This post really belongs under the hydronics forum but I don't seem to have posting priviledges in that area so here goes:
Our company is not yet in the hydronics business but is working on developing solutions for the residential oil fired hot water radition retrofit business.
The main obstacle is that existing radiator installations were designed for higher water temperatures (160-180F) and than we are trying to use more economical water temps commonly used in geothermal installations (100-115F). Luckily we've found that most past installations were greatly oversized and this works in our favour. However, we are still short of meeting the design heat loss once you degrade raditator output at lower temperatures.
We considered using a 2nd stage heating source to boost water temp when called for by 2nd stage thermostat, zone controller etc, however, doing so is futile in our case since the return water temperature is higher than our original incomming water temperature and this would effectively negate and reverse our heat exchanger.
Therefore I am wondering whether we could increase the pump speed as a means of incresing flow and therefore boosting radiator output. On paper this seems like it should work but our lack of experience in this field makes me wonder whether there are reasons this should not be considered with an older installation desgined for lower speed, higher temp installations.
Anyone out there with practical and theoretical experience on this matter? I believe most installations will have current pump speeds of 3-5 G/M so we would anticipate rasing this by a factor capable of maybe doubling the heat output of the rads without blowing gaskets.
Your feedback would be appreciated.