steam sizing

Dale

We have people turn off series loop rads and freeze a loop. Interested in just what sort of piping layout. I think many of these are fixed as best as possible with continous circulation and an indoor/outdoor reset. Perhaps the upstairs is piped as a zone already. Customer will need to spend the money to have you find out.

Paul Fredricks_9

Existing house. W/M 768 steam boiler. Rated for 177K BTU's net. Unit is fired at 1.35 GPH which will deliver about 140K BTU's.

The heat loss on the house 128K BTU's. The measured radiator load is 250,000 BTU's. It seems the house is quite over radiated. They have some radiators turned off on the lower floors because it over heats in those areas.

The customer says the current system doesn't get heat to the third floor radiators, but they don't want to heat the third floor.

I know you're supposed to size to the radiation load with steam, but that would up-size the boiler quite a bit. What would you do?

Jamie Hall

not a bit surprised

that some of the radiators don't get much heat -- if your measured load (EDR) is right, the boiler is significantly undersized for the system and it is something of a wonder that it works at all.

In steam, the boiler must match the EDR of the system (plus pickup -- your mains are insulated, aren't they?); the heat loss on the house has nothing to do with it.

1. You could size the boiler properly, using a vaporstat for control and putting the thermostat in the best place (probably downstairs somewhere). That would get heat everywhere it was needed and there was radiation. If the thermostat is downstairs, it won't overheat there... because the thermostat will turn the boiler off.

2. Or you could disconnect some of the radiators, thus lowering the EDR and the boiler size (don't leave them connected and turned off; someone will turn them on, sure as shootin').

3. Or you could start replacing radiators... urk.

Myself I'd go with option 1.

Paul Fredricks_9

I haven't seen the job, just getting the info from one of the sales guys. The homeowner has turned off radiators, so I'm not too worried about her turning them back on.

Of course, the best thing would be a room by room analysis of heat loss and necessary radiation. Then eliminating radiators and see what's left. Of course, all that costs money and takes time. Not sure what the customer is willing to do. My fear would be that anything less will result in complaints the we have to deal with.

I'm also told by the sales rep that he doesn't think the chimney can handle a boiler with a 250K output. Of course, that's what must have been there originally.

Paul Fredricks_9

I think you missed it. This is a steam system. From what I'm told there are small rooms with 2 radiators in them and the customer shut one off to limit the over heating.

The Steam Whisperer (Formerly Boilerpro)

If its two pipe, Google Frank Gifford and check out his article.

on adding orifices to the system to reduce the radiation. Tunstall turned me onto this. Heat loss can have plenty to do with the sizing of the replacement boiler. Orifice heating sysems have always used much smaller boilers than there radiation dictates.

Boilerpro

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Paul Fredricks_11

It's one pipe. But now that you say that, couldn't we just slow the radiator venting a bit? Seems to me that would do the same thing. Vent the mains like crazy and then slow the rad vents so that the rooms get up to tempat a nice easy pace.

The Steam Whisperer (Formerly Boilerpro)

That's what I do

The most difficilt part is finding slow enough rad vents. I typically use Hofmann adjustables set from 1 to about 2.5. That's how the system worked in the old days, why not now. It usually takes about 2 to 3 hours of continuous firing before the rads get completely hot and the system heats very smoothly.

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Jamie Hall

I learn something useful

every single day on the Wall. Thanks guys!

Paul Fredricks_9

As a wrap up to this thread, I was told by the sales guy that the homeowner just wants to swap out the boiler. Read that as not spend any money they don't have too. Of course, they are probably being short sighted and would save plenty if they did they whole thing the right way the first time.

I like the slow venting idea for the radiators. I'll have to file that away for future use.