Heat Source Choice

Alan(CaliforniaRadiant)Forbes

has already been completed (done by another contractor), but I wonder how you guys would have done it.

This is a house in the SF Bay Area:

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Alan(CaliforniaRadiant)Forbes

Three stories

with steam heating.

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Alan(CaliforniaRadiant)Forbes

The owners

remodeled their kitchen (plenty of windows and 20 foot high ceilings)

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Alan(CaliforniaRadiant)Forbes

and also

their master bathroom

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Alan(CaliforniaRadiant)Forbes

Your choice

of the heat source is either the existing steam boiler (Smith; ~500 MBTU)

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Alan(CaliforniaRadiant)Forbes

Or the

existing domestic water heater (Bradford-White 100 gallon, 199 MBTU).

Which one would you use and why?



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[Deleted User]

It depends...

on the total connected loads. I'd have done an EDR survey to see if the boiler was matched to load. If it was close, or under I'd probably have gone to the DHW w/HX if it was capable of carrying the load. If no on either, I'd probably conside setting another heat source.

Seen too many jobs where the steamer was close or under, and someone got the idea of using the hot condensate to drive another load, and when it gets cold outside, the steamer don't make steam.

What did the competition do?

ME

Alan(CaliforniaRadiant)Forbes

They used

the steam boiler and the only problem is that their radiant system will only come on if the thermostat for the main house is on and that's difficult for the owners to understand. Everytime they want their floors warm, they have to think about whether or not the steam system is on.

The installers wired the pump on the boiler side to a summer-winter switch; it was running 24/7, even during the summer since the owners didn't know they had to go down and turn the switch off when the seasons changed. I re-wired it to an end switch.

Good point about adding up the connected load, ME. It's important to do the homework.

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Alan(CaliforniaRadiant)Forbes

One nice feature

is that they used dual sensor thermostats. They have a floor sensor and an air sensor and you can set them to keep a minimum floor temperature.

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[Deleted User]

MMMmmm...

see a lot of that where the installers don't modify the control logic of the boiler to reflect its dual use. I just think a lot of them don't realize that it can be done that way, consequently the HO gets a bum deal. I usually wire in an aquastat in the boiler so that if there is a call for the hydronic side, that it limits the condensate temperature to 180 degrees F. If there is a call for steam, then the 180 is overridden and the boiler operates off of its pressure control. Easy enough to do. Hardest part is getting a sensor immersed into the hot condensate, and where there's a will, there IS a way.

ME

Steve Bergerson

Go Nuclear

On larger projects like this one, I tend to lean towards a residential pebble bed nuclear reactor to generate the steam... : )

Alan(CaliforniaRadiant)Forbes

That's a great idea,

Mark, but don't you want as high a temperature of hot water as possible going to the HX?

By the way, I didn't mention that there is a thermostatic temperating valve on the radiant side.

Best wishes,

Alan

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[Deleted User]

Most HXers

are sized based on 180 degree F entering water temperature. You could go as high as 210 in SFO without generating steam. It would be a short trip to steam if that were the case. I always look at things as if I'm the one responsible for paying the gas bill... The lower, the better.

ME

DanHolohan

Ask them

if we can have Wetstock III there.