Aquastat L7224/L7248 disable for water when tankless hot water heater installed

Reply

  #1  
Old 02-07-13, 06:40 PM
Member
Thread Starter
Join Date: Feb 2013
Location: Usa
Posts: 5
Received 0 Votes on 0 Posts
Aquastat L7224/L7248 disable for water when tankless hot water heater installed

I moved into a house recently with only oil hookup. I have a Crown TZW100 boiler that heats my home baseboard radiators and also my water (sinks, showers, dishwasher, washer, etc.). The unit cycles to keep hot water available for use. This was getting expensive so I looked into a separate hot water heater. The current boiler wasn't keeping the water temp hot throughout a shower. (I figure I am putting out too much gpm). Decided to go with a tankless hot water heater. I need to know how to prevent my current boiler from trying to heat water. I will only need it during winter for heat. I have an Aquastat L7224/L7248 control connected.

Anyone know how this can be done? Thanks
 
Sponsored Links
  #2  
Old 02-07-13, 08:23 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Take a look and see if this helps you out...

You need to turn the "LOW LIMIT" to OFF.

Leave the HIGH LIMIT set at 180.

https://customer.honeywell.com/resou...0s/68-0281.pdf

Your unit may be an older one and some of the features that are in this manual may not (will not) be available on your aquastat due to firmware changes made over the years.
 
  #3  
Old 02-07-13, 08:33 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
The newer models of the 7224 allow turning off the Low Limit, but I just scanned this manual and did not see instructions for doing so. It's possible that all you will be able to do is turn it down to 110 ... you might have to change a'stats in order to defeat the low limit on yours.
 
  #4  
Old 02-09-13, 11:03 AM
Member
Thread Starter
Join Date: Feb 2013
Location: Usa
Posts: 5
Received 0 Votes on 0 Posts
Thanks...doesn't look like I can turn it off. I did lower it to 110. In the process of connecting the water heater. I'll see what happens and look into another aquastat. Again thanks for the help.
 
  #5  
Old 02-09-13, 12:13 PM
Member
Thread Starter
Join Date: Feb 2013
Location: Usa
Posts: 5
Received 0 Votes on 0 Posts
Aquastat only drops to 110. Unit still turns on, but not as often. Do you think I could tie my hot water line into it? That would make it so hot water was going into the coil and the temperature wouldn't drop enough for the unit to kick on. Wondering if you have heard of this before or if you think it might damage something. Thanks
 
  #6  
Old 02-09-13, 03:05 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Do you think I could tie my hot water line into it? That would make it so hot water was going into the coil and the temperature wouldn't drop enough for the unit to kick on. Wondering if you have heard of this before or if you think it might damage something.
You mean the hot water out of the new heater? Through the boiler and then to the home?

No, that makes no sense. All you would succeed in doing is cooling the hot water to the home (if the boiler is cooler than the hot water) and heating the boiler with the water heater.

I've heard and seen ALL KINDS of weird things!
 
  #7  
Old 02-09-13, 04:18 PM
Member
Thread Starter
Join Date: Feb 2013
Location: Usa
Posts: 5
Received 0 Votes on 0 Posts
The way I was looking to set it up was so that there would be no cold water line going in. The hot water heated in the boiler would just cycle right back into the boiler. The water would be hot so the boiler won't need to heat it and it won't turn on.

The new tankless heater is connected after the boiler line so the hot water line out of my boiler is useless now. I just don't know how to prevent it from heating water that I don't need...thus wasting oil.
 
Attached Images   
  #8  
Old 02-09-13, 04:29 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
The way I was looking to set it up was so that there would be no cold water line going in. The hot water heated in the boiler would just cycle right back into the boiler. The water would be hot so the boiler won't need to heat it and it won't turn on.
Sorry, I'm still not following you.

You are thinking of connecting the two pipes on the boiler together? No, don't do that.

When you disconnect the pipes from the boiler, leave them OPEN, don't even cap them. If you do put caps on them, don't solder them, just slip them on and leave them.

No matter what you do, whether or not you flow water through the coil, the boiler will still fire up whenever it cools below it's LOW setpoint.

If you can't turn 'off' the low limit on your aquastat, the only thing you can do is change the aquastat.
 
  #9  
Old 02-09-13, 04:32 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
This one allows you to turn OFF the LOW LIMIT if not needed:

L7224U1002 - Honeywell L7224U1002 - 120 Vac Oil Electronic Aquastat
 
  #10  
Old 02-09-13, 06:50 PM
Member
Thread Starter
Join Date: Feb 2013
Location: Usa
Posts: 5
Received 0 Votes on 0 Posts
Thanks for clearing things up. I'll probably just pick up that aquastat. I appreciate your help.
 
  #11  
Old 02-09-13, 10:37 PM
Member
Join Date: Feb 2013
Location: usa
Posts: 9
Received 0 Votes on 0 Posts
Kinda of the same thing as you, but we just poped on a shark bite shut off on the hot side. We were pulling a lot of hot water with the tankless and old oil setup.Low limit down to 90. This also lets your boiler run every so often and if you need to you can fall back if the tankless acts up. Just open your shut off and your back to having hot water.
 
  #12  
Old 02-09-13, 10:41 PM
Member
Join Date: Feb 2013
Location: usa
Posts: 9
Received 0 Votes on 0 Posts
Also don't cut your water line into the boiler. Not sure about your setup, but there might be an auto feed for the system, plus service if you ever drain it. How are you going to refill the system?
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: