Cold pipes when zone starts - any pipe/boiler crack risk?

Si_zim

HI



I have a steam boiler running a hot water baseboard zone in the addition. Main house on steam has a small setback at night for comfort (5F) and a larger one during the day (8F). The addition is currently manually controlled which has me worried about shock to hot pipes and the boiler should anyone crank it up. Right now the addition is run at 70F during the day and set down to 65F at night - but the pipes (basic foam insulation) run in the crawlspace which gets pretty cold. Have a Taco circulator which probably would pump the cooler water back into the boiler pretty quick - and if steam is being called for I can imagine it would be bad.



Am I being paranoid or is there real risk of cracks as it gets colder out? Should we just keep the addition at 70F and burn extra gas to be safe?



Thanks for any input



Simon

kcopp

Well it depends....

what is the boiler size?. What is the amount of heat in the addition? And how is it piped? If you have a good sized boiler and small addition not a problem. but if the hot water baseboard is a huge load and its piped direct then you may have an issue. Do you get your domestic hot water off the boiler by way of a coil?

Si_zim

size details

its a 125000 btu boiler. About 30 linear feet of baseboard in the addition.

About 30 ft of lightly insulated copper pipe out in the crawlspace piped via a Taco circulator, with a small bypass round the boiler and flo control valve.

The boiler just does steam for the main house (about 250sq ft EDR I think) and the baseboard heating... not domestic hot water.

kcopp

you are fine.

not much chance of a thermal crack.

nicholas bonham-carter

Foam insulation

If you can get into the crawl space again, I suggest you replace the foam with fiberglass, as the temperatures are above what the foam is capable of tolerating. Even fiberglass batts of 2 inches would work better than foam.--NBC

Si_zim

thanks all

It's a bit of  relief to hear we should be ok. I'll still try to make any setbacks slight in these colder temperatures.



Yes - foam was from prior owner. Looks like he hasn't even sealed it - the plastic pieces are still covering the adhesive. I doubt it's doing too much. I have some 1" fiberglass on order - will get back in there soon to sort it out.