Question regarding normal/typical boiler operation

cmattina

I’m happy to be a new member here and was hoping for a little advice. I just bought a new house with a veissman vitio gas 050 boiler installed in 2007. The house is quite old, is two stories (with high ceilings) and has old cast iron rads. I am unfamiliar with the system, however, I’ve been finding out the hard way.

One: the feed valve was shut off when I went to start it up for the fall. So I turned it on and it took a bit for the pressure to get up to 10 psi… then, I started bleeding the rads. After a few hours, I then found out the PRV doesn’t work as the pressure began to rise without the heat on. I tried adjusting the PRV and it had no effect.

Two: I figured I could just shut the feed off at 12 psi, pump the expansion vessel to match it, and bob would be my proverbial uncle. However, with the feed valve off and the heat on, the pressure would not stop rising to 30psi.

Three: I spoke to a HVAC guy and he said it sounds like the expansion vessel wasn’t taking the pressure from the heated water. I took the expansion vessel off and it was completely full of water with rubbery black flecks.

Four: i figured I would change the PRV while I was checking the vessel out. The new PRV seems to work good. I let the cold system get to 15psi (controlled by the PRV), and put on a new vessel after pre-setting it to 15 psi (like the gauge on the boiler)

Five: I then turned my heat on and the pressure rose from 15 to 21.5 (according to my digital tired gauge on the vessel and visual inspected at the boiler) in about an hour. I think the water temp got to 140F but the rads were smoking hot.

Is this normal? I assume when I am running the boiler all the tiem the house temp will be more stable and the boiler wont need to go from 80F to 140F in an hour…

Jamie Hall

More or less... the pressure rise seems to be a bit excessive to me, but maybe not. How did you size the new expansion tank? And did you set the pressure in it when it was empty? Sounds like you did...

Zman

It sounds like you may have a converted gravity system. These have high water volume and in turn would require a larger expansion tank if you desire a constant system pressure. As mentioned, there is nothing wrong with the pressure range you have.
Is your boiler a condensing model?
Carl

cmattina

Hi sorry, i cut and paste that post and i missed my little introdcution.

Jamie Hall said:

More or less... the pressure rise seems to be a bit excessive to me, but maybe not. How did you size the new expansion tank? And did you set the pressure in it when it was empty? Sounds like you did...

I put the same model tank as was already on it. I didn't do any calculations... though in hindsight it would have been an opportunity to do so...

cmattina

Jamie Hall said:

More or less... the pressure rise seems to be a bit excessive to me, but maybe not. How did you size the new expansion tank? And did you set the pressure in it when it was empty? Sounds like you did...

The tank came with 12 psi pre set, since my boiler was at 15psi (set by the prv)... i put another 3 psi in the tank before installing.

cmattina

Zman said:

It sounds like you may have a converted gravity system. These have high water volume and in turn would require a larger expansion tank if you desire a constant system pressure. As mentioned, there is nothing wrong with the pressure range you have.
Is your boiler a condensing model?
Carl

I'm not sure if it is condensing. it is described in the manual as "cast iron" "wet base" and "atmospheric" condensing is not mentioned.

i used the same extrol 30 tank that was already on there... but whose to say the original installer put the right tank on it.

cmattina

Hatterasguy said:

140° supply water temperature to CI rads is quite normal. It might even go higher when the temperature drops.

Your 80°F temperature when the system was cold can only be possible if no call for heat has occurred in the last six hours.

Asking the system to climb from 80°F to 140°F will certainly cause the pressure in the system to rise from 15 psi to 21.5 psi.

Be assured there is no issue with 21.5 psi.

However, if you prefer, you could drain a gallon of water out of the system and drop the pressure from 21.5 psi to about 18 psi or so.

So would i let it get up to pressure (warm/hot), then drain the water out until I get it to 18-20psi. Then that will be my top pressure?

The reading i get on my digital tire gauge, taken at the pressure vessel.... is that the same pressure as the boiler has? or will there be a variance

cmattina

Hi sorry, i cut and paste that post and i missed my little introdcution.

Jamie Hall said:

More or less... the pressure rise seems to be a bit excessive to me, but maybe not. How did you size the new expansion tank? And did you set the pressure in it when it was empty? Sounds like you did...

I put the same model tank as was already on it. I didn't do any calculations... though in hindsight it would have been an opportunity to do so...

cmattina

Jamie Hall said:

More or less... the pressure rise seems to be a bit excessive to me, but maybe not. How did you size the new expansion tank? And did you set the pressure in it when it was empty? Sounds like you did...

The tank came with 12 psi pre set, since my boiler was at 15psi (set by the prv)... i put another 3 psi in the tank before installing.

cmattina

Zman said:

It sounds like you may have a converted gravity system. These have high water volume and in turn would require a larger expansion tank if you desire a constant system pressure. As mentioned, there is nothing wrong with the pressure range you have.
Is your boiler a condensing model?
Carl

I'm not sure if it is condensing. it is described in the manual as "cast iron" "wet base" and "atmospheric" condensing is not mentioned.

i used the same extrol 30 tank that was already on there... but whose to say the original installer put the right tank on it.

cmattina

Hatterasguy said:

140° supply water temperature to CI rads is quite normal. It might even go higher when the temperature drops.

Your 80°F temperature when the system was cold can only be possible if no call for heat has occurred in the last six hours.

Asking the system to climb from 80°F to 140°F will certainly cause the pressure in the system to rise from 15 psi to 21.5 psi.

Be assured there is no issue with 21.5 psi.

However, if you prefer, you could drain a gallon of water out of the system and drop the pressure from 21.5 psi to about 18 psi or so.

So would i let it get up to pressure (warm/hot), then drain the water out until I get it to 18-20psi. Then that will be my top pressure?

The reading i get on my digital tire gauge, taken at the pressure vessel.... is that the same pressure as the boiler has? or will there be a variance

SWEI

The Vitogas is a conventional (non-condensing) boiler -- though one of the best-built of that type. The castings are made from a special iron alloy that tolerates low return temperatures, so if you have an outdoor rest control it will have the ability to increase both comfort and efficiency of the system. The Vitotronic is quite pricey, but if you already have one, stick with it.

You need to isolate and drain the wet side of the expansion tank before you can read the pressure on the air side.