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Re: Slowing Down Flow
Posted: Sat. Feb. 11, 2012 11:40 am
by steamup
whistlenut wrote:Was this system working well when fired on oil? It is baffling that a simple boiler addition causes this kind of a problem. That K6 will blow you out of the house with capacity, so something is just plain NOT RIGHT! Can you scratch a flow diagram for us, please. Also is this a primary, secondary setup? Somehow something simple is being overlooked. I didn't read all the early posts, but if we go back to the KISS principal, we WILL find the answer, quickly. I assume this must be a 007 or similar circ, so why is there any consideration of flow being reduced? Are you sure something stupid, like a washer, piece of solder, a piece that plugs up something did not get inside the piping? I HAVE seem this, and no amount of formula crunching will resolve that one!!!! Understand that Einstein probably did not do the sweating, fitting or checking before this was installed. We ALWAYS check pipe just in case some idiot stuffed a piece of stryfoam in the end of the pipe at the warehouse....candy wrappers, ciggy packs......it happens every day....and these idiots reproduce...and vote. Ever stuff a potato into an exhaust pipe of 'a friend' back in the day? You get the idea. Those problems are much harder to resolve.
Reminds me of one of my jobs where a pipefitter left a rag in a 8" pipe. Even the pros make mistakes.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 8:47 am
by Hollyfeld
I'll get to working on a diagram for us this week. I would also like to add in the length of radiators and make the sketch worth-while.
but... This morning it was 19*F and the inside temp was at 67*F. I had the thermostat set to 70* and expected the house to be around 64* this morning with all the wind sucking the heat out last night. Zone is calling for heat, boiler is stoking.
Aquastat settings - 170/190
Boiler temp this morning - 185*
Pressure - 27ish
Surface mounted Supply temp (not wrapped yet) - 149
Surface mounted Return temp (not wrapped yet) - 147
These surface mounted thermometers are embarassing
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 8:55 am
by Rob R.
Your pressure is getting awfully close to the relief valve's opening point (30 psi).
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:16 am
by Hollyfeld
Rob R. wrote:Your pressure is getting awfully close to the relief valve's opening point (30 psi).
Yep.
That's how it gets whenever the temp in the boiler is above 180*.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:38 am
by bja105
Hollyfeld wrote:Rob R. wrote:Your pressure is getting awfully close to the relief valve's opening point (30 psi).
Yep.
That's how it gets whenever the temp in the boiler is above 180*.
Then you need a bigger expansion tank, if its an Extrol or similar bladder type. If its an old style expansion tank, you need to "drain" it, which really means to add air to it.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:41 am
by bja105
Slowing down your flow is not going to help you get more heat into the space, you'll just get a bigger temperature drop from supply to return. You need to supply hotter water to the system to increase your output.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:43 am
by Sting
Hollyfeld wrote:I'm trying to get my system down to a delta T of 20*. I have a shut-off valve on the return closed about 1/2 way and (2) adjustable flow valves (i think thats what they are) closed about 1/2 of the way. These valves are located on two separate loops of the same zone and are located just before these two loops become one and head back to the boiler. One loop serves half of my first floor, and the other serves the other side of the first floor and the loft. I was able to get my Delta T to around 12*, but no higher. I can hear the flow through the system now, which I do not like
. The only other valves I have inline with the system are isolating the pump. I'm hesitant to close these at all, but figured I would ask here if that is an available option.
Thanks
Hollyfeld wrote:That is what my system looks like. When you say get them balanced, are you talking about getting heat from both of those loops or actually getting a better Delta T from them?
Balancing a system accomplishes all
Hollyfeld wrote:
This morning the outside temp was 22*.
Thermostat setting - 68*
Inside temp - 67* (with the thermo calling for heat)
Boiler was at 175.
Supply temp reading on pipe mounted thermometer - 155
Return temp reading on pipe mounted thermomter - 152.
Hollyfeld wrote:
Aquastat settings - 170/190
Boiler temp this morning - 185*
Pressure - 27ish
Surface mounted Supply temp (not wrapped yet) - 149
Surface mounted Return temp (not wrapped yet) - 147
Hollyfeld wrote:Perhaps then the answer is to anticipate the coming cold temps and ramp up the temps?
NO! see again the great explanation by Steam up below! Yes I read you have some noise when you choke the flow – either the pump is too large or you choke valve is a gate valve – no mater - a slight noise will be a minimal distraction and it will proof that next summer a small modification will fix this vs a fu¬ll revamp of the load radiation.
Choke the flow some more and get the supply and return temp to a 10 % difference
Then lets see what the system will do in these colder temps – all it takes is no cost twist of a valve – what can it hurt to try? Gee maybe the system will even work better!
steamup wrote: Heat transfers from the water to the air. High to low. The hotter the water or hotter the average temperature, the greater the heat transfer. The greater the delta t, the lower the average water temperature and the lower the overall average heat transfer. Typical design for finned tube is 20 deg delta T. If design hot water temp is 180, then 160 would be the return and finned tube sized on 170 deg. average water temperature. If you have a smaller delta t than 20, it just means that the flow is greater than what a 20 deg delta t heat loss from the radiation would dictate.
.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:44 am
by Sting
Hollyfeld wrote:Perhaps then the answer is to anticipate the coming cold temps and ramp up the temps?
The correct answer to this question is – “It Depends”
Now your into system control by degree day load – this is not system balance – First things first – You will not gain performance with an outdoor reset, or manual temp control – if the system is not functioning correctly in the first place
Kind Regards
Sting
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:53 am
by Sting
bja105 wrote:Slowing down your flow is not going to help you get more heat into the space, you'll just get a bigger temperature drop from supply to return. You need to supply hotter water to the system to increase your output.
Think about that statement above for a moment.....
The boiler changes the energy stored in the coal to energy stored in the water
The system moves the energy bearing liquid out to the load where the radiation gives up the energy to the dwelling
DAAA --- If you send out 140 degree water and it comes back at 140 degrees -- or if you send out 200 degree water and it comes back at 200 degrees
HOW MUCH ENERGY DID THE WATER GIVE UP TO THE LOAD ?????
Bueler --- Bueler --- LOL
Answer for the cheep seats ----->NONE Because the water shot thru the system so fast - it never had a chance to leave the energy it was carring behind, and return to the boiler to pick up more. _ actually it cannot pick up more energy if its returning at boiler temperature ..
This is such a rookie mistake
see rule 42 of a small group I posted earlier this week -- if you subscribe to be a professional you must obey all 100
42. Raise the water temperature to 200 degrees when you can't get a down-fed convector supplied by diverter tees hot. When that doesn't work, raise the water temperature to 220 degrees.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 9:57 am
by bja105
A few more things.
Don't believe any boiler mounted thermometer, they are usually off a bit. If you replace it, there is no promise that the new one is better. Part of it is the gauge inaccuracy, part is the location. The temperature at the boiler mounted thermometer is not necessarily the supply water temperature. I use a digital thermometer taped to the pipe, with a bit of Armaflex taped over that.
If you hear "water" circulating, you have air in the system. You will not hear only water circulate. Take a clear water bottle with a bit of air at the top. When you shake it, you hear it. Now fill it to the top and cap it, with no air bubble. When you shake it, you don't hear it. You don't hear water circulate in your baseboard, you hear air bubbles.
I don't think your air is the main problem, I think it is your too cool supply water temperature.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 10:11 am
by bja105
Sting, the more important temperature differential in action here is the difference between the radiation's temperature and the temperature of the air in the house. We are proving that 148 degree water does not heat the house. I assure you, if the oil boiler was turned on, it would supply hotter water than the coal boiler is supplying.
I have heard this theory that fast moving water doesn't give up its heat, but it is mostly nonsense. 12 years as a pro in this field have proven it. If we get the water temperature up, we will start getting a bigger temperature drop through the baseboard.
Yes his pump may be pumping faster than needed, but that won't effect the amount of heat rejected by the baseboard. It will make more noise and shorten pump life, but it wont hurt heat output.
If we slow the water flow, but keep the same supply temperature, we will REDUCE BTUH's to the system.
My question, is why is the supply temp so low? Is it cycling on limit, or is the boiler firing at full capacity but heating the water? Is the supply temp really that low?
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 10:23 am
by bja105
Sting wrote:
see rule 42 of a small group I posted earlier this week -- if you subscribe to be a professional you must obey all 100
42. Raise the water temperature to 200 degrees when you can't get a down-fed convector supplied by diverter tees hot. When that doesn't work, raise the water temperature to 220 degrees.
His most recent numbers
"Aquastat settings - 170/190
Boiler temp this morning - 185*
Pressure - 27ish
Surface mounted Supply temp (not wrapped yet) - 149
Surface mounted Return temp (not wrapped yet) - 147"
We are not talking about raising anything to 200 or more, we need to get his supply as hot as his settings are currently asking for. . His low limit is 170, but his actual supply temp is 149. Assuming all his numbers are correct, why so cool? I agree with his 170/190 setting. Every baseboard is rated a certain btuh at a certain water temperature. I have never seen one rated for 150 degree water, they are rated for 180 degree water. Yes, it can work with cooler water, but we would need more radiation, sized for the load and the unusual water temp.
There may be multiple problems, but the most important problem is too cool water supplied to the system. There is a reason outdoor reset systems supply the hottest water at the coldest outdoor temps. Not one of them modulates pump speed.
Original poster, at these numbers, is the boiler cycling on limit, or burning full out?
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 11:11 am
by Hollyfeld
I believe the boiler is cycling on limit trying to get the zone satisfied. I could be incorrect here
The supply and return temps were about 151 last I checked and the thermostat was satisfied.
Boiler - 182*
Pressure - 23
The zone is finally at temp at 70*F. It has also warmed up outdoors 5*.
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 11:36 am
by bja105
Hollyfeld wrote:I believe the boiler is cycling on limit trying to get the zone satisfied. I could be incorrect here
I assume you don't have a meter?
Keystoker owners, how can Hollyfield tell that its cycling on limit if he doesn't have a meter?
Is there any chance that the water temp at the aquastat is really at the limit settings, but the water leaving is that much cooler? Where is the aquastat? Can you post a pic?
I'm inclined to think his aquastst is off, but I don't want to turn this thing into a steam boiler finding out.
Is either relief valve leaking?
Re: Slowing Down Flow
Posted: Sun. Feb. 12, 2012 11:47 am
by bja105
I have been looking at this manual.
http://www.keystoker.com/manuals/KeystokerBoilerManual.pdf
It says there are at least 4 ports in the top of the boiler, which one is your supply connected to. It should be 1 1/4".
How many pumps do you with between both boilers and the system? Its possible that there is no or little flow through the coal boiler, but the system pump is working. That could explain boiler cycling on limit, but cool radiator temps. Do you have any pics of the piping?