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Water temps? Not enough heat.

Started by overclocking, January 04, 2016, 10:41:38 PM

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overclocking

Hi guys, seems I am having a problem somewhere and it's got me a bit perplexed.

House has 3 zones currently, one large, two small. Built in 96, I would consider it fairly well insulated, with 4k total,but only 2600 sq feet requiring heat.

My gas boiler keeps kicking on, it's 9* out and hearing the lp gasser light up makes me cringe.

At first I thought my boiler went out, so I went to check her and it was 191* and idle.

So next I went in the basement to see what the gasser was up to and it was running and running for a while with the indoor boiler temp around 190. I cut the power to the gas valve thinking it was reverse heating the water in my 1400.

Thermostat set to 70*  in the house, and after hours I wasn't able to reach 70, 65 was max.

Back outside I went to check the OWB. She's still at 190 idle with no indoor gasser running, so the boiler seems to be keeping up fine.

Back inside I remembered that my gas boiler has an outdoor reset switch that adjusts the water temp on a curve based on outdoor temp. That explained why it was running, it was set to turn on when water return temp dropped below 160, if outdoor was below 30, so I backed it off to 150 turn on temp.

Well here it is hours later and still haven't seen 70 indoor temp. The wood boiler is working fine at 180-190, the pumps are pumping, zone valves are calling.  The water temp not getting hot enough is the only thing I can suspect.

House side:
It's coming back to the boiler from the zones entering the 50 plate exchanger at 140ish* and it's leaving the exchanger at about 160 getting sent back to the radiators.

Wood side:
The side of the exchanger from the OWB enters at around 176 from the best reading I could get from a digital laser thermometer and is dropping to 155 headed back to the OWB.

I just cleaned the Hx with acid a few months ago, so i am hopeful it isn't build up.


Any ideas are appreciated.

Ivan49

 Are you sure your pumps ae good? I had a similar problem and I took my pump motor off ans it was bad but still pumping just not as fast as it should be. New pump and everything works fine now

doctorb

Your OWB sounds fine.  You're not exchanging heat well at all.  Ivan is correct.  Check the pumps.  Hot water (176) seems to be making it to your basement from the OWB.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

r.man

I can do a rough check on my pump by gauging the temps going into and out of my slab coil while the fan is running. Should be a noticeable difference, but if the outgoing is cool that indicates poor flow, airlock or pump problem. Do you know what your temperatures at the heat exchanger would be normally? I have never owned a plate exchanger so I don't know how bad or good your numbers are.
Life is too short or my list is too long, not sure which. Dec 2014

LittleJohn

Can you check the temp at one of the radiators, cause if a pump is out your system my still some "ghost" or phantom flow that moves the water, just very slowly.

Also do you have any kind of mixing valves in the system???

overclocking

I believe my pumps should be ok, I can hear them moving the water and all the baseboards are warm, but they don't feel as hot as they should be. Usually when the pump has air in it it will bang and pop when the gas boiler kicks on because the water is moving too slow and starts to boil.

Am I wrong at believing the outdoor boiler shouldn't have any problem keeping me at 70 when it's so cold out? When I got up today the temp inside had dropped even lower inside.

I am going to do some more testing, I am going to check the water temp at the thermo regulator and see if maybe it's looping some of the hot water right back to the boiler.

If my wood boilers 190, what should I expect going into the Hx?

r.man

If the boiler water goes directly to the hx as the first device it sees then anything less than 190 is loss. I would expect up to 5 degrees F loss but you should also take a manual temperature of the outgoing pipe at the boiler to check for a difference in the two thermometers.
Life is too short or my list is too long, not sure which. Dec 2014

overclocking

Ok I will do that then.

What temp should my desired output be from the Hx to the house system? This morning the temp coming out if the Hx is 160 into the baseboards, and coming back at 130.

I was under the impression you lose 20* from the Hx, so in a perfect world I should be getting at least 170 when my boiler is 190.

r.man

overclocking I don't know what the temp differences are supposed to be on a plate hx, I tried to find it on the net but I was only getting non OWB numbers. Maybe some members with 50 plate units will chime in with some real world data.
Life is too short or my list is too long, not sure which. Dec 2014

Roger2561

overclocking - just because you can hear the pump making sounds doesn't necessarily mean its pumping water.  The impeller may have broke or stuck.  What make is your pump?  Do you know if it's original equipment?  Roger
Roger

overclocking

Hi Roger,

The pump on the house boiler is original large BG pump, I will get some numbers off it later. I would think though if it's not circulating then it couldn't be returning 130* water and heating the baseboards at the end of the larger loop. It does make me wonder though if maybe the zone valve for the main loop isn't opening all the way and it's restricting flow.

The pump on the OWB is taco original as well and I have a spare for that one just incase. I will get numbers off that one too.

Do you run a Hx? If so what are the exit temps on the house side?

Thanks!

JSNH

I would check the Taco. The impeller in my Taco 009 is plastic and it broke(I think it was 4 years old). I heard it rubbing while it was running but a few weeks before that I noticed a decrease in the heat delivered to the house. I suspect the impeller had started to break weeks before the failure. Yours my be doing the same thing. I went with a new cartridge for mine.

r.man

If the temperature coming into the house is too low it could be the pump but it could also be a restriction. If you have a spare pump and it isn't too hard to swap then doing so would either fix the problem or eliminate the pump as a suspect.
Life is too short or my list is too long, not sure which. Dec 2014

Holmes

Gas boiler 190 degree water about 650 btu's per linier foot output on baseboard radiation. 160 degree water about 450 btu per foot output.  140 degree water about 325 btu per foot output.  On cold days you are starting off a minimum of 30 % fewer btus, then you go down to 50% of the btus the gas boiler was delivering.  I question the cleaning of the heat exchanger.  Any way you reverse flow [ backwards flush the heat exchanger] . Do it into a clean bucket with hoses and see if you get any sediment. Sounds like a pump problem or a blockage.
Think like a farmer.

Bert

I had a problem with a check valve in my radiant floor system.  The valve was held partially open by some sediment and instead of the water returning to the owb it was circulating inside the house. It was hard to figure out because I was still getting hot water from the furnace but  it was being diluted from the open valve once it entered the floor system. Probably not your case if you are running a HX. But something to think on. My OWB water goes through my whole home in the radiant floor tubing. Is it right? probably not. Does it work? Yes. Its 13 degrees out and 75 in the house.
Saw you tomorrow!

Gearbox

On my gasser I had to lower my hi limit to 160 . It still kicks on till the return water gets up to 140 . Mostly the heat  exchanger can't raise the 70 degree water to 150 in one pass thru the exchanger . On the second pass the gas flame should go out . I am running Taco t011 pumps . I still burn a small amount of gas but very little .
A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

Ivan49

 Here's where I would start. Take the motor cartridge out of the Taco pump. I have a feeling you will find your problem here. I bet you when you remove it the motor shaft and impeller will drop down about an inch. It will still run but won't push the water fast enough to get the heat you want I just went thru the same thing and the pump was running so I did not check it. I had boiler up to temp but house would not heat up. After messing around for a couple days I pulled the pump and that is what I found. The temp here monday night was -10 and the house was 74. Before I could not have got it to 70 at that temp.   

overclocking

So I am still fighting this problem. I ruled out the house pump, but haven't taken the OWB pump off yet. Today I measured and am getting 180 at my water heater. It's coming out of the Hx at about 150. + or - with 180* water in the Hx. So today on the OWB side it entered 180 and left 150. On the house side it entered Hx 130, exited 155-160.

I think the Hx might not be working, or the thermo valve is impeding flow.
I wish I knew what someone else was getting on the house side out of their exchangers.

My baseboards In the house are only 130 with an Infared reading.

Hard to take the system down to trouble shoot when it's only 15 here.

thecfarm

Those Taco,as a whole unit,are real easy to replace. Time wise,on mine OWB, a ½ hour easy.I need a spare too,but don't have one yet.  ::)
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Holmes

Those numbers makes it look like everything is working ok.  You may need a larger circulator feeding the outdoor boiler water to the HX. More flow will give you a smaller delta t and get more heat into the house.
Think like a farmer.

overclocking

Quote from: Holmes on January 19, 2016, 07:33:22 AM
Those numbers makes it look like everything is working ok.  You may need a larger circulator feeding the outdoor boiler water to the HX. More flow will give you a smaller delta t and get more heat into the house.

Thanks.

Do you think adding a second taco inside the house would suffice?

I was thinking the numbers were ok too.

I did an experiment today and bypassed the OWB and set the gas boiler to normal operation. It pains me to hear that thing kick on because I only have a 500 gallon tank and it will eat it in a month. I like to save it for emergencies because they won't deliver gas where I live until April. So once it's gone, there's no safety net.

Anyway, even with my baseboards circulating 180-190* water I couldn't get it over 62 when it was 10 out.

So I just ordered 1000ft of pex and a few manifolds to set up subfloor heating on the main floor.

My plan is to hook up my third Hx and run the subfloor heat off a separate Hx. It will grab the cooler water that comes out of the first Hx, then circulate it through the floors via 250ft 1/2inch loops.

I think the additional btu is what I might need.

Holmes

A 2nd circ might work but a larger , more gpm pump , would be better.  The pump sizing is done by feet of head which is Friction loss, NOT height.
Think like a farmer.

Jerrymn1

I would check your screens in the heat exvhanger to see if they are plugged I had that problem,  stove would run fine but when the electric boiler called for heat it would just run ln electric. Check Your pipes after the exchanger to see if you get hot or mild temps to your Furnace

Jerrymn1

Check your y strainers for blockedge that was my problem

doctorb

Jerrymm1-

I have never had to do that.  How do you check heat exchanger strainers?
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

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