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Veissmann boiler questions

First post here - bought a house in Central NH that came with a late 90's Veissmann setup. SR-VR control unit and VBC-18 boiler. Been cold enough lately to expose just how poorly set up this thing is - I know it's supposed to be an amazing system, but we can't ever get it even close to what we're setting the thermostat temp at. Set it for 72 and you're lucky if the room gets up to 64. I cleaned the boiler and replaced a noisy blower in the fall, pretty sure the furnace is working properly, just that we're missing something in the settings. 2 story house with forced hot water registers circa 1950. Outdoor sensor is installed and passed the resistance test in the service manual. All registers have been bled and TACO valves are tested and working properly.

Here are my questions so far -
Using a brand new Honeywell "round" thermostat. What should we set as far as cycles per hour?
Should we be wired into the R&W wires?
What should we aim for as far as resting pressure? I've tried moving it around 10-20PSI and don't seem to see a change in how the system performs.
Max water temp is set to 75 C, should we mess with this?
The curve continues to mystify us. We've tried cranking it up to max, leaving it at default, moving it around, and just can't get a satisfactory result.
Been through all the available literature and still stumped.

We've already gone through almost 3/4 a tank of oil and have yet to really feel warm in this house. Hoping someone can shed some light on this!


  • Robert O'Brien
    Robert O'Brien Member Posts: 3,522
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  • bigorangeboiler
    bigorangeboiler Member Posts: 2
    Hi Robert - I've been through all of those and can't find the info I'm looking for, especially the thermostat info.
  • GW
    GW Member Posts: 4,619
    That control is ancient. Get a new control I say

    Your heat bills and lack of heat are likely inefficient insulation and infiltration issues, you think it’s the boiler? If the boiler water is hot and the distribution is good, it’s the house

    What temp is the boiler running at on a so so 30 degree day?

    Cycles per hour- you have an old mercury or a newer round? I would guess 3 CPH

    Yes R and W

    Max 75c- I’d you’re ambitious you can fiddle with this. Lower the better but it all depends on your system (radiators etc)

    Pressure 10 to 15 is normal for one story or 12 to 17 is good on two story. Don’t overthink this one too much
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Zman
    Zman Member Posts: 7,496
    What type of radiators do you have or is it infloor?
    How big is the house? What type of construction?

    I think you need to start breaking down the problem. Is the water going out very hot and coming back very cold? Does the boiler run all the time or does it cycle off and on.

    Pictures are always great.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Jellis
    Jellis Member Posts: 228
    are you getting good radiation of heat at your radiators?
    75 deg C is 167F? we commonly set our boilers to a hi limit of 180' F to get good radiation higher temps in some situations. I would recomend 180' high limit and a 160 low limit.
    Does your boiler run constantly? Does it run for a short time and shut off?