Poor Heat

Brad White_191

Sorry, Walter, but BTUs are BTUs. Oil or gas, the ratings are the ratings. Yes, oil is somewhat more efficient, (hotter flame for one thing), but we are talking the range of 85% for oil and 82% for gas for average current equipment which is not condensing. Up-sizing means even less efficiency.

Walter_11

I recently converted from oil to gas and installed a new hot water Weil McLain 140,000 btu furnace. The oil furnace was a 100,000 btu. The problem is that I'm not getting enough heat out of the base board radiators. I have the old type of radiators that are built into the walls. The house was built in 1950 and is a single level house. It has a one pipe system using monoflo tee. The water pressure into the boiler is set at 18 psi. The limit control is set on 160 degrees. The temperature on the supply line is 150 degrees and within 5 minutes of running time the temperature on the return reaches 150 degrees also. I have bled all the air out of the system several times. When I converted, I drained the system completely and did not fill it up for about two weeks. The previous system worked fine and had no problems at all. The reason why I converted to gas was because the oil tank (afraid it might be leaking). I have talked to the boiler manufacturer and he feels that the boiler is running well and the problem is in the monoflo valves. I have read several articles about the monoflo valves and they say it can be a nightmare after draining the system. I also read that you cannot buy replacement steel monoflo valves. Is this true?
One other problem I noticed that when I did a quick push down on the air Schrader valve on the expansion tank, I did get air coming out and some water. One of the risers has a galvanized nipple which is going into the radiator. This radiator is only warm, and I’m thinking that the nipple has restricted the flow to the radiator because I drained the system and let it lay idle for a while. I was thinking that there might be some kind of restriction in the system, but the water re-circulates back into the boiler very quickly and there is not much of a heat difference between the two. One plumber told me that I should remove all the monoflo valves and pipe the radiators in series which should eliminate my problem. However, the radiator in the kitchen would be the warmest and by the time it gets to the last bedroom, this would result in a heat loss.
Could you give me some help why I'm not getting enough heat in the house? The radiators are warm, but are not supplying enough heat and the circulator pump is running all the time. This happens during the real cold days (below 30 degrees), otherwise the thermostat is working fine when the outside temperature is warmer. The thermostat is not reaching temperature and this is why the system keeps on running. What do you think the problem could be? Is there a better way to bleed the system with the monoflo valves? Is there anymore information you need?

nicholas bonham-carter

monoflow

do a search using the button on the orange banner above for "monoflow". maybe someone else's problem is the same as yours. at this busy time of the year, your response time may vary.--nbc

Steamhead (in transit)

When you say

"The temperature on the supply line is 150 degrees and within 5 minutes of running time the temperature on the return reaches 150 degrees also"

that tells me the heat is not being transferred to the radiators. What size circulator is on that system?

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Walter_11

The pump is a B&G Model Number: NRF-22.

When the thermostat calls for heat the burners kick in and warm the water to 150 degrees. The return side is 120 degress. It circulates from the supply side to the return side and within 5 minutes both sides are at equal temperature. This is what I'm trying to tell you.

Walter_11

I did the search and the radiators (I'm calling them radiators but I dont know exactly what they're really called. There screwed to the wall because two pipes are coming up from the floor so there is no legs that I can change the pitch of them.) Maybe you can tell me the exact term for them. Also, it's basically saying that there's air in the system. What's the best way to get it out?

Brad White_191

This is why we are trying to help

Are there isolation or balancing valves on the branches? Are they open?

As Steamhead said, there is little if any heat being sent out to the radiators, it is just rat-racing around the main.

Can you post a photo of the boiler and near boiler piping? I have seen re-pipe jobs where the direction was reversed, where a loop was split and one side run opposite of it's counterpart.... lots of possibilities.

You can still get steel monoflow valves I believe, by the way.

I also have to comment and ask why a 100 MBH boiler was replaced with a 140 MBH boiler. Experience shows that if the house originally had a 100 MBH boiler, it may well have been over-sized right there. Once the house was insulated and improved, that boiler likely was double the size it needed to be. Now, to justify a 140 MBH boiler, one would hope you put on an addition that added 200 percent to your house. Point being, a calculated heat loss is the only decent way to size a boiler. I have never seen that kind of over-sizing in a retrofit when no addition was planned. What is the story there?

I see no reason to go to series flow. Once working, a monoflow system allows individual room control and balancing without closing down the others.

Are the radiators fully vented for certain? Meaning one at a time?

Steamhead (in transit)

You might need a bigger pump

Monoflo systems have higher back-pressure levels than other systems, because the flow splits so many times. That little pump might not be able to produce proper flow in your radiation.

100,000 BTU/hour requires roughly 10 gallons per minute. The NRF-22 will produce that amount of flow, but only if the head (back-pressure) is about 8 feet.

The Taco 0010 is a bit more powerful, and will pump 10 GPM at 10 feet of head. Plus, its curve is not as steep as the NRF, so the flow doesn't drop off as fast as the head increases.

Do you remember what model pump was installed on your old boiler?

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Brad White_191

Vents

I suspect that you have convectors. These often have small pipe nipples with a key operated air vent on top. If not a key, you may have one that allows a screwdriver to work. Lefty-Loosey, Righty-Tighty

Brad White_191

Respectfully

even if you were pumping half the flow, you would still get about 90% of the output from the emitters. Even an NRF-22, if the curve settles at say, 6 GPM, that would impose only about 36% of the full 10 GPM head loss... it would settle at a point where perceptible heat would still be transferred.

For this reason, I still suspect an air problem, not that to call the pump selection ideal though.

PLUMBARIS

Air Trap

Can you see the lines feeding the rads off the main. they need to pitch up all the way, if there are any high spots ie reverse bellies air will set there and not purge out.These systems can be damning to purge but work well after.

Walter_11

The model number on the old boiler is Taco Model 007-F4R.

Walter_11

The reason why i went to a bigger boiler is because i was told that with oil it produces more heat and you always go a little bigger with gas.

there is balancing valves on the branches and they are open. (I never moved them)

These radiators dont have vents on them. I think because the radiators have covers, and I would have to destroy some of the wall to take the covers off.

Walter_11

Yes this is what I have and this is how i bled them to get the air out

Walter_11

I can see the lines feeding the radiators off the mains, but i cant pitch them up because the convectors (radiators) are bolted to the wall. It worked fine before I changed the boiler, so why should i need to pitch them again?

Walter_11

What is the difference between those two pumps? and i think your right i agree it might be an air problem

walnuts

160 should be enough, but try 180. bleed the convectors when the pump is running, and then again when the pump is off. Also did the old boiler run off a zone valve or a flow check, the picture looks like a zone valve possibly restricting flow.

PLUMBARIS

Pitch

They need pitch so air bubbles flow to the rads and then to the vents.Im not saying alot of pitch, but like I said if there are any high spots YOU WILL NOT GET IT PURGED.

Steamhead (in transit)

Performance curves for pumps in question

see attached. The Taco one is for the 005, scroll to the end and you'll see the chart for all the 00 models.

The 007 will pump a bit more than the NRF-22, and the 0010 is the next step up.

Also, where is the pump mounted? Best location, by far, is on the system supply pipe after the air separator and expansion tank connection. This is known as "Pumping Away".

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Walter_11

I raised the temperature to 170 last nite and it help alot. It kept the house at 70 degree all day today. (outside temp was 17 to 28 degree) The day Before the house was 65 degree when it that cold out. Im been bleeding the convectors that way.

Walter_11

Here are pictures of the old boiler (oil) and the new boiler (gas). They are piped the same way and the pump is on the return side.

jim bannister_2

poor heat

Does the burner stay on all the time? First, close the valve on the return and purge the convectors. Then open that valve and close the valve on the supply and purge the convectors again. Open both valves and raise the limit up to 190 degrees. The thermostat is not being satisfied on a cold day because the temperature of 160 degrees is too low for convectors. If this does not do the trick, check to see that the supply and return piping is not reversed as this would change the directional flow through the monoflow tees. At a temperature of 160 degrees and an oversized boiler, the burner is probably shutting off on limit.

walnuts

sounds good but, did the old boiler run off a zone vave or a dedicated pump? If it works don't change it.

Walter_11

It ran off zone valves and they're still there.

PLUMBARIS

Vents

Are you correct in saying these convectors have no vents on them.I have never seen a monoflow system with out rad vents of some type.

Walter_11

I can not see these convectors because they have metal cover on them. ( I cant see whats behind the metal covers) But in the top right corner they have a bleeder which I use to bleed them. Is that the vent?

Walter_11

Do you have any Idea who made convectors in the 1950's?
I would like to find some information about them?
Web site?

LIBOB

Air

Try jacking up the pressure. Sometimes those pressure gauges are not too reliable. Be careful not to pop the relief valve. Go to the furthest or highest rad and see what you get. Let the water flow. Sometimes that little pocket of air just needs a couple of extra psi to push out. Send a picture of the rads and the vents

Steamhead (in transit)

How

is the expansion tank connected to the system? I see it in the old photo but not the new one. Is it hooked up to an air separator? Post a pic of that area if you can.....

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tccoggs_2

DO you have any other pics?? From the side of the unit with where the expansion tank is, is what I would like to see. I could swear that the airscoop is mounted upside down with the expansion tank on top, but its a bit hard to tell. Is that Gas valve legal?? Looks like a regular Ball valve, but not sure if that carries stamp for AGA.

I found the problem in the Pic, the gas is off, that explains the lack of heat......... Only kidding

If you got water out of the top of the expansion tank schrader valve, then the bladder may be shot, and the tank isn't doing its job.

This looks like a National Grid cut and slide job, leave the rest of the issues alone.



Anyhow, sounds like your airbound as other have said, remove the covers and bleed until the radiator gets warm all over. As Brad said, Your pump might be slightly undersized, but not to the point where your getting no heat.

With a monoflow system, you would have been better off pumping away. I realize here that you only replaced the boiler and not the near boiler piping, but it would have been a great time to correct some issues and optomize performance.

Unknown

why didn't the installer

Why didn't the installer used the best air scoop available, right in the boiler itself! I piped with the pump on the supply with monoflow, castiron baseboards, with proper sized pre charged tank. Two zones.. No compliants..