split radiators into zones

feld123

Hi all,

I'm a newbie here, so pardon if i post anything wrong

I manage a 16 unit apartment complex that gets heated by single pipe steam, that part of the units are are used by a school, & part of the units have been converted into 5 offices each.

1 have 4 different times that we need the steam to work:
1) part of the school 5:00am - 11:00am, then 7:30pm - 10:30pm
2) part of the school only needs morning hours 6:30-8:30am
3) residential 24hours (with different temperatures at different hours, as described by law)
4) Offices 8:30am - 7:30pm

meanwhile if 1 of these 4 needs steam, the whole building gets heated & that a huge waste. For example, currently only 4 units are occupied by residential tenants, so they need 24 hour steam, but I need to heat the entire building.

So my question is, is there a possibilty that i should install a thermostat in each room & also a solenoid valve or airvent on each radiator, & this will shut off the radiator of this room when not needed. For example set the offices to close the valves at 7:30pm each night?

Thanks in advance

nicholas bonham-carter

Where is the thermostat location now?
You can try some TRV’s on the areas which only need heat part of the time, but they are expensive and have no timers on them.
When only a small number of radiators are on for heating, the boiler runs less efficiently, and so they are used for comfort, more than economy.
My suggestion is to make the system well balanced, with very good main venting at very low pressure. Short set backs (less than 12nhours), in my opinion will not save fuel.—NBC

Jamie Hall

If -- and only if -- the piping is laid out so that each of your proposed zones can be easily cut off from the rest of the system, then yes you can zone it. But there are two problems. First, as @nicholas bonham-carter said, you are essentially looking at large setbacks on the zones which are turned off (or down). Large setbacks and steam (or any other system with relatively high mass radiation) aren't really that good an idea -- you don't save much, as you have to heat the space back up again. The other problem is that when some -- or a majority -- of the zones are off, the boiler will be wildly oversized. There are various ways to work around this, varying from relatively simple, such as cycling on pressure (which is really only a good idea if the boiler is only a few tens of percent oversize) to using various timer schemes (which could be integrated into, and varied, by the zoning controls). Again, efficiency does take a hit.

One real caution, if you were to go ahead and do zoning: the zone valves which you might consider using must be full port -- that is, the passage in the valve must be straight through, and the same interior diameter as the pipe. Depending on the pipe size, these can get a bit pricey...

Also, you would need to add piping to ensure that any possible condensate -- both before and beyond the valves -- can return freely to the boiler at all times.

Fred

You almost need to break each requirement down into four separate boilers, including mains and return piping. Hardly practical to do from a cost and retrofit perspective. If a single boiler is properly sized for the smallest zone, it will be undersized for the larger zones and if it is sized for the largest zone, it will be well over sized for the smaller zones. Each situation has its own set of issues.
There may be some steam rated zone valves available, I'm not sure but even then the boiler would almost always be oversized except for the times when all zones call for heat. Even with zone valves, it is also dependent on how the mains and radiators are piped. If they are not piped based on how you want to zone the building, you are still out of luck.