Lack of heat

grenwa05

just trying to get some ideas on where to check for possible causes on the following issue:



When showering, our hot water seems to go away for about 4-5 minutes about 1 minute into the shower (sometimes longer, sometimes shorter) then it will come back, then go away again. I thought maybe the boiler just needed a cleaning so I did that. As of right now, we have 2 zones with 2 Taco 007 pumps no priority controls for the domestic water coming out of the tankless coil. First thought, maybe the pump for the 2nd floor is shot? We make sure the t-stats are turned off when showering so the baseboard doesn't take away the heat.



Any suggestions welcomed. Thanks....I do work for a heating supply company so I do have some decent knowledge of how to replace things and test them.

kcopp

What do you....

Have for a Hot water system? Kind of soulds like a tankless coil...  Sounds like it is "Limed up" and is not transfering heat well. Either replace the coil or do an acid wash to get all the crud out. How hard is your water? A long term solution needs to deal w/ that....kpc

icesailor

Lack of domestic hot water:

You may have a few problems.

What are the "Hi" settings and "Low Limit" settings on the boiler control on the front of the boiler? The "Low Limit" should be at 160 degrees with the "Hi" at least 20 degrees higher than the "Low".

The other thing is that you have two circulators. One will be wired through the boiler control and a thermostat wire will be connected to the "TT" terminals on the control. The other circulator can be a problem. it MUST be wired through the "ZC/ZR" terminals on the boiler control. Even if it is wired through a zone controller like a Taco ZC 50*. If not, the heat circulators will run when you need to make hot water.

If it comes back like you describe, the coil can't be all that bad. There's a thermostatic mix valve on the boiler tankless. It may be bad.

A bunch here will tell you to put in an indirect. I don't do that.

grenwa05

tankless

I really don't think it's the tankless coil because we have plenty of hot water on the 2st floor. I'm going to adjust down the Watts 70A tempering valve because I just remembered that it was jacked up all the way. So I figure turning it down to start would be a good idea (to like 120 degrees). I'll check the Hi & Lo limits when I get home.

Charlie from wmass

Watts tempering valve

thats your issue. I prefer Sparco mixing valves for this type of application. The watts do not seem to hold up very well. You may still need an acid wash and to adjust your boiler water temperature. The pumps have no bearing on your domestic hot water. so first floor or tenth floor its not a circulator issue.

grenwa05

tempering valve

not sure why I kept thinking the pumps had something to do with the DHW!!!???? thanks for clarifying that up for me : )

I'll grab a new sparco mixing valve and bring it home and give it a shot. Thanks for the input!!! VERY appreciated

Ron Jr._3

I agree with Charlie

We've been having a bad time with the Watts 70As . Hottest temp is supposed to be 160 . Many top out at 115 - 120 on brand new installs . Most people do not like that from a 6 hour old system .......  

icesailor

Lack of DHW

Yup, You're right. It couldn't possibly have anything to do with the pumps. Or the settings of the boiler thermostat. No one EVER wired the second circulator direct so that it didn't start the burner because it wasn't wired through the ZC/ZR terminal and wouldn't  start the burner on a heat call and kick it up to the high limit control. And there is absolutely no possibility that some one individual may have decided to turn down the operating temperature to 140 degrees, just above the condensing exhaust temperature and the boiler water isn't hot enough to add enough BTU's into the DHW coil. It just never happens.

Funny though, I see it all the time. If it gets hot at the beginning of a shower, then gets cool and then slowly comes back, in my world, that's the operating control set too low.

Oh yeah, and a third world test? Turn up the thermostat that starts the burner up 10 minutes before you want to get in the shower. Then, the system is running on high limit. If the water stays hot, the setting is too low.

grenwa05

tempering valve

You were right on. I actually just grabbed a 70A repair kit and did that last night and the shower ran perfect all night and this morning. So i'm going to leave it as is and if it starts acting up again, I'll just have someone come over and take that one out and put a Sparco in. Thanks for the help, most importantly, WIFE got a nice hot shower and is HAPPY : )



Thanks again