Boiler is providing heat but no lasting DHW

Reply

  #1  
Old 01-15-19, 05:41 PM
T
Member
Thread Starter
Join Date: Jan 2019
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
Boiler is providing heat but no lasting DHW

So I have an older Weil=Mclain furnace in my new house and we have heat, and all the heat pipes for the radiators are hot as hell. The pipe for DHW is hot for a moment when you call for hot water and the water is piping hot however, it only lasts for all of 20 seconds before going to luke warm. This is in the shower and sinks. Even as the furnace runs it doesn't provide DHW. I have the aquastat set at 180 HI, 150 LO and Diff at 15 and that should be providing plenty of hot water.

Is the aquastat bad? I can't figure it out and I had the local company out and they sent two dummies that claimed the mixing valves in my showers were bad. Any help would be appreciated!!!
 
Sponsored Links
  #2  
Old 01-15-19, 06:13 PM
A
Member
Join Date: Mar 2010
Location: USA
Posts: 3,926
Received 51 Votes on 49 Posts
Do you get hot water longer if you stand outside the tub and let a slow flow run from the tub spout?

Do you ever get a nice long hot shower, notably if at least one zone in the house is calling for heat?

It is not unusual for the domestic hot water coil to become lined with calcium or sediment which causes its gallons per minute rating to be much lower than when it was new.
 
  #3  
Old 01-15-19, 06:29 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 56,394
Received 747 Votes on 702 Posts
Welcome to the forums.

Do you get hot water longer if you stand outside the tub and let a slow flow run from the tub spout?
How about if you stand on one foot ?

Check the temperature gauge on the boiler. If it's up around 180.... it's more than likely a coil problem.
 
  #4  
Old 01-15-19, 08:17 PM
T
Member
Thread Starter
Join Date: Jan 2019
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
The boiler gets to temp at 180 and stays there. We haven't had the water tested but it seems like its hard. The coil maybe needs an acid bath?
 
  #5  
Old 01-15-19, 08:47 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 56,394
Received 747 Votes on 702 Posts
I had mentioned an acid bath in another thread and it appears it's not as popular as it used to be. I'd certainly have that done first. Hang tight...... the boiler guys will be in the AM.
 
  #6  
Old 01-16-19, 01:38 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,927
Received 40 Votes on 38 Posts
The simplest first thing to do is to:

1) Get your boiler up tp temp.

2) Turn on your hot water faucet ONLY, in the tub. You check it there because that is your biggest draw.

3) Put your hand on the HOT outlet pipe from the coil, directly out of the coil and before the mixing valve. It should be extremely hot when starting and maintain that temp if the coil is good. If the coil itself is limed up the water will get cool pretty fast.

This will quickly tell you it's the coil and not the mixing valve or your faucets.

Hope this helps a little.
 
  #7  
Old 01-16-19, 03:55 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 56,394
Received 747 Votes on 702 Posts
No mixing valve on the boiler..... it's on the shower faucets.

Same test applies with checking the out line of the coil.
 
  #8  
Old 01-16-19, 06:29 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 734
Received 14 Votes on 14 Posts
While tankless coils are a very efficient source of DHW in winter, they have limits.

ttremblay92's issue may be due to scaling or blockage, but limited capacity is common.

A good way to efficiently get more hot water capacity in winter and lower cost DHW in summer is with a hybrid setup.

Install a separate direct fired water heater. Use aquastat on water heater to activate circulator pump for tankless coil heat source in winter and direct fire tank in summer.

In summer flip switch and aquastat starts water heater burner.

Have used this hybrid system for years to increase hot water capacity of tankless system in winter at lower cost than direct fired water heater.

Directly fired water heater in summer is more economical than running main boiler. If going to add separate tank, get one with heater. Then spend another $200 on circulator and plumbing.

Long term fuel cost savings provide good pay back. I have used this on a 60 year old Weil-McLain for 20 years.
 
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: