Two out of Three Loops are Cold

allthumbs

When I moved into my current home, the following winter proved disappointing. The house couldn't get above 67 deg. I lived with this situation hoping that when I needed a new boiler the problem would be solved. That wasn't the case. The heating contractor was called back but said there was nothing wrong with the installation. I put up with the situation for another ten years, until I retired, and then decided to see if I could make any improvements. I put more insulation in the attic. No help. I upgraded the circulator from Taco 007 to B&G 100. No help. I educated myself from the internet and found some easy "rules of thumb" in the Red School House guides and brochures put out by B&G. I zeroed in on three rules that shouldn't be violated:
1. No 3/4" loop should exceed 67 feet.
2. Maximum velocity for 3/4" baseboard should not exceed 4GPM. (avoiding erosion, noise, zone valve slap)
3. Delta T in the dead of winter, for a well functioning loop, should be about 20 degrees.

All three of my loops exceed rule 1.
Given the excessive lengths of the loops I was sure none were going at 4GPM
Two of the loops have an exactly 20 degree delta in the dead of winter.
The longest loop had a 30 degree delta in the dead of winter.

I decided to start with the longest loop. The equivalent length with elbows and standard port zone valve I calculated as 175 feet. The load line intersected the B&G pump curve at 3GPM. So, I was entitled to another 1GPM in that loop. I found that a Taco 0010 curve intersected at 4GPM. I went out and bought the 0010. I turned down the thermostats in the other zones to ensure maximum flow. No joy! The delta was still 30 deg. You can guess my next move as a diy guy. I replaced the standard port zone valve with a full port. Great joy! That part of the house was now warm for the first time. I must have miscalculated the equivalent length of the standard port. The longest loop must have been closer to 200 ft equivalent. That exercise occurred back in 2004. I've lived with cold loops in the bedrooms and the finished basement ever since. I estimate equivalent length of about 140 ft. for each of the remaining loops. I'm older now, and colder, and I want to change out the last two zone valves with full port. I figure I can conservatively get another 2500 BTU in each of those loops by changing the zone valves. It could make all the difference. I'll be violating the 20 deg. delta rule. Is that ok?

STEVEusaPA

A 007 to a B&G 100 isn't an upgrade.
67' isn't loop length, it's length of fin tube on a circuit.
Maybe recalculate your head and properly size a circulator.
Or a Delta T circulator.

ethicalpaul

This is the steam forum. You’d get more help in a radiant or hot water heating forum. Maybe @Erin Holohan Haskell will kindly move the thread for you

Jamie Hall

And no, there's no problem with violating the 20 degree suggestion -- it's a suggestion, not a regulation! The only possible problem is that if all your radiation is in series -- one to the next to the next etc. -- the last ones down the line won't put out as much heat as the ones at the beginning.

And as @STEVEusaPA points out, that 67 foot figure -- which, again, isn't a regulation, just a good suggestion -- is the actual radiating elements -- not the pipe. Hydraulically, it's the total length of the pipe you are interested in -- plus the allowance for fittings and valves and what have you.

EBEBRATT-Ed

@allthumbs

All zone valves have a different C value or flow coefficient.

I fixed a job recently that had 1" zone valves. The existing Honeywell valves had a 3.5 Cv so they would flow at 3.5 gpm with a 1 psi pressure drop. Couldn't get enough flow

I installed Taco 1" valves that had a 7.5 or 8 Cv. so it would flow 7.5 gpm with a 1 psi drop.

Big difference.

I would check the Cv of you existing valves and change them to valves with a higher Cv before you change the pumps

Erin Holohan Haskell

ethicalpaul said:

This is the steam forum. You’d get more help in a radiant or hot water heating forum. Maybe @Erin Holohan Haskell will kindly move the thread for you

I moved it to The Main Wall. Thanks.

EBEBRATT-Ed

@young plumber.

You need a B & G "system syzer" They make a plastic wheel calculator or you can download their program to your computer for free from Xylem Water (they own B & G.)


For the system I gave the example for it was an 1 1/4" Monoflow loop with a 1" Honeywell zone valve with a 3.5 Cv. (3.5gpm @1psi pressure drop)

You plug that into the B&G wheel . We needed 6gpm. So a 3.5Cv valve with 6 gpm going through it the PD was 4.6' of head or about 2psi. The 007 pump they had wouldn't do it.

I swapped the valve to a 1" Taco. I think the Cv was 7.5. So the Taco with 6 gpm going through it is .65psi or 1.5feet of head.

So basically you plug into the wheel what the valve Cv is of the valve you want to use then substitute the flow you need and the wheel (or program) tells you what the pressure drop will be. You add the PD to your system calculations

Alan Welch

Are your heating elements clean, dampers open, and  not blocked by furniture or carpeting?

Big Ed_4

Setting up a large parrelle system with zone valve and one circulator and to get it balanced is very tricky . They all will have a different risistance . As you are experiencing some zones will dog until the others are satisfied . Dumping the zone valves and going separate circulators from the start is the way to go .. I would use zone valve on say low load zones .. Mono Flow system never .

HomerJSmith

I always thought 2 out of 3 were good odds. Sorry, bad joke.

I think that a B&G 100 is a low head pump with a very flat pump curve. It was the standard for years with conventional boilers. Low head energy means that if there is a lot of resistance to flow in the sys, the 100 just doesn't have enough poop to make it.

A 20 deg delta T is not etched in stone. What ever works.