Base boards not getting hot.

Nick_R

I have a two room apartment that I am trying to heat. Each room is on a separate floor, have their own zones and are pretty small with shorter sections of baseboard. The boiler is wall hung. It has two taco circulaters that push the hot water through one check valve each. The check valves work. The return pipes converge twelve feet from the boiler before they enter the boiler. The pressure is normal. The output temp on the boiler is 182 degrees. The return temp is sometimes the same as the output and the boiler shuts off while the zones are still calling for heat.

The baseboards are not getting as hot as they should. As a result the rooms stay cool and the system is constantly running. Someone once told me that if the water is flowing to fast the baseboards will not get hot. Could this be true?

Thanks in advance for any insight,
Nick

HVACNUT

It could be as simple as purging the zone, or it can be much more. Can you post some pics of the boiler and piping? Not too close.
Is there outdoor reset?
The fact that the return temp is the same as the supply temp is a little weird even if they're very short loops.
Most mod con boilers will go into a soft lockout when there's not enough diff in S & R temps.

unclejohn

Sounds like air or bad pump. Need some pictures.

STEVEusaPA

Sounds like too big a boiler, not enough heat emitters. What part of the world are you in where you need 180° water today?

Ironman

Are the dampers open on the BBs? Has new carpet been installed?

rick in Alaska

Does the pressure gauge read accurately? If the pressure is too low, you will only get some gravity flow.
Also, are the dampers on the baseboard open?
Rick

Nick_R

I apologize for taking so long to reply and I appreciate that all of you took the time to ask questions. Here are some answers to your questions and an update.

1. I live in New Hampshire.
   
2. No outdoor reset.
   
3. The BTU of the boiler is a max of 140k. It is a Takagi Jr. I had really good luck with the one at my personal residence where I heat 1200sqft of radiant floor and another 1200sqft with a hydronic air handler, so I installed one here as well.
   
4. I cleaned and straightened the fins, the BB dampeners are open and neither room has carpet.
   
5. I have a Flir thermal camera for my phone. I find this tool tricky to use. Some reflective surfaces doesn't return accurate temperatures. When I look at my dampeners I see a temp of 124 to 130ish. Does this seem normal?
   

UPDATE:
First, I do believe that both floors had air in the pipes. I can't believe how much time and water it takes to bleed the air out of a system!!!
I installed an additional 7 feet of fin on the second floor and added bleeders. So far the second floor works great.

The first floor still has the same issue. It's a really odd room. Not much room for baseboard, and without getting into a ton of detail none of the walls are adjacent to a heated space. This really changed my BTU calculation. Right now the room has 14ft of 3/4 inch fin. This is about half the amount that I need. I don't have enough wall space to add enough.

I purchased a Smith hydronic wall mounted heater. It is about 7k btu @ 180deg. I am going to branch off of the main loop using a a T and a venturi T.
I have two mounting options. I can mount this in the wall about two feet above the main loop. This installation seems simple but it will be far away from the coldest part of the room.
The second option is to install it in the suspended ceiling at the end of the room that really needs heat. This will require that I run 1/2 pex from the basement, up through a closet and across the suspended ceiling to the heating unit. It will be about 25ft of pex in each direction with a 10ft rise. Will this option have additional challenges? I can't find any documentation that references branch length for this type of heater.
Since this heater will be installed before my baseboards, should I be concerned with the delta across the hydronic heater reducing the output of the baseboards? How many feet of head will a venturi T add?
Okay, just one more question. This unit did not come with a temp switch. The instructions say to wire it to a thermostat. This room already has a thermostat.
Should I wire it to the existing thermostat and a 110v relay?
The fan is only 39watts. Can I run it off of the same relay as the Taco 007?

kcopp

Sounds like you have a tankless water heater and not a boiler.
They generally require special piping and bigger circulators.
Now that you added a venturi tee and a "kickspace type" heater set up you may have made the piping have more restriction. Do you have pix? Where in NH?

Nick_R

@kcopp I actually haven't added it yet. It's sitting on the floor infront of me right now while I contemplate my next step. What would you like pix of? I live in the Manchester area.

From what I understand this specific tankless water heater is rated for space heating applications when pinned correctly. It has a solenoid to govern GPM so I'm not sure if increasing the size of the circ would matter. The unit I have at home also has a remote that displays GPM. With a 40 degree delta the unit flows around 3 GPM. I am aiming for a 20 degree delta overall here. I'd need to get out the chart to see what GPM that ends up being, but I know that as of now my baseboard temp is coming back around the same as its leaving the boiler so (as design) the boiler shuts off while the water continues to circulate.

Ironman

Nick_R said:

@kcopp I actually haven't added it yet. It's sitting on the floor infront of me right now while I contemplate my next step. What would you like pix of? I live in the Manchester area.

From what I understand this specific tankless water heater is rated for space heating applications when pinned correctly. It has a solenoid to govern GPM so I'm not sure if increasing the size of the circ would matter. The unit I have at home also has a remote that displays GPM. With a 40 degree delta the unit flows around 3 GPM. I am aiming for a 20 degree delta overall here. I'd need to get out the chart to see what GPM that ends up being, but I know that as of now my baseboard temp is coming back around the same as its leaving the boiler so (as design) the boiler shuts off while the water continues to circulate.

To get a 20* delt T, you would need 6 gpm. There's no way any standard residential circulator will produce that with the head of the heat exchanger in that water heater. (Yes, it's a water heater, not a boiler).

The heat exchanger is designed to have house water pressure (60 psi) entering and an open faucet exiting. To achieve 6 gpm, a ups15-58 could overcome 14 ft. of head (6 psi).

I'm sorry to burst your bubble, but you have the wrong appliance.

This comes up on here almost weekly (using a tankless in place of a boiler) and the results are always the same.

My response is always the same: if a tankless could replace a boiler, then there would be no need to make boilers.

Nick_R

@Ironman Thank you for chiming in. Considering that the appliance isn't going anywhere would it be more appropriate to replace the baseboards with wall mounted radiators?

Ironman

Nick_R said:

@Ironman Thank you for chiming in. Considering that the appliance isn't going anywhere would it be more appropriate to replace the baseboards with wall mounted radiators?

No, that's not gonna do anything to address the issue of the high resistance to flow in the heat exchanger.

The only things I know to suggest are:
1. Remove the water restrictor at the inlet.
2. Pipe it p/s with a large circulator (ups26-99) pumping the water heater.

How about posting some pics of what you've got?

kcopp

@Nick_R I am over in the seacoast.
I also agree to pipe the tankless WH primary secondary to get your flow rates.
1 circulator just for your heater and they another to do your heating zone.

Nick_R

Ironman said:

Nick_R said:

@Ironman Thank you for chiming in. Considering that the appliance isn't going anywhere would it be more appropriate to replace the baseboards with wall mounted radiators?

No, that's not gonna do anything to address the issue of the high resistance to flow in the heat exchanger.

The only things I know to suggest are:
1. Remove the water restrictor at the inlet.
2. Pipe it p/s with a large circulator (ups26-99) pumping the water heater.

How about posting some pics of what you've got?

Sorry for the delay. At the airport.

I don't believe its possible to remove the restrictor. This is not a strictly mechanical system. It is digitally controlled. The solenoid that controls flow is dynamic. Removing it would cause a fault error.

At my primary residence I have had a Takagi Jr heating my home for 12 years. It heats 1200sqft via radiant floor and another 1200sqft via hydronic air handler. It's a 100 year old house with giant windows and 10 foot ceilings. The idea that I can't heat this tiny apartment with the same unit seems ridiculous. There must be another issue.

Nick_R

@kcopp Thanks for that example. It explains a lot. That is the setup that I have at my residence. I appreciate it.

Nick_R

@Ironman The reason why I proposed using wall hung rads was because the return water in that zone was coming back hot enough that the boiler would shut off. (Return temp = to supply temp) I know that I don't have enough BB to heat the room. I also don't have enough room to add more BB. I thought the wall hung radiators would provide more BTU's in a smaller footprint.

Jamie Hall

Wall hung radiators -- if they are big enough -- will give you more heat. You need to compare the heat loss of the room to the heat output of the radiation...

DZoro

Is it piped like @Kcopp posted at the 2 room apartment?
You mentioned the old 12 year old system is primary/secondary, the "new" Takagi's are even more restrictive than the old ones. So there is no forgiveness with the primary/secondary piping and pump size.

D

Nick_R

@DZoro thanks for the info. The two appliances are the same model. I bought them around the same time. I held onto the second one as a back up for my house for a number of years. (I had my doubts about using a hot water heater as a boiler and they were so cheap, why not buy two). I installed this one in the apartment and I thought it was fine. None of my tenants complained. I recently started spending a lot of time in this apartment to renovate it and noticed that when it hits 20 degrees or less the downstairs doesn't keep up. Maybe my prior tenants just didn't care. It is a small place and my renters usually work a lot and just need a place to sleep and shower.