Aquastat at 200, output still only 130?

MattT

I'm stuck on this one... I have a Utica 100btu gas fired boiled for my forced hot water baseboards (M100AGB). It's struggling to maintain 67 degrees in my house.  3 zones, but I only use 2. I only began to notice this when the temps in the Boston area drop below 10 degrees or so.  I set the aquastat at 200 and measuring with a thermometer I'm only getting 130 after the expansion tank.  System only has 1 circulator on the return side.  Odd thing is at the immediate cast pipe coming out of the boiler it's almost 200 but a few inches away it's 130 on the copper? Any help would be greatly appreciated.  Circulator (taco 007-f5) is constanly running becuse thermostat is always calling for heat.  Boiler fires up every 10-15 minutes and seems to be fine otherwise.  Unable to tell pressure because guage is broken, No gurgling sounds heard either.  Any help would be much appreciated.

MikeAmann

That infrared heat gun will not read correctly on a shiny surface. Paint a spot on the pipe with some flat black Rustoleum and try again. If it really was 130, you should almost be able to touch the pipe and not get burned.

STEVEusaPA

If you temperatures are right, your circulator isn't circulating...
Carefully touch the pipes where you feel the disparity. 130° & 200° are quite different to the (quick) touch.

HVACNUT

It certainly seems the circulator isn't moving water. It might be gravitating and that's why the boiler cycles. 
How do the pipes above the zone valves feel?
Is the circulator hot? Too hot? Be careful. 

MattT

I'm leaning toward the infrared thermometer reading the copper pipe incorrectly as MikaAmann has suggested and I'm going to try putting some flat black on the pipe and test again.  The circulator is working because I have a tow kick heater in my kitchen that is blowing warm air and only activates when it sense 120 degree water (I believe).  But even if the output is correct my house is still struggling to stay at temp.  21 new high efficiency windows, 4 new exterior doors, minimal drafts. Taco circulator is getting to about 205-210 degrees when moving water and running. I'll check with the flat black paint on the supply and returns when I get home tonight.  Thank you for the responses.  

mattmia2

Some water will usually flow via gravity, as the water is heated it rises out of the boiler because it becomes less dense and as it cools it becomes more dense and falls back to the boiler. That may be enough circulation to trip the aquastat in the toekick heater (and the fan in the toekick heater may make that part circulate more because it cools the water more readily). This lesser flow cold be transferring enough heat to heat your house some but not get it up to temp.

MattT

MikeAmann, you are correct sir. A little flat black paint and im getting accurate readings.  Actually saw 204 at the supply and 181 at the return.  Second floor seems to get warm fairly quick.  I'm wondering is this unit it just undersized for the 2100sqft house? The only zone that appears to be added since the house was built in 1986 was the basement, but I usually run an electric space heater for the extra 900sqft in the basement when we use it.

Hot_water_fan

I'm wondering is this unit it just undersized for the 2100sqft house?

Doesn't sound like it. If it was undersized, you'd have constant operation, not cycling. Try turning on the basement zone, warming that up should warm the first floor.

MattT

Ya the only constant operation it seems is the circulator pump. The boiler seems to be cycling appropriately.  I'll leave the basement zone on a steady 65-67 and see if that makes a difference with the first floor maintaining the proper temperature. It's going to be 8 degrees overnight so i should be able to tell.  I've been leaving the 1st and second floors at 69 degrees and not setting them back at night because it will never get back up to temp in the cold mornings, and I watch as they creep to 68 then 67 at night while thermostat constantly calls for heat.

HVACNUT

What type of emitters?
If baseboard, no carpet bunched underneath, fins are clean, no long drapes blocking. Is there enough baseboard? For Slant/Fin 30 or equivalent, I think it puts out 600 BTU per linear foot at 180°. Not positive but I think you can get 23K BTU from a 3/4" copper loop max. Corrections to my memory are more than welcome. 


And you neglected to tell us the thermostat is a Nest. Is it wired constant 24v or are only R and W being used?

MattT

1st floor is all hardwood floor throughout, I pinned the drapes up so they aren't anywhere near the baseboards.  I have 3 nest thermostats for the 3 different zones and they are all wired with a constant 24V C wire.  I do have those NeatHeat plastic type baseboard covers throughout the house.  Wondering if they are actually restricting the heat that much despite the manufacturer saying they wont effect performance. They seem to have plenty of airflow from bottom to top. I'm running out of ideas here, and that 1 circulator pump is running non-stop to try and get the zones up to temp.

Most rooms have 14' baseboards except the double living room that has 2 14' baseboards on either side under windows. Bathrooms are 4ft baseboards. About 130ft of baseboard total including basement when I measured last week.

MattT

Ya heating the basement did not affect the 1st floor.  Watched thermostat in my livingroom drop from 69 to 66 overnight last night while it was 8 degrees. Took a few hours to drop but something is definitely up with the system.

Jamie Hall

Do I have this straight? The actual supply temperature is around 200 and the actual return temperature is around 180? That's a quite reasonable delta T -- if that's on the return from the baseboards. However, the boiler is cycling on and off -- which simply means that the boiler is producing more power, when it is running, than the system can absorb. Are all the returns at the same temperature? Is there a bypass?

The amount of baseboard you mention -- 130 feet -- should be able to absorb about 75,000 BTUh at those temperatures, which is very nearly the full power of that boiler (you don't say whether the 100,000 BTUh rating is input or output) so while the boiler may cycle, the on times should be much longer than the off times. I'm wondering about low flow in one of the heating circuits.

Hot_water_fan

Is there anything impeding first floor flow? Also, has the baseboard been modified?

A combination of these would work:
1. Add more baseboard/panel radiators/etc.
2. Add higher output baseboard (same linear feet, more BTU/foot).
3. Reduce heat load (air sealing/insulation), paying attention to the first floor in particular.
4. Increase flow rate to increase output (with 204 supply and 181 return, you have an average temp of 193. You could double the flow and bring that up to 199). This increases electricity usage, but it's only needed 1% of the year. This is only if the 1st floor zone is flowing freely already.
5. Live with it, maybe adding an electric space heater downstairs for the coldest days of the year.

MattT

When I run all zones the return is right around the same 178-180.  And the input is 100,000 BTU. DOE heating capacity is 83,000. 

As far as anything impeding the first floor flow: nothing I can think of aside from those NeatHeat covers.  My next day off I may pull them off, clean the fins (again) and removed the from metal/tin front cover and dampner before reinstalling the Neatheat covers to see if it makes a difference (just leaving the backing plate).  They are supposed to install directly overtime but I may try it as a test to see if I can increase airflow and heat transfer.

Despite the brand new doors and windows throughout the house with argon between the glass...im to the point I bought sheet magnets cut them to size to put over the AC supply and returns while my AC and air handler are off for the winter.  Also used some of that heat shrink plastic wrap and sealed the front of my fire place to prevent drafts since we never use it.

When I did a home energy audit last year the only insulation upgrade recommendation they had was my attic could use a few more inches of blown-in   on top of the existing insulation.

Now Hot_water_fan, what would you recommend for a circulator to increase flow (currently have the Taco 007 F-5). 

Again, i appreciate all the responses while I attempt to rectify this issue. I'm no HVAC guy but I certainly don't have a problem digging into things.

Hot_water_fan

When I run all zones the return is right around the same 178-180. And the input is 100,000 BTU. DOE heating capacity is 83,000.

I'd like to know three more supply and return pairs - to/from basement, 1st floor and 2nd floor. Is that what you mean by 178-180?

EBEBRATT-Ed

You are pretty much maxed out. your 130 feet of baseboard will do about 78,000 depending on the water temp.

your 100,000 btu input boiler is only going to do 100,000x.82=82,000-15% piping and pick up=70,000 Being hot all the time the pick up doesn't mean much your probably putting out 75,000 and the baseboard is balancing that.

The baseboard drives what the system does not the boiler. Add some more baseboard but it will lower your water temperature a little and increase efficiency but won't do very much

HVACNUT

Is the kick heater piped in series with the rest of the loop, or a branch off of the loop?

MattT

I will get those measurements in the next few days (doubles all week at work).  And the kick heater is piped in series with loop.  It replaced a 6ft section baseboards (used same exact pipes) when I renovated my kitchen, and it's a QuietOne 4,000 BTU I believe (tried to keep same BTU as baseboard it was replacing, but apparently should have gone a little bigger).

Peter_26

Is the bottom picture the covers you have installed?

MattT

No mine are a little different, they only have the holes on the top.  And curtains have been pinned up higher since this pic.

Also the angle of the pic makes it look like there is no space under the cover, but there is about 1.5 inches or so between hardwood floor and cover.

HVACNUT

There's only one way to find out. Remove them and see what happens. 

bburd

Those new covers look more restrictive than the old style, and may be limiting airflow— therefore heat. Also, they should be at least an inch off the floor so they can draw in cool air at the bottom.

MattT

I'm going to have to pull them and see how it does. Nothing to lose at this point.  Unfortunately it's going to be a a balmy 19 degrees for a low this week so i probably wont be able to duplicate the issue.  This weekend however is looking like it's going to be 5 degrees though.

mattmia2

bburd said:

Those new covers look more restrictive than the old style, and may be limiting airflow— therefore heat. Also, they should be at least an inch off the floor so they can draw in cool air at the bottom.

If they were restricting the output of the emitters the return temp would go up.

Are the dampers on the old covers fully open underneath the new covers?

What is the temp of the finn tube near the middle of a run if you take the cover off?

The boiler cycling on the aquastat tends to indicate that there isnt much flow or the covers are restricting output of the emitters.

The 20 degree delta t indicates there is heat being emitted. Maybe the delta t is more if it is working properly.

Did it ever work?

Peter_26

We might not get a follow-up message after the covers are removed. Hate when that happens!

MattT

No you will... I'm on a double today and haven't been able to test it yet.  You guys have spent time replying and attempting to assist me, so it's the least I can do.  Especially if the thread will help someone in the future.

Peter_26

Awesome! Sometimes the problem is solved and the solutions are never posted. I wish everyone that posted had the same thoughts. Thanks!

MattT

Alright so it was about 6 degrees last night when I tested my system.  I ran all 3 zone at once and let the boiler heat the water until the point that it shut off but water was still circulating.

Basement supply 176 return 172 (shortest loop and it was added in after the fact so it appears the supply is tapped into my second floor supply) 

1st Floor supply 200 return 171

2nd Floor supply 194 return 176

I also tested the return after removing the NeatHeat covers on my 1st Floor and there was no discernable difference in return water temp.

I did however remove the front metal cover and damper of the baseboards before replacing the NeatHeat covers to see if that will increase the heat output, but I don't expect much change from that. 

According to the thermostat it does appear it was still calling for heat at all times overnight.

mikeg2015

IR cant read shiny surfaces. You need to put black tape on the copper and it will read close-ish. Better to use a clamp probe.

Here’s the basic “boiler not heating” checklist.

- check pump amps, make sure its flowing and loaded.
- - make sure all baseboards are hot… if not they might be air locked, bleed them or flush somehow.
- Make sure pump is facing the right direction so water flows towards the bottom of the boiler and leaves the top.
- make sure boiler has adequate pressure. Radiators get air locked easier when pressure is low and pump suction can cavitate.

FYI expansion tanks are supposed to be sideways. They fail faster that way. Should ve vertical up or down and a ball valve to isolate it is better so you don't need to drain the boiler to change or test.

MattT

I painted a section of all copper pipes with flat black paint, I feel confident these are accurate readings