Effect of total water content

ralman

Your advice is a above my level of understanding. I will try to read more information on this and post questions if necessary. Thank you!

ralman

I am just trying to understand the effects of water content.

I have a 17 gallon capacity boiler connected to a 65 gallon monoflo distribution system, A better description is at the bottom if you need more info. I have been learning a lot here. If I have the boiler repiped pri/sec and an outdoor reset installed I am thinking I will end up with longer burner cycles/higher fuel bills. If this is true; What other options or strategies are available to get a more fuel efficient heating system. 6 gallon per day average is unacceptable.



I have an oil fired peerless boiler 121,000 BTU gross output, 17 gallon capacity in boiler, 65 gallon capacity in the system, Domestic hot water coil, 1.25" monoflo tee system, 185 feet of base ray CI baseboard. My aquastat setting are 180 high, 150 low, 15 differential. The monoflo pipe system has a split return. 20' of 1.5" iron pipe which is teed into 151' of 1.25" iron pipe. There is 176' of .75" iron pipe risers. The pipes are in the basement of a 1500 square foot 1950 ranch style home. The basement is finished and heated with the exception of the garage area. Garage stays above 60 degrees because of the bare pipes running through it. As an example, At a 30 degree outside temperature, I clocked five 3 minute boiler cycles during a 1 hour time period. 3 for heat, 1 for just boiler low aquastat call, then 1 more for heat. I used an infrared thermometer on supply pipe above the flow check valve a few minutes after the boiler turns off, 122 degrees measured. The short side return was 109 degrees, the long side return is 98 degrees.

Joe Brix

Those cold return temps

can't be good for the boiler. Do you want the garage heated? That's costing you money and sucking many BTU's out of your system. Is the boiler getting to high limit in only 3 minutes or is the thermostat cycling that quickly?

ralman

I agree

Those cold return temps can't be good for the boiler.

I agree from what I have been learning here. On a call for heat all 17 gallons of 165 degree water go out to the large distribution system and 65 gallons of much cooler water returns. The problem is worse above 30 degrees and during the daytime (solar gain) because the time between heat calls are longer, bringing system water temp even lower.


Do you want the garage heated? That's costing you money and sucking many BTU's out of your system.

I am not sure how to proceed on this one. I have read that black iron pipe within the envelope (the garage is under the house) does not need to be insulated since the heat loss is within the heated space. This cheats me out of the opportunity to control those BTU's. I have checked the heat loss of pipe charts on this website and the BTU heat loss can be calculated. However, I can't find any information on the BTU's I lose to the metal itself on a heat call. I suspect the large metal surface area cooled down to 80 degrees acts as a heat sink during a heat call, as well as losing BTU's to standby heat loss.


Is the boiler getting to high limit in only 3 minutes or is the thermostat cycling that quickly?

The thermostat cycles that quickly. This is my second winter in this home. I have never had the boiler shut down for a high temp which my aquastat is set for 180. I don't have the circulator shutting off on low limit which is 150(-10 degrees) during a heat call when the 65 gallons of cold return water circulates back through the boiler. I am not sure if the infrared reading taken off the pipe is an accurate way to measure.

Thank you very much for your assistance.

Joe Brix

I don't think a low reading

A copper pipe would transfer heat levels beter, so your iron pipe is probably reading a little lower then the actual temp but it stil sounds like the delta temp drop through your system is very large.

You should insulate the garage piping. I think you need a constant circ set up with much lower operating temps almost like a radiant system. I suggest a reverse indirect to act as a buffer tank, and get rid of the tankless coil. Make the boiler run longer but less often.
Sounds like all this water mass is in one zone. Might want to try spliting the zone or creating more zones. Your delta is too large: water is cooling off too fast as it has a great deal of piping to work around.

ralman

How does that buffer tank and constant circulation effect the

> A copper pipe would transfer heat levels beter,

> so your iron pipe is probably reading a little

> lower then the actual temp but it stil sounds

> like the delta temp drop through your system is

> very large.

>

> You should insulate the garage

> piping. I think you need a constant circ set up

> with much lower operating temps almost like a

> radiant system. I suggest a reverse indirect to

> act as a buffer tank, and get rid of the tankless

> coil. Make the boiler run longer but less often.

> Sounds like all this water mass is in one zone.

> Might want to try spliting the zone or creating

> more zones. Your delta is too large: water is

> cooling off too fast as it has a great deal of

> piping to work around.

ralman

How does that buffer tank and constant circulation effect the

> A copper pipe would transfer heat levels beter,

> so your iron pipe is probably reading a little

> lower then the actual temp but it stil sounds

> like the delta temp drop through your system is

> very large.

>

> You should insulate the garage

> piping. I think you need a constant circ set up

> with much lower operating temps almost like a

> radiant system. I suggest a reverse indirect to

> act as a buffer tank, and get rid of the tankless

> coil. Make the boiler run longer but less often.

> Sounds like all this water mass is in one zone.

> Might want to try spliting the zone or creating

> more zones. Your delta is too large: water is

> cooling off too fast as it has a great deal of

> piping to work around.

Constantin

Insulate the pipes!

Get the heat loss down, then re-measure the return water temperatures during regular cycles.

What does this boiler vent into? If it's a direct vent (i.e. out the wall) then your issues with flue gas condensation may be minimal. If it's venting into a tall, unlined chimney, you may have some serious issues to worry about.

Repiping the boiler could also give you the opportunity to install outdoor reset with a bit of mixing, an option that could be very interesting for your application.

Ron Schroeder

Hi Ross,

Bare metal will always give an inacurate reading with an infrared thermometer. Either paint the area that you are reading or stick a paper lable on it as a target for more accuracy.

For the same temperature, bare copper usually reads lower than bare iron due to lower emissivity.

Ron

Jed_2

Geesh!

I'm having a tough time following the logic of this thread. It's a 1500ft² RANCH house, with a heated basement, if I understand Ross's description correctly. How many thermostats are there? I'm assuming one. Monoflo system serving both levels. Where's the t'stat. How is it behaving? What's the t'stat reading for room temp? Is the house cold? What's the circ on that Peerless? What's the heat Loss of the house? 165' of c.i. baseboard will deliver 570 or so BTU/H/FT. at 180°F SWT, but for how long for 165'(especially given down time)? Constantin, how tall do you think a chimney can be in a RANCH? Unless this ranch is very poorly insulated, I suspect that boiler is 100% oversized. Upsize the cir., put a Beckett Heat Manager on it, an let'er rip.

Jed