I’ve been told by previous owner who didn’t put it in) it’s way too small. 

This house is split in 2 units. 

HomerJSmith

Indeed it can be too small, not much you can do about that. But, I have a 3200 sq ft house with a 45 gal indirect tank. I never run out of hot water, ever. It has its own pump and the programing for the hot water with Vision 1 sensor is set at 150 deg tank temp and is reduced to 125 degs with a mixing valve, giving you more hot water capacity. If your tank has a sensor well use the Vision 1 sensor. Using a Taco 570 zone valve to the water heater is a poor choice. Using a pump with a check valve is a much better choice. Do this right and you'll have hot water coming out of your ears.
Converting a steam sys to a hot water sys adds a lot of water volume to the boiler that the boiler has to heat up which might produce a slower response to space heating. Is that boiler an 80M or 140M?

SENorthEast1895er

ahh, sorry. no, i meant the indirect tank is too small. Munchkin 140M. 2700 sq feet, and 660 EDR, if I recall correctly.

HomerJSmith

If you pipe it correctly and get rid of the expansion tank replacing it with a diaphragm tank, you will have all the hot water you need and space heating, too. Look, the recovery of the indirect tank is dependent on the flow and the temp of the boiler supply water. The CV of a 1" valve is 7.0 plus there are other losses in the piping tank and Muchkin heat exchangers. A Taco 0010 (which you have as the boiler pump?) has 8.5 'hd at 14 gpm. Your head loss, the way it is configured now, is probably greater than that which means that you don't have the flow thru the indirect that you really need for recovery.
Re-piping your sys would make all your problems go away, I think, and you could use your ODR.

SENorthEast1895er

there’s a single 007-f5 for the whole system.

a repipe is the dream, but not in the cards at the moment ($$$, i assume) given that i have no idea how long the boiler will last

I like to think I could do some chunk of the work myself (running the primary loop and hooking in the secondary, removing old cast iron pipe), but i think there might be more to it than i realize. (i’ve been reading a bit of Dan holohan)

(can i run a primary loop with PEX? If so, this might be easier than I realized)

But before i even think of doing any of that, I need to focus home improvement on some exterior issues.

HomerJSmith

there’s a single 007-f5 for the whole system

A Taco 007 ain't going to cut it. The Munchkin 140M needs a Taco 0010 pump. You are so, so, under powered pump wise. You don't have the flow you need. I suspect you are short cycling like crazy.
You can run anything with Pex A with 02 barrier with the right size pex.