Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Next steps? Hot Water zone not heating

PigPen Member Posts: 3
Happy Thanksgiving all!

Apologies for the long post but I’m looking for some help and it appears to me that the more information I give, the better advice I’ll likely receive. I greatly appreciate any assistance here. I’m probably at the point where I need to bring in a professional but I’m short on funds at the moment and would sure like to determine what my next step could be that doesn’t involve a $400 - $600 house visit.

My situation in a nutshell: the hot water zone for my heating system is not working correctly so while the rest of my house is warm and comfortable, I have no hot water. I’m looking to understand what to look at next.
The details (with pictures):

I’m running a Buderus furnace with hot water heating. I currently have 6 zones on my system (a little overdone if you ask me but so far, it’s worked well). One of the zones is the hot water tank.

As you’ll see in this picture, I’m using Honeywell Motorized Valves (model: v8043f1036). The valves are at the return portion of the system with a shared pump below the valves.

Based in this picture, you can see that the hot water thermostat appears to be correctly calling for heat in that the motor has been engaged and the arm has activated the End Switch. That said, no water is being drawn.

My assumption was that the End Switch was blown and that I’d need to order a replacement valve head as it doesn’t appear that the End Switch can be replaced by itself. That said, I wanted to make sure this was the case so today, I switched the Valve Head from another, verified-working, zone (the Breezeway). After completing the switch, I tested the system but still had no luck. That said, the Breezeway continued to work correctly even with the suspect Valve Head from the Hot Water zone so now I know that Head was good.

At this point, I’m thinking one of two things is happening:
1. The thermostat is not functioning. I think this somewhat unlikely because I’m seeing the motor engage and the arm contact the End Switch. That means it’s working, correct?

2. The actual valve in the sweat zone is not functioning. This doesn’t seem right either in that I’m currently limping through the holiday by locking the zone below the valve and drawing water through the hot water tank by using the release faucet directly below the motor. I’m getting good water flow through the system and this is getting me to be able to have lukewarm water for showers and the like.

So … what do I look at next? If you have ideas, please let me know. I’m definitely a laymen so if you could describe your actions precisely, I’d appreciate it. Or send links to videos, etc.

Thanks so much for reading through this ramble. I wish you and yours a fantastic holiday season!


  • Zman
    Zman Member Posts: 7,542
    What type of water heater do you have? How is it piped?
    That is some dizzying wiring, do all the end switches tie together and go to the boiler? Are the connections solid?
    Pictures of the hot water heater and piping would help.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • PigPen
    PigPen Member Posts: 3
    At work right now so I won't be able to add more photos until later today. But I can attempt to answer your questions based on memory and description:

    1. The hot water tank is the bottom half of my Buderus system. The furnace / boiler is the top half. Hot water feeds out of the boiler and then splits to the 6 zones of the house. One of those zones is the hot water tank so the hot water from the boiler is piped through the hot water tank to heat it. The pipe exits the back and feeds to the valve I've shown.
    2. Yes. All the End Switches are in-line and tied together. I believe the connections are solid (because other zones are working) but I want to address this in more detail. Again, lay person here so please don't pick on me if I get this wrong ... but ... on other posts, I've read that whenever a zone asks for heat, the furnace ALWAYS kicks on. That doesn't happen in my system. I don't know if by design or by error (or if by error, whether this is recent). You'll note that the close up of the Hot Water zone valve shows two extra wires connected to it. This is the feed for the system back to the controller that fires the pump and boiler. We replaced the controller about 6-8 years ago. Perhaps this is my problem again? How would I check?
    EBEBRATT-Ed Member Posts: 15,304
    I am assuming by your post that you have 1 pump that supplies all your zones including your hot water tank.

    If you believe the zone valve to your tank is open (and you can open it manually with the lever). Turn the thermostats on all your other zones down to close all the other valves and see if you get flow to the water heater then.

    Check the water pressure in the boiler system it should be 12-15 psi with a cold boiler maybe 20 or so when hot.

    Pictures of the piping will help (although if it looks like the wiring which is a mess) maybe we don't want to see it
  • PigPen
    PigPen Member Posts: 3
    You're correct, one pump runs the entire system. You can see that pump in the bottom left of this picture.

    I'll try to close off the other zones to see if I can get draw (I actually tried this yesterday without luck).

    Water pressure in that 15-20 range.

    Happy to take pictures of the piping later tonight.

    Based on my first reply above, I'm really wondering whether I have a problem with my control panel. I'm using a Honeywell L8148A Aquastat Relay. We replaced this a number of years ago. I wonder if this is gone bad again. Would you happen to know how to troubleshoot whether that is the actual problem? And any idea on level of difficulty to replace that? The part isn't particularly expensive and the inner workings are minimal.
    JUGHNE Member Posts: 11,021
    With one pump for everything, the DHW zone valve manually open and the boiler firing you should be making hot water.

    However the boiler may produce cooler water for heating the house and ramp up to do DHW.

    What type of heating radiation do you have?
  • lchmb
    lchmb Member Posts: 2,997
    if the zone valve is open, (multiple at that) and your boiler water is hot, since this is a cold start system, I'd suspect your circulator is not functioning. Whether it's not getting power or getting power and burnt out would be the question I'd look at...
  • BornForDying
    BornForDying Member Posts: 40
    Sometimes the valve itself will seize up in the body. If you take off the head you can try operating the valve by hand.