Ask Me Help Desk - Recommended heating system pressure

Hi all,

We have a natural gas fired boiler/furnace/whatever-it's-called heating system (i.e. I don't know the exact technical term for this machine. I do know that it boils water only for the heating system - we have a separate water heater for regular hot water use). The system supposed to heat the house by pumping hot water (not steam) to radiators throughout the house.

We've never had real good heat in the attic, because the water pressure was too low to reach that high up, and my father couldn't figure out how to adjust the pressure such that it should stay up - no matter what he did, it always dropped back down to 25 PSI. Now that I've learned a little bit about how the system works, I figured out how to raise the water pressure (by adjusting the pressure reducing valve on the cold water feed, and then tightening the locknut). So my question is: given that the boiler is in the basement, and it's got to handle a total of four floors of height (3 floors aboveground + the basement), how high should I make the pressure? Is there a "danger level" - an amount that I should not exceed?

To get technical, you have a boiler. Its water filled so it's a boiler. If you had forced air it would be called a furnace. 95% of people call what ever they have a furnace.
On the boiler pressure issue, 25 psi is high for a residential boiler. Normal operating pressure is around or below 15 psi. You have a pressure relief valve that is set to discharge @ 30 psi. If your dad was setting the pressure higher than that, the relief valve would open to drop the pressure back under 30 psi. You should never exceed normal operating pressure established by the boilers manufacture recommendation.
What you can do is have a technician install a bigger horsepower circulating pump. If this is a single zone system (one thermostat in the house) you could have the attic zoned separately w/ its own thermostat and circulating pump. This may be expensive depending how the system is installed and if the piping is somewhat accessible to do what is needed.

Hmmmm... I think I better clarify the situation a little. Here are some interesting facts:

1) The tag on the TPR valve says "50 PSI", not 30.
2) The pressure kept dropping back to 25 PSI. The reason for this was that there is a PRV (pressure reducing valve) installed on the cold water inlet, the tag of which says "25-75 PSI". The screw on top of the valve was WAY loose, so naturally the valve cut the pressure to the lowest setting it knew how - in this case, 25 PSI.
3) The boiler actually has 3 zones: basement, 1st floor, and 2nd floor + attic.
4) Various people throughout the years (plumbers that have come to fix various things, appliance repairmen, plumbing supply employees, etc.) all advised my dad that raising the pressure is the way to go - i.e. that the water could not get all the way to the attic since there is not enough pressure.

As you can see, based on the above information, I'm a bit confused regarding what you told me. Perhaps my boiler is not really a residential unit - maybe they installed a commercial-grade unit since it's got to handle four floors? Or do you have any other suggestions?

I'll try to get a picture of the situation to post ASAP.

Thanks,
Moishe

It doesn't sound to me like it is the pressure. At 15 PSI, the water should be able to get to about 30 feet above the boiler. 25 PSI would reach about 50 feet.

In terms of pressure and ability to serve distant fixtures, a hot water system should not function much differently than plumbing supply piping. It sounds more like either a blockage in the pipe or heat loss associated with the longer run to the attic. You might ask speedball about it.

If your attic is on the tail end of the 2nd flr loop, by the time it circulates to the attic, that could be the main reason why there is limited attic heat or there could be air blockage. (good points made by dclynch) Do you hear gurgling in the attic pipes? That is a sign there is air in the lines. If so the zone will need to be purged.
BTW, how well is the attic insulated. Is it safe to assume it is a finished, well insualted area?

It sounds like you have air in the baseboard radiators in the attic. You will need to bleed the air out of the attic radiators.

Quote:

Originally Posted by skiberger

Do you hear gurgling in the attic pipes? That is a sign there is air in the lines. If so the zone will need to be purged.

Well, ever since the system was put in about 17 years ago, it always made a lot of noise - lots of water-hammer-like sounds (in fact, that's how we can often tell when the system kicks in - when our house starts making more noise than a carpenter's workshop), but as a kid, I was never "on the ball" about such matters enough to pay attention to the various sounds - i.e. I wouldn't be able to tell you if there were only banging sounds, or gurgling also - all I can remember is a lot of noise from inside the walls over the years.

However, now that you mention it, I remember sitting in the living room on more than one occasion thorughout this winter and hearing, in the back of my mind, some gurgling sounds coming from the direction of the ceiling (which is the floor of the second story - part of the same zone as the attic). If I remember correctly, here's more or less how it happened each time: first it was quiet. Then suddenly, I'd hear a loud gurgle, sometimes lasting more than a full second. Then quiet again. Then the banging would start, banging quickly (several bangs per second) for several seconds, then gradually slowing down until it was only banging once every second or two, and then it would stop. Throughout the banging, I think there was also occasionally a small gurgle.

Is that what you mean? And what can I do about it - how do I "purge" the zone? Where the three zones come off the boiler, each zone has a gate valve, followed by a hose bib. Do I simply shut the valve, attach a hose to the bib, and open the hose bib valve? Or is there more to it than that? Or am I completely on the wrong track?

Quote:

Originally Posted by skiberger

BTW, how well is the attic insulated. Is it safe to assume it is a finished, well insualted area?

Finished - yes. Well insulated - I don't know. Here's the story:

The house itself was built a VERY long time ago (I don't know exactly how long, but I do know that (a) the walls were lath-and-plaster and (b) the electrical system included antiquities such as ungrounded+unpolarized receptacles, and also a number of twist-lock receptacles). When my dad bought the house two decades ago, the entire house was gutted and re-finished. The only thing left intact was the attic - the only changes were some new tiles in the bathroom, a couple of new windows, and some other things - and, of course, the new radiators - but the walls (including the insulation, AFAIK) were the same old stuff. So to answer your question: yes, it's insulated, but I have no way of knowing how well: the insulation may have deteriorated with age, or perhaps the techniques used way back when the house was built were not so good - anything is possible.

Quote:

Originally Posted by Lotta

It sounds like you have air in the baseboard radiators in the attic. You will need to bleed the air out of the attic radiators.

I don't think they're considered baseboard units per se - they're about two feet high, built partially into the wall. They're the kind that are made of many sections, each a couple of inches wide, so the contractor can decide exactly what size the radiator should be, and the radiator is assebled by welding (or whatever process is used to attach) as many of these sections together as necessary, with a special "end piece" at either end.

And yes, we've bled the air out of the radiators many times over the years, but that didn't seem to solve the problem.

How many pipes enter/exit into each radiator?

One or two?

Two. Look at the attached picture. See that pipe on the left, under the radiator? There's one like that on the other end of the radiator (also coming out of the floor, making a 90 degree turn, and entering the radiator body) only the other one does not have that small slotted-screw-like valve on it. As far as I can tell, all the radiators in the house have two pipes like that, with a valve on one of them, and a small cap on an upper corner to bleed the radiator.

Try this and see what you find. Turn the heat on for the attic and let the other radiators for that zone get hot. Then open the vent screw on the attic radiators and see if you get any water to come out. You may have to have a cloth to keep from getting the hot water on you.

Do you get a strong stream of water/steam?

Quote:

Originally Posted by PalmMP3

Hi all,

We have a natural gas fired boiler/furnace/whatever-it's-called heating system (i.e. I don't know the exact technical term for this machine. I do know that it boils water only for the heating system - we have a separate water heater for regular hot water use). The system supposed to heat the house by pumping hot water (not steam) to radiators throughout the house.

We've never had real good heat in the attic, because the water pressure was too low to reach that high up, and my father couldn't figure out how to adjust the pressure such that it should stay up - no matter what he did, it always dropped back down to 25 PSI. Now that I've learned a little bit about how the system works, I figured out how to raise the water pressure (by adjusting the pressure reducing valve on the cold water feed, and then tightening the locknut). So my question is: given that the boiler is in the basement, and it's gotta handle a total of four floors of height (3 floors aboveground + the basement), how high should I make the pressure? Is there a "danger level" - an amount that I should not exceed?

3 fl + basement is about 38 ft; equal to 16.5 PSi. so you need about 22 psi... hot water should not have any banginnngg noise... yours indicate too much air in the water ( bleed the air out at the highest point)... do you have some kind of valve after the pump (adjust this valve will change the pressure,** some pumps will trip out when pressure(flow) is too high). You may losing water somewhere

The second floor radiators don't make noise?
Try bleeding the attic again. While the zone is operating open the bleeder just enough that the air pushes out, when you get all water coming out of the valve, the radiator is bled. (you probably already now this because you've said you've bled them over the years.) If this doesn't work you may have to purge the zone.

Yo!

I know it maybe a silly question... but have you tried venting the radiators in the attic?

It is not a silly question but I hope it is fixed by now. The post is from 2006

Have you tries balancing the system more,sounds like it could be heating the floors below faster and they are robbing the heat.. try turning off the rads below and see if the attic rads heat.